Resumo em Inglês:

Two species of smut fungi (Basidiomycota) are reported here for the first time for Panama. Narasimhania alismatis (Doassansiales) was found on Sagittaria guayanensis and Tolyposporium kuwanoanum (Ustilaginales) on Cyperus tenuis, a new species of host plant. The name of the latter fungus is a new combination based on the currently accepted name Ustanciosporium kuwanoanum. This species belongs to the genus Tolyposporium because of sori with peridia, teliospores in balls, teliospores without hyaline appendages, and LSU rDNA sequence data. Ustanciosporium cyperi is morphologically rather similar to T. kuwanoanum, so it is also placed into the genus Tolyposporium. The concept of the genus Tolyposporium is discussed.

Resumo em Inglês:

The yellow dwarf disease in winter cereal crops is caused by species of Barley yellow dwarf virus (BYDV) and Cereal yellow dwarf virus (CYDV) (Luteoviridae). These viruses are transmitted to grasses (Poaceae) by aphids (Aphididae) and the frequency of virus population is affected by oscillations in the vector and host populations. Seasonal fluctuations of BYDV-PAV, BYDV-MAV, and CYDV-RPV in aphids and grasses were analyzed in corn in the summer, and wheat and oat plots in the winter in Coxilha, RS, Brazil. Among the aphids collected, 12.7% transmitted B/CYDV, and 92.6% of those aphids were Rhopalosiphum padi while 7.4% were Sitobion avenae. The viruses that R. padi transmitted were BYDV-PAV (95.4%), CYDV-RPV (2.3%), and BYDV-MAV+PAV (2.3%), while S. avenae only transmitted BYDV-PAV. Among the wheat and oat plants collected, 65.8% were seropositive, all of which were infected with BYDV-PAV and 0.7% of which were also infected with BYDV-MAV. The population dynamics of the virus was similar in aphids and plants, with peaks in the winter crop season. The 35 isolates of BYDV-PAV analyzed were able to infect wheat and oat, being transmitted by R. padi (EF=94.4%), S. avenae (EF=76.1%), and M. dirhodum (EF=63.4%). They were not transmitted by S. graminum or S. maydis. Since several common vector species efficiently transmit BYDV-PAV, this may explain why it is the dominant virus species in the "yellow dwarf pathosystem" in Southern Brazil.

Resumo em Inglês:

The aims of the present study were to assess the efficiency of hybrid sorghum mixtures for the management of anthracnose and analyze the virulence diversity and structure in the pathogen populations developed in response to these mixtures. Proportions of 25%, 50% and 75% of the susceptible BRS304 hybrid in relation to the resistant IG150 hybrid were evaluated. Six weekly evaluations of severity were performed. The data were transformed into area under disease progress curve (AUDPC). The isolates of