Resumo em Português:

RESUMO: Plantas de regiões áridas têm maior potencial alelopático do que plantas cultivadas à medida que crescem sob um ambiente estressante. Foi realizado um experimento para investigar o potencial herbicida de extratos aquosos de quatro plantas terrestres secas, incluindo frutas e videiras Citrullus colocynthis, e partes acima do solo das plantas Rhazya stricta, Crotalaria burhia e Calligonum polygonoides, com quatro concentrações (25%, 50%, 75% e 100%) de extratos inicialmente preparados contra a ervilhaca-silvestre, uma planta daninha comum de trigo na região estudada. Estas plantas foram recolhidas da área de terra seca (30,03° N e 70,38° E, 129 m metros acima do nível do mar - condições quase desérticas) de Dera Ghazi Khan, Punjab, Paquistão. Todas as quatro plantas exibiram potencial herbicida pronunciado, com 9% a 91% de supressão de diferentes parâmetros na planta daninha L. aphaca. Foi observada inibição máxima na germinação (36-91%). Observou-se também supressão significativa na contagem de folhas (9-65%), comprimento do tiro (12-59%), comprimento da raiz (4-62%), peso fresco do caule (17-71%), peso fresco da raiz (10-60%), peso seco do caule (15-72%), peso seco da raiz (13-64%) e número de nódulos (34-89%). A inibição máxima foi apresentada por R. stricta seguida de C. colocynthis: frutos. Ao contrário, em caso de nodulação, supressão máxima foi produzida pelo extrato de C. burhia. Foi observada a menor supressão para o extrato de C. polygonoides. Esses achados encorajam o uso de plantas terrestres secas disponíveis localmente com forte potencial de alelopatia, que podem ser usadas no controle não químico de plantas daninhas e, portanto, reduzir a dependência do controle químico.

Resumo em Inglês:

ABSTRACT: Dry land plants owing to their capability to grow under stressful environment have shown higher allelopathic potential as compared to cultivated plants. An experiment was conducted to investigate the herbicidal potential of aqueous extracts of four dry land plants viz. fruit and vine of Citrullus colocynthis, and above ground parts of Rhazya stricta; Crotalaria burhia and Calligonum polygonoides, with four concentrations (25, 50, 75 and 100%) of initially prepared extracts against Lathyrus aphaca, a common weed of wheat in the studied region. These plants were collected from dry land area (30.03° N and 70.38° E, 129 m above sea level, almost desert conditions) of Dera Ghazi Khan, Punjab, Pakistan. All the four plants exhibited pronounced herbicidal potential with 9 to 91% suppression of different parameters in L. aphaca). Maximum inhibition was recorded in germination (36-91%). Significant suppression in leaf count (9-65%), shoot length (12-59%), root length (4-62%), shoot fresh weight (17-71%), root fresh weight (10-60%), shoot dry weight (15-72%), root dry weight (13-64%), and nodule numbers (34-89%) was also observed. The highest inhibition was exhibited by R. stricta followed by C. colocynthis: fruit. However, in case of nodulation maximum suppression was produced by C. burhia extract. Least suppressant activity was observed for the C. polygonides extract. These results encourage the potential use of locally available dry land plants possessing strong allelochemical properties for nonchemical control of weeds ultimately reducing reliance on chemical control.

Resumo em Português:

RESUMO: A longevidade de sementes sob diferentes condições ambientais é considerada um dos fatores mais importantes na propagação e persistência de espécies exóticas. Os experimentos foram conduzidos de forma a determinar a persistência das sementes no solo e os efeitos de submersão em água, inundação de solo e altas temperaturas na germinação e viabilidade de Euphorbia manchada (Chamaesyce maculata) e leiteiro (Euphorbia heterophylla) como duas espécies exóticas em diferentes regiões da província de Golestan. As sementes de Euphorbia manchada colocadas a uma profundidade de 10 cm mantiveram a sua viabilidade acima de 95% depois de um ano, enquanto as de leiteiro ficaram completamente destruídas depois da exumação do solo. Sementes de ambas as espécies foram incapazes de germinar após submersão, mas 92% das sementes de Euphorbia manchada mantiveram-se viáveis sob essa condição durante 14 dias. Não se observou germinação após nove semanas de submersão. A duração da submersão afetou drasticamente a germinação das sementes de leiteiro, uma vez que após seis dias de submersão não ocorreu germinação. Doze dias após a inundação, a emergência de Euphorbia manchada decresceu 57%, comparada com a do controle. Dez por cento das sementes de leiteiro emergiram quando a submersão foi mantida até 12 dias, enquanto no controle 96% germinaram. A germinação de sementes de Euphorbia manchada sujeitas a 140 oC durante cinco minutos foi de 5%. A viabilidade de sementes de leiteiro foi completamente perdida a 120 oC e 140 oC durante cinco minutos. Esses resultados sugerem que Euphorbia manchada é capaz de formar banco de sementes persistente. Sementes desta espécie foram parcialmente tolerantes à submersão em água, mas as de leiteiro mostraram-se suscetíveis a essa submersão. A queima de resíduos agrícolas também pode ajudar a prevenir o aumento do banco de sementes de ambas as espécies.

Resumo em Inglês:

ABSTRACT: Seed longevity under different environmental conditions is considered as one of the most important factors in the spread and persistence of an exotic species. The Experiments were conducted to determine seed persistence in soil, effects of submergence in water, flooding of the soil, and high temperatures on germination and viability of spotted spurge (Chamaesyce maculata) and wild poinsettia (Euphorbia heterophylla) as two exotic species in different regions of Golestan province. Spotted spurge seeds buried at depth of 10 cm maintained their viability above 95% after a year, while wild poinsettia seeds were destroyed completely after exhuming the soil. Seeds of both species were unable to germinate under submergence, but 92% of the spotted spurge seeds remained viable under this condition for 14 d. No germination was observed after 9 weeks submersion. Submersion duration drastically affected seed germination of wild poinsettia, so that no germination occurred after 6 d submersion. Twelve days after flooding, spotted spurge emergence decreased by 57% compared to the control. Ten percentage of wild poinsettia seedlings emerged when flooding was kept up to 12 d after sowing, while control had 96% emergence. Germination of spotted spurge seeds subjected to 140 oC for 5 min was 5%. Viability of wild poinsettia seed was completely lost at 120 and 140 C for 5 min. These results suggest that spotted spurge is capable of forming persistent seedbank. Seeds of spotted spurge were partially tolerant to submersion in water, but wild poinsettia seed are susceptible to submergence. The burning of crop residue could also prevent augmenting the soil seed bank of both species.

Resumo em Português:

RESUMO: Verbascum L. é o maior gênero da família Scrophulariaceae e inclui várias espécies de importância medicinal. A alta diversidade morfológica entre as espécies do gênero Verbascum causa problemas na delimitação das espécies. Neste estudo, as propriedades morfológicas, anatômicas, palinológicas e de sementes de Verbascum exuberans foram investigadas. É uma planta endêmica local restrita às províncias de Manisa e Izmir, na Anatólia Ocidental. Na seção transversal da raiz, os elementos do xilema ocupam uma área considerável. A parte superior das células da epiderme na seção transversal da haste é coberta por uma camada de cutícula distinta. A veia principal da folha é moldada como feixe bicolateral. Idioblastos não foram observados na epiderme das folhas de V. exuberans. Sementes de V. exuberans são marrom-escuras e oblongas a prismáticas e alveoladas. O hilo é curto e orbicular. A ornamentação do revestimento da semente é reticulado-rugosa. Grãos de pólen geralmente radialmente simétricos, isopolares, prolatos, tricolpados. Tectum é padrão reticular.

Resumo em Inglês:

ABSTRACT: Verbascum L. is the largest genus of the family Scrophulariceae and includes several species are of medicinal importance. The high morphological diversity among the species of the genus Verbascum causes problems in the delimitation of the species. In this study, morphological, anatomical, palynological and seed properties of Verbascum exuberans were investigated. It is a local endemic restricted to the provinces of Manisa and Izmir in West Anatolia. In the root cross-section, the xylem elements occupy a considerable area. The upper part of the epidermis cells in the stem cross-section is covered a distinct cuticle layer. The main vein of the leaf is shapped as bicollateral bundle. Idioblasts were not observed in the epidermis of the leaves of V. exuberans. Seeds of V. exuberans are dark brown and oblong to prismatic and alveolate. Hilum is short and orbicular. The seed coat ornamentation is reticulate-rugose. Pollen grains usually radially symmetrical, isopolar, prolate, tricolpate. Tectum is reticulate.

Resumo em Português:

RESUMO: Após a poda da mandioca, inicia-se um novo ciclo de crescimento, sendo necessário o controle das plantas daninhas. Portanto, objetivou-se neste estudo avaliar a seletividade e a eficiência da aplicação sequencial de herbicidas isolados e em misturas em tanque com e sem adição de adubo foliar, depois da poda da mandioca. Realizaram-se dois experimentos com delineamento experimental de blocos casualizados com quatro repetições. Os tratamentos do experimento 1 consistiram em: testemunha sem capina, testemunha capinada, mesotriona, mesotriona/mesotriona, [mesotriona+adubo foliar]/[mesotriona+adubo foliar], mesotriona/[mesotriona+adubo foliar], [mesotriona+cletodim], [mesotriona+cletodim+adubo foliar]/[mesotriona+ cletodim+adubo foliar], [mesotriona+cletodim]/[mesotriona+cletodim], [mesotriona+cletodim]/clorimuron, [mesotriona+ cletodim]/clorimuron+adubo foliar], [mesotriona+cletodim+adubo foliar]/[clorimuron+ cletodim+adubo foliar], [mesotriona+cletodim]/[clorimuron+cletodim]. Os tratamentos do experimento 2 consistiram em: testemunha sem capina, testemunha capinada, clorimuron, [clorimuron+adubo foliar]/[clorimuron+adubo foliar], clorimuron/clorimuron, clorimuron+cletodim, [clorimuron+cletodim+adubo foliar]/[clorimuron+cletodim+adubo foliar], [clorimuron+cletodim] /[clorimuron+cletodim], [clorimuron+cletodim]/[mesotriona+adubo foliar], [clorimuron+cletodim]/mesotriona, [clorimuron+cletodim+adubo foliar]/[mesotriona+cletodim+adubo foliar], [clorimuron+cletodim]/[mesotriona+cletodim]. As doses utilizadas em ambos os experimentos de mesotriona, cletodim e clorimuron foram de 240, 120 e 20 g ha-1, respectivamente, enquanto para o adubo foliar utilizaram-se 2,5 L do produto comercial (Amino Plus®). A primeira aplicação ocorreu 50 dias após a poda, e a segunda, aos 22 dias após a primeira aplicação. No experimento 1, a aplicação do mesotriona, mesotriona/mesotriona e [mesotriona+cletodim]/[mesotriona+cletodim] apresentaram seletividade à mandioca e foram eficientes no controle de plantas daninhas. No experimento 2, o clorimuron+cletodim]/mesotriona, [clorimuron+cletodim+adubo foliar] /[mesotriona+cletodim+ adubo foliar] e [clorimuron+cletodim]/[mesotriona+cletodim] foram eficientes no controle, porém todos os tratamentos não foram seletivos. A adição de adubo foliar à calda não contribuiu para o aumento da seletividade.

Resumo em Inglês:

ABSTRACT: A new cycle of growth begins after pruning of cassava, and weed control is necessary. Thus, this study aimed to evaluate the selectivity and efficiency of sequential application of herbicides alone and in mixture with and without of foliar fertilizer after pruning of cassava. Two experiments were carried out in a randomized block design with four replications. The treatments of Experiment 1 consisted of control without weeding; control with weeding; mesotrione; mesotrione/mesotrione; mesotrione + foliar fertilizer/mesotrione + foliar fertilizer; mesotrione/mesotrione + foliar fertilizer; mesotrione + clethodim; mesotrione + clethodim + foliar fertilizer/mesotrione + clethodim + foliar fertilizer; mesotrione + clethodim/mesotrione + clethodim; mesotrione + clethodim/chlorimuron; mesotrione + clethodim/chlorimuron + foliar fertilizer; mesotrione + clethodim + foliar fertilizer/chlorimuron + clethodim + foliar fertilizer; mesotrione + clethodim/chlorimuron + clethodim]. Treatments of Experiment 2 consisted of control without weeding; control with weeding; chlorimuron; chlorimuron + foliar fertilizer/chlorimuron + foliar fertilizer; chlorimuron/chlorimuron; chlorimuron + clethodim; chlorimuron + clethodim + foliar fertilizer/chlorimuron + clethodim + foliar fertilizer; chlorimuron + clethodim/chlorimuron + clethodim; chlorimuron + clethodim/mesotrione + foliar fertilizer; chlorimuron + clethodim/mesotrione; chlorimuron + clethodim + foliar fertilizer/mesotrione + clethodim + foliar fertilizer; chlorimuron + clethodim/mesotrione + clethodim. The doses of mesotrione, clethodim, and chlorimuron used in both experiments were 240, 120, and 20 g ha-1, respectively, while 2.5 L of the commercial product Amino Plus® was used as foliar fertilizer. The first application was carried out at 50 days after pruning and the second application at 22 days after the first application. In Experiment 1, the application of mesotrione, mesotrione/mesotrione, and mesotrione + clethodim/mesotrione + clethodim showed selectivity to cassava and were efficient in weed control. In Experiment 2, chlorimuron + clethodim/mesotrione, chlorimuron + clethodim + foliar fertilizer/mesotrione + clethodim + foliar fertilizer, and chlorimuron + clethodim/mesotrione + clethodim were efficient in weed control, but no treatment was selective. The addition of foliar fertilizer to the spray solution did not contribute to increase selectivity.

Resumo em Português:

RESUMO: A alelopatia tornou-se uma ferramenta primordial para o controle de plantas daninhas em plantas cultivadas sem deteriorar o meio ambiente. Os efeitos alelopáticos de extratos aquosos de sorgo e sorgo em pó em um único híbrido de milho (Zea mays L.), híbrido HC-8080, e um arbusto de verão (Echinochloa colona L.) foram avaliados no laboratório de pesquisa da Agronomia, Faculdade de Agricultura, Universidade Gomal, Dera Ismail Khan, KPK, Paquistão. Os tratamentos foram: T1: controle (testemunha não tratada); T2: extrato aquoso de sorgo com taxa de 5 mL kg-1 de solo; T3: extrato aquoso de sorgo com taxa de 10 mL kg-1 solo; T4: extrato aquoso de sorgo a com taxa de 15 mL kg-1 de solo; T5: sorgo em pó a com taxa de 5 g kg-1 de solo; T6: sorgo em pó a com taxa de 10 g kg-1 de solo; e T7: sorgo em pó a com taxa de 15 g kg-1 de solo. Os resultados revelaram que o extrato aquoso de sorgo com 15 mL kg-1 de solo foi o tratamento mais deletério, tendo reduzido a porcentagem de germinação (GP) em milho e E. colona em 23,57% e 47,03%, o índice de germinação (GI) em 22,30 % e 42,14%, o comprimento de raiz em 32,25% e 62,54% e o comprimento de parte aérea em 23,22% e 62,76%, respectivamente, em relação ao controle. Da mesma forma, 15 g kg-1 de sorgo em pó reduziram os mesmos parâmetros, em 18,85% e 41,09%, 15% e 33,53%, 9,3% e 54,69% e 15,88% e 45,34% em milho e E. colona, respectivamente, em relação aos outros tratamentos em pó. Portanto, conclui-se que extratos de sorgo em pó podem ser usados para controlar plantas daninhas eficientemente, porém seu efeito deletério na cultura correspondente também deve ser uma consideração importante.

Resumo em Inglês:

ABSTRACT: Allelopathy has become a paramount tool for controlling weeds in crop plants without deteriorating the environment. Allelopathic effects of sorghum aqueous extracts and sorghum powder on a single cross maize (Zea mays L.) hybrid “HC-8080” and a summer weed, jungle rice (Echinochloa colona L.) were assessed in the research laboratory of Agronomy, Faculty of Agriculture, Gomal University, Dera Ismail Khan, KPK, Pakistan. The treatments included: T1: control (untreated check), T2: sorghum aqueous extract at a rate of 5 mL kg-1 soil, T3: sorghum aqueous extract at a rate of 10 mL kg-1 soil, T4: sorghum aqueous extract at a rate of 15 mL kg-1 soil, T5: sorghum powder at a rate of 5 g kg-1 soil, T6: sorghum powder at a rate of 10 g kg-1 soil and T7: sorghum powder at a rate of 15 g kg-1 soil. The results unveiled that sorghum aqueous extract at a rate of 15 mL kg-1 soil was the most deleterious treatment which reduced the germination percentage (GP) in maize and E. colona by 23.57% and 47.03%, germination index (GI) by 22.30% and 42.14%, root length by 32.25% and 62.54% and shoot length by 23.22% and 62.76%, respectively over control. Similarly, 15 g kg-1 soil sorghum powder reduced the same parameters respectively by 18.85% and 41.09%, 15% and 33.53%, 9.3% and 54.69% and 15.88% and 45.34% in maize and E. colona, respectively and stood better than other powder treatments. Therefore it is concluded that sorghum extracts and powder can both be used to control weeds efficiently but their deleterious effect on the corresponding crop should also be an important consideration.

Resumo em Português:

RESUMO: Nesta pesquisa foram estudadas possíveis atividades antibacterianas e antioxidantes da planta daninha caruru-de-mancha (Amaranthus viridis L.), com o uso da solução DPPH (1,1-diphenyl-2-picrylhydrazyl, para remoção da atividade de radicais livres). Extratos de diferentes partes dessa planta foram preparados em n-hexano, clorofórmio e acetato de etila. A atividade antibacteriana foi medida utilizando extratos de concentração de 100 mg mL-1 contra quatro espécies bacterianas fitopatogênicas mortais: Pseudomonas syringae Van Hall, Ralstonia solanacearum Smith, Erwinia carotovora (Jones) Holland e Xanthomonas axonopodis Hasse. Nos ensaios com antioxidantes foram utilizados extratos de 10, 20 e 30 mg mL-1, mantendo o DPPH como controle. Nesses bioensaios, a fração acetato de etila da folha do caruru-de-mancha apresentou a melhor atividade antibacteriana e antioxidante. A fração foliar do acetato de etila apresentou o maior diâmetro da zona de inibição (IZD), onde causou 21 mm de IZD contra P. syringae e 19 mm de IZD contra E. carotovora. Esse extrato também apresentou 22%, 52% e 84% de atividade antioxidante nas concentrações de 10, 20 e 30 mg mL-1, respectivamente. Não existem na literatura relatos disponíveis que descrevam a atividade antibacteriana do extrato de raiz de A. viridis contra P. syringae. Além disso, a atividade antioxidante dos extratos de raiz e caule em n-hexano, clorofórmio e acetato de etila foi investigada pela primeira vez no mundo. Concluiu-se que as atividades biológicas observadas durante a presente investigação podem ser devidas à presença de constituintes bioativos, os quais poderiam ser aproveitados como antibacterianos naturais e antioxidantes.

Resumo em Inglês:

ABSTRACT: In the present study, antibacterial and antioxidant [1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity] activities of a weed, slender amaranth (Amaranthus viridis L.) were investigated. Extracts of different plant parts were prepared in n-hexane, chloroform and ethyl acetate. Antibacterial activity was measured by using 100 mg mL-1 concentration extracts against 4 deadly phytopathogenic bacterial species viz. Pseudomonas syringae Van Hall, Ralstonia solanacearum Smith, Erwinia carotovora (Jones), Holland and Xanthomonas axonopodis Hasse. In antioxidants assays, 10, 20 and 30 mg mL-1 extracts were used keeping DPPH as control. In these bioassays, ethyl acetate fraction of A. viridis leaf exhibited the best antibacterial and antioxidants activity. Ethyl acetate leaf fraction showed the highest inhibition zone diameter (IZD) where it caused 21 mm IZD against P. syringae and 19 mm IZD against E. carotovora. This extract also showed 22, 52 and 84% antioxidant activity at 10, 20 and 30 mg mL-1 concentrations, respectively. Previously there is no report available that describes antibacterial activity of root extract of A. viridis against P. syringae. Moreover, antioxidant activity of stem and root extracts in n-hexane, chloroform and ethyl acetate was investigated first time in the world. It was concluded that the biological activities observed during the present investigation may be due to the presence of bioactive constituents that can be harnessed as natural antibacterials and antioxidants.

Resumo em Português:

RESUMO: Este estudo teve como objetivo destacar o efeito do ácido naftalenoacético (ANA) e regimes de irrigação sobre a produtividade do arroz grosso sob condições agroecológicas de Dera Ismail Khan, no Paquistão. O experimento foi composto por dois fatores, com quatro níveis (0, 60, 90 e 120 mL ha-1) de ANA e lâminas de irrigação (60, 75, 90 e 105 cm). Os dados foram descritos para observar a altura da planta (cm), perfilhos produtivos (m2), porcentagem de esterilidade (%), rendimento biológico (t ha-1) e rendimento de grãos (t ha-1) de arroz grosso. A relação custo-benefício (BCR) também foi calculada. Os resultados indicaram que a aplicação de ANA foi muito eficaz em aumentar o rendimento de arroz e, consequentemente, resultou em melhor valor de BCR. A máxima produtividade de arroz foi obtida com a aplicação de 90 mL ha-1 de ANA como regulador de crescimento a 75 cm de profundidade de irrigação. Os dados experimentais confirmam que a aplicação de ANA a 90 mL ha-1 na profundidade de irrigação de 75 cm aumenta a produtividade de arroz e assegura melhor retorno econõmico; assim, a inclusão deste tratamento sob condições áridas pode ser útil para impulsionar a produtividade de arroz.

Resumo em Inglês:

ABSTRACT: The study aimed to highlight the impact of naphthalene acetic acid (NAA) and irrigation regimes on the productivity of coarse rice under agro-ecological conditions of Dera Ismail Khan, Pakistan. The experiment was comprised of two factors with four levels (0, 60, 90, 120 mL ha-1) of NAA and irrigation at the depths (60, 75, 90 and 105 cm) of soil profile. The data was interpreted to observe the plant height (cm), productive tillers (m-2), sterility percentage (%), biological yield (t ha-1), and grain yield (t ha-1) of coarse rice. The benefit cost ratio (BCR) was also calculated. The results indicated that the application of NAA was found very effective in improving paddy yield and hence resulted in better BCR value. The maximum paddy yield was attained under the application of NAA 90 mL ha-1 as PGR (NAA) at 75 cm irrigation depth. The experimental data confirm that the application of NAA at the rate of 90 mL ha-1 with irrigation upto depth of 75 cm increases grain yield in rice and ensures better economic returns, thus inclusion of 90 mL ha-1 as PGR (NAA) at 75 cm irrigation depth under arid conditions assist in boosting paddy yield.

Resumo em Português:

RESUMO: O presente estudo foi realizado para verificar o potencial antifúngico do extrato de caule de Sisymbrium irio L. contra Fusarium oxysporum f. sp. cepae (FOC). Em bioensaios preliminares, diferentes concentrações (1% a 5%) de extratos de folhas, caules e frutos foram avaliadas contra o FOC. Todos os extratos foram eficazes contra o patógeno. No entanto, o extrato de folhas foi o mais eficaz, causando 25-41% de redução na biomassa FOC. O fracionamento do extrato metanólico das folhas foi feito por dois solventes orgânicos: n-hexano e clorofórmio. Diferentes concentrações (1,56 a 200 mg mL-1) dessas frações foram testadas contra o FOC. As frações de n-hexano e clorofórmio mostraram atividade inibitória contra o patógeno e resultaram em redução de 77-93% e 80-96% na biomassa de FOC, respectivamente. A análise por CG-EM mostrou a presença de 24 compostos em n-hexano e 4 compostos em fração clorofórmica. Na fração n-hexano, o β-sitosterol (18,64%) foi o composto mais abundante, seguido pelo ácido orótico, éster bis (terc-butildimetilsilil) terc-butildimetilsilílico (12,18%), éster de ácido 10-octadecenoico metil (7,90%) e Ter de di-isoctilo do ido 1,2-benzenodicarboxico (6,05%). Os principais compostos identificados na fração clorofórmica foram o ácido 1,3-benzenodicarboxílico, o éster bis (2-etil-hexílico) (50,82%) e o ftalato di-n-octilo (33,00%). Este estudo conclui que as frações de n-hexano e clorofórmio do extrato metanólico das folhas de S. irio contêm potentes constituintes antifúngicos para o manejo do FOC.

Resumo em Inglês:

ABSTRACT: The present study was carried out to check the antifungal potential of Sisymbrium irio L. shoot extract against Fusarium oxysporum f. sp. cepae (FOC). In preliminary bioassays, different concentrations (1 to 5%) of leaf, stem and fruit extracts were evaluated against FOC. All the extracts were effective against the pathogen. However, the leaf extract was found the most effective causing 25-41% decrease in FOC biomass. The fractionation of methanolic leaf extract was done by two organic solvents namely n-hexane and chloroform. Different concentrations (1.56 to 200 mg mL-1) of these fractions were tested against FOC. The n-hexane and chloroform fractions showed inhibitory activity against the pathogen and resulted in 77-93% and 80-96% reduction in biomass of FOC, respectively. GC-MS analysis showed the presence of 24 compounds in n-hexane and 4 compounds in chloroform fraction. In n-hexane fraction, β-sitosterol (18.64%) was the most abundant compound followed by orotic acid, bis(tert-butyldimethylsilyl)-, tert-butyldimethylsilyl ester (12.18%), 10-octadecenoic acid, methyl ester (7.90%) and 1,2-benzenedicarboxylic acid, diisooctyl ester (6.05%). Major compounds identified in chloroform fraction were 1,3-benzenedicarboxylic acid, bis(2-ethylhexyl) ester (50.82%) and di-n-octyl phthalate (33.00%). This study concludes that n-hexane and chloroform fractions of methanolic leaf extract of S. irio contain potent antifungal constituents for the management of FOC.

Resumo em Português:

RESUMO: A fim de examinar a aplicação de vários herbicidas para o controle de plantas daninhas na cultura do trigo, um estudo de campo foi realizado na Área de Pesquisa Agronômica da Faculdade de Agricultura da Universidade Gomal, Dera Ismail Khan, Khyber Pakhtunkhwa (KPK), durante o ano 2015-2016. O experimento foi realizado em delineamento de blocos completos casualizados (RCBD) com parcelas subdivididas, com três repetições. A parcela principal foi composta pelo tempo de aplicação dos herbicidas, enquanto o uso de herbicidas foi atribuído às subparcelas. Os dados revelaram que a maioria dos parâmetros de plantas daninhas, características fisiológicas e atributos agronômicos das plantas cultivadas foram significativamente afetados pelas práticas de manejo das plantas daninhas, incluindo o uso de herbicidas em diferentes intervalos de tempo durante o teste de plantas daninhas. A técnica de capina manual superou todas as demais práticas de manejo de plantas daninhas em quase todos os parâmetros estudados. Esta técnica foi considerada o tratamento mais eficaz contra todas as plantas daninhas predominantes e obteve o maior rendimento de grãos de trigo sob condições climáticas de Dera Ismail Khan.

Resumo em Inglês:

ABSTRACT: In order to examine application of various herbicides for controlling weeds in wheat crop, a field trial was conducted at the Agronomic Research Area, Faculty of Agriculture, Gomal University, Dera Ismail Khan, Khyber Pakhtunkhwa (KPK) during the year 2015-2016. The experiment was laid out in a randomized complete block design (RCBD) with split-plot arrangements having three replications. The main plot was comprised application time of herbicides while the use of herbicides was assigned to sub-plots. The data revealed that most of the weed parameters, physiological traits and agronomic attributes of crop plants were significantly affected by weed management practices including the use of herbicides at different time intervals over the weedy check. Hand weeding technique excelled all other weed management practices in almost all the parameters studied. This technique was found to be the most effective treatment against all prevailing weeds and obtained the highest grain yield of wheat under climatic conditions of Dera Ismail Khan.

Resumo em Português:

RESUMO: A perda de rendimento induzida por plantas daninhas na cultura do trigo é uma grande ameaça à segurança alimentar no Paquistão. Uma compreensão abrangente da competição de culturas de plantas daninhas é muito importante para desenvolver um manejo sustentável e econômico dessas plantas. Para esse propósito, foram conduzidos estudos de campo de dois anos para determinar o efeito de diferentes populações de cardo-mariano na fenologia e rendimento da safra de trigo no esquema de cultivo de trigo de arroz de Sargodha, Paquistão, durante 2013-2014 e 2014-2015. O experimento consistiu de sete tratamentos: controle (livre de plantas daninhas), teste de plantas daninhas (sem controle) e densidade populacional do cardo-mariano de 5, 10, 15, 20 e 25 plantas m-2. Em resposta ao aumento da densidade de plantas daninhas, observou-se redução gradual no rendimento e nas características relacionadas com o rendimento do trigo. Comparado ao controle livre de plantas daninhas, reduções significativas em número de perfilhos produtivos m-2 (20% e 18%), altura de plantas (15% e 18%), comprimento de espiga (19% e 26%), número de grãos espigão-1 (23% e 26%), peso de mil grãos (28% e 28%), grãos (29% e 30%) e rendimento biológico (20% e 24%) de trigo ocorreram em e além da densidade populacional de cardo-mariano de 5 plantas m-2 durante 2013-2014 e 2014-2015, respectivamente. Pode-se concluir que a planta daninha Cardo-mariano deve ser controlada se sua densidade populacional atingir 5 plantas m-2, a fim de evitar perdas significativas no rendimento de grãos do trigo.

Resumo em Inglês:

ABSTRACT: Weed-induced yield loss in wheat crop is a great threat to food security in Pakistan. A comprehensive understanding of weed-crop competition is very important to develop sustainable and cost-effective weed management. For this purpose, two-year field studies were conducted to determine the effect of different blessed milkthistle densities on the phenology and yield of wheat crop in a rice-wheat cropping scheme in Sargodha, Pakistan during 2013-2014 and 2014-2015. The experiment comprised seven treatments: control (weed free), weedy check (weedy without any control) and blessed milkthistle densities of 5, 10, 15, 20 and 25 plants m-2. In response to increasing weed density, a gradual reduction in yield and yield-related traits of wheat was noted. Compared to the weed-free control, a significant reduction in number of productive tillers m-2 (20% and 18%), plant height (15% and 18%), spike length (19% and 26%), number of grains spike-1 (23% and 26%), 1000 grain weight (28% and 28%), grain (29% and 30%) and biological (20% and 24%) yields of wheat occurred at and beyond blessed milkthistle density of 5 plants m-2 during 2013-2014 and 2014-2015 respectively. It can be concluded that blessed milkthistle weed must be controlled if its population density reaches 5 plants m-2 in order to avoid significant grain yield losses in wheat.

Resumo em Português:

RESUMO: Plantas medicinais têm sido utilizadas em todo o mundo por seres humanos como droga e remédio para várias doenças desde tempos imemoriais. Um estudo foi planejado para contar com a atividade antimicrobiana e triagem fitoquímica de Euphorbia helioscopia. As plantas foram recolhidas e testadas contra algumas estirpes padrão e alguns microrganismos patogênicos humanos (Escherichia coli, Bacillus subtilis, Staphylococcus aureus, Klebsiella pneumoniae, Salmonella typhi e Pseudomonas aeruginosa) e três estirpes fúngicas (Trichoderma, Rhizopus nigricans e Aspergillus niger). As concentrações de amostras de extração (500 e 1.000 mg mL-1) foram utilizadas contra patógenos. A ciprofloxacina foi usada como controle positivo no caso de cepas bacterianas, e o colfrimazol foi utilizado contra a cepa fúngica, enquanto o dimetilsulfóxido foi usado como controle negativo. Os resultados indicaram que a potência positiva dos poços do extrato aquoso apresentou diâmetro de 36 mm de inibição contra Escherichia coli e o extrato etanólico a 1.000 mg mL-1 apresentou zona de inibição máxima (34 mm) contra a zona de inibição de Bacillus subtilus (36 mm) contra Klebsiella pneumoniae e 33 mm de zona de inibição contra Trichoderma harzianum. Da mesma forma, extrato de água na concentração de 1.000 mg mL-1 resultou em maior valor de zona de inibição (36 mm) contra Staphylococcus aureus, uma zona de 30 mm de inibição contra Salmonella typhi, zona de 36 mm de inibição contra Pseudomonas aeruginosa, zona de inibição de 32 mm contra Rhizopus nigricans, zona de 34 mm de inibição contra Acremonium e zona de inibição de 34 mm contra Aspergillus niger. As bactérias mais suscetíveis foram K. pneumonia e Bacillus subtilis, enquanto E. coli foi a bactéria mais resistente e mostrou zona de inibição. O extrato etanólico continha taninos, lipídios, proteínas totais, carboidratos, flavonoides, alcaloides e polifenóis.

Resumo em Inglês:

ABSTRACT: Medicinal Plants have been used throughout the world by human beings as a drug and remedies for various diseases since time immemorial. A study was planned to count into the antimicrobial activity and phytochemical screening of Euphorbia helioscopia. The plants were gathered and tested against some standard strains and some human pathogenic microorganisms i.e Escherichia coli, Bacillus Subtilis, Staphylococcus aureus, Klebsiella pneumoniae, Salmonella typhi, Pseudomonas aeruginosa and three fungal strain Trichoderma, R hizopus nigricans, Aspergillus niger. The concentrations of extracting samples (500 and 1,000 mg mL-1) were used against pathogens. Ciprofloxacin was used as positive control in case of bacterial strains and Colfrimazol was used against the fungal strain while dimethyl sulfoxide as negative control. The outcomes indicated that the positive wells potency of Water extract had a 36 mm diameter of zone of inhibition against Escherichia coli and ethanol extract at 1,000 mg mL-1 had maximum (34 mm) zone of inhibition against Bacillus subtilus (36 mm) zone of inhibition against Klebsiella pneumonia and 33 mm of zone of inhibition against Trichoderma harzianum. Likewise, water extract at a concentration of 1,000 mg mL-1 resulted highest value of zone of inhibition (36 mm) against Staphylococcus aureus, a zone of inhibition ( mm) against Salmonella typhi, 36 mm zone of inhibition against Pseudomonas aeruginosa, (32 mm) zone of inhibition against Rhizopus nigricans, a 34 mm zone of inhibition against Acremonium and (34 mm) zone of inhibition against Aspergillus niger. The most susceptible bacteria were K. pneumonia and Bacillus subtilis, while E. coli was the most resistant bacteria and showed zone of inhibition. The ethanolic extract had tannins, lipid, total proteins, carbohydrates, flavonoids, Alkaloid and polyphenolics.

Resumo em Português:

RESUMO: Neste trabalho, as morfologias polínicas de 21 táxons, nove delas endêmicas da Turquia, pertencentes ao gênero Salvia (Lamiaceae: subfamília Nepetoideae: tribo Mentheae: subtribo Salviinae): S. aethiopis L., S. argentea L., S. aytachii Vural & Adigüzel, S. blepharochlaena Hedge & Hub.-Mor., S. cadmica Boiss., S. ceratophylla L., S. cryptantha Montbret & Aucher, S. frigida Boiss., S. fructicosa Miller, S. halophile Hedge, S. napifolia Jacq., S. microstegia Boiss. & Bal., S. recognita Fisch. & Mey. S. sclarea L., S. smyrnaea Boiss., S. suffruticosa Montbret & Aucher, S. tchihatcheffii (Fisch. & Mey.) Boiss., S. tometosa Bertol, S. verbenaca L., S. viridis L. e S. wiedemanni Boiss., coletados em toda a Turquia, foram intensamente estudadas usando luz (LM) e uma microscopia eletrônica de varredura (MEV). Os objetivos deste estudo foram investigar as morfologias polínicas de 21 táxons da sálvia turca (nove dos quais são endêmicos) e apresentar características semelhantes e diferentes dos táxons. Os grãos de pólen inteiros investigados tinham uma estrutura de simetria tanto isopolar como radial. No geral, os tipos de abertura foram principalmente hexacolpato, mas também foi determinado que o tipo de abertura de S. viridis era hexacolpato e octacolpato. Os grãos de pólen tinham formas características de esferoide, suboblato, prolato e subprolato. A ornamentação exina era birreticulada e reticulado-perfurada. Foi determinado pelos resultados de estudos palinológicos que a morfologia do pólen mudou entre os táxons estudados. Como conclusão, os resultados do presente estudo mostram que caracteres palinológicos, como formato do pólen, comprimento do eixo polar (P), comprimento do eixo equatorial (E), números de abertura e tipos e ornamentação exótica, exibem diferenças notáveis entre os táxons estudados.

Resumo em Inglês:

ABSTRACT: In this presented work, the pollen morphologies of twenty-one taxa, nine of them endemic from Turkey, belonging to the genus Salvia (Lamiaceae: sub-family Nepetoideae: tribe Mentheae: sub-tribe Salviinae), S. aethiopis L., S. argentea L., S. aytachii Vural & Adigüzel, S. blepharochlaena Hedge & Hub.-Mor., S. cadmica Boiss., S. ceratophylla L., S. cryptantha Montbret & Aucher, S. frigida Boiss., S. fructicosa Miller, S. halophile Hedge, S. napifolia Jacq., S. microstegia Boiss. & Bal., S. recognita Fisch. & Mey. S. sclarea L., S. smyrnaea Boiss. S. suffruticosa Montbret & Aucher, S. tchihatcheffii (Fisch. & Mey.) Boiss., S. tometosa Bertol, S. verbenaca L., S. viridis L., and S. wiedemanni Boiss. and collected throughout the Turkey, have been intensively studied by using light (LM) and a scanning electron (SEM) microscopy. The objectives of this study are to investigate the pollen morphologies of twenty-one taxa of Turkish Salvia (nine of which are endemic) and to present similar and different characteristics of the taxa. The investigated whole pollen grains had a structure of both isopolar and radial symmetry. Overall, types of aperture were mostly hexacolpate, but it was also determined that the aperture type of S. viridis was both hexacolpate and octacolpate. The pollen grains had characteristic shapes of spheroidal, suboblate, prolate and subprolate. The exine ornamentation was bireticulate and reticulate-perforate. It was determined by the results of palynological studies that pollen morphology changed amongst these studied taxa. As a conclusion, the results of the present study show that palynological characters such as pollen shape, polar axis length (P), equatorial axis length (E), aperture numbers and types and exine ornamentation, exhibit remarkable differences amongst the studied taxa.

Resumo em Português:

RESUMO: O uso de materiais com alto teor de carbono orgânico vem sendo estudado para a remoção de herbicidas em água, como o carvão ativado. Poucas alternativas de baixo custo são investigadas para a substituição desse tipo de material na remoção de herbicidas em água. Nesse contexto, o objetivo desta pesquisa foi avaliar resíduos agroindustriais (bagaço de uva branca, palhada de milho, casca de amendoim e casca de soja) como adsorventes do diuron e hexazinone em água potável. Amostras de água potável foram coletadas de fonte para o consumo humano. Foram adicionadas cinco concentrações (1, 2, 3, 4 e 5 mg mL-1) de cada herbicida em amostras de água potável. Os tratamentos consistiram em 10 mL da solução de água e herbicidas com 0,1 g de cada resíduo agroindustrial. A sorção foi avaliada utilizando o método do equilíbrio em batelada. A cromatografia líquida de alta eficiência (HPLC) foi utilizada para determinar a quantidade restante de herbicida em solução. O Kf (coeficiente de Freundlich) para o diuron foi mais pronunciado (9,94-11,93 mmol(1-1/n) L1/n kg-1) do que para o hexazinone (2,31-4,61 mmol(1-1/n) L1/n kg-1) em todos os adsorventes. A sorção percentual de diuron foi maior com bagaço de uva branca (51,15%) e casca de amendoim (52,44%), e a do hexazinone, com palha de milho (22,77%) e bagaço de uva branca (21,48%), em comparação com outros resíduos agroindustriais dos dois herbicidas. Embora a sorção de diuron tenha sido mais pronunciada que a de hexazinone, os valores de sorção obtidos neste estudo foram inferiores a 52,44% e considerados insatisfatórios em termos de remoção eficaz da água contaminada.

Resumo em Inglês:

ABSTRACT: Materials with high organic carbon content are studied for the removal of herbicides from water, such as activated carbon. Low cost alternatives should be investigated for the substitution of this type of material in the removal of herbicides from water. In this context, the aim of this research was to evaluate four agro-industrial residues (white grape bagasse, corn straw, peanut shell and soybean hull) as adsorbents of diuron and hexazinone in drinking water. Samples of drinking water were collected from sources used for human consumption. Five concentrations (1, 2, 3, 4 and 5 mg mL-1) of each herbicide were added to the potable water samples. Each experimental unit consisted of 10 mL of a solution of water and herbicide with 0.1 g of each agro-industrial residue. Sorption was evaluated using the batch equilibrium method. High performance liquid chromatography (HPLC) was used to determine the amount of herbicide present in the aqueous solution. The Kf (Freundlich coefficient) of diuron was higher (2.99-11.93 mmol(1-1/n) L1/n kg-1) than hexazinone (2.31-4.61 mmol(1-1/n) L1/n kg-1) for all adsorbents used. Diuron percentage sorption was higher with white grape bagasse (51.15%) and peanut husk (52.44%), and hexazinone with corn straw (22.77%) and white grape marc (21.48%), than other agro-industrial waste for both herbicides. Even though the sorption of diuron was more pronounced than that of hexazinone, the sorption values obtained in this study were less than 52.44% and considered unsatisfactory in terms of effective removal from contaminated water.

Resumo em Português:

RESUMO: Em sistema orgânico durante a estação “seca”, a competição das plantas daninhas com a cultura do quiabo aumenta o período crítico de interferência dessas espécies e as perdas de rendimento. Assim, objetivou-se neste trabalho determinar o período crítico de interferência das plantas daninhas no cultivo de quiabo orgânico durante a estação “seca”, em São Luís - MA. O experimento foi conduzido de outubro/2014 a janeiro/2015 em blocos ao acaso com quatro repetições. Os tratamentos foram os períodos de 7, 14, 21, 28, 35, 42 dias após o transplantio da cultura com controle e convivência da comunidade infestante. As espécies com maior índice de valor de importância foram Cynodon dactylon, Eleusine indica, Amaranthus spinosus e Commelina benghalensis. O PCPI foi de 4 a 53 dias após o transplantio, e as perdas de rendimentos foram de 69,5%. A cultura do quiabo em sistema orgânico durante a estação “seca” deve ser livre de plantas daninhas até o início da colheita, a fim de evitar elevadas perdas de rendimento.

Resumo em Inglês:

ABSTRACT: In organic systems during the dry season, competition of weeds with okra increases the critical period of interference of these species and yield losses. The objective of this research was to determine the critical period of weed interference in organic okra during the dry season in São Luís - MA. The experiment was conducted from October/2014 to January/2015 in randomized blocks, with four replicates. The treatments were the periods of 07, 14, 21, 28, 35, 42 days after the transplanting of the crop with control and coexistence of the infesting community. The species with the highest importance value index were Cynodon dactylon, Eleusine indica, Amaranthus spinosus and Commelina benghalensis. The CPWI was 04 to 53 days after transplanting and yield losses were 69.5%. The organic okra cropping system during the season dry should be free of weeds until the beginning of the harvest to avoid high yield loss.

Resumo em Português:

RESUMO: Esta pesquisa foi realizada com o objetivo de determinar a riqueza e a composição das comunidades de plantas daninhas associadas às plantações de banana no departamento de Magdalena (Colômbia). Entre setembro de 2016 e maio de 2017, uma área total de 174 hectares foi avaliada em quatro zonas agroecológicas (Alta, Média, Baixa e Norte). Em cada área, foram selecionadas três fazendas representativas, realizando coletas botânicas em lotes cultivados. Foram incluídas informações sobre ciclos de vida, hábito de crescimento e origem de cada espécie registrada. A composição florística foi representada por 204 espécies, incluídas em 143 gêneros e 54 famílias. Poaceae, com 31 espécies, foi a família com maior riqueza específica, seguida por Fabaceae (12) e Asteraceae (11). Do total de espécies registradas, 113 são perenes (55%) e 91 anuais (45%); 141, ervas (70%); 38, videiras (18%); e 25, árvores ou arbustos (12%). As espécies nativas predominam sobre as introduzidas. Foi determinado que a riqueza de espécies não difere significativamente entre as quatro áreas produtoras, ao passo que a composição varia. A presença de espécies comuns relatadas como plantas daninhas de importância global foi registrada em todas as áreas, entretanto algumas delas foram registradas em apenas uma das zonas, gerando um padrão diferenciador de composição. Comparações com inventários locais mostraram mudanças na composição do complexo de plantas daninhas ao longo do tempo. É destacada a presença de várias espécies que não foram listadas como plantas daninhas na região.

Resumo em Inglês:

ABSTRACT: This study was conducted to determine the richness and composition of weed communities associated with banana plantations in Magdalena department, Colombia. Between September 2016 and May 2017, a total of 164 hectares were assessed over four agroecological zones (Alta, Media, Baja and Norte); in each zone, three representative farms were selected where, through zigzag paths, botanical collections were made in cultivated lots. Information on life cycle, growth habit and origin of each species was included. The floristic composition was represented by 204 species distributed among 143 genera and 54 families. Poaceae, with 31 species, was the family with the highest species richness, followed by Fabaceae (12) and Asteraceae (11). From the total species recorded, 113 are perennial (55%) and 91 are annual (45%); 141 species are herbaceous (68%), 38 are climbers (20%), and 25 are arboreal or shrubby (12%). Native species predominate over introduced species. The species richness does not differ significantly between the sampling zones, but the weed community composition does. The presence of common species reported as important weeds worldwide was recorded in the four zones. However, some species were recorded in only one of the zones, generating a differential composition pattern. Comparison with local inventories showed changes in the composition of the weed complex over time. The presence of various species not previously considered weeds in the banana crops of this region is highlighted.

Resumo em Português:

RESUMO: Herbicidas com grande capacidade de lixiviação, como o hexazinone, tendem a atingir com mais facilidade as camadas mais profundas do solo, afetando a disponibilidade do produto na solução do solo pela retenção. Portanto, é importante compreender o comportamento do hexazinone em uma variedade de profundidades do solo. O objetivo desta pesquisa foi avaliar os processos de sorção e dessorção do hexazinone ao longo do perfil do solo. Os processos de sorção e dessorção do 14C-hexazinone [triazine-6-14C] em três profundidades do solo (0-10, 10-20 e 20-30 cm) foram avaliados pelo método de equilíbrio de batelada em lotes, analisando-se a radioatividade do herbicida foi quantificada por espectrometria de cintilação líquida. Foram utilizadas cinco diferentes concentrações do hexazinone (0,12, 0,19, 0,25; 0,31 e 0,38 µg mL-1) em solvente metanol. As concentrações do herbicida em equilíbrio e sorvidas no solo foram ajustadas usando isotermas de acordo com os modelos Linear, Freundlich e Langmuir. A sorção do hexazinone nas profundidades do solo de 0-0, 10-20 e 20-30 cm apresentou coeficientes de Freundlich (Kf) decrescentes com valores de 0,18, 0,11 e 0,08 g (1-1/n) L1/n kg-1 (50,49, 47,58 e 46,37% sorvido); e na dessorção os Kf foram de 7,96, 7,93 e 9,82 mmol (1-1/n) L1/n kg-1 (26,17, 26,58 e 28,68% dessorvido), respectivamente. A pequena diferença no teor de carbono orgânico entre as profundidades do solo foi suficiente para afetar a retenção do hexazinone, interferindo na biodisponibilidade deste produto na solução do solo para o controle de plantas daninhas.

Resumo em Inglês:

ABSTRACT: Herbicides with a high leaching capacity, such as hexazinone, tend to reach deeper soils more easily, where retention of the product affects its availability in the soil solution. Therefore, it is important to understand the behavior of hexazinone at a variety of soil depths. The objective of this research was to evaluate the sorption and desorption of hexazinone throughout the soil profile. The sorption and desorption processes of 14C-hexazinone [triazine-6-14C] at three soil depths (0-10, 10-20, and 20-30 cm) were evaluated by the equilibrium batch method, and the radioactivity of the herbicide was quantified by liquid scintillation spectrometry. Five different concentrations of hexazinone (0.12, 0.19, 0.25, 0.31, and 0.38 µg mL-1) in a methanol solvent were used. The concentrations of the herbicide in equilibrium and sorbed in the soil were adjusted by using isotherms according to the Linear, Freundlich, and Langmuir models. Hexazinone sorption at soil depths of 0-10, 10-20, and 20-30 cm showed decreasing Freundlich coefficients (Kf) with values of 0.18, 0.11, and 0.08 g (1-1/n) L1/n kg-1 (50.49, 47.58, and 46.37% sorbed), and in the desorption the Kf were 7.96, 7.93, and 9.82 g (1-1/n) L1/n kg-1 (26.17, 26.58, and 28.68% desorbed), respectively. The small difference in organic carbon content between soil depths was sufficient to affect hexazinone retention, interfering with the bioavailability of this product in the soil solution for weed control.

Resumo em Português:

RESUMO: A presença das plantas daninhas na área de cultivo do repolho promove redução de produtividade e qualidade do produto comercial. Diante da dificuldade de manejo e escassez de produtos registrados para o controle de plantas daninhas na cultura do repolho, objetivou-se com este trabalho avaliar a tolerância do cultivar de repolho Astrus Plus ao 2,4-D e dicamba. Para isso, dois experimentos foram conduzidos: um em condições controladas e o outro em campo. No primeiro ensaio avaliou-se a ação dos herbicidas sobre o crescimento inicial da cultura, sendo mensurada a matéria seca da parte aérea e raiz e a intoxicação das plantas. No segundo, foram avaliadas as intoxicações nas plantas e os componentes de produção da cultura. O ensaio em ambiente protegido comprovou a hipótese de o repolho apresentar tolerância aos herbicidas aplicados, pois não foram observadas intoxicação de plantas e alterações na matéria seca. Todavia, no ensaio em campo, observou-se que o herbicida 2,4-D causou intoxicações e reduções nos componentes de produção que comprovam que este herbicida é severamente tóxico à cultura. No entanto, o dicamba não provocou danos à cultura na fase inicial de cultivo e não reduziu a produtividade, indicando potencial uso. Conclui-se que o cultivar de repolho Astrus Plus é tolerante ao dicamba. O 2,4-D não causa intoxicações a este cultivar em condições controladas, mas, em campo, o repolho não foi tolerante, podendo levar as plantas de repolho à morte.

Resumo em Inglês:

ABSTRACT: The presence of weeds in cabbage cultivation areas causes a reduction in the productivity and quality of the commercial product. Given the difficulties in management and the scarcity of registered products for weed control in cabbage cultivation, this study aimed to evaluate the tolerance of the cabbage cultivars Astrus Plus to the herbicides 2,4-D and dicamba. Two experiments were performed; one under controlled conditions and another conducted in the field. The efficacy of the herbicides on the initial growth of the crop was evaluated in the first experiment, measuring the dry matter of the aerial part, the root of the plant, and evaluating the intoxication of the plants. Plant poisoning was also evaluated in the second experiment, along with crop production. No changes in the dry matter and plant poisoning were observed after the analyses performed in the controlled environment, showing that the cabbage presented tolerance to the applied herbicides. On the other hand, results from the experiments performed in the field showed that herbicide 2,4-D poisoned the cabbage causing reductions in production. Dicamba did not cause any damage in the initial phase of cultivation to this crop, with no reductions in its production. These results indicated the potential use of this herbicide in cabbage cultivation. It can be concluded from this study that the cultivar Astrus Plus is tolerant to dicamba. Under controlled conditions, 2,4-D does not cause toxicity to this cultivar, different from its effect when used in the field, where this herbicide can kill the cabbage plants.

Resumo em Português:

RESUMO: Tendo em vista a rápida evolução das populações de Conyza sumatrensis resistentes ao glifosato, é necessário entender a diversidade genética com vistas a melhorar as estratégias de manejo dessa planta daninha. Diante do exposto, objetivou-se com este trabalho investigar a dissimilaridade genética entre 15 biótipos de C. sumatrensis de diferentes regiões geográficas usando marcadores moleculares microssatélites. Os biótipos foram cultivados em casa de vegetação, para obtenção de material vegetal para extração de DNA. Dezenove marcadores microssatélites (SSR) foram desenvolvidos para os biótipos de C. sumatrensis. A dissimilaridade genética foi estimada pelo coeficiente de Jaccard (JC), e os biótipos, agrupados pelo método UPGMA. Os resultados demonstraram alta dissimilaridade (JC = 7,14 a 82,62) do material analisado, com os biótipos formando cinco grupos. A alta diversidade genética de C. sumatrensis indica que os biótipos podem apresentar distintas respostas a diferentes estratégias de manejo e que os mecanismos de resistência a herbicidas podem ser um dos fatores envolvidos na variabilidade genética das espécies.

Resumo em Inglês:

ABSTRACT: In view of the rapid evolution of Conyza sumatrensis populations resistant to glyphosate, it is necessary to understand the genetic diversity aimed to improve strategies for managing this weed. We investigated the genetic dissimilarity among 15 biotypes of C. sumatrensis from different geographic regions using microsatellite loci. The biotypes, were cultivated in a greenhouse to obtain vegetal material for DNA extraction. Nineteen microsatellite markers (SSR), were developed for C. sumatrensis biotypes. The genetic dissimilarity was estimated by the Jaccard coefficient (JC) and the biotypes grouped by the UPGMA method. The results demonstrated a high dissimilarity (JC = 7.14 to 82.62) of the analyzed material, with the biotypes forming five groups, being one group formed just by the susceptible biotype and in the others grouped by biotypes from distinct locations in the same group The high genetic diversity of C. sumatrensis indicates that the biotypes may show different responses to different management strategies, and that the mechanisms of resistance to herbicides and characteristics of evolution of populations due to adaptability may be some of the factors involved in the genetic variability of the species.

Resumo em Português:

RESUMO: O objetivo deste estudo foi identificar e quantificar as espécies daninhas em uma área de cultivo de acerola orgânica no Distrito de Irrigação dos Tabuleiros Litorâneos (DITALPI), município de Parnaíba-PI. A amostragem fitossociológica ocorreu no pico da estação chuvosa, antes da adoção das técnicas de manejo dessas plantas pelos agricultores. Foram amostradas 30 parcelas de 0,25 m2, instaladas nas entrelinhas da cultura, que incluíram as plantas do estrato herbáceo-subarbustivo. Foram calculadas, com base na ocorrência e cobertura de cada espécie, a cobertura absoluta e relativa e a frequência absoluta e relativa. Ao final do trabalho, registraram-se 25 espécies, distribuídas em 13 famílias, entre as quais Poaceae foi a mais significativa. Commelina benghalensis destacou-se com maior frequência. O índice de diversidade de Shannon (H’) e a equabilidade representaram, respectivamente, 2,30 nats ind-1 e 0,69. Cinco espécies responderam por 79,33% da cobertura absoluta no DITALPI. As espécies apresentaram padrão heterogêneo na distribuição no campo, e as de maior poder de infestação na cultura da acerola foram Commelina benghalensis, Urochloa plantaginea, Panicum maximum, Amaranthus spinosus, Cynodon sp. e Cyperus aggregatus. Por se tratar de uma área de cultivo orgânico, o conhecimento destas espécies é essencial para a escolha da melhor forma de controle por parte dos agricultores.

Resumo em Inglês:

ABSTRACT: This study aimed to identify and quantify the weed species in an area of organic acerola cultivation in the Distrito de Irrigação dos Tabuleiros Litorâneos do Piauí (DITALPI) in Parnaíba, Piauí, Brazil. Phytosociological sampling was completed in the rainy season, before the farmers adopted management techniques for the plants. Thirty plots of 0.25 m2 were sampled. The plots were located between crop rows, which consisted of herbaceous-subshrub plants. The absolute and relative covers and the absolute and relative frequencies of each species were calculated based on the occurrence and cover of each species. In total, 25 species comprising 13 families were registered, among which the Poaceae family that presented the largest number of species. Commelina benghalensis occurred the most frequently overall. Shannon’s diversity index (H’) and evenness were calculated as 2.30 nats ind-1 and 0.69, respectively. Five species accounted for 79.33% of absolute cover at DITALPI. The species were distributed heterogeneously within the field, and Commelina benghalensis, Urochloa plantaginea, Panicum maximum, Amaranthus spinosus, Cynodonsp., and Cyperus aggregatus were the species most likely to infest the acerola crop. As DITALPI is an area of organic cultivation, understanding these species is essential to help farmers select the best form of control.

Resumo em Português:

RESUMO: O consumo da batata yacon tem sido cada vez mais difundido pelo mundo devido às suas propriedades nutricionais e farmacêuticas. Em razão do crescente interesse comercial pela yacon, há demanda por estudos sobre o seu manejo agrícola, entre os quais estão os efeitos da competição de plantas daninhas com a yacon, fato ainda pouco conhecido. Assim, realizou-se este trabalho com o objetivo de avaliar os efeitos da convivência das plantas daninhas no desenvolvimento e crescimento da yacon. O delineamento experimental foi inteiramente casualizado, com tratamentos constituídos pela convivência com quatro espécies de plantas daninhas: tiririca (Cyperus rotundus L.), trapoeraba (Commelina benghalensis L.), caruru (Amaranthus viridis L.) e picão-preto (Bidens pilosa L.), além da testemunha (yacon ausente de daninhas), com sete repetições. O experimento foi conduzido em casa de vegetação, em vasos de 10 dm3. Foram avaliados altura das plantas, número de folhas, número de hastes, área foliar, acúmulo de massa fresca e seca (total e por partes) e clorofila A, B e total. A convivência com as plantas daninhas provocou diminuição no desenvolvimento da yacon (altura, número de folhas, número de hastes e área foliar), na capacidade fotossintética (redução dos teores de clorofilas A, B e total) e na produção, pois também diminuiu o acúmulo em biomassa fresca e seca das raízes tuberosas. A trapoeraba e o caruru foram as plantas daninhas que mais prejudicaram o desenvolvimento e crescimento da yacon.

Resumo em Inglês:

ABSTRACT: The consumption of yacon has been increasing around the world due to the nutritional and pharmaceutical properties of this plant. The growing commercial interest in yacon (Smallanthus sonchifolius) generates a demand for crop management research studies, including the effect of weed competition on yacon, which was not yet studied. Thus, this study was performed with the objective of evaluating the effects of weed competition on yacon development and growth. The experimental design was completely randomized with four treatments and seven replicates. Treatments were yacon with the interference of four weed species: Cyperus rotundus L. (nutgrass), Commelina benghalensis L. (tropical spiderwort), Amaranthus viridis L. (slender amaranth) and Bidens pilosa L. (hairy beggarticks). The experiment was conducted in a greenhouse, using 10 dm3 pots. Plant height, number of leaves, number of stems, leaf area, fresh and dry mass weight (total and partial), and chlorophyll A, B and total were evaluated. The weed competition resulted in a decrease in the yacon development (height, number of leaves, number of stems, leaf area), photosynthetic rate (decreased chlorophyll content A, B and total) and yield, as also decreased the accumulation of fresh and dry biomass of tuberous roots. C. benghalensis L. and A. viridis L. were the weeds most affecting the development and growth of yacon.

Resumo em Português:

RESUMO: A sorção de pesticidas no solo é o principal fator responsável por regular o destino de pesticidas no ambiente, afetando a degradação microbiológica e química, volatilização e lixiviação. O principal objetivo deste trabalho foi estudar o efeito da fase orgânica de solos vulcânicos sobre a sorção de pesticidas agrícolas. A sorção e dessorção de oito solos vulcânicos cujos constituintes flúvico e húmico de sua matéria orgânica eram variáveis. Os resultados mostraram que, para todos os pesticidas, a sorção foi bem descrita por uma isoterma de Freundlich, e os valores 1/nads indicam que o mecanismo de sorção poderia ser explicado principalmente por reações físicas em todos os solos. Carbaryl e flumioxazin foram mais adsorvidos, com Kf média de 7,78 e 7,16 mL g-1, enquanto hexazinone e metsulfuron-methyl foram os pesticidas mais lábeis, com Kf de 0,86 e 0,81 mL g-1, respectivamente. A fração orgânica do solo foi o principal fator relacionado à sorção de todos os pesticidas estudados. Especificamente, o teor de ácido húmico regulou a atração entre o pesticida e o solo, principalmente através dos grupos carboxílicos.

Resumo em Inglês:

ABSTRACT: Pesticide soil sorption is a primary factor that influences the fate of pesticides in the environment, affecting regulation of microbiological and chemical degradation, volatilization and leaching. The main goal of this research was to study the effect of the organic phase of volcanic soils on sorption of agricultural pesticides. Sorption and desorption of eight agricultural pesticides were studied on eight volcanic soils that varied in the fulvic and humic constituents of their organic matter. For all pesticides, sorption was well described by a Freundlich isotherm where 1/nads values indicated that the sorption mechanism could be mainly explained by physical reactions in all soils. Kf values for carbaryl and flumioxazin were the highest with average values of 7.78 and 7.16 mL g-1, respectively. By contrast, hexazinone and metsulfuron-methyl had the lowest average Kf: 0.86 and 0.81 mL g-1, respectively, indicating that they were the least attracted to the soils. The organic fraction of the soil was the main soil factor related to the sorption of all study pesticides. Particularly, humic acid content regulated the sorption between pesticide and soil, especially through the carboxylic groups.

Resumo em Português:

RESUMO: Vários fatores determinam as perdas de rendimento de grãos devido à competição com plantas daninhas, entre eles as espécies infestantes. Entre as espécies daninhas de ocorrência comum em lavouras de soja das diferentes regiões do Brasil, destacam-se as da família Rubiaceae, representadas principalmente por Borreria latifolia e Richardia brasiliensis. O objetivo do presente estudo foi avaliar os efeitos da interferência das espécies B. latifolia e R. brasiliensis sobre o desenvolvimento das plantas e os componentes do rendimento e produtividade da soja. Dois estudos foram conduzidos em delineamento de blocos ao acaso com quatro repetições. Os tratamentos foram resultantes de um bifatorial, em que o primeiro fator foi constituído pelas espécies B. latifolia e R. brasiliensis, e o segundo, pelas densidades de 0, 2, 4, 6, 8, 10 e 12 plantas m-2. Em ambos os cultivares de soja, foram avaliados altura de planta, área foliar e clorofila total nos estádios V6 e R5 da cultura, número de vagens por planta, número de grãos por vagem, massa de mil grãos e perda de rendimento de grãos. O rendimento de grãos de ambos os cultivares de soja foi negativamente afetado pela interferência com as espécies B. latifolia e R. brasiliensis. B. latifolia foi mais competitiva com a cultura da soja do que R. brasiliensis, provocando maiores reduções em todas as variáveis analisadas. Cada planta de B. latifolia por m2 é capaz de reduzir o rendimento de grãos de soja em 3 a 4,4%, enquanto cada planta de R. brasiliensis reduz o rendimento em 2 a 2,6%. Para ambas as espécies rubiáceas, a redução do rendimento da soja decorrente da competição foi motivada pelo decréscimo no número de vagens por planta, número de grãos por vagem e massa de mil grãos.

Resumo em Inglês:

ABSTRACT: Weed species is one of the factors contributing to grain yield losses due to crop-weed competition. Two of the most common weeds of soybean fields in Brazil are from the Rubiaceae family: Borreria latifolia and Richardia brasiliensis. This study aimed to evaluate the effects of B. latifolia and R. brasiliensis on plant development, yield components, and soybean productivity. Two assays were conducted in a randomized block design with four replications, using a two-level factorial design, in which the first factor consisted of the species B. latifolia and R. brasiliensis and the second factor consisted of the densities 0, 2, 4, 6, 8, 10, and 12 plants m-2. Plant height, leaf area and total chlorophyll in the V6 and R5 stages, number of pods per plant, number of grains per pod, 1000-grain weight, and grain yield loss were evaluated in both cultivars. Grain yield of both soybean cultivars was negatively affected by the interference with B. latifolia and R. brasiliensis. The species B. latifolia was more competitive with soybean when compared to R. brasiliensis, causing higher reductions for all variables. Each B. latifolia plant per square meter is able to reduce the yield of soybean by 3 a 4.4%, while each R.brasiliensis plant reduces yield by 2 a 2.6%. For both species, the reduction in soybean yield due to competition was caused by a decrease in the number of pods per plant, number of grains per pod, and 1000-grain weight.

Resumo em Português:

RESUMO: Spermacoce latifolia, S. verticillata e Richardia brasiliensis (família Rubiaceae, tribo Spermacoceae) são plantas daninhas tolerantes ao glyphosate nas áreas de soja do Brasil. Mudanças na flora daninha para espécies tolerantes ao glyphosate nas áreas de soja evidenciam a necessidade de adoção de práticas que conservem a eficácia desse herbicida. Este estudo avaliou o efeito de aplicações de herbicidas em golpe simples e duplo no controle de S. latifolia, S. verticillata e R. brasiliensis antes da semeadura da soja. O delineamento foi o de blocos casualizados, com tratamentos em esquema fatorial. O fator A constou de três tratamentos de herbicidas sistêmicos aos 10 dias antes do plantio (DBS), enquanto o fator B constou de três tratamentos de herbicidas de contato aplicado aos 0 DBS (“plante e aplique”). As aplicações em golpe simples e duplo foram seguidas por aplicações em pós-emergência de glyphosate ou 2,4-D + glyphosate quando a cultura da soja atingiu três folhas expandidas. A eficácia do controle de cada espécie-alvo foi avaliada visualmente aos 14 dias após a semeadura (DAS), bem como aos 0 e 28 dias após a aplicação em pós-emergência (DAA) da cultura. As aplicações de golpe duplo geralmente proporcionaram maiores níveis de eficácia de controle para as plantas daninhas alvo da família Rubiaceae do que as aplicações em golpe simples. Glyphosate + 2,4-D, glyphosate + 2,4-D + diclosulam ou glyphosate + [halauxifen-metílico + diclosulam] seguido de glufosinato ou paraquat atingiram, pelo menos, 90% de controle de S. latifolia e R. brasiliensis, mas não controlaram S. verticillata (<80%). O glufosinato a 457 g i.a. ha-1 foi equivalente ao paraquat a 400 g i.a. ha-1 como herbicida de contato nas aplicações em golpe duplo, especialmente nas primeiras avaliações.

Resumo em Inglês:

ABSTRACT: Spermacoce latifolia, S. verticillata, and Richardia brasiliensis (family Rubiaceae, tribe Spermacoceae) are glyphosate-tolerant weeds in the soybean producing areas of Brazil. The weed shifts to glyphosate-tolerant weeds across soybean-producing areas has shown the need for adoption of practices that conserve the efficacy of glyphosate. This study evaluated the effect of single- and double-knockdown herbicide applications on the control of S. latifolia, S. verticillata, and R. brasiliensis prior to soybean sowing. Trials were designed as a randomized block and treatments were arranged as a factorial. Factor A was three systemic herbicide treatments 10 days before sowing (DBS), while Factor B was three contact herbicide treatments applied 0 DBS (“sow and apply”). The single- and double-knockdown applications were followed by post-emergence applications of glyphosate or 2,4-D + glyphosate when the crop reached three leaves. The efficacy of control of each weed species was visually evaluated 14 days after sowing (DAS), as well as 0 and 28 days after post-emergence application (DAA). The double-knockdown applications generally provided higher levels of control for the target weeds of the Rubiaceae family than the single-knockdown applications. Glyphosate + 2,4-D, glyphosate + 2,4-D + diclosulam or glyphosate + [halauxifen-methyl + diclosulam] followed by glufosinate or paraquat achieved at least 90% of control of S. latifolia and R. brasiliensis, but did not control S. verticillata (<80%). Glufosinate at 457 g a.i. ha-1 was equivalent to paraquat at 400 g a.i. ha-1 as a contact herbicide in the double-knockdown applications, especially on the first assessment dates.

Resumo em Português:

RESUMO: Entre várias práticas de manejo de plantas daninhas, o controle químico delas é considerado o método mais efetivo. No entanto, a dose ideal e a combinação adequada de herbicidas com adjuvantes desempenham papel vital no controle de plantas daninhas em um nível aceitável e produzem o rendimento máximo da cultura. Um estudo de campo foi conduzido para investigar o efeito de pós-emergência do herbicida isoproturon sozinho ou com combinação de adjuvantes no trigo de inverno e suas plantas daninhas relevantes. As doses de herbicida foram isoproturon a 175 g i.a. ha-1, isoproturon a 140 g i.a. ha-1 e isoproturon a 105 g i.a. ha-1, aplicado sozinho ou com adjuvantes Ad-500 ou biopotenciador a 400 mL ha-1 cada, e a verificação de plantas daninhas como tratamento controle. Entre todos os tratamentos, isoproturon a 175 g i.a. ha-1 + biopotenciador a 400 mL ha-1 foi mais eficaz no controle de Melilotus indica, Anagallis arvensis, Phalaris minor e Fumaria indica, pois ele reduziu a atividade fotossintética e a biomassa fresca e seca dessas plantas daninhas. No caso do trigo, os maiores perfilhos produtivos, altura da planta, peso de mil grãos e rendimento biológico e de grãos foram obtidos com isoproturon a 175 g i.a. ha-1 + biopotenciador a 400 mL ha-1, devido à supressão máxima de plantas daninhas. No entanto, observaram-se valores mais altos de parâmetros de troca de gás do trigo quando nenhum herbicida foi pulverizado. Conclui-se que o isoproturon a 175 g i.a. ha-1 + biopotenciador a 400 mL ha-1 pode ser uma abordagem rentável para obter o melhor rendimento de trigo, juntamente com a supressão máxima das plantas daninhas.

Resumo em Inglês:

ABSTRACT: Among various weed management strategies, chemical weed control is considered the most effective method. However, optimum dose and suitable combination of herbicide with adjuvants play a vital role in controlling weeds at an acceptable level and produce maximum crop yield. A field study was conducted to investigate the effect of post-emergence herbicide isoproturon alone or with combination of adjuvants on winter wheat and its associated weeds. The treatments were isoproturon at 175 g a.i. ha-1, 140 g a.i. ha-1 and 105 g a.i. ha-1 applied alone or with adjuvants Ad-500 or Bio-enhancer at 400 mL ha-1 each and weedy check as a control treatment. Isoproturon at 175 g a.i. ha-1 + Bio-enhancer at 400 mL ha-1 was most effective treatment for control of Melilotus indica, Anagallis arvensis, Phalaris minor and Fumaria indica as it decreased the photosynthetic activity, fresh and dry biomass of these weeds. In case of wheat, highest productive tillers, plant height, 1000-grain weight, biological and grain yield were achieved with isoproturon at 175 g a.i. ha-1 + Bio-enhancer at 400 mL ha-1. However, highest values of gas exchange parameters of wheat were observed where no herbicide was sprayed. It can be concluded that isoproturon at 175 g a.i. ha-1 + Bio-enhancer at 400 mL ha-1 might be a profitable approach to achieve optimal yield of wheat by causing the maximum suppression of these tested weeds. Moreover, the herbicide at reduced dose with adjuvants was not much effective in terms of weed control or increased yield.

Resumo em Português:

RESUMO: Os insetos da família Bruchidae (Coleoptera) são importantes depredadores; suas larvas se alimentam e vivem em sementes de uma grande variedade de plantas. Na Argentina, não há registros dos níveis de depredação de sementes de Ipomoea nil (Convolvulaceae) causada por esses insetos. Assim, o objetivo deste trabalho foi registrar a incidência das espécies do gênero Megacerus como depredadores de sementes de I. nil, importante planta daninha da cultura de algodoeiro em área de irrigação de Santiago del Estero. Megacerus maculiventris foi a única espécie de bruquídeo identificada como depredadora de sementes dessa planta daninha, tendo a porcentagem de depredação variado de 0,84% a 15,66% nos anos agrícolas de 2004 a 2008. Os resultados demonstraram que o número de sementes depredadas por cápsula é independente do número de sementes por fruto. Contudo, foi verificado que o inseto depreda uma semente por cápsula e que a maior frequência de depredação ocorre nos frutos com mais de três sementes. Os níveis de depredação de I. nil por M. maculiventris são baixos em relação aos registrados em outros hospedeiros por bruquídeos do gênero Megacerus.

Resumo em Inglês:

ABSTRACT: The insects of the family Bruchidae (Coleoptera) are important predators; their larvae feed upon and live in the seeds of a wide variety of plants. In Argentina, there not exists background information concerning the levels of predation of Ipomoea nil (Convolvulaceae) seeds caused by these insects. Thus, the aim of this work was to record the incidence of the species of the genus Megacerus as predators of I. nil seeds, an important weed affecting cotton growing in the irrigation area of Santiago del Estero. Megacerus maculiventris was the only bruchine species identified as predator of this weed. The predation percentage ranged from 0.84 to 15.66% in the agricultural years 2004-2008. It was attested that the number of predated seeds per capsule is independent from the number of seeds per fruit. However, it was proved that the insect predates just one seed per capsule and the highest predation frequency occurs in fruits containing more than three seeds. The levels of predation of I. nil by M. maculiventris are low in relation to those registered in other hosts by bruchines of the genus Megacerus.

Resumo em Português:

RESUMO: A erva-cabecinha (Phalaris minor) é a segunda planta daninha mais problemática nos campos de trigo do Irã, pois tem desenvolvido resistência aos herbicidas inibidores da ACCase. Marcadores moleculares de intersequência repetitiva simples (ISSR) foram utilizados para avaliar a variação genética entre e dentro de populações resistentes e suscetíveis aos inibidores de ACCase de P. minor do Irã, a fim de elucidar a origem da resistência e sua dispersão. Dezesseis populações de P. minor de diferentes regiões do Irã foram analisadas usando sete primers ISSR. As relações genéticas obtidas a partir da análise UPGMA revelaram a presença de mais de um genótipo entre as populações resistentes aos herbicidas. Os resultados indicaram que a alta similaridade genética e proximidade física entre as populações resistentes de P. minor nas diferentes regiões foi devido principalmente à polinização cruzada, à dispersão mecânica de sementes e a fatores ecológicos locais. Assim, infere-se que ocorreu uma seleção independente, assim como a movimentação de sementes resistentes, explicando a ocorrência e dispersão da resistência nessas populações.

Resumo em Inglês:

ABSTRACT: Littleseed canarygrass (Phalaris minor) is the second most serious and problematic grass weed in wheat fields in Iran, and has developed resistance to ACCase inhibiting herbicides. Inter-simple sequence repeat (ISSR) analysis was used to assess genetic variation between and within ACCase inhibitor-resistant and susceptible P. minor populations in Iran and to determine the origin of resistance and its dispersal. Sixteen P. minor populations from different regions in Iran were analysed using seven primers. Genetic relationships generated using UPGMA analysis indicated the presence of more than one genotype among the herbicide resistant populations. The results indicated that the high genetic similarity and physical proximity among the resistant P. minor populations in the different regions is mainly due to cross pollination, mechanical seed dispersion and local ecological factors. These findings suggested that independent selection as well as movement of resistant seeds had occurred, which could explain the presence and dispersion of ACCase inhibitor-resistance in these populations.

Resumo em Português:

RESUMO: Ipomoea hederaceae Jacq. é uma espécie exótica que está se tornando um problema crescente em lavouras de soja da província de Golestan, Irã. Considerando que há pouca informação disponível sobre a biologia dessa espécie no Irã, experimentos foram conduzidos para investigar os efeitos de diferentes fatores sobre a germinação de sementes e emergência de Ipomoea hederaceae. A máxima germinação ocorreu em temperatura constante de 20 oC (82%) e em temperatura alternada de 15/25 oC (94%). A germinação foi reduzida com o aumento da salinidade e do estresse hídrico. A concentração de cloreto de sódio e o potencial osmótico que inibiram 50% da máxima germinação foram de -1,64 e -1,03 Mpa, respectivamente. O pH foi um fator limitante para a germinação, pois houve efeitos inibitórios das condições alcalinas sobre a germinação. Os resultados demonstraram que o pré-tratamento das sementes com temperatura elevada, maior que 100 oC, resultou em decréscimo da germinação. A germinação decresceu de 82% para 3% com o aumento da temperatura de 100 oC para 130 oC. Não houve diferenças de emergência de plântulas em profundidades de enterrio entre 1 e 10 cm, mas a emergência foi reduzida com o aumento da profundidade de enterrio de 10 para 14 cm, e nenhuma plântula emergiu a 15 cm de profundidade. Os resultados de experimentos com inundação também revelaram que as sementes dessa espécie são sensíveis a esse estresse, tanto que a emergência após três dias de inundação foi de 9%.

Resumo em Inglês:

ABSTRACT: Ivy-leaved morning-glory (Ipomoea hederacea Jacq.) is an exotic species that is becoming an increasing problem in soybean fields of Golestan province, Iran. Because little information is available on the biology of this weed species in Iran, experiments were conducted to investigate the effects of different factors on seed germination and emergence of Ivy-leaved morning-glory. Maximum germination occurred at constant temperature of 20 oC (82%) and alternating temperature of 15/25 oC (94%). Germination was reduced with increasing salinity and drought stresses. Sodium chloride concentration and osmotic potential that inhibited 50% maximum germination were -1.64 and -1.03 MPa, respectively. Acidity was a limiting factor for the germination, due to inhibiting effect of alkaline conditions on germination. However, the results showed that high temperature pretreatment >100 oC decreased seed germination. Germination decreased from 82 to 3% as temperature increased from 100 to 130 oC. There was no significant difference between seedling emergence in burial depths of 1 to 10 cm, but emergence reduced with increasing burial depth from 10 to 14 cm, and no seedling was emerged from a depth of 15 cm. The results of the flooding experiment also revealed that the seeds of this species are sensitive to this stress, so that emergence was 9% after 3 d flooding.

Resumo em Português:

RESUMO: Para avaliar o efeito de herbicidas de pré-emergência, extratos vegetais e folhada sobre a produção e os componentes da produção de milho, foi realizado um experimento de campo na New Developmental Farm, University of Agriculture Peshawar-Pakistan, durante a safra de verão de 2016. O cultivar de milho Azam foi semeado em delineamento em blocos casualizados (DCB) com quatro repetições e dez tratamentos, ou seja, capina manual, Dual Gold 960 EC (S-metolacloro 1 L ha-1), Stomp 330 EC (pendimetalina 2,5 L ha-1), atrazine 1,25 L ha-1, extrato de Eucalyptus camaldulensis L. (125 g L-1), extrato de Ammi visnaga L. (125 g L-1), cobertura plástica preta, cobertura de palha de trigo, cobertura de serragem e cobertura de plantas daninhas. Os dados revelaram que capina manual e herbicidas afetaram significativamente a densidade de plantas daninhas (m-2), biomassa de plantas daninhas (kg ha-1), altura de plantas (cm), peso de grãos (g), número de grãos (kg ha-1) e rendimento de grãos (kg ha-1). Todos os parâmetros significativos da cultura foram comparáveis entre as parcelas tratadas com capina manual, atrazina, S-metolacloro e pendimetalina. No entanto, atrazina e S-metolacloro provaram ser os herbicidas mais econômicos, com rendimento máximo (4.636,4 e 4.562,8 kg ha-1, respectivamente). Entre os extratos vegetais, E. camaldulensis apresentou resultados satisfatórios na supressão de plantas daninhas e aumento na produtividade de milho (3.441,6 kg ha-1). Assim, o uso de herbicidas (atrazina e S-metolacloro) nas doses indicadas e na capina manual é recomendado para o controle efetivo das plantas daninhas e, em última instância, o alto rendimento da cultura do milho.

Resumo em Inglês:

ABSTRACT: To examine the effect of pre emergence herbicides, plant extracts and mulches on yield and yield components of maize, a field experiment was carried out at New Developmental Farm, The University of Agriculture Peshawar-Pakistan during summer crop season 2016. Maize variety “Azam” was sown in Randomized Complete Block (RCB) design having four replications and ten treatments i.e. hand weeding, Dual Gold 960 EC (S-metolachlor 1 L ha-1), Stomp 330 EC (pendimethaline 2.5 L ha-1), atrazine 1.25 L ha-1, Eucalyptus camaldulensis L. extract (125 g L-1), Ammi visnaga L. extract (125 g L-1), black plastic mulch, wheat straw mulch, saw dust mulch and weedy check. The data revealed that hand weeding and herbicides significantly affected the weed density (m-2), weeds biomass (kg ha-1), plant height (cm), kernels weight (g), number of kernels ear-1, biological yield (kg ha-1) and grain yield (kg ha-1). All the significant parameters of crop were comparable among the hand weeding, atrazine, S-metolachlor and pendimethaline treated plots. However, atrazine and S-metolachlor proved to be the most economical herbicides giving maximum yield (4636.4 and 4562.8 kg ha-1), respectively. Among plant extracts, E. camaldulensis showed satisfactory results in suppressing weeds and enhancing yield of maize i.e. (3441.6 kg ha-1). Hence, the use of herbicides (atrazine and S-metolachlor) at the recommended rates and hand weeding is recommended for effective weed control and ultimately high yield of maize crop.

Resumo em Português:

RESUMO: A presente pesquisa teve como objetivo determinar os períodos anterior à interferência (CTWR) e total de prevenção da interferência (CWFP) das plantas daninhas na cultura do milho, em sistemas de plantio direto e convencional em ambiente de elevada altitude, na região Sul do Brasil. Para isso, oito experimentos foram conduzidos em campo em Guarapuava-PR, durante a safra 2016/2017, utilizando os híbridos P2530® (convencional) e P3271H® (transgênico geneticamente modificado para tolerância ao glifosato) em sistema de semeadura direta e convencional com resíduos culturais de aveia-preta (Avena strigosa). O delineamento experimental foi o de blocos casualizados com cinco repetições. Os tratamentos foram divididos em períodos de CTWR e CWFP das plantas daninhas durante 0, 7, 14, 28, 42, 63 e 126 dias após a emergência da cultura (DAE). Entre as plantas daninhas, verificou-se predomínio apenas de espécies eudicotiledôneas durante todo o ciclo da cultura em ambos os sistemas de produção. Os resultados de produtividade permitiram estabelecer para os híbridos P2530® e P3271H®, cultivados em semeadura convencional com incorporação da palha ao solo, períodos críticos de prevenção à interferência (CPWC) entre 23 a 39 DAE e 23 a 35 DAE, respectivamente. Para a semeadura direta sobre a palha de aveia-preta, não foram estabelecidos CPWC, sendo constatada a necessidade de apenas um único controle pontual entre os períodos de 21 a 33 DAE e 23 a 31 DAE para os híbridos P2530® e P3271H®, respectivamente. A semeadura direta em palha de aveia-preta constituiu-se estratégia eficiente para reduzir a matointerferência e a necessidade de práticas de manejo.

Resumo em Inglês:

ABSTRACT: The objective of this study was to determine the coexistence periods of weeds (CTWR = critical timing of weed removal) and control (CWFP = critical weed-free period) in maize crops in no-tillage and conventional systems at high altitudes in southern Brazil. To this end, four experiments were conducted in Guarapuava-Paraná during the 2016/2017 crop season using P2530™ (conventional) and P3271H™ (transgenic genetically modified for glyphosate tolerance) hybrids in no-tillage and conventional systems with crop residues of black oat (Avena strigosa). The experimental design was a randomized complete block with five repetitions. The treatments were divided into periods of CTWR and CWFP for 0, 7, 14, 28, 42, 63, and 126 days after the emergence of crops (DAE). Among the weeds, only eudicotyledonous species predominated throughout the crop cycle in both production systems. The productivity results established for P2530™ and P3271H™ hybrids in a conventional system with the incorporation of straw in the soil indicated a critical period of weed control (CPWC) from 23 to 39 DAE and 23 to 35 DAE, respectively. For direct sowing (no-tillage system) on black oat straw, no CPWC was established, as it required only one single point of control between the periods of 21 to 33 DAE and 23 to 31 DAE for the P2530™ and P3271H™ hybrids, respectively. The direct sowing in black oat straw constituted an efficient strategy to reduce weed interference and the necessity of weed management practices.

Resumo em Português:

RESUMO: O presente estudo objetivou avaliar os efeitos aditivos do extrato aquoso de Cuscuta (akasbel) isoladamente e em combinação com doses cheias e reduzidas de herbicidas comercialmente disponíveis contra plantas daninhas na cultura do trigo durante o ano de 2016-2017. O estudo foi conduzido em delineamento experimental de blocos casualizados (RCBD) com três repetições. Os resultados mostraram que a capina de mão e o uso de herbicidas Allymax e Axial (doses cheia e meia recomendadas) controlaram significativamente todas as plantas daninhas prevalecentes e aumentaram o rendimento e os parâmetros contribuintes de rendimento sobre a verificação de plantas daninhas e aplicação única de extrato aquoso de cuscuta. A capina de mão e Allymax (dose total) mostraram população mínima de plantas daninhas, densidade relativa, biomassa de plantas daninhas fresca e seca e maior índice de área foliar (LAI), duração da área foliar (LAD), taxa de crescimento da cultura (CGR), altura da planta, peso de mil grãos e rendimento de grãos, enquanto a taxa de assimilação líquida (NAR), teor de clorofila, número de perfilhos, comprimento de espiga, grãos de espiga-1 e rendimento biológico foram máximos apenas na capina de mão. Esses resultados sugerem que, a fim de atingir o maior rendimento de trigo, o campo deve ser mantido livre de plantas daninhas por capina de mão (se o trabalho não é um fator limitante) ou usar a dose recomendada do herbicida Allymax para o manejo eficiente de plantas daninhas em trigo.

Resumo em Inglês:

ABSTRACT: The present study was to assess the additive effects of cuscuta (akasbel) aqueous extract alone and in combination with full and reduced doses of commercially available weedicides against weeds in wheat crop during the year 2016-2017. The study was conducted in a randomized complete block design (RCBD) with 3 replications. The results showed that hand weeding and use of weedicides Allymax and Axial (full and half recommended doses) significantly controlled all prevailing weeds and increased yield and yield contributing parameters over the weedy check/control and sole application of cuscuta aqueous extract. Hand weeding and Allymax (full dose) showed minimum weed population, relative density, fresh and dry weed biomass and higher leaf area index (LAI), leaf area duration (LAD), crop growth rate (CGR), plant height, 1000 grain weight and grain yield while net assimilation rate (NAR), chlorophyll content, number of tillers, spike length, grains spike-1 and biological yield were maximum only in hand weeding. These findings suggest that in order to attain highest wheat yield, the field should be kept free from weeds by hand weeding (if labour is not a limiting factor) or use recommended dose of weedicide Allymax for efficient weed management in wheat.

Resumo em Português:

RESUMO: A prática do plantio direto tem papel significativo na erradicação das plantas daninhas e na conservação da água do solo na produção agrícola. Na agricultura semiárida, as chuvas de monção (65%) são a principal fonte de água em Potohar, no Paquistão, que pode ser efetivamente usada sobretudo para produção de culturas de inverno. A fim de avaliar o impacto de diferentes sistemas de preparo do solo nos sistemas de cultivo predominantes e na biomassa de suas plantas daninhas em condições semiáridas, foi realizado um experimento de campo na Fazenda de Pesquisa da Universidade Árida de Koont Rawalpindi (Paquistão) durante as safras 2013-14 e 2014-15. Os sistemas de preparo do solo, como tratamentos, foram: (a) três cultivos com cultivador, como tratamento controle; (b) placa de molde com dois cultivos; (c) arado de cinzel com dois cultivos; e (d) preparo mínimo (somente o plantio realizado no momento da semeadura) com glifosato. A semeadura foi feita com broca para todos os sistemas de cultivo, ou seja, a, b e c, exceto c, que foi plantada no canteiro (feita pelo plantador de canteiros). Além dos tratamentos de lavra, diferentes sistemas de cultivo [(a) trigo - pousio, (b) trigo e brássica - pousio, (c) trigo e grão-de-bico - pousio e (d) trigo-feijoeiro (cultura de adubo verde)] também foram utilizados para rotações de dois anos. Em média, nos dois anos de estudo, o efeito interativo dos tratamentos (placa de mofo com dois cultivos) para a rotação trigo e brássica - pousio mostrou redução na biomassa seca de plantas daninhas de Anagallis arvensis (pimpernel-azul, 55,6%), Asphodelus tenuifolius (cebola-da-selva, 42,3%), Chenopodium album (arrepio-comum, 40,8%), Circium arvense (cardo-rastejante, 53,1%), Convolvulus arvensis (planta daninha, 56,6%) e Cynodon dactylon (Vilfa stellata, 45,8%) dentro de 60 dias após a semeadura ( DAS), em comparação com o tratamento controle (três cultivos em sistema de cultivo de trigo e pousio). Tendências semelhantes foram observadas no estágio de maturidade da cultura. Os resultados do experimento mostraram que uma melhor supressão de biomassa de plantas daninhas pode ser alcançada usando o arado de aiveca para o cultivo, seguido pelo sistema de cultivo de trigo-brássica e/ou consórcio de trigo/grão-de-bico para condições de solo semiárido no Paquistão.

Resumo em Inglês:

ABSTRACT: Tillage practice has a significant role on weeds eradication and soil water conservation in crop production. Under semiarid agriculture, the monsoon rains (65%) are major source of water in Potohar, Pakistan, which can effectively be used mostly for winter crops production. To evaluate the impact of different tillage system for prevailing cropping systems and their weeds biomass under semiarid conditions, field experiment was conducted at the Arid University Research Farm Koont Rawalpindi (Pakistan) during crop growth seasons 2013-14 and 2014-15. Tillage systems as treatments were (a) three cultivations with a cultivator, as control treatment, (b) mold-board with two cultivations, (c) chisel-plough with two cultivations and (d) minimum tillage (only tillage performed at sowing time) with glyphosate. Sowing was made using drill for all cropping systems i.e. a, b, and d except c which was planted on bed (made by bed planter). In addition to ploughing treatments, different cropping systems (a) wheat - fallow (b) wheat and brassica - fallow, (c) wheat and chickpea - fallow and (d) wheat - cluster bean (green manure crop) were also used for minimum two years rotations. On average in both study years, interactive effect of treatments (mold board with 2 cultivations) for the rotation wheat and brassica - fallow showed a reduction in weeds dry biomass of Anagallis arvensis (blue pimpernel, 55.6%), Asphodelus tenuifolius (jungle onion, 42.3%), Chenopodium album (common goosefoot, 40.8%), Circium arvense (creeping thistle, 53.1%), Convolvulus arvensis (field bind weed, 56.6%) and Cynodon dactylon (vilfa stellata, 45.8%) within 60 days after sowing (DAS) as compared with the control treatment (three cultivations on a wheat - fallow cropping system). Similar trends were observed at the crop maturity stage. Results of the experiment showed that better weed biomass suppression can be achieved by using moldboard plough for cultivation with followed by wheat- brassica cropping system and/or wheat - chickpea intercropping for semiarid soil condition in Pakistan.

Resumo em Português:

RESUMO: Atualmente, o capim-amargoso é uma das plantas daninhas mais importantes nas áreas de produção de grãos do Brasil. O objetivo deste trabalho foi avaliar a eficiência de associar a roçada ao controle químico de capim-amargoso entouceirado. Dois experimentos em campo foram realizados. No primeiro, buscou-se avaliar a influência da altura de roçada (0, 5, 10, 15 e 20 cm) sobre o controle de capim-amargoso com a complementação com aplicações de glyphosate + clethodim após a roçada. O segundo experimento foi constituído por tratamentos que iniciaram a operação de roçada durante a entressafra em diferentes períodos: 50 (antecipado), 35 (intermediário) e 20 (tardio) dias antes da semeadura da soja. Os tratamentos foram seguidos de aplicações de herbicidas conforme a necessidade até a colheita da soja. Quanto menor a altura de roçada associada à aplicação de herbicidas, melhor é o controle de capim-amargoso. Os sistemas de manejo (antecipado, intermediário e tardio) foram eficientes para o controle de capim-amargoso na entressafra e na cultura da soja. Sistemas de manejo que se iniciam com a roçada apresentam controle semelhante ou superior ao dos sistemas constituídos apenas por controle químico, podendo a roçada substituir uma aplicação de herbicidas.

Resumo em Inglês:

ABSTRACT: Currently, sourgrass is one of the most important weeds in grain production areas in Brazil. The objective of this work was to evaluate the efficiency of associated systems composed by mowing and chemical control against clumped sourgrass. In the first experiment, different mowing heights (0, 5, 10, 15 and 20 cm), coupled with complementary applications of glyphosate + clethodim, were evaluated on sourgrass control. The second experiment was composed by programs starting with fallow mowing at different times, 50 (early), 35 (intermediate) and 20 (late) days before soybean sowing. After mowing, treatments were followed by herbicide applications according to the need until soybean harvest. The shorter the mowing height associated with herbicide application, the better the control of sourgrass. The weed management programs (anticipated, intermediate and late) were efficient on sourgrass control during fallow and along soybean cycle. Weed management programs starting with mowing provided better or similar control compared to systems that employed chemical control only, indicating that mowing can replace one of the herbicide applications.

Resumo em Português:

RESUMO: Neste estudo, objetivou-se avaliar a sorção, dessorção e degradação do diuron em dois solos antropogênicos (Terra Preta de Índio - TPI) em contraste com um solo arenoso (Neossolo Quartzarênico órtico - NQo). O estudo de sorção-dessorção foi realizado por método de equilíbrio em lote, e a degradação, em frascos biométricos utilizando o diuron radiomarcado no 14C. Os valores do coeficiente de Freundlich (Kf) variaram de 13,50 a 50,41 µmol (1-1/n) L1/n kg-1 na TPI-2 e TPI-1, respectivamente, e indicaram uma sorção muito alta do diuron nos solos antropogênicos, seguindo a ordem: TPI-1 ≥ TPI-2 > NQo (99,10, 98,95 e 60,8%, respectivamente). A dessorção do diuron foi muito baixa nos solos antropogênicos, variando de 1,36 (TPI-1) a 1,70% (TPI-2), e de 24% para o NQo. A mineralização acumulada do diuron para 14C-CO2 foi < 3% aos 70 dias após a aplicação do herbicida, independentemente do solo estudado. Houve a formação de 35 e 44% de resíduo ligado para TPI-2 e TPI-1, maiores que para o NQo (17%). Em contraste, o resíduo extraído para o NQo variou de 72 a 91% e, para as TPI-1 e TPI-2, de 48 a 83% durante o tempo de incubação. O tempo de meia-vida da degradação (DT50) do diuron nos solos antropogênicos foi de 66,65 e 68,63 dias para TPI-1 e TPI-2, respectivamente, e para o NQo, de 88,86 dias. Evidenciou-se a formação de apenas um metabólito do herbicida em todos os solos. A aplicação de diuron em áreas agricultáveis na presença de solos antropogênicos da Amazônia pode ter um controle químico das plantas daninhas ineficiente, pois estes solos podem diminuir a biodisponibilidade do herbicida na solução do solo devido aos altos teores de CO, em que apresentou alta sorção e baixa dessorção do herbicida, além da degradação mais rápida, comparado com o solo arenoso.

Resumo em Inglês:

ABSTRACT: The aim of this study was to evaluate diuron sorption, desorption and degradation in two anthropogenic soils (Terra Preta de Índio - TPI) in contrast to a sandy soil (Quartzarenic Neosol - NQo). Sorption-desorption studies were performed by the batch equilibrium method and biodegradation in biometric bottles using radiolabeled diuron in 14C. Freundlich coefficient (Kf) values ranged from 13.50 to 50.41 µmol(1-1/n) L1/n kg-1 in TPI-2 and TPI-1, respectively, indicating very high diuron sorption in anthropogenic soils, following the order: TPI-1 ≥ TPI-2 > NQo (99.10, 98.95 and 60.8%, respectively). Diuron desorption was very low in anthropogenic soils, ranging from 1.36 (TPI-1) to 1.70% (TPI-2), and 24% to NQo. Accumulated diuron mineralization to 14C-CO2 was < 3% at 70 days after herbicide application, regardless of the assessed soil. Formation of 35 and 44% residue bound to TPI-2 and TPI-1 was observed, higher than to NQo (17%). In contrast, the residue extracted from NQo varied from 72 to 91%, ranging from 48 to 83% for TPI-1 and TPI-2 during the incubation period. The degradation half-life (DT50) of diuron in anthropogenic soils was of 66.65 and 68.63 days for TPI-1 and TPI-2, respectively, while a period of 88.86 days was observed for NQo. The formation of only one herbicide metabolite in all soils was evidenced. The application of diuron in arable areas in the presence of anthropogenic Amazonian soils may lead to inefficient chemical weed control, since these soils may reduce herbicide soil bioavailability due to high OC contents, where high sorption and low herbicide desorption are noted, as well as faster degradation compared to sandy soil.

Resumo em Português:

RESUMO: O uso da soja transgênica resistente ao glyphosate pode causar impactos diretos ou indiretos nos componentes do agroecossistema. O impacto direto é provocado pela inserção do gene de resistência, e o indireto está relacionado às alterações nas práticas de manejo. Dessa forma, este trabalho objetivou avaliar o impacto da soja resistente ao glyphosate e seu manejo com esse herbicida sobre a comunidade de artrópodes do dossel das plantas. Os tratamentos foram: soja transgênica e não transgênica com capina mecânica das plantas daninhas; e soja transgênica com uma e três aplicações de glyphosate. As populações de artrópodes no dossel das plantas foram amostradas ao longo de dois cultivos. A incorporação do gene de resistência ao glyphosate não afetou a riqueza e a abundância de artrópodes no dossel das plantas. Já a aplicação do glyphosate reduziu a riqueza de predadores e de fitófagos mastigadores e sugadores nos tratamentos com três aplicações desse herbicida. No segundo ano de cultivo a densidade total de artrópodes foi menor na soja transgênica com três aplicações de glyphosate em relação aos demais tratamentos. O mesmo ocorreu com a densidade do fitófago mastigador Cerotoma arcuatus nos dois anos de cultivo. Já as densidades dos fitófagos succionadores Bemisia tabaci, Caliothrips brasiliensis e Tetranychus sp. foram maiores na soja transgênica com três aplicações de glyphosate do que nos demais tratamentos. A aplicação de glyphosate (uma ou três) reduziu densidades do predador Solenopsis sp. e do detritívoro Hypogastrurasp.

Resumo em Inglês:

ABSTRACT: This study aims to evaluate the impact of glyphosate-resistant soybean and its management with glyphosate on the canopy arthropod community. We study the direct impact of the insertion of the resistance gene and the indirect impact of management practices, specifically herbicide application. To do this, we use the following treatments: non-GM and GM soybean with mechanical weed control and GM soybean with one and three applications of glyphosate. Arthropods in the crop canopy were sampled over time in all treatments. The incorporation of the glyphosate resistance gene did not affect the richness and abundance of arthropods in the plant canopy. Glyphosate application reduced the richness of predators and chewing and sucking phytophagous arthropods in treatments with three herbicide applications. In the second season, total arthropod density was the lowest in transgenic soybean with three glyphosate applications. The density of Cerotoma arcuatus, a chewing phytophagous arthropod, followed similar trends, while both glyphosate treatments (one or three applications) reduced the densities of the predator Solenopsis sp. and the detritivore Hypogastrura sp. Meanwhile, the densities of the sucking phytophagous arthropods Bemisia tabaci, Caliothrips brasiliensis, and Tetranychus sp. were the highest in transgenic soybean with three glyphosate applications.

Resumo em Português:

RESUMO: A deriva de herbicida, por falhas de aplicação, pode causar intoxicação em plantas de eucalipto, comprometendo o crescimento destas. Entretanto, a adição de produtos protetores como Fertiactyl Pós® à calda tem se mostrado eficiente na redução da intoxicação de plantas de eucalipto expostas à deriva de herbicidas. Em face do exposto, objetivou-se neste trabalho avaliar o efeito protetor do Fertiactyl Pós® sobre a redução de danos causados pela deriva dos herbicidas glyphosate, 2,4-D e a mistura glyphosate + 2,4-D em plantas de eucalipto. O experimento foi conduzido em esquema fatorial 3 x 2 + 1, correspondendo a três herbicidas: glyphosate (1.440 g ha-1), 2,4-D (680 g ha-1) e mistura em tanque de glyphosate + 2,4-D (1.440 g ha-1 + 680 g ha-1); duas doses de Fertiactyl Pós® (0 e 3,0 L ha-1); e uma testemunha sem aplicação. Antes da aplicação, a parte superior da copa do eucalipto foi protegida com sacos de polietileno, de modo a permitir que a calda atingisse apenas o terço inferior do dossel. A adição do Fertiactyl Pós® à calda com os herbicidas glyphosate e 2,4-D reduziu a intoxicação das plantas de eucalipto em 21,9% e 15,2%, respectivamente, aos 40 dias após a aplicação (DAA), em relação à aplicação dos respectivos herbicidas sem adição de Fertiactyl Pós®. A deriva da mistura glyphosate + 2,4-D potencializou a intoxicação das plantas do eucalipto em relação à aplicação isolada dos respectivos herbicidas e não houve resposta da adição do Fertiactyl Pós® na redução da intoxicação das plantas quando se aplicaram os herbicidas em mistura.

Resumo em Inglês:

ABSTRACT: Herbicide drift, due to application failures, can cause intoxication in eucalyptus plants, compromising their growth. However, the addition of protective products such as Fertiactyl Pós® to the syrup has been shown to be efficient in reducing intoxication of eucalyptus plants exposed to herbicide drift. Given this, the objective of the present study was to evaluate the protective effect of Fertiactyl Pós® on the reduction of damage caused by the herbicides glyphosate, 2,4-D and the glyphosate + 2.4-D mixture in eucalyptus plants. The experiment was conducted in a 3 x 2 + 1 factorial scheme, corresponding to three herbicides: glyphosate (1,440 g ha-1), 2,4-D (680 g ha-1), glyphosate + 2.4- D (1,440 g ha-1 + 680 g ha-1); two doses of Fertiactyl Pós® (0 and 3.0 L ha-1) and one control without application. Prior to application, the top of the eucalyptus was covered with polyethylene bags to ensure the syrup only reached the lower third of the canopy. The addition of Fertiactyl Pós® to the syrup with glyphosate and 2.4 D herbicides reduced the intoxication of eucalyptus plants by 21.9 and 15.2%, respectively, at 40 days after application (DAA) when compared with the application of the respective herbicides without the addition of Fertiactyl Pós®. The glyphosate + 2.4-D mixture drift intensified the intoxication of the eucalyptus plants in comparison with the application of the respective herbicides in isolation. Besides, the addition of Fertiactyl Pós® to the glyphosate + 2,4-D mixture did not prevent plant intoxication.

Resumo em Português:

RESUMO: O estresse causado por temperaturas extremas configura-se como um dos principais elementos que limitam a distribuição geográfica e o crescimento sazonal de diversas plantas, provocando severo atraso no seu desenvolvimento, reduzindo a taxa fotossintética e sinalizando a síntese de compostos de defesa. Diante das mudanças ambientais em curso e dos danos que essas mudanças podem causar na fisiologia e no crescimento das plantas, o objetivo deste trabalho foi compreender as interações entre temperatura, fisiologia e crescimento, bem como caracterizar o impacto que a alteração da temperatura exerce sobre o desenvolvimento inicial de Vernonia ferruginea Less. Para determinação de parâmetros fisiológicos e de crescimento, plântulas dessa espécie foram acondicionadas em câmaras de germinação com as temperaturas constantes dos tratamentos previamente ajustadas (10, 20, 25, 30 e 35 oC) por 60 dias. A faixa ótima de temperatura para crescimento inicial de V. ferruginea está entre 25 e 30 oC. O estresse causado pelas temperaturas subótimas e supraótimas afetou a homeostase celular e provocou atraso no crescimento e desenvolvimento das plântulas. Em situações estressantes, observou-se a inibição do crescimento e a ativação de mecanismos de resposta para a adaptação e manutenção da homeostase celular mediante o acúmulo do osmoprotetor prolina, e carboidratos solúveis. Adicionalmente, as plantas apresentaram desenvolvimento normal dentro de uma ampla faixa de temperatura, apesar do atraso no desenvolvimento, da alteração nas trocas gasosas e na síntese de substâncias relacionadas ao sistema de defesa.

Resumo em Inglês:

ABSTRACT: Stress caused by extreme temperatures is one of the main elements that limit the geographical distribution and the seasonal growth of several plants, causing a severe delay in their development, reducing the photosynthetic rate and signaling the synthesis of defense compounds. Considering the current environmental changes and the damages that these changes can cause in plant physiology and growth, the objective of this work was to understand the interactions between temperature, physiology and growth, and to characterize the impact of temperature changes on the initial development of Vernonia ferruginea Less. Seedlings of this species were conditioned in germination chambers at previously adjusted constant temperatures (10, 20, 25, 30, and 35 oC) for sixty days, in order to evaluate physiological and growth parameters. The optimum temperature range for the initial growth of V. ferruginea is between 25 and 30 oC. The stress caused by sub-optimal and over-optimal temperatures affected cell homeostasis and caused a delay in the growth and development of seedlings. In stressful situations, growth inhibition and the activation of response mechanisms were observed for the adaptation and maintenance of cellular homeostasis through the accumulation of the proline osmoprotectant and soluble carbohydrates. Additionally, plants presented a normal development within a wide temperature range, despite the development delay, the change in gas exchanges and the synthesis of substances related to the defense system.

Resumo em Português:

RESUMO: Altas doses de nitrogênio favorecem o crescimento vegetativo do milho e a perda no rendimento de grãos devido ao acamamento de plantas. Este efeito pode ser mitigado pelos reguladores de crescimento. Objetivou-se com este estudo avaliar o efeito do regulador de crescimento trinexapac-ethyl na resposta de híbridos de milho as doses de nitrogênio em cobertura. O experimento foi conduzido em Lages, SC, em dois anos agrícolas, testando dois híbridos (P1630 e P30F53) e quatro doses de nitrogênio em cobertura (0, 150, 300 e 450 kg de N ha-1), com e sem o uso de trinexapac-ethyl. O delineamento experimental foi em blocos casualizados dispostos em parcelas sub-subdivididas, com três repetições por tratamento. Avaliaram-se a altura de plantas e inserção de espiga, o acamamento e quebra de plantas, o rendimento de grãos e os componentes do rendimento. O rendimento de grãos aumentou de forma quadrática com o incremento das doses de nitrogênio. Os máximos rendimentos de grãos foram de 15.784 e 15.257 kg ha-1, em 2014/2015 e 2015/2016, respectivamente. Doses maiores do que 150 kg ha-1 de N, independentemente da utilização do regulador de crescimento, promoveram, no máximo, incrementos no rendimento de grãos de 14,7% a 18,1%. A aplicação de trinexapac-ethyl reduziu o comprimento dos entrenós superiores do colmo e a massa de mil grãos, mas não interferiu na porcentagem de plantas acamadas e no rendimento de grãos. Portanto, o uso de trinexapac-ethyl não aumenta a resposta do rendimento de grãos do milho ao incremento na dose de nitrogênio em cobertura.

Resumo em Inglês:

ABSTRACT: High nitrogen rates favor maize vegetative growth and grain yield losses due to stem lodging. The use of growth regulators can mitigate such effect. This work was carried out aiming to evaluate the effect of trinexapac ethyl on maize hybrids response to side-dress nitrogen rates. The experiment was carried out in Lages, Santa Catarina State, South of Brazil, during two growing seasons with two hybrids (P1680 and P30F53), and four nitrogen rates (0, 150, 300 and 450 kg N ha-1) were tested, with and without the presence of trinexapac ethyl. The experimental design was in randomized blocks arranged in split-split plots, with three replications per treatment. The plants height and ear insertion height, plant lodging and breaking, grain yield and yield components were evaluated. Grain yield increased in a quadratic way with increased nitrogen rate. The highest grain yields were 15,784 and 15,257 kg ha-1, in 2014/15 and 2015/16, respectively. Application rates higher than 150 kg of N ha-1, regardless of the use of the plant growth regulator, promoted maximum grain yield increases, ranging from 14.7 to 18.1%. The application of trinexapac-ethyl reduced the upper stem internode length, 1000-grain dry weight and did not affect the percentage of lodged plants and grain yield of both hybrids. Therefore, the use of trinexapac-ethyl did not enhance the maize grain yield response to increased rates of side-dress nitrogen.

Resumo em Português:

RESUMO: Foi conduzido um estudo com foco nos diferentes níveis de capacidade de campo no Laboratório de Ciências de Plantas Daninhas do Departamento de Agronomia da University of Agriculture Faisalabad. Erva-de-jacaré fresca foi colhida em campo para a preparação de estacas (2 cm de comprimento). Essas estacas foram mantidas em vasos por 25 dias, em níveis de 25%, 50%, 75% e 100% da capacidade de campo. Os resultados dos experimentos revelaram que, em todos os níveis de capacidade de campo, houve crescimento e brotação dos fragmentos de erva-de-jacaré. A elevação da umidade levou a aumento significativo da capacidade de emergência e sobrevivência das plantas de erva-de-jacaré até um certo nível. Comparado com o controle (25% CC), o tempo de emergência dos brotos no regime de umidade máxima (100% da CC) diminuiu em 40% (12,94 dias contra 7,17 dias). Já a taxa de sobrevivência dos fragmentos diminuiu em 60% (5 contra 1,75), embora a taxa de sobrevivência e o crescimento tenham aumentado inicialmente com 50% de CC e 75% de CC. Os valores máximos de crescimento e brotação foram observados a 50% da capacidade de campo. A capacidade de campo afeta a capacidade de brotação dos fragmentos de erva-de-jacaré, mas tem pouca influência nos parâmetros de crescimento. Os resultados sugerem que a erva-de-jacaré é capaz de suportar bem a escassez de água, assim como consegue brotar e crescer em solos totalmente submersos.

Resumo em Inglês:

ABSTRACT: A study focusing on different field capacity levels was planned in the Weed Science Lab, Department of Agronomy, University of Agriculture Faisalabad. Fresh alligatorweed was harvested from the Agronomy fields and cuttings (2 cm length) were made from it. These cuttings were placed at 25%, 50%, 75% and 100% field capacity levels in pots for 25 days. The results of the experiments revealed that at all field capacity levels, fragments of alligatorweed were able to sprout and grow. Increased moisture levels significantly increased the emergence ability and survival of the alligatorweed plants upto a certain level. Compared with the control (25% FC), emergence time of the sprouts in the maximum moisture regime (100% of FC) decreased by 40% (12.94 days vs.7.17 days). By contrast, the survival rate of the fragments decreased by 60% (5 vs. 1.75) although survival and growth rate increased at first with 50% FC and 75% FC. Maximum sprouting and growth were found at 50% field capacity. Field capacity does affect the sprouting capacity of alligatorweed fragments but it has only a little influence on growth parameters. The results suggest that alligatorweed can sustain dry conditions to a great extent and also has the ability to sprout and grow in fully submerged soils.

Resumo em Português:

RESUMO: Em condições de baixa luminosidade, biótipos de arroz daninho e arroz cultivado apresentam variação morfofisiológica, tendo implicações na competição entre plantas. O objetivo desse trabalho foi avaliar a competitividade relativa entre arroz cultivado e arroz daninho, em ambiente sob plena radiação e sob redução de luminosidade. Foram conduzidos três experimentos, em ambiente protegido, utilizando delineamento experimental completamente casualizado, com quatro repetições. Os tratamentos do experimento I foram arranjados em série aditiva e nos experimentos II e III em série de substituição. Os experimentos II e III foram conduzidos concomitantemente, avaliando a convivência do cultivar de arroz com o arroz daninho. Os tratamentos foram constituídos por proporções de plantas: 100:0 (monocultivo de arroz cultivado); 75:25; 50:50; 25:75 e 0:100 (monocultivo de arroz daninho), mantendo-se constante a população total de plantas (240 plantas m-2) obtido no experimento I. O experimento II foi conduzido com plena radiação solar e o III sob redução de 50% de luminosidade. As variáveis analisadas foram: matéria seca da parte aérea e estatura de plantas, aos 35 dias após a emergência. A análise da competição entre plantas foi realizada por aplicação de diagramas e interpretações dos índices de competitividade. Para a variável matéria seca da parte aérea ocorreu prejuízo mútuo entre os competidores, já para estatura das plantas houve equivalência na competição pelos recursos do meio. Independente do ambiente avaliado, o arroz daninho apresenta habilidade competitiva superior ao arroz cultivado, indicando a necessidade de métodos integrados para o manejo dessa espécie daninha.

Resumo em Inglês:

ABSTRACT: Cultivated and weedy rice biotypes exhibit morphophysiological variations under low light, affecting competition between plants. The aim of this study was to assess relative competitiveness between cultivated and weedy rice under full and low light. Three experiments were conducted in a greenhouse, using a completely randomized design with four repetitions. The treatments in the experiment I were arranged in additive series while in the experiments II and III treatments were arranged in replacement series. Experiments II and III were carried out concomitantly to assess coexistence between the rice cultivar and weedy rice. The treatments consisted of different plants proportions: 100:0 (cultivated rice monoculture), 75:25, 50:50, 25:75 and 0:100 (weedy rice monoculture), keeping the total plant population obtained in experiment I (240 plants m-2) constant. Experiment II was conducted with full solar radiation and III under 50% light. The variables analyzed were shoot dry weight and plant height, 35 days after emergence (DAE). Competition among plants was evaluated via graphs and by interpreting competition indices. Concerning shoot dry weight, mutual losses were recorded between competitors, whereas equal competition for resources was observed for plant height. Weedy rice was more competitive than cultivated rice regardless of the light environment assessed, indicating the need for integrated methods to control this weed.

Resumo em Português:

RESUMO: Raphanus raphanistrum L. (nabo) se destaca entre as plantas daninhas que causam os maiores prejuízos à cultura do girassol, em função do ciclo de desenvolvimento e adaptabilidade. Objetivou-se com esta pesquisa determinar os períodos de interferência da cultura do girassol convivendo com nabo, os efeitos da competição na produtividade e seus componentes. O experimento foi conduzido a campo, em delineamento experimental de blocos casualizados com quatro repetições. Os tratamentos foram arranjados em esquema fatorial, sendo o fator A composto pela convivência ou controle de nabo na cultura do girassol e o fator B, por sete períodos (0, 7, 14, 21, 28, 35 e 90 dias após a emergência da cultura). Avaliou-se a estatura, o diâmetro de capítulos, a produtividade de aquênios e a massa seca das plantas daninhas e da cultura. A presença de nabo afeta negativamente o acúmulo de massa seca, o diâmetro de capítulo, o peso de mil aquênios e reduz a produtividade de girassol, quando o nabo convive durante todo o ciclo da cultura, porém não influencia a estatura das plantas. O controle químico de nabo deve ser realizado ao final do período anterior à interferência, o qual, para a cultura do girassol, é de 13 dias após a emergência, sendo suficiente para evitar a interferência de plantas daninhas até o final do período total de prevenção à interferência, que ocorre até os 17 dias após a emergência da cultura.

Resumo em Inglês:

ABSTRACT: Raphanus raphanistrum L. (wild radish) stands out among the weeds that cause greatest damage to the sunflower crop, due to the development cycle and adaptability. The objective of this research was to determine interference periods of sunflower interacting with wild radish, and the effects of competition on yield and its components. The experiment was conducted in the field in a randomized block design with four replications. The treatments were arranged in a factorial design with factor A composed of wild radish coexistence or control in sunflower, and factor B, for eight periods (0, 7, 14, 21, 28, 35, 42 and 135 days after crop emergence). It was evaluated height, diameter of chapters, achene yield and dry matter of weeds and crop. The presence of wild radish adversely affects the accumulation of dry mass, head diameter, thousand grain weight and reduces sunflower productivity when the wild radish interacts during the whole crop cycle, but does not affect on plant height. Chemical control of wild radish may be adopted at the end of period prior to interference, which for sunflower crop is 13 DAE, and the application is sufficient to avoid weed interference until the end of the total period of interference prevention which occurs until 17 days after crop emergence.

Resumo em Português:

RESUMO: A competição e as interações entre plantas daninhas são o foco de muitos pesquisadores para tornar a decisão de gerenciamento dessas plantas precisa e econômica. Portanto, foram realizados estudos de campo em dois anos consecutivos (2012-13 e 2013-14) em dois locais diferentes: Peshawar (34.0167o N, 71.5833o E) e Chitral (35o50’46" N, 71o47’9" E), da província de Khyber Pakhtunkhwa (KPK), Paquistão. O objetivo dos estudos foi determinar a capacidade competitiva da aveia selvagem (Avena fatua L.) com trigo (Triticum aestivum L.) em dois locais ecologicamente diferentes, bem como os possíveis efeitos na quantidade e qualidade dos grãos de trigo. Em estudos de campo, o experimento foi delineado em delineamento de blocos ao acaso (delineamento de aditivos) com três repetições, nas quais a taxa de sementes de trigo (var. Ata-Habib) foi de 125 kg ha-1, enquanto a aveia selvagem foi plantada a 0, 5, 10, 15, 20, 25, 30, 35 e 40 plantas m-2. Dados de campo mostraram que os efeitos de diferentes densidades de aveia selvagem durante os dois anos foram proeminentes, visto que diminuíram significativamente as variáveis relacionadas ao rendimento de grãos e biológicas do trigo. A densidade de aveia selvagem acima de 5 plantas m-2 resultou na diminuição dos componentes da produção de trigo. Esses resultados mostraram que a aveia selvagem iniciou a competição no estágio inicial do trigo. Todas as outras variáveis relacionadas à produção de trigo foram diminuídas pela densidade crescente de aveia selvagem, o que indica que esta compete com o trigo durante toda a safra. As perdas de rendimento de grãos no trigo variaram de 2-35% durante o ano 1 e 1-21% durante o ano 2 na densidade de aveia selvagem de 5-40 plantas m-2. As variáveis de qualidade dos grãos de trigo mostraram que o teor de proteína nesses grãos diminuiu com a maior densidade de aveia selvagem. Durante o ano 2, o teor de glúten em Chitral diminuiu com o aumento da densidade de aveia selvagem. À luz dos estudos atuais, sugere-se que a presença de aveia selvagem diminua todas as variáveis relacionadas ao rendimento ecobiológico do trigo.

Resumo em Inglês:

ABSTRACT: Crop-weed competition and interactions are the focus of many researchers to make the weed management decision accurate and economical. Therefore, field studies were conducted in two consecutive years (2012-13 and 2013-14) at two different locations viz Peshawar (34.0167o N, 71.5833o E) and Chitral (35o50’46" N, 71o47’9" E) of Khyber Pakhtunkhwa (KPK) province, Pakistan. The aim of the studies was to determine the competitive ability of wild oat (Avena fatua L.) with wheat (Triticum aestivum L.) at two ecologically different locations and the possible effects on quantity and quality of wheat grains. In field studies, the experiment were laid out in randomized complete block design (additive design) with three replications in which the seed rate of wheat (var. Ata-Habib) was 125 kg ha-1 while wild oat was planted at 0, 5, 10, 15, 20, 25, 30, 35, and 40 plants m-2. Field data showed the effects of different wild oat densities during both the years were prominent by significantly decreasing the grain and biological yield-related variables of wheat. Wild oat density above 5 plants m-2 resulted in decreasing the wheat yield components. These results showed that wild oat started competition at initial stage of the wheat. All other yield related variables of wheat were decreased by the increasing density of wild oat, which is indicated that wild oat compete with wheat throughout the crop season. The grain yield losses in wheat ranged from 2-35% during year 1 and 1-21% during year 2 at wild oat density of 5-40 plants m-2. The quality variables of wheat grains showed protein content in wheat grains were decreased at higher density of wild oat. During year 2, the gluten content in Chitral was decreased with increasing density of wild oat. In light of the present studies, it is suggested that presence of wild oat decrease all eco-biological yield related variables of wheat.

Resumo em Português:

RESUMO: A aplicação consecutiva de herbicidas levou à evolução de plantas daninhas resistentes a eles. Essa resistência é frequentemente associada a um custo de adaptação. Assim, um delineamento inteiramente casualizado com três repetições foi conduzido para avaliar o custo de adoção dos biótipos de aveia selvagem de inverno resistentes ao haloxyfop-R methyl ester (Avena ludoviciana Durieu) com a mutação Ile-2041-Asn, em comparação com os suscetíveis. Os biótipos pré-germinados de aveia selvagem de inverno da geração F2 foram semeados em vasos de 0,2 m2 contendo 50 cm de solo franco-arenoso ao ar livre, e seus parâmetros de crescimento, incluindo número de perfilhos, altura da planta, folhas por planta, área foliar por planta, índice de clorofila, peso seco da folha e peso seco da planta, foram medidos aos 30, 70, 100, 115 e 130 dias após o plantio. Também foram calculados índice de área foliar, razão de área foliar, área foliar específica, taxa de crescimento relativo, taxa de assimilação líquida e taxa de crescimento de culturas. A produção de sementes, o peso de mil grãos e a área da folha-bandeira foram medidos no final do período de crescimento. De acordo com os resultados, nenhum custo de adoção foi observado entre os biótipos suscetíveis e resistentes, indicando que os primeiros podem não superar os resistentes no campo. Embora a imposição de nova pressão seletiva via aplicação de um herbicida com modo de ação diferente possa controlar biótipos suscetíveis e resistentes, a rotação do herbicida deve ser adaptada a fim de impedir maior evolução da resistência. Além disso, os mesmos métodos não químicos de manejo de plantas daninhas, como seleção cuidadosa da data da semeadura, podem ser implementados para melhorar os efeitos adversos dessa planta daninha na produção agrícola.

Resumo em Inglês:

ABSTRACT: Consecutive application of herbicides has led to the evolution of herbicide-resistant weeds. This resistance is often associated with a fitness cost. Hence, a completely randomized design experiment with three replications was conducted to evaluate the fitness cost of haloxyfop-R methyl ester resistant winter wild oat biotypes (Avena ludoviciana Durieu) possessing Ile-2041-Asn mutation compared to susceptible ones. The pre-germinated F2 generation winter wild oat biotypes were sown in 0.2 m2 pots containing 50 cm of silty-loam soil outdoors and their growth parameters including tiller number, plant height, leaves per plant, leaf area per plant, chlorophyll content index, leaf dry weight, and plant dry weight were measured 30, 70, 100, 115 and 130 days after planting. Leaf area index, leaf area ratio, specific leaf area, relative growth rate, net assimilation rate, and crop growth rate were also calculated. Seed production, 1000 kernel weight, and flag leaf area were measured at the end of the growth period. According to the results, no fitness cost was observed between susceptible and resistant biotypes, indicating that susceptible biotypes may not overcome resistant ones in the field. Although imposing a new selective pressure via application of an herbicide possessing a different mode of action may control both susceptible and resistant biotypes, herbicide rotation must be adapted to impede the evolution of further resistance. Also, the same non-chemical weed management methods such as careful selection of sowing date can be implemented to ameliorate adverse effects of this weed on crop production.

Resumo em Português:

RESUMO: A adoção de tecnologias que preconizam a utilização de culturas resistentes a herbicidas é alternativa para controle de plantas daninhas, porém pode causar estresse oxidativo e alterar o metabolismo secundário da cultura. Dessa forma, o objetivo deste trabalho foi avaliar as alterações no metabolismo secundário de plantas de soja contendo as tecnologias Cultivance® (CV), tolerância às sulfonilureias (STS) e Roundup Ready® (RR), submetidas à aplicação da mistura dos herbicidas imazapyr e imazapic nos sistemas de manejo em “plante/aplique e “aplique/plante”. Foram realizados dois experimentos em campo, onde cultivares de soja foram submetidos a doses crescentes da mistura dos herbicidas imazapyr e imazapic. Aos dez dias após a emergência da cultura, foi realizada coleta da parte aérea e armazenada a -83 oC, até a quantificação das variáveis. O cultivar BRS382CV apresenta, em geral, menores teores de clorofila comparado aos cultivares CD249STS e NA5909RR, e o aumento da dose da mistura dos herbicidas imazapyr e imazapic diminui o teor de clorofila das cultivares. O estresse causado pelo herbicida induz maior formação de EROs, ocasionando elevada resposta do sistema antioxidante através das enzimas SOD, CAT e APX.

Resumo em Inglês:

ABSTRACT: Technologies that advocate the use of herbicide-resistant crops are alternatives to weed control, but they may cause oxidative stress and change secondary metabolism of plants. Therefore, this study aimed to evaluate changes in the secondary metabolism of soybean plants which contained Cultivance® (CV), sulfonylurea-tolerant soybean (STS) and Roundup Ready® (RR) technologies submitted to the application of the mixture of herbicides imazapyr and imazapic in “plant-apply” and “apply-plant” management systems. Two field experiments, in which soybean cultivars were submitted to increasing doses of the mixture of herbicides imazapyr and imazapic, were performed. Aerial parts of plants were collected 10 days after crop emergence and stored at -83oC, until quantification of variables. In general, the soybean cultivar BRS382CV exhibited lower contents of chlorophyll than cultivars CD249STS and NA5909RR. Besides, increasing doses of the mixture of herbicides imazapyr and imazapic decreased contents of chlorophyll in the cultivars. Stress caused by herbicides induced more generation of ROS and effective response of the antioxidant system through enzymes SOD, CAT and APX.

Resumo em Português:

RESUMO: O feijão-preto [Vigna mungo (L.) Hepper] é uma importante cultura leguminosa cuja produção é severamente afetada pela podridão do carvão causada por Macrophomina phaseolina. Este estudo objetivou buscar uma alternativa ambientalmente acessível aos fungicidas sintéticos para o manejo dessa doença. A biomassa seca de uma planta alelopática (Sonchus oleraceous L.) foi usada para combater a ameaça. Solo de barro fumigado, pré-inoculado com M. phaseolina, foi alterado com diferentes doses de biomassa seca da planta daninha, que variaram de 0,5% a 3%. A aplicação de 2% de biomassa de plantas daninhas controlou completamente a doença. A inoculação do solo com M. phaseolina (controle positivo) reduziu o peso seco da parte aérea e o rendimento de grãos de feijão-preto em 59% e 91%, respectivamente, sobre o controle negativo. A aplicação de diferentes doses de alteração do solo no solo inoculado por patógenos aumentou o peso seco da parte aérea e o rendimento de grãos de feijão-preto em 107-307% e 438-7.400%, respectivamente, sobre controle positivo. O maior efeito positivo no crescimento e produtividade de feijão-preto no solo contaminado por M. phaseolina foi registrado devido a uma alteração de 2,5%. A inoculação com M. phaseolina aumentou significativamente as atividades de peroxidase (POX) e fenilalanina amônia liase (PAL). Entretanto, a aplicação de diferentes doses de biomassa de S. oleraceous ao solo diminuiu gradualmente a atividade dessas enzimas. O presente estudo concluiu que a aplicação de 2,5% de biomassa seca de S. oleraceous pode controlar completamente a podridão de carvão em feijão-preto e aumentar significativamente o crescimento e o rendimento da cultura.

Resumo em Inglês:

ABSTRACT: Urdbean [Vigna mungo (L.) Hepper] is an important leguminous crop whose production is severely affected by charcoal rot disease caused by Macrophomina phaseolina. This study was undertaken to seek an environmental friendly alternative to synthetic fungicides for management of this disease. Dry biomass of an allelopathic weed Sonchus oleraceous L. was used to combat the menace. Fumigated sandy loam pot soil, pre-inoculated with M. phaseolina, was amended with different doses of dry biomass of the weed ranging from 0.5% to 3%. Application of 2% weed biomass completely controlled the disease. Soil inoculation with M. phaseolina inoculation (positive control) reduced shoot dry weight and grain yield of urdbean by 59% and 91%, respectively, over negative control. Application of different doses of soil amendment in pathogen inoculated soil enhanced shoot dry weight and grain yield of urdbean by 107-307% and 438-7400%, respectively, over positive control. The highest positive effect on growth and yield of uedbean in M. phaseolina contaminated soil was recorded due to 2.5% amendment. M. phaseolina inoculation significantly enhanced peroxidase (POX) and phenyl alanine ammonia lyase (PAL) activities. However, application of different doses of S. oleraceous biomass to the soil gradually decreased activities of these enzymes. The present study concludes that application of 2.5% dry biomass of S. oleraceous can completely control charcoal rot of urdbean and significantly enhance crop growth and yield.

Resumo em Português:

RESUMO: Solanum nigrum L. (erva-moura), uma planta daninha perene anual de curta duração, tornou-se uma planta daninha problemática em sistemas agrícolas na China central. Foram conduzidos experimentos em laboratório e em casa de vegetação para examinar a influência de vários fatores abióticos na germinação de sementes de erva-moura para o desenvolvimento de programas eficazes de controle de plantas daninhas. As sementes germinaram em temperaturas constantes de 15 a 30 oC, mas não ocorreu germinação em temperaturas abaixo de 10 oC ou acima de 35 oC. Também foi observada germinação das sementes em regimes de temperaturas alternadas de 15/5 oC a 40/30 oC, com germinação máxima (> 93,5%) nas temperaturas alternadas de 25/15 oC e 30/20 oC. Houve redução da germinação à medida que o potencial osmótico se tornou mais negativo, e nenhuma germinação foi observada a ≤ 0,8 MPa. Além disso, foi observada redução da germinação em função do estresse salino e alcalino, e nas concentrações ≥ 200 mM de NaCl ou ≥ 150 mM de NaHCO3 não ocorreu germinação. A germinação das sementes não foi afetada de forma significativa pelos valores de pH de 5 a 10, porém a emergência de plântulas sofreu influência significativa da profundidade de sementes, com emergência máxima (93,1%) a 1 cm de profundidade.

Resumo em Inglês:

ABSTRACT: Solanum nigrum L. (black nightshade), an annual to short-lived perennial weed, has become a problem weed in farming systems in central China. Laboratory and greenhouse experiments were conducted to examine the influence of various abiotic factors on seed germination of black nightshade to develop effective weed control programs. Seeds germinated at a range of constant temperatures from 15 to 30 oC, but no germination occurred at temperatures below 10 oC or above 35 oC. Seeds also germinated at alternating temperature regimes from 15/5 to 40/30 oC, with maximum germination (> 93.5%) at the alternating temperatures of 25/15 and 30/20 oC. Germination decreased as osmotic potential became more negative, and no germination was observed at ≤ -0.8 MPa. Moreover, germination was reduced by saline and alkaline stresses and no germination occurred at ≥ 200 mM NaCl or ≥ 150 mM NaHCO3 concentrations. Seed germination was not significantly affected by pH values from 5 to 10. Seedling emergence was significantly affected by burial depth with maximum emergence (93.1%) at 1 cm depth.

Resumo em Português:

RESUMO: O objetivo deste trabalho foi avaliar a competitividade e determinar o nível de dano econômico de papuã infestante da cultura do milho. Os tratamentos foram compostos por densidades de milho (2,60; 3,10; 3,65; 4,00; e 4,80 plantas m-1) e dez populações de papuã para cada densidade de semeadura da cultura. Como indicadores de infestação, avaliou-se a população de plantas, área foliar, cobertura de solo e massa seca da parte aérea de papuã. A massa seca da parte aérea do papuã apresentou melhor ajuste ao modelo da hipérbole retangular e às perdas de produtividade de grãos, devido à interferência da planta daninha estimada satisfatoriamente por esse modelo. A semeadura das densidades de milho de 2,60; 3,10 e 3,65 plantas m-1 de todas as características avaliadas foram mais competitivas do que as demais na presença do papuã. A semeadura das densidades de 2,60, 3,10 e 3,65 plantas m-1 aumentou o nível de dano econômico, justificando a adoção de medidas de controle do papuã nas populações mais elevadas. Os valores de NDE variaram de 1,58 a 9,37 plantas m-2 para as densidades de 4,00 e 4,80 plantas m-1 de milho, as quais foram menos competitivas com o papuã.

Resumo em Inglês:

ABSTRACT: The objective of this work was to evaluate the interference and to determine the level of economic damage (NDE) of the weed when infesting the corn crop. Treatments were composed by corn densities (2.60, 3.10, 3.65, 4.00 and 4.80 plants m-1) and 10 Alexandergrass populations for each crop seeding density. The population of plants, leaf area, soil cover and shoot dry mass of Alexandergrass were evaluated as indicator of infestation. Shoot dry mass of Alexandergrass presents better adjustment to the model of rectangular hyperbole, and losses of grain yield due to interference of the weed were satisfactorily estimated by this model. Corn sowing densities of 2.60; 3.10 and 3.65 plants m-1 in average, were more competitive of all evaluated variables in the presence of Alexandergrass. Corn densities of 2.60; 3.10 and 3.65 plants m-1 increase the level of economic damage, justifying the adoption of control measures of Alexandergrass when in higher populations. NDE values ranged from 1.58 to 9.37 plants m-2 at the densities of 4.00 and 4.80 maize plants m-1, which were less competitive with Alexandergrass.

Resumo em Português:

RESUMO: As plantas daninhas e os microrganismos associados à sua rizosfera podem apresentar interações que influenciam na habilidade de absorção de nutrientes, fator importante em plantas em competição. Dessa forma, avaliou-se neste trabalho a atividade microbiana, o potencial de solubilização de fósforo inorgânico (Pi) e a atividade de fosfatases ácidas em solo cultivado com combinações de soja (Glycine max) e plantas daninhas. Para isso, cultivou-se a soja em monocultivo e em competição com Bidens pilosa, Brachiaria decumbens (Syn. Urochloa decumbens) e Eleusine indica, em duas condições de competição: a) sem contato entre raízes das espécies; e b) com contato entre raízes das espécies. Para evitar o contato entre raízes das espécies em competição, bem como separar o substrato em um mesmo vaso, utilizou-se uma tela de náilon de 50 µm de abertura. O experimento foi conduzido em blocos casualizados, com quatro repetições. A soja em competição com plantas daninhas reduziu a oxidação da matéria orgânica por unidade de biomassa microbiana, diminuindo o quociente metabólico, em comparação com a soja em monocultivo. O contato entre as raízes da soja e das espécies de plantas daninhas promoveu o aumento da solubilização de Pi em 51%, 39% e 31% para B. pilosa, B. decumbens e E. indica, respectivamente, em relação ao cultivo de cada espécie com a tela de separação. A atividade microbiana, a solubilização do Pi e a atividade de fosfatases ácidas foram alteradas pelas espécies de plantas e, pelas combinações de plantas daninhas e soja em competição, principalmente, quando houve contato entre raízes. Assim, a atividade microbiológica do solo pode influenciar nas estratégias de competição e desenvolvimento das plantas.

Resumo em Inglês:

ABSTRACT: Weeds and microorganisms interacting with their rhizosphere may influence nutrient absorption, which is an important factor for plant competition. The purpose of this study was to evaluate the microbiological activity, inorganic phosphorus solubilization (Pi) and acid phosphatase in the cultivated soil, in a combination of soybean (Glycine max) plants and weeds. Soybeans were cultivated in monoculture and in competition with Bidens pilosa, Brachiaria decumbens (Syn. Urochloa decumbens) and Eleusine indica, under two conditions: a) plants competing without contact between the roots b) plants competing with contact between the roots. A nylon screen with a 50 µm mesh was added to prevent contact between the roots of the species in competition so that the substratum could be separated in the vase. The experiment was conducted in randomized blocks, with four replications. The soybeans in competition with weeds led to lower oxidation of organic matter per unit of microbial biomass, resulting in a lower metabolic quotient, compared with the soybean monoculture. The contact between soybean roots and B. pilosa, B. decumbens and E. indica maintained a strong influence, raising the solubilization of Pi, respectively valued at 51, 39 and 31% in relation to the cultivation of each species with a nylon screen. Microbiological activity, inorganic phosphorus solubilization and acid phosphatase were altered by plant species, combinations of weeds and soybean plants in competition; by root contact in some cases. Thus, the microbiological activity of the soil can influence competition strategies and plant development.

Resumo em Português:

RESUMO: O presente estudo teve como objetivo avaliar o potencial de deriva de glifosato durante aplicação aérea mediante o uso de plantas de arroz como sentinelas, a fim de determinar o efeito da deriva na cultura do arroz irrigado. Para isso, foi realizado um experimento em campo utilizando delineamento inteiramente casualizado com quatro repetições, avaliando diferentes distâncias [testemunha (sem aplicação), 0; 12,5; 25; 50; 75; 100; 150; 200; 300; e 400 m] a partir do local de aplicação. O experimento foi realizado nas Granjas 4 Irmãos, localizada no município de Rio Grande, RS. A dose de aplicação de glifosato foi de 1.920 g e.a. ha-1 (Roundup Transorb®, sal de isopropilamina de glifosato 480 g e.a. L-1). Para estimação da taxa de deriva nas plantas sentinelas, foi elaborada uma curva de dose-resposta, aplicando doses crescentes de glifosato em plantas de arroz e avaliando o nível de injúria. As taxas de deriva estimadas mediante o nível de injúria em plantas sentinelas foram de 14% (150 m), 13% (200 m) e 5% (400 m). Foi observado morte de plantas nas distâncias entre 0 a 50 m, enquanto em distâncias entre 75 e 150 m a taxa de sobrevivëncia foi de 25 a 50%, causando redução na produtividade. Já nas distâncias entre 200 e 400 m não houve redução na produtividade quando comparada com a testemunha, inclusive quando os níveis de injúria atingiram de 52 a 82%. Dessa forma, conclui-se que a deriva de glifosato de 5% atingiu até 400 m da faixa de aplicação. Considerando a recomendação de deriva zero, distâncias maiores que 400 m deverão ser adotadas para evitar sintomas em plantas de arroz. Sugere-se a utilização de distâncias maiores que 400 m em estudos futuros.

Resumo em Inglês:

ABSTRACT: This study aimed to evaluate the potential for glyphosate drift during aerial application using rice plants as sentinels, aiming to determine the effect of drift on irrigated rice crops. For this purpose, a field experiment was performed using an entirely randomized design with four replicates, evaluating different distances from the site of application [control (no application), 0, 12.5, 25, 50, 75, 100, 150, 200, 300, and 400 m]. The experiment was carried out at the Granjas 4 Irmãos farm, located in the Rio Grande city, Rio Grande do Sul State, Brazil. The glyphosate dose application was 1,920 g e.a. ha-1 (Roundup Transorb®, 480 g e.a. L-1 glyphosate isopropylamine salt). A dose-response curve was developed to estimate the drift rate in sentinel plants, by applying increasing glyphosate doses in rice plants and assessing the injury level. The drift rates estimated by the injury level in sentinel plants were 14% (150 m), 13% (200 m), and 5% (400 m). Death of the experimental units was observed for distances between 0 and 50 m, while in distances between 75 and 150 m, 25 to 50% of the plants survived, reducing productivity. In the distances between 200 and 400 m, there was no reduction in productivity when compared to the control, even when the injury levels reached 52 to 82%. Thus, we concluded that a 5% glyphosate drift reached up to 400 m from the application range. Considering the recommendation of zero drift, distances greater than 400 m should be adopted to avoid symptoms in rice plants. We suggest using distances of more than 400 m in future studies.

Resumo em Inglês:

Abstract Background: Soybean cultivation has been an option used to diversify the production system and perform herbicide rotation in irrigated rice crops in the lowland soils of the Rio Grande do Sul State, southern Brazil. However, elevated salinity levels have been detected in these soils that can inhibit plant growth due to the reduction of the osmotic potential of the soil solution and can causes toxicity. The combination of stress factors in the plantation areas can intensify deleterious effects, such as changes in salinity associated with herbicides that trigger oxidative stress in crops. Objective: This study aimed to evaluate osmotic potential, cell damage, and enzyme activities of the antioxidant metabolism on soybean after treatment with herbicides and salinity stress conditions. Methods: For this purpose, completely randomized design was used in a factorial scheme with three replicates. The A factor included four herbicide treatments, as follows: control (no herbicide), sulfentrazone, S-metolachlor, and sulfentrazone + S-metolachlor. The B factor was represented by the following three salinity levels: 0 (control), 60, and 120 mM NaCl, which were applied 24 hours after soybean sowing. Results: The results showed a significant alteration in the osmotic potential of soybean plants, mainly at higher salt concentrations. Although an increase in the lipid peroxidation has been detected in some treatments, antioxidant enzyme action combined with osmotic adjustment to reduce oxidative damage were mechanisms found to be employed by plants to reduce hydrogen peroxide levels. Conclusions: We concluded that herbicide treatment, in combination with saline stress, can alter physiological and biochemical processes of soybean plants.

Resumo em Inglês:

Abstract Background: Parthenium weed (Parthenium hysterophorus L.) is an invasive weed that has invaded vast regions of Pakistan in a relatively very short period of a decade or two, threatening the crop fields of the agrarian fed country. Parthenium hysterophorus L. is native of central South America and Gulf of Mexico, has now turned out to be a weed of global significance due to its alarming invasions and profuse spread in approximately all parts of the world. Its invasion is probably due to the contamination of its seeds in the imported grains from other countries of the world. Objective: During comprehensive sampling from Pakistan and Australia, it was observed that parthenium weed accessions exhibited several distinct morphological features present at different geographical regions. Therefore this study focuses on the use of plastid DNA barcodes (psbA-trnH) to evaluate the extent of variations in nucleotide sequences between the parthenium weed sampled accessions. Methods: The variability or genetic diversity was evaluated through sequencing of the amplified products and data was subjected to phylogenetic analysis in Molecular Evolutionary Genetic Analysis (MEGA; version 6.06) software. Results: In Maximum Likelihood tree, mainly two clades with three subdivisions are evident which showed increased heterogenity. The results of sequence based markers showed 12 haplotypes of P. hysterophorus populations (having two parsimony informative sites) with 10 indels and a few SNPs (single nucleotide polymorphisms). Conclusions: The results advocate that there have been multiple introductions of parthenium weed into Pakistan.

Resumo em Inglês:

Abstract Background: Palyno-morphological and foliar epidermal studies plays a very important role in the correct identification and differentiation of two weeds of genus convolvulus. Objective: The aim of the study is to determine the medicinal uses of the two important weeds for correct systematic identification. Methods: Both the qualitative and quantitative features were measured with the help of Light microscopy (LM) and scanning electron microscope (SEM). Results: Variations were observed in both the weeds, i.e Convolvulus arvensis (bindweeds) and Convolvulus prostatus (soft bindweed) in epidermal cells, stomatal size and number, guard cell shape and size, subsidiary cell and diversity of trichomes. Paracytic type of stomata was found in both the weed species. Stomata shape in Convolvulus arvensis is elliptical and oval to oval oblong in Convolvulus prostratus. Weed species have a difference in size, shape, polarity and exine ornamentation. Tricolporate pollen type was observed. The shape of pollen grains is Prolate, Perforate. By using these Palyno-morphological characteristics a taxonomic key is prepared for the identification of these weed plants. Conclusions: High fertility rate i.e Convolvulus arvensis 96% and in Convolvulus prostatus is 90 % shows the weed species are well adapted in the area. Systematics studies of the weed play a very important role not only incorrect identification but also differentiation with other weed plants and subsequently for the conservation purposes.

Resumo em Inglês:

Abstract Background: Megathyrsus maximus (Jacq.) is a perennial weed that affects many crops. In Argentina, sugarcane is the most affected. Objective: Study effective techniques to break dormancy and the effect of environmental factors on the germination of this weed. Methods: Experiments were carried out in cabinet incubators twice, with five replicates per treatment. The experimental unit was made up for 50 seeds. Results: Seed dormancy was strongly associated with the presence of glumes. Manual extractions of glumes and immersion in sulphuric acid were the most effective techniques for breaking dormancy. Megathyrsus maximus did not depend on light to germinate, and it did so both under a 12 h-light-dark photoperiod and in complete darkness, with maximum mean germination percentages of 73 and 76%, respectively. Mean germination percentage (G) and coefficient of germination (CG: number of germinated seeds per day) showed that this weed responded to a wide range of temperatures, the optimal varied between 25 and 35 °C. Both mean germination percentages and CG decreased as osmotic potential became increasingly negative (0 MPa to -0.6 MPa), and as sodium chloride solution concentrations increased (10 to 130 mmol L-1). No germination was observed at -0.8 MPa and with a 150 mmol L-1 sodium chloride solution. Conclusions: The optimal germination conditions for M. maximus can be found in central sugarcane areas in Argentina, since soils are in ideal conditions and are kept under irrigation. In marginal areas, M. maximus germination would depend on rainfall and certain sodium chloride concentrations in the soil.

Resumo em Inglês:

Abstract Background: Competition with weeds and the lack of selective herbicides registered for birdsfoot trefoil crops affect their development and limit their productivity. Objective: This study aimed to evaluate selectivity of post-emergent herbicides for weed control in birdsfoot trefoil crops. Methods: Experiments were carried out in a greenhouse and on a field, in both vegetative and reproductive development stages of birdsfoot trefoil crops. Treatments were composed of post-emergent herbicides recommended for soybean, corn and garlic cultivation. Phytotoxicity (PHYTO), plant height (HEI), shoot dry matter (SDM) and root dry matter (RDM) were evaluated. Data were submitted to the analysis of variance and when means were significant, they were compared by the Duncan’s Test (p≤0.05). In order to determine post-emergent herbicides which were selective to the crop, those that provided PHYTO below or equal to 15% were recommended, since they did not significantly interfere with morphological variables HEI, SDM and RDM, by comparison with the control. Results: Unlike results found in the vegetative stage, birdsfoot trefoil plants were more tolerant to phytotoxic effects of herbicides imazethapyr, chlorimuron-ethyl, cloransulam-methyl and fomesafen in the reproductive stage. The variables were negatively affected by the herbicides bentazon, glyphosate and carfentrazone-ethyl, with PHYTO higher than 40% at 20 days after treatment in the vegetative stage. Conclusions: Herbicides imazethapyr, chlorimuron-ethyl and flumetsulam, when applied as post-emergent ones, regardless of the development stage of the species, are selective to birdsfoot trefoil crops, without affecting crop development, whereas herbicides cloransulam-methyl and fomesafen are not selective to them.

Resumo em Inglês:

Abstract Background: Information on the carryover of herbicides applied to the destruction of cotton stalks, as well as the withdrawal period necessary to prevent the development and productivity of the crop in succession from being affected are limited in the literature. Objective: The objective was to identify the carryover effect promoted by herbicides used in the management of the destruction of cotton stalks and to estimate the host free period for sowing soybean in succession. Methods: Two individual experiments were conducted simultaneously, one for single application and the other for sequential application of herbicide treatments. The experiments were installed in a factorial scheme (15x5), in a randomized block design with four replications. The first factor evaluated was herbicide treatments and the second factor was five soybean sowing times after application (0, 30, 60, 90 and 120 days). The herbicides used in the treatments were 2,4-D, glyphosate, saflufenacil, [imazapic + imazapyr], dicamba, fluroxypyr and sulfentrazone. Results: As this work was conducted, the results provide a carryover indicator. It is concluded that the single application and the sequential application of the glyphosate + dicamba + saflufenacil treatment has great carryover potential for soybean crops, with the host free period for sowing the crop exceeding 120 days after application. Conclusions: The treatments 2,4-D, 2,4-D + glyphosate, glyphosate + saflufenacil + fluroxypyr had the lowest host free period intervals, even when in sequential application. The treatment with application of 2,4-D alone showed the lowest carryover potential for soybean.

Resumo em Inglês:

Abstract Background: Substantial losses to crops can occur due to the presence of sourgrass in agroecosystems, which is promoted by its seed dispersal ability. Environmental factors can affect sourgrass germination and emergence. Objective: The objective of this study was to determine the effects of water restriction, salinity, and depth of sowing on the sourgrass germination and emergence processes. Methods: Experiments using sourgrass seeds were conducted under controlled conditions simulating osmotic and saline stress and seeding depths. The data collected was submitted to analysis of variance and adjusted to models by regression analysis. Results: Smaller osmotic potentials reduced germination, normal seedlings, and increased quiescence, with no germination occurring from -0.80 MPa. Salinity caused a decrease in germination from 20 mM NaCl, influencing the percentage of normal and abnormal seedlings and quiescent seeds. Seed depth influenced the emergence of seedlings, with the maximum percentage of emergence (83%) in the seeds placed on the substrate surface. The maximum depth from which sourgrass seedlings emerged was 7.6 cm. Conclusions: The results lead to the conclusion that the sourgrass germination process tolerates low osmotic potentials and salinity levels. Despite being small sized seeds, they can emerge from high depths. These characteristics justify its occurrence in several regions and agroecosystems, especially in perennial and no-till crops lacking soil cover.

Resumo em Inglês:

Abstract Background: Lettuce-production areas in Brazil are frequently infested by pigweed plants, which can interfere with production by competing for resources or releasing allelopathic compounds in the environment. Objective: The present study evaluated the effect of redroot pigweed (Amaranthus retroflexus) density and distribution on lettuce crop (Lactuca sativa L.). Methods: The cultivars Lídia, Verônica, Lucy Brown and Salad Bowl were used. After transplanting, these plants coexisted until harvest with four pigweed plants (equivalent to 16 plants m-2) located within or outside planting rows, or with one pigweed plant located at the center of the plot (4 plants m-2), as well as a control without weed. The experiment was conducted in an open and semi-controlled area, with treatments arranged in a 4x4 factorial scheme, in a completely randomized experimental design with three replicates. Evaluations included: the number of leaves, fresh matter (lettuce only), height, leaf area and dry matter of lettuce and redroot pigweed plants. Results: The coexistence with redroot pigweed caused yield losses of up to 45% for cultivar Lídia; 41% for Salad Bowl; 33% for Verônica; and 28% for Lucy Brown. Conclusions: The density of 16 plants m-2 of redroot pigweed was the one that most negatively affected the growth of the cultivars, in which the positioning in the planting lines resulted in greater interference to the crop growth. Among the cultivars tested, Lucy Brown showed greater tolerance to coexistence with redroot pigweed plants, while the cultivar Lídia was the most sensitive to the imposed interference.

Resumo em Inglês:

Abstract Background: Talquezal (Paspalum virgatum L.) has become one of the main pasture weeds due to its association with the Urochloa brizantha death syndrome, a disease that causes the progressive death of clumps of susceptible grasses in patches, which leads to weed colonization and pasture degradation. Understanding the weed emergence pattern is essential in decision making for management strategies. Objective: Thus, this study aimed to evaluate the emergence pattern of talquezal seedlings according to its origin and the amount of straw covering the soil. Methods: The experiment was carried out in a greenhouse in a completely randomized design, with six replications and treatments arranged in an 8 × 3 factorial scheme with eight amounts of Urochloa brizantha straw covering the seeds (0, 0.5, 1.0, 2.0, 4.0, 6.0, 8.0, and 10.0 ton ha-1) and three collection sites (Rondonópolis, Redenção, and Cacoal). The effect of the origin and amount of straw was evaluated by the percentage of emergence, relative emergence frequency, mean emergence time, emergence synchrony, and emergence speed index of seedlings obtained over 35 days after sowing. Results: Talquezal seeds showed high seedling emergence vigor regardless of their origin under amounts of straw lower than 4.0 ton ha-1. Conclusions: The result suggests that the amounts of U. brizantha straw higher than 4.0 ton ha-1 on the soil surface, the lower is the percentage of Talquezal seedling emergence.

Resumo em Inglês:

Abstract Background: Inconsistent control of Barnyardgrass has been reported repeatedly by farmers in major rice growing areas of Iran and Turkey. Objective: Thus, a greenhouse study was conducted to investigate the resistance of Barnyardgrass to acetyl CoA carboxylase (cyhalofop-butyl) and acetolactate synthase (penoxsulam, bispyribac-sodium) inhibiting herbicides. Methods: The seeds were sown in pots in a greenhouse and after screening, were sprayed with various rates of cyhalofop-butyl, penoxsulam and bispyribac-sodium herbicides at 3-4 leaf stage. Four weeks later, the above ground biomass was cut, dried in an oven and weighted. The results were then analyzed in the R software (drc package) using a four or three parameter log-logistic function. All experiments were repeated twice. Results: While 30% of biotypes collected from Turkey were not controlled by ACCase inhibitors at twice the recommended rates, no resistance was observed in Iran’s samples. Only one biotype exhibited cross-resistant to penoxsulam and bispyribac-sodium in Iran, which was due to consecutive application of herbicides with modes of action similar to these herbicides. In contrast, several Turkish biotypes showed cross-resistance as well as multiple resistance to ACCase and ALS inhibitors. Conclusions: The rapid expansion of herbicide resistance in both countries indicate the necessity of adopting integrated weed management practices to hinder the further evolution of resistance in future.

Resumo em Inglês:

Abstract Background: Plants synthesize compounds of specialized metabolism to defend themselves against biotic and abiotic stresses. These compounds could be used as models for pesticide development. Among the species that have not yet been studied for the potential to produce active compounds is the kidney leaf mud plantain (Heteranthera reniformis). Objective: The goal was to evaluate the effect of hexanic, ethyl acetate and methanolic extracts of H. reniformis leaves on cress (Lepidium sativum) seed germination to determine which one have the highest biological activity; and to evaluate different concentrations of extract with the highest biological activity on lettuce (Lactuca sativa), barnyard grass (Echinochloa sp.) and giant arrowhead (Sagittaria montevidensis) germination. Methods: The seeds were placed on petri dishes containing two sheets of germitest paper, and after the application of the extract, they were sealed and placed in growth chambers with controlled temperature and photoperiod. The variables analyzed were 1st and 2nd germination count, germination speed index and length of the aerial part and roots. Results: The ethyl acetate extract provided greater phytotoxicity on cress than the other extracts. In general, the highest concentration of ethyl acetate extract was the most efficient in reducing variables for all species. Conclusions: The ethyl acetate extract of H. reniformis presents inhibitory activity on the seeds of cress, lettuce, giant arrowhead and barnyard grass, but this activity was dependent on the concentration of the extract and the species studied. H. reniformis synthesizes compounds with phytotoxic activity and purification of extracts is required to isolate, identify and characterize the action mechanism of the compounds with herbicide activity, so that in the future these can be used as models for the development of herbicides.

Resumo em Inglês:

Abstract Background: The application of Acetyl CoA carboxylase (ACCase) inhibitors prior to sowing of grass crops may result in crop damage due to residual effect of these herbicides in soil. The hypotheses was that different corn hybrids and ACCase herbicides can result in different plant-back intervals after burndown treatments. Objective: This work was planned to determine safe plant-back periods for three corn hybrids where ACCase herbicides clethodim and haloxyfop-methyl are applied. Methods: Herbicides were sprayed at 21, 14, 7, 2 and 0 days before sowing (DBS) at 192 g a.i. ha-1 (clethodim) and 120 g a.i. ha-1 (haloxyfop-methyl). Individual experiments were carried out with three hybrids: KWS9110 and 2B587 with glyphosate and glufosinate tolerance and Enlist with aryloxyphenoxypropionate tolerance. Results: Haloxyfop-methyl resulted in higher damage potential compared to clethodim for the hybrids KWS9110 and 2B587. For these hybrids, significant crop stand and grain yield reductions were observed mainly when haloxyfop was applied closer to sowing date (7, 2 and 0 DBS). Conclusions: Based on the effects on corn grain yield, a safe plant-back period for haloxyfop was estimated to be 8 and 11 days for the hybrids KWS9110 and 2B587, respectively. For the Enlist corn hybrid, there were no yield decreases, even when haloxyfop was applied at 0 DBS. Clethodim did not affect corn yield of any hybrid in any application time.

Resumo em Inglês:

Abstract Background: Antifungal activity of slender amaranth (Amaranthus viridis L.) is well documented but such studies are scarce in Pakistan, especially against plant pathogens. It was hypothesized that A. viridis has antifungal activity against fungal phyto-pathogens also. Objective: Identification of antifungal constituents from leaf extracts of A. viridis. Methods: Different organic solvent extracts of A. viridis leaves were evaluated against 5 plant pathogenic fungal species viz. Alternaria alternata, Aspergillus flavus, Drechslera australiensis, Fusarium oxysporum and Macrophomina phaseolina. Antifungal activity of A. viridis was determined by serial dilution method. Six levels (0, 5, 10, 15, 20 and 25 mg mL-1) of treatments of each n-hexane, chloroform and ethyl acetate were employed against all fungal species in a Completely Randomised Design (CRD). Results: Generally, all organic solvent extracts reduced the fungal biomass significantly with the increase in extract concentration but ethyl acetate leaf fraction exhibited pronounced activity and reduced the fungal growth up to 44% in A. alternata, 39% in A. flavus, 48% in D. australiensis, 48% in F. oxysporum and 45% in M. phaseolina. Gas Chromatography Mass Spectrometry (GCMS) analysis of ethyl acetate leaf fraction revealed 09 compounds. Out of these 9 compounds, one compound identified as 1,2- Benzenedicarboxylic acid, mono (2-ethylhexyl) ester) showed 58.5% peak value. Conclusions: It was concluded that 1,2- Benzenedicarboxylic acid, mono (2-ethylhexyl) ester) being in the highest concentration in the ethyl acetate leaf fraction of A. viridis may be responsible for antifungal activity. This compound can serve as structural analog to develop ecofriendly fungicides.

Resumo em Inglês:

Abstract Background: Plant-derived compounds are alternatives of synthetic insecticides in sustainable agriculture. Objective: This study investigated the phytotoxic effect of higher concentrations (2, 4, 8 and 16%) of four plants extracts (Azadirachta indica, Mentha arvensis, D. stramonium and Citrus limonium) on cotton plants. Methods: Each concentration was replicated four times to check the phytotoxic effect (CO2-in, CO2-out, H2O-in, H2O-out and photosynthesis absorption rate (PAR) in randomized complete block design. Data was recorded after 12, 24, 48 and 72 hours of spray with the help of Photosynthetic CL 340 meter. Results: The results showed that CO2-in was more affected by the D. stramonium (131.65±0.38) at 8% concentration. The overall progress showed that C. limonium was more affected the CO2-in of cotton crop. CO2-out was less affected by the C. limonium (117.83±1.46) at 4% concentration than M. arvensis (116.99±1.25) at 8% concentration and D. stramonium (115.77±0.74) at 16% concentration, but was more affected by the A. indica (118.15±0.71) at 4%. H2O-in was more affected by the C. limonium (0.39±0.05) than D. stramonium, A. indica and M. arvensis at 16% concentration. H2O-out of cotton was least affected by the D. stramonium (7.63±0.01) at 2% and more affected by the C. limonium (1.56±0.15) at 16% concentration. PAR was more affected by the A. indica (931.47±8.39) at 4% concentration and least affected by the M. arvensis (1499.7±9.94) at 8% concentration. Conclusions: Different dosages of various botanicals influenced the opening and closing of stomata and photosynthesis of cotton plants.

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Abstract Background: The resistance of weeds to herbicides is a problem that has been increasingly studied because of its great importance in agriculture and rapid growth of this phenomenon worldwide. The quick detection of resistant plants is extremely important for resistance management. Weed resistance to herbicides can be detected through field, greenhouse and laboratory tests. A fast way of detecting resistance is using tissue culture method, where is possible to use resistant plant clones and obtain results faster than whole-plant method in greenhouse. Objective: The aims of the research were to detect the resistance of blackjack to herbicides inhibitors of the acetolactate synthase (ALS), addition in vitro cultivation; determine the herbicide concentration of imazethapyr to 95% control of the susceptible plant population; evaluate explants growth; and, determine the herbicide concentration added to the culture medium where is possible to distinguish a resistant from a susceptible plant. Methods: Experiments were carried out in greenhouse and tissue culture laboratory. Screening was performed to select resistant and susceptible biotypes, tests for specie establishment and dose response curves in vitro were made. Results: The herbicide concentration added to the culture medium that provided 95% susceptible biotype control and efficiently differentiated susceptible biotype from resistant one was 0.6μM of imazethapyr. Conclusions: This method helps recommendations of weed management and provides a quick decision to alternative control of this specie, thus avoiding major damage to the crops.

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Abstract Background: Allelopathic plants like safflower (Carthamus tinctorius) can be considered as natural herbicides for weeds management in field. But there is not enough research on safflower genotypes allelopathy potential. Objective: So in this study, allelopathic effect of the four safflower genotypes on weeds (Amaranthus sp., Hordeum spontaneum), crops (Sesamum indicum, Triticum aestivum) and on autotoxicity of Carthamus tinctorius was evaluated in bioassay using sandwich method. The results can be used in the management of weeds in safflower fields and also in the rotation with other crops. Methods: Two genotypes with high allelopathic potential and two genotypes with low allelopathic potential were selected from forty genotypes of safflower. Growth traits including radicle length, hypocotyl length, shoot length, fresh biomass weight and germination percentages were measured. Results: Results showed that Amaranthus sp. and C. tinctorius displayed the most and least susceptibility to safflower residues, respectively. Khorasan (Khorasan330) and Egypt (PI657800) had the greatest with Kerman (CTNIR9) and Australia (PI 262424) had the least inhibitory effects on target plants. PI 262424 stimulated hypocotyl growth by 51%, 18% and 7% in H. spontaneum, T. aestivum and C. tinctorius, respectively. CTNIR9 enhanced this trait by 16% in T. aestivum and 10% in C. tinctorius. In large-seeded species (H. spontaneum, T. aestivum and C. tinctorius, Kerman (CTNIR9) and Australia (PI 262424) stimulated seedling growth. Conclusion: It can be concluded that effectiveness of allelopathic residues of safflower on target plants depended on the seed size of target plant with smaller seed size (Amaranthus sp.) were more susceptible to allelopathic residues than those with larger ones. In addition radicle length was affected more than other growth traits by safflower residues.

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Abstract Background: Continuous use of commercial herbicides is posing a severe threat to environment and creating herbicide resistant weeds. Allelopathy offers a promising alternative to commercial herbicides for sustainable weed management. The farmers are highly concerned with maximum yield as well as cost of the weed control techniques. Objective: To investigate economic and weed control efficiency of allelopathic crop water leachates mixed with lower rates of herbicide. Methods: Rapeseed (Brassica napus L.), sunflower (Helianthus annuus L.) and sorghum (Sorghum bicolor L.) crop leachates (18 L ha-1 each) tank mixed with lower doses (25, 33 and 50% of recommended dose) of S-metolachlor+atrazine were sprayed as pre-emergence for horse purslane (Trianthema portulacastrum L.) management in maize (Zea mays L.). Label dose (1,080 g a.i. ha-1) of herbicide (S-metolachlor+atrazine) and a weedy check treatment were also maintained. Results: The results showed that rapeseed+sunflower+sorghum allelopathic leachates mixed with half dose (540 g a.i. ha-1) of S-metolachlor+atrazine was effective against horse purslane and increased maize yield (grain) by 45% and 5% as compared with control and label dose of herbicide, respectively. Likewise, economic analysis showed that the same treatment was most economical with 40% and 9% higher net benefits than control and label dose of herbicide, respectively and 2407% marginal rate of return. It also gave an additional benefit of US$ 24.07 for investment of every US$1. Conclusions: By using this technique, herbicides use can be minimized by 50% for sustainable weed management without compromising maize yield and net benefits.

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Abstract Background: The use of commercial mix and tank mix with two or more herbicides is a widespread practice. However, despite its several possible benefits, little is known about its effect on the behavior of the molecules in the soil, which can increase or reduce the leaching potential of these molecules. Objective: This study evaluated the leaching potential of the herbicides diuron and sulfentrazone applied, using commercial mix and tank mix, in soils with different textures. Methods: The herbicides diuron (1,750 g ha-1) and sulfentrazone (875 g ha-1) were applied in three soils with different textures (clayey, medium, and sandy), using a commercial mix (Stone®) and a tank mix (Herburon 500 BR + Boral®). Subsequently, the treated soils were reconstituted in soil columns subjected to rainfall simulations with accumulated rainfall volumes of 40, 80, and 120 mm; the leached solutions were collected and analyzed by LC-MS/MS. Results: The results indicated a low descending movement of diuron in the three soils evaluated, when applied using commercial and tank mixes with sulfentrazone. Higher rainfall volumes (80 and 120 mm) were required to increase the diuron movement (≈20% of diuron applied). Sulfentrazone showed a high leaching potential in the soils, whereas the tank mix increased the leaching potential in sandy soil with the rainfall depths of 80 and 120 mm. Conclusions: The formulations did not affect the leaching potential of the herbicides in clayey and medium soil. However, the tank mix promoted greater leaching of the herbicides in the sandy soil when compared to the commercial mix.

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Abstract Background: The application of appropriately timed herbicide is an affordable approach to optimize the activity of herbicides. Objective: The study aims to determine the best night-time to apply glufosinate, oxyfluorfen, and paraquat with emphasis on the role of the period of dark exposure after herbicide application. Methods: The study was conducted at two fields in Iran, the fresh weight: dry weight (FW/DW) ratio of five weed species treated with glufosinate, oxyfluorfen, and paraquat at 0.5x and 1x of labeled doses after sunset or before sunrise was assessed. Results: The application time-of-day effect for tested herbicides was affected by application dose of herbicide and was more pronounced when the herbicides were applied at the 0.5x as compared to at the 1x. In 14 out of 18 cases, foliage tissues were more desiccated with the sunset applications of herbicides at the 0.5x than with the sunrise applications. When applications were made after sunset, an increased foliage tissues desiccation of Chenopodium album L. treated with paraquat (29.6%) in field 1 and C. album treated with glufosinate (27.2%) or paraquat (23.7%), and Malva neglecta Wallr. treated with glufosinate (21.6%) or oxyfluorfen (31.6%) in field 2 was detected by increasing the dose from 0.5x to 1x. Except 4 out of 18 cases, the herbicides applied either at the 0.5x after sunset or at the 1x before sunrise resulted in similar FW/DW ratio in all weed species. Conclusions: If contact herbicides are used at night-time after sunset, it is possible to take advantage of their reduced doses.

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Abstract Background: The study of the interactions between equipment, application methods, and spray mixtures is fundamental to optimize the application of pesticides. The determination of the best combination of these factors can reduce the drift during the application of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Objective: The objective this paper is to study the influence of nozzle models, working pressures, and surfactant adjuvant in reducing the drift of 2,4-D. Methods: The spectrum of nozzle drops was determined for a conventional flat jet; flat jet with air induction; double plane jet with air induction; deflector flat jet with air induction; and an empty cone with air induction at pressures of 200, 300, 400, and 500 kPa. This was quantified in a wind tunnel with four drifts: water; water + surfactant adjuvant; water + 2,4-D; and water + 2,4-D + surfactant adjuvant, applied by the five nozzle models at four working pressures. The data was evaluated by analysis of variance and, when significant, by the Tukey test and regression at 5% significance level. Results: The interactions between the nozzle models, working pressure, and spray mixture directly influenced the 2,4-D drift. Conclusions: The use of surfactant adjuvant must be carried out carefully, according to the nozzle model, working pressure, and spray mixture. The conventional single fan jet nozzle is more sensitive to increased working pressure and has a high potential to cause drift compared with the models with air induction.

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Abstract Background: Salvia officinalis a medicinal plant which is severely affected by weeds competition. Objective: The objective of this study was to determine the growth and physiological responses of S. officinalis to some light-dependent herbicides. Methods: A factorial experiment was conducted to determine the effects of oxadiargyl (T), bentazon (B), oxyfluorfen (O), metribuzin (M), phenmedipham+desmedipham (P) at 0.75 (1), 1 (2) and 1.25 (3) rates on growth and physiological parameters of S. officinalis. Results: All herbicides initially caused visual injury to S. officinalis. SPAD values were decreased by all herbicide treatments except for low rate of phenmedipham+desmedipham and oxadiargyl. The relative leaf water content (RLWC) decreased following herbicide treatments except in P1, P2, B1, and B2. Membrane stability index decreased by herbicide treatments however there were no differences among control and P1, P2, B1, B2, O1, O3, M3, T1, T2, and T3. All rates of oxyfluorfen and oxadiargyl, P1, B1 and B2 had no marked effect on the maximum quantum efficiency of PSII (Fv/Fm). Plant growth was not affected by herbicide treatments probably due to the recovery of the plants at the end of the experiment excepting for metribuzin. Essential oil content increased as the herbicide rate increased based on herbicide type. Conclusions: The results showed that S. officinalis had the ability to recover over time depending on the herbicide type and rate. Results showed that phenmedipham+desmedipham and bentazon are suitable and metribuzin unsuitable herbicides for weeds selective control in S. officinalis.

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Abstract Background: Garlic cultivation is characterized by low capacity of competition with weed, mainly due to the characteristics of the canopy and it´s slow initial growth that make it difficult to cover the soil. Objective: This work aimed to evaluate the efficiency and selectivity of herbicides applied in the pre-emergence of two garlic cultivars in the edaphoclimatic condition of Santa Catarina State. Methods: Two experiments were carried out in the commercial garlic area with Ito and Chonan cultivars. Both experiments were conducted in randomized block design. The traits for Ito cultivar were without weed control, with weed control, with linuron (810 g ha-1), diuron (1,000 g ha-1), pendimethalin (1600 g ha-1), S-metolachlor (1200 g ha-1), oxyfluorfen (720 g ha-1) or flumioxazin (40 g ha-1). For the experiment with Chonan cultivar the treatment composed by oxadiazon (1000 g ha-1) was included. The analyzed variables were based on weed community control and phytotoxicity, stand, diameter of bulbs and productivity of garlic. Results: The infesting species of the experiment with the cultivar Ito were Stellaria media and Stachys arvensis, whereas for Chonan, only the first was found. The herbicides applied in pre-emergence were efficient in controlling these species until 45 days after application - DAA. The highest injuries at 45 DAA were caused by S-metolachlor, with 33% for Ito cultivar and 10% for Chonan. The best herbicides, taking into account weed control and productivity, were pendimethalin and S-metolachlor, for the Ito cultivar, and pendimethalin, oxyfluorfen, and flumioxazin for the Chonan cultivar. Conclusions: The pendimethalin stood out for presenting excellent weed control and being selective for both garlic cultivars.

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Abstract Background: The effect of low rates of glyphosate has been widely studied in several crops. Low nitrogen stress reduces carbohydrate synthesis and we hypothesize that hormesis from glyphosate occurs at low nitrogen availability. Objective: To evaluate the effects of glyphosate hormesis at different levels of nitrogen on the growth and yield of white oat. Methods: A two-factor factorial (2x7) was conducted in field testing at nitrogen levels (50 and 90 kg ha-1) and low rates of glyphosate rates (0 - 180 g a.e. ha-1). The glyphosate was applied at the second node already formed. The growth and yield were evaluated. Results: Plant height was not affected by the nitrogen levels. A low rate of glyphosate induced a plant height increase up of around 10%, but the stimulus was no maintained over in the time. Glyphosate hormesis had a greater effect on dry weight under low nitrogen than under high nitrogen conditions. The glyphosate provided a 43% increase in dry weight at a low nitrogen level when applied at rates consistent with a 4.1% field rate. Glyphosate hormesis increased the yield by approximately 30%, and the yield was higher yield under low nitrogen conditions. Conclusions: The plant height stimulus from low doses of glyphosate was not sustained over time. Glyphosate hormesis stimulus persisted and culminated in an increase in dry weight and grain yield. The hormesis effect on dry weight and yield is more pronounced under lower nitrogen availability.

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Abstract Background: Weed interference is a major limiting factor for economically viable soybean production. Appropriate timing of weed management would enable farmers to make more efficient use of resources for weed management. Objective: The objective of this study was to determine the critical period for weed competition and appropriate timing of weed management for optimum yield of soybean. Methods: The treatments consisted of periods of weed infestation and weed removal for the first 14, 28, 42 and 56 days after sowing (DAS), and till harvest in a randomized complete block design with three replications in 2016 and 2017. Results: Soybean yields in both years ranged from 914-945 kg ha-1 with no weed control to 1,984-2,127 kg ha-1 in the weed-free plots; a yield loss of 53-56. Weed infestation for the first 14 DAS had no detrimental effect on growth and yield of soybean provided the weeds were subsequently removed. Increasing period of weed interference from 14 to 42 DAS resulted in a steady decline in growth and yield of soybean. Yield losses equivalent of 32-37 kg ha-1 resulted for each day that weed control was delayed between 14 and 42 DAS. Subsequent weed control after 42 DAS did not improve growth and yield significantly, nor obviate yield depression of the crop compared to crop weed-infested till harvest. Conclusions: Results indicated that the critical period of weed competition in soybean was between 14 and 42 DAS. Hence soybean should be maintained weed-free during this period to avoid high yield loss.

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Abstract Background: Waste-land weeds present around the fields exert their allelopathic influence on crops through their leaf leachates and rhizospheric soils. Objective: A study was conducted to investigate the phytotoxic action of four common waste-land weeds Parthenium hysterophorus L., Achyranthes aspera L., Lantana camara L. and Withania somnifera L. through their aqueous extracts and rhizospheric soils against winter crops Avena sativa L., Cicer arietinum L., Hordeum vulgare L. and Triticum aestivum L. Methods: Experiments were conducted in Agronomy laboratory in College of Agriculture at the University of Sargodha. In first experiment, 5% (w/v) water extract from entire plant of each weed was applied to germinating seeds of crops whereas in second experiment, crop seeds were subjected to the rhizospheric soil of each weed for germination test. Results: Results revealed that aqueous extracts of weeds were more phyto-inhibitory compared to their rhizospheric soils. Minimum germination percentage (42.5%), germination index (7.4), seedling vigor index (665.3), root length (3.27 cm), seedling length (14.15 cm) and seedling biomass (74.2 mg) of crops were recorded in response to aqueous extract of P. hysterophorus. Root growth of the crops was affected more compared to the shoot growth. Minimum germination percentage was observed in A. sativa (13.3) by the action of L. camara aqueous extract. Rhizospheric soil of L. camara and P. hysterophorus resulted in minimum germination percentages (57.5 and 58.3, respectively) and seedling vigor indices (1472.5 and 2008.4, respectively) of crops. The lowest germination (30%) and germination index (3.7) was observed for T. aestivum seeds germinated in the rhizospheric soil of W. somnifera. Among crops, A. sativa and C. arietinum were more susceptible to the aqueous extracts whereas T. aestivum to rhizospheric soils of weeds. Conclusions: It can be concluded that waste-land weeds especially P. hysterophorus and L. camara negatively affect the crops by their allelopathy.

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Abstract Background: The analysis of information generated from experiments involving different treatments, can be done by multivariate statistical analysis techniques, such as discriminant analysis, to analyze data obtained from predefined groups. Objective: Verify, through discriminant analysis, the differences among cover crop (Avena strigosa, Chenopodium quinoa, Cichorium intybus, and fallow land) treatments with respect to main crop soybean yield. Methods: For weed control, these cover crops were subjected to different management techniques, namely mowing, the application of glyphosate or the application of paraquat. The experimental design consisted of completely randomized blocks in a 4 × 3 × 2 factorial scheme, with four replications, consisting of the following factors: Factor A: (treatment) cover crops of A. strigosa, C. quinoa, C. intybus, and fallow land; Factor B: (management) plots were subdivided and treated with the application of paraquat or glyphosate, or the mowing of cover plants; Factor C: the plots were sub-subdivided and managed by one or two applications of a post-emergence herbicide. In order to evaluate the percentage of correct classifications of the different management techniques and treatments, a data matrix was elaborated for evaluation of variables relating to the soybean crop and the data were standardized by log - log 10 - log (n; 10). Multivariate analysis was performed using Fisher's linear discriminant method. Results: Discriminant analysis selected four variables with discriminatory power relating to the A. strigosa, C. quinoa, C. intybus and fallow, which contributed to 100% of the explained variance. Conclusions: Treatment with oats used as a cover crop provided higher soybean crop yield, whereas in terms of management, weed control using glyphosate provided the best results with all cover crops.

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Abstract Background: Parthenium hysterophorus L., commonly known as parthenium weed, poses severe economic and environmental hazards to the agro-ecosystems of Pakistan. Objective: To estimate the yield loss and critical competition period of this weed in the spring sown maize crop. Method: Field studies were conducted at an agronomic research area in the College of Agriculture at the University of Sargodha in Punjab-Pakistan during two consecutive year spring seasons (2014 and 2015). Treatments were comprised of viz., control plots (weed free), and parthenium competition durations of 2, 3, 4, 5 and 6 weeks after crop emergence (WAE), as well as weedy check for the full growing season of the crop. Results: Study results showed that the prolongation in parthenium competition duration from 2 WAE to the full crop season resulted in an increase in dry weight up to 541% and 450% in the years 2014 and 2015, respectively. Plant height, stem diameter, biological yield, 1000 grain weight and grain yield decreased significantly at 2 or more WAE parthenium competition periods. The maximum reduction in plant height (8.8 and 11.3%), stem diameter (30.6 and 12.7%), cob number m-2 (35.8 and 33.9%), grain rows cob-1 (26.6 and 29.4%), 1000 grain weight (15 and 9.8%), grain (34.1 and 39.1%) and biological yield (31.4 and 27.9%) were recorded with the longest parthenium competition duration (6 WAE) during the years 2014 and 2015, respectively. Conclusion: Based upon the results above, it is concluded that the critical competition period of parthenium in spring maize, as determined by a three-parameter logistic model, is 17 to 28 and 16 to 26 days after crop emergence during the years 2014 and 2015, respectively. Therefore, this weed must be controlled during these periods in order to avoid significant grain yield loss.

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Abstract Background: Weedy rice (Oryza sativa L.) is the main weed of rice crop. The high genetic variability of weedy rice contributes to the high phenotypic diversity between biotypes and different responses to environmental stress. Objective: The present study aimed to evaluate the response of imidazolinone-susceptible and -resistant weedy rice populations to increased atmospheric [CO2]. Methods: The experiment was arranged in a complete randomized design with six replications. The treatments included two [CO2] concentration (700 and 400 μmol mol-1) and three treatments: resistant genotype (IMI-resistant) treated with imazethapyr; resistant genotype without imazethapyr, and a susceptible genotype without imazethapyr. Results: The IMI-resistant and -susceptible weedy rice responded similarly to [CO2] enrichment. Enhanced [CO2] increased competitive ability of the weedy rice populations tested, by means of increased plant height. Weedy rice seed production also increased with enhanced [CO2] by means of increased photosynthesis rate and reduced transpiration (increased water use efficiency). Increased seed production also means increased weed persistence as it increases the soil seedbank size. The application of imazethapyr on IMI-resistant weedy rice did not alter its response to [CO2]; conversely, increased [CO2] did not change the resistance level of weedy rice to imazethapyr. High [CO2] increased spikelet sterility, but this beneficial effect was negated by the overall increase in production of filled grains. Conclusions: Enhanced [CO2] concentrations increases weedy rice growth, photosynthesis rates, seed production and spikelet sterility; the imidazolinone application does not affect the response of weedy rice to enhanced [CO2] affects weedy rice response to imidazolinone herbicide.

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Abstract Background: Weed control in the pre-harvest of the coffee crop is essential to enable mechanized coffee harvesting. Objective: Testing the efficacy of pre-emergent herbicides, applied after brush shredder or desiccation operations, on the weed control during the coffee crop’s pre-harvest. Methods: Two separate trials were accomplished in commercial Coffea arabica crops in the Cerrado Mineiro Region. In the first one, oxyfluorfen and sulfentrazone were applied after either brush shredder or burndown operation; in the second, they were tested as a tank mixture with glyphosate. Results: In the first assay, the brush shredder use, associated to the rains that follow, stimulated a sharp weed infestation during the pre-harvest, which was not observed in desiccated plots. A sole application of oxyfluorfen or sulfentrazone, following either brush shedder or desiccation operation, effectively controlled the weeds; however, the sequential applications on burndown areas may be needless. The applied herbicides did not intoxicate the coffee plants nor affect their growth. In the second assay, both herbicide mixtures were highly efficient on the weed control through post-emergence application during the pre-harvest, what was not observed with a sole application of glyphosate. In both experiments, a dry period during winter, associated to the operations to gather fallen coffee fruit, collectively contributed to control weeds. Differently from oxyfluorfen, the residual effect of sulfentrazone was high enough to control weed even in the beginning of the rainy season. Conclusion: Sulfentrazone and oxyfluorfen were effective on the weed control in the pre-harvest of the coffee crop, mainly when applied after brush shedder operations.

Resumo em Inglês:

Abstract Background: Weedy rice belongs to the same taxon as irrigated rice (Oryza sativa L.), and is the main weed of the crop. However, it exhibits different traits that produce greater competitive capacity using solar radiation. In competition for light, plants invest in photoassimilates for the shoots and can reduce their root development. Objectives: The objective of this work is to evaluate the initial growth of weedy and cultivated rice roots in response to light competition. Methods: The experiment was conducted in a greenhouse (hydroponic system), using a completely randomized design, arranged in a 2x2x6 factorial scheme, with five replications. Factor A consisted of the weedy rice biotype Q35B and the rice cultivar IRGA 424; factor B of light competition conditions (presence or absence of 75 weedy rice plants); and factor C of assessment time. At 0, 7, 14, 21, 28 and 35 days after transplanting, samples were taken from each experimental unity to measure the root area, perimeter, length, number of tips, and root dry weight (RDW), and shoot dry weight (SDW). Results: Competition for light reduced the area, perimeter, length, number of root tips, reduced the RDW and the SDW of both, the weedy rice biotype and crop rice. However, regardless of the competitive condition, the weedy rice showed a higher area, perimeter, initial growth, number of tips, RDW and SDW than that of cultivated rice. Conclusion: Weedy rice exhibits greater competitive capacity using the resources beneath the soil.

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Abstract Background: Knowledge about the action of glyphosate alone and associated with adjuvants in the effectiveness to control aquatic plants is important in the decision-making on its use. Objective: This study aimed to evaluate the effectiveness of glyphosate and five adjuvants in the control of Myriophyllum aquaticum. Methods: Glyphosate (Rodeo®) at doses of 1.5, 3.5, 5.5, and 7.5 L ha-1 was sprayed alone and associated with Aterbane® BR, Veget’oil®, Dash® HC, Assist®, and Agral® (0.5% v v-1), in addition to the control, with a spray solution volume of 200 L ha-1. The effectiveness of control was evaluated using the scores of a visual scale at 3, 7, 15, 21, 30, 45, and 60 days after application (DAA), regrowth, and dry matter accumulation at 60 DAA. Results: The best effectiveness of control of the glyphosate alone was 85% at the dose of 7.5 L ha-1, increasing to 100% when associated with Aterbane® and Veget’oil®. The control reached 100% for all glyphosate doses associated with Dash®. Moreover, glyphosate at the dose of 7.5 L ha-1 associated with Assist® provided a 98% control, while glyphosate doses of 3.5, 5.5, and 7.5 L ha-1 associated with Agral® provided a 100% control. Glyphosate at doses of 5.5 and 7.5 L ha-1 associated with Dash® and Agral® was more effective in reducing the regrowth and dry biomass (100%). Thus, glyphosate + Dash® and Agral® promoted the highest control (above 95%), the lowest regrowth, and the highest reduction in the dry biomass of M. aquaticum. Conclusions: The addition of Aterbane® BR, Dash®, and Agral® to glyphosate improved the effectiveness of control of M. aquaticum and contributed to reducing the applied herbicide dose.

Resumo em Inglês:

Abstract Background: The study of both intra- and interspecific competitions in Wheat (Triticum aestivum L.) agroecosystem is quite complex and it is essential to understand the influence of nitrogen in these competitions. Objective: The aim of this study was to evaluate the effect of different competitive models on nitrogen balance in wheat ecosystem agriculture (Chamran cultivar). Methods: A field experiment was performed using split-plot based on randomized complete block design (RCBD) with three replications. The main and sub-plots consisted of different nitrogen rates (control, 50, 100 and 150 kg nitrogen ha-1) and different competitive patterns (no, intraspecific, interspecific competition and intra- and interspecific in combination) were applied to the sub-plots, respectively. Weed density in the interspecies competition was applied through the equal planting of two narrow leaves (Avena sativa L.) and broadleaf (Sinapis arvensis L.) weed species. Results: The dry matter (DM) accumulation and nitrogen content (NC) at anthesis was higher than that at maturity stage for all competition treatments as well as nitrogen rates. The trend of nitrogen translocation efficiency (NTE) and nitrogen harvest index (NHI) was different from dry matter translocation efficiency (DMTE), and both were highest in interspecific competition treatments. Moreover, the highest grain yield in no competition treatment resulted in a lower dry matter and NTE. Conclusions: It was concluded that the capacity for nitrogen accumulation in the stem, was associated with a high nitrogen uptake, nitrogen assimilation and high post-anthesis nitrogen remobilization efficiency. In additions, high NHI could be used in the development of cultivars with the desired N balance.

Resumo em Inglês:

Abstract Background: Enlist E3™ soybean is tolerant to 2,4-D, glyphosate and ammonium-glufosinate and were developed for effective management of herbicide resistant weeds such as glyphosate Herbicides, even being selective, can cause damage to crop metabolism, affect growth and development and interfere with seed physiological quality. Objective: The aim of this research was to evaluate the physiological quality of Enlist E3™ soybean seeds submitted to herbicide application. Methods: The field trial was carried out in a randomized block design with four replications. The treatments tested were 2,4-D choline + glyphosate, 2,4-D choline, glyphosate + 2,4-D amine and ammonium-glufosinate; and control without application, sprayed at V6 soybean growth stage. After harvest, the seeds were submitted to first germination count, accelerated aging, germination speed index, shoot and root length, shoot and root dry mass and electrical conductivity tests. Results: The management of Enlist E3 soybeans with Enlist herbicides (2,4-D choline + glyphosate and 2,4-D choline) as well as glyphosate + 2,4-D amine and glufosinate did not negatively impact soybean parameters such as: vigor, germination count, accelerated aging, germination speed, aerial part and primary root length, aerial part and root dry mass and electrical conductivity. Conclusions: Those herbicides can be recommended to be used on post emergence (V6) of Enlist E3 soybean.

Resumo em Inglês:

Abstract Background: Conyza stricta L. (Horse weed) is an annual problematic weed in an agricultural ecosystem and considerably decreases the crop yield and quality. Objective: To determine the most effective pre and post emergence herbicides and their dose to control C. stricta in sugarcane crop. Methods: A two years field study comprised of six herbicides treatments along with weedy check and hand weeding. The design of study was RCBD with three replications. Results: Hand weeding recorded more leaf area index (LAI), crop growth rate (CGR) and net assimilation rate (NAR), biological and stripped yield. However, greater LAI, CGR and NAR, biological and stripped yield were recorded by acetochlor + atrazine at the rate of 2,715 g ha-1 (pre emergence) and dicamba at the rate of 466 g ha-1 (post emergence). All the treatments produced statistically comparable harvest index except weedy check, which produced less harvest index. Minimum C. stricta density and dry weight were recorded for acetochlor + atrazine at the rate of 2,715 g ha-1 and dicamba at the rate of 466 g ha-1. Acetochlor + atrazine at the rate of 2,715 g ha-1 (pre emergence) and dicamba at the rate of 466 g ha-1 (post emergence) gave better C. stricta control with high herbicides efficiency index. Conclusion: Acetochlor + atrazine at the rate of 2,715 g ha-1 (pre emergence) or dicamba at the rate of 466 g ha-1 (post emergence) may be used for efficient control of C. stricta in sugarcane.

Resumo em Inglês:

Abstract Background: The pre-emergence herbicides diclosulam and flumioxazin are used to weed control in soybean. We hypothesized management of the new emergence of weeds in the early development stages of the soybean could alter the periods of interference. Thus, the period prior to interference allows and increases the canopy closure spaces before the critical period and disfavors the development of weeds inside the vegetative canopy. Objective: This study aimed to evaluate whether the period prior to interference of soybean cultivars was altered due to the application of residual pre-emergence herbicides. Methods: Two experiments were conducted with the soybean cultivars ‘NA 5909 RG’ and ‘P95R51’. One day before sowing in the main plots, the herbicide treatments paraquat (control without residual herbicide), paraquat+diclosulam, and paraquat+flumioxazin were applied. In the sub-plots, the increasing periods of coexistence of soybean with weeds of 0, 7, 14, 21, 28, 35, 42, and 49 days after the emergence of soybean were allocated. Results: The control without residual herbicide had the lowest period prior to interference and the most considerable reductions in grain yield when compared with residual herbicides in both experiments. The presence of residual herbicide increased the period prior to interference because they controlled the initial emergence of the major weeds in the experimental area. Conclusions: The use of the herbicides with residual activity diclosulam and flumioxazin increased the period prior to interference of ‘NA 5909 RG’ and ‘P95R51’ in areas infested mainly with horseweed and radish.

Resumo em Inglês:

Abstract Background: Sourgrass (Digitaria insularis) is a highly disseminated weed in Brazil. It is a perennial grass weed that has high infesting capacity in agricultural areas and presents glyphosate-resistant biotypes. An effective post-emergence control of sourgrass plants depends on their phenological stage at the time of herbicide application. Objective: This work was developed with the objective of evaluating the effect of the sourgrass phenological stage at the time of herbicide application on the efficacy of ACCase-inhibiting herbicides. Methods: Two independent experiments were conducted under greenhouse conditions to evaluate two ACCase-inhibiting herbicides: clethodim, and haloxyfop. The treatments were applied using a completely randomized block design, with an 8×4 factorial arrangement consisted of 8 herbicide rates (4, 2, 1, 1/2, 1/4, 1/8, and 1/16 times the recommended rate, and a control plot without herbicide application) and four phenological stages of sourgrass. Results: The development of sourgrass plants after tillering decreased the efficacy of the herbicide molecules; however, clethodim and haloxyfop were efficient to control sourgrass at earlier developmental stages. Morphological, anatomical, and physiological changes in older plants may explain the lower susceptibility to herbicides. Conclusions: Other control techniques should be considered for sourgrass plants at later developmental stages, such as sequential application or herbicide mixtures, to increase the efficacy of ACCase herbicides.

Resumo em Inglês:

Abstract Background: The use of pre-emergent herbicides is an important tool to control weeds, however the tolerance of soybean to these herbicides can vary according to the type of soil. Objective: The aim of this study was to evaluate sulfentrazone and diclosulam soybean selectivity in a sandy soil, in order to establish these herbicides as supporting tools in weed control. Methods: The treatments consisted of six doses of sulfentrazone (150 to 400 g ha-1) and diclosulam (25.2 to 75.6 g ha-1), and an untreated control. A field study was repeated in two growing seasons (2013/14 and 2014/15) in a sandy soil. Results: The occurrence of injury depended on the growing season. The first season presented lower rainfall rates during the crop cycle. The recommended dose of sulfentrazone (200 g ha-1) caused 26% and 10% of plant injury at 15 days after the treatment for the first and second season, respectively. For diclosulam, the recommended dose of 35.3 g ha-1 caused 20% and 8% of plant injury, respectively, for the first and second season. However, at the recommended doses, only for diclosulam and in the rainy season there was a reduction in soybean productivity. Conclusions: The herbicide sulfentrazone, although causing visual soybean plant injury, present satisfactory selectivity at recommended doses and can be used as an important tool on weed control on sandy soils. Similar response was observed for diclosulam in 2013/14. However, in a rainfall season diclosulam impacted on soybean yield at the recommended dose for sandy soils, with selectivity depending of the growth season.

Resumo em Inglês:

Abstract Background: The use of electrostatic spray has the potential to optimize pesticide applications; however, further studies are required to verify its effectiveness. Objective: The objective of this work was to evaluate the electrostatic application system for the chemical control of weeds with glyphosate and adjuvant in different carrier volumes. Methods: The physicochemical properties of the spray solution, charge/mass relations, spray deposition on weeds, losses to the soil, effectiveness of weed control, and spray drift were evaluated. The field experiment was designed to have randomized blocks with four replications in a 2x2x2+2 factorial: the presence or not of electrostatic spray; with and without adjuvant (soybean lecithin + propionic acid); two carrier volumes (50 and 90 L ha-1); a control without applications and a conventional spray rate (150 L ha-1) for additional treatments. The study was performed in duplicate. Results: The electrostatic system energized the droplets during the application of glyphosate and adjuvant; however, this did not influence the deposition on the weeds, the losses to the soil, and the drift. The adjuvant improved the effectiveness of weed control in various situations, changed the spray solution properties, and reduced the losses due to drift. Conclusions: The adjuvant used proved to be an important tool in application technology. The effectiveness of weed control, in general, was not influenced by the electrostatic system.

Resumo em Inglês:

Abstract Background: Weed management is a challenge in paddy rice production, mainly due to the dispersal of a population resistant to herbicides. Objective: To assess the efficacy of chemical weed control in the off-season to reduce weedy rice and other species in water-seeded or drilled rice. Methods: Two experiments were carried out in a flat field to water-seeded or drilled rice, in randomized block design. The water-seeded system treatments were organized in a split-plot design. In the plot were evaluated two water management in the off-season (with or without continuous flooding), and in the subplot nine herbicides-treatments were evaluated (Check, clomazone at 0.72 and 1.08 kg a.i. ha-1, oxadiazon at 1.00 and 1.50 kg a.i. ha-1, oxyfluorfen at 0.312 and 0.48 kg a.i. ha-1, S-metolachlor at 1.44 kg a.i. ha-1, and flumioxazin a 0.075 kg a.i. ha-1). In the drilled rice experiment, the treatments were organized in a two-factor factorial. The factor A was nine herbicides treatments (the same herbicide and rates applied in water-seeded experiment) and the factor B was two application time (73 and 43 days before of rice-sowing). Results: Off-season management was efficient to reduce weedy rice infestation only on the paddy rice system using the pre-germinated seeds. In this assay, flumioxazin was an efficient alternative to giant arrowhead control, however the selectivity of this herbicide treatment needs to be studied. In dry-seeded system, herbicide sprayed in off-season reduced barnyardgrass infestation until the paddy rice sowing. Conclusions: The off-season management was efficient to reduce weedy rice and giant arrowhead infestation in water-seeded system, and barnyardgrass infestation in drill-seeded system.

Resumo em Inglês:

Abstract Background: Fleabane plants (Conyza spp.) resistant to glyphosate herbicide are found infesting areas in the Central-West and Southeast regions of Brazil, but its management is not a concerning problem for summer crops in these regions as in the South region of Brazil. Objective: To evaluate the management of adult fleabane plants at the summer soybean crop and off-season (autumn-winter), monitoring new emergences to assess the dynamics of plants from November 2018 to March 2020, and the residual effect of herbicides applied at the end of the rainy season in the Cerrado biome, in Brasília, DF, Brazil. Methods: Four field experiments were developed from November 06, 2018 to April 02, 2020; all under randomized block design, with four replications, in factorial or split-plot arrangement, with visual weed control evaluations (0% to 100%) and seedling counting. Results: The highest fleabane infestations in soybean crops were found before sowing, and were partially or fully controlled by pre-sowing chemical/management treatments, which did not interfere with the soybean seed yield. The fleabane biological cycle ended in November-December (1st year), and December-January (2nd year). Conclusions: The most significant fleabane emergence in the areas was found in February and March. The treatments with saflufenacil and glufosinate-ammonium, followed by 2,4-D, were the most efficient and fastest control of adult fleabane plants.

Resumo em Português:

RESUMO: O sulfentrazone é um herbicida com ação em pré-emergência que inibe a protoporfirinogênio oxidase (Protox). Sua utilização tem ênfase em áreas de expansão, como a soja em terras baixas, soja e cana-de-açúcar em áreas de cerrado, e também na implantação de florestamentos de eucalipto. A inserção do sulfentrazone em programas de manejo de plantas daninhas resistentes, principalmente ao glifosato e a inibidores da acetolactato sintase (ALS), vem obtendo sucesso. Contudo, as informações sobre o comportamento ambiental desse herbicida são limitadas, sendo ainda mais restritas quando se trata de áreas de terras baixas, onde frequentemente são observados problemas quanto à seletividade do sulfentrazone, em razão das peculiaridades edafoclimáticas desse ambiente. Nesse âmbito, esta revisão teve por objetivo relacionar as principais características do sulfentrazone com sua dinâmica ambiental e sua seletividade, compreendendo esses processos, a fim de otimizar sua utilização.

Resumo em Inglês:

ABSTRACT: Sulfentrazone is a pre-emergence herbicide that inhibits protoporphyrinogen oxidase (Protox). Its use has emphasis on areas like soybeans planted in lowlands, soybean, and sugarcane in areas of cerrado, and also in the implementation of eucalyptus afforestation. The use of sulfentrazone into resistant weed management programs mainly to glyphosate and acetolactate synthase (ALS) inhibitors has been successful. However, the information on the environmental behavior of this herbicide is limited, even more restricted when it refers to the lowland areas where problems are frequently observed regarding the selectivity of sulfentrazone, due to the soil and climatic peculiarities of this environment. In this context, the present review aims to describe the main characteristics of sulfentrazone to its environmental dynamics.

Resumo em Português:

RESUMO: As mudanças climáticas caracterizadas pelo aquecimento global e frequente ocorrência de períodos prolongados de seca têm demandado o cultivo de culturas multiúsos, que são resistentes à temperatura e à seca. Neste artigo é avaliado o potencial de produção de pera de cacto [Opuntia ficus indica (L.) Mill.] como uma cultura de forragem alternativa e de baixo custo, juntamente com os recentes avanços em seu cultivo e utilização como cultura de alimentos para complementação da segurança alimentar de uma população em rápido crescimento. As características botânicas, ecológicas e fisiológicas que permitem que a pera de cactos sobreviva sob condições agroclimáticas adversas, têm sido objetivamente elaboradas. Uma variedade de impedimentos que dificultam o cultivo em larga escala e as futuras necessidades de melhoramento da produção de biomassa e da qualidade nutricional também foram identificadas. O potencial da pera de cacto para reduzir a desertificação, juntamente com a sustentabilidade para a agricultura moderna, comercial e rentável em terras secas torna uma planta excepcional. Seu rendimento de biomassa anual (caules chamados cladódios) de 40-50 t ha-1 com manejo agronômico adequado pode sustentar 5-6 vacas adultas alimentando uma família de 12-16 pessoas. Entretanto, o crescimento lento, o menor rendimento da fruta, a qualidade nutritiva pobre da forragem e o medo de a pera do cacto tornar-se uma planta daninha nociva restringem seu cultivo popularizado, exigindo assim um melhoramento genético abrangente e um pacote de tecnologia agronômica.

Resumo em Inglês:

ABSTRACT: Climate change characterized by global warming and frequent occurrence of prolonged drought spells has necessitated the cultivation of multi-purpose crops which are temperature and drought hardy. This paper evaluates the production potential of cactus pear [Opuntia ficus indica (L.) Mill.] as an alternate and low-cost forage crop along with the recent advancements in its cultivation and utilization as food crop for supplementing the food security of rapidly increasing populace. The botanical, ecological and physiological traits enabling cactus pear to survive under harsh agro-climatic conditions have been objectively elaborated. A variety of impediments hampering its wide-scale cultivation and future breeding needs for improving the biomass production and nutritional quality have also been identified. The potential of cactus pear to reduce desertification along with imparting sustainability to modern, commercial and profitable agriculture in dry-lands makes it an exceptional plant. Its annual biomass (stems called cladodes) yield of 40-50 t ha-1 with an appropriate agronomic management may sustain 5-6 adult cows supporting a family of 12-16 people. However, its slow growth, less fruit yield, poor nutritional quality of forage and the fear of cactus pear becoming a noxious weed restricts its popularized cultivation and thus demands a comprehensive genetic improvement and agronomic technology package.

Resumo em Inglês:

Abstract Background: Weeds are unwanted and undesirable plants which deteriorate the quality of agricultural products and interfere with farming activities. Most of the weeds (indigenous and invasive) seeds get preserved in soil horizons as weed seed bank which ensure their survival leading to the spoilage of quantitative and qualitative functioning of agricultural farms. Objective: To keep weeds below threshold level, elimination of weeds seed before germination can be a viable and pro-ecological approach. To achieve this objective, weed seeds reserved in the soil which serve as an effective pool to ensure their survival necessitate weed-seed bank management. Thus the ultimate goal was to synthesize and analyze research findings on weed seed bank management leading to formulating the most effective strategy encompassing viable control of weeds in maize. Methods: This study reviewed and analyzed the characteristics which impart botanical superiority to weeds and impact of all prevalent weed control strategies on weed seed bank, weeds density and maize yield. The research findings pertaining to different agronomic practices and technological packages were critically analyzed to sort out the most effective and eco-friendly approach to control weed-seed bank and weeds density in maize crop. Results: The synthesis and critical evaluation of research findings pertaining to weed control methods revealed that manual and mechanical methods were eco-friendly but involved expensive labor, while the chemical approach involving the use of herbicides led to serious deterioration of agro-environmental resources. Two or more techniques used in coherence which encompassed deep tillage to burry weeds seed and prevented their germination through mulches of biotic and synthetic materials along with optimizing sowing method especially raised bed technique reduced weed seed bank and weeds density in maize. Conclusions: It is inferred that integrated approach entailing cultural, manual, mechanical and chemical control can be developed as a pro-environmental and farmer friendly approach for weed control by reducing weed seed reserves which can potentially lead to higher economic returns through higher maize yield.

Resumo em Inglês:

Abstract Background: Rice lines displaying resistance to quizalofop-p-ethyl (quizalofop), an acetyl coenzyme A carboxylase (ACCase)-inhibiting herbicide, were developed to facilitate control of imidazolinone-resistant weedy rice (red rice), as well as other susceptible grasses. Objective: To assess the sensitivity of weedy rice accessions from Brazil to quizalofop. Methods: Two bioassays were conducted on the greenhouse from March to June 2016, in a completely random design with a two-factor factorial combination of treatments and four replications. The factor A was weedy rice accession and factor B was quizalofop rates (0, 25 and 50 g a.i. ha-1). It was assessed a total of 84 genotypes in the two bioassays, composed of 78 weedy rice accessions, 4 rice cultivars, and 2 lines resistant to aryloxyphenoxypropionate (AOPP) herbicides. Quizalofop was applied the 2-leaf stage. Weedy rice control was evaluated at 28 and 22 days after treatment (DAT), respectively for bioassay I and II, using a scale of 0% (no control) to 100% (dead). Results: All weedy rice accessions were susceptible to quizalofop, being controlled 100% with 50 g a.i. ha-1. Rice lines SC 964 and SC 965, resistant to AOPP herbicides, were not injured by quizalofop. Conclusions: quizalofop is an effective tool for weedy rice control in ACCase-resistant rice.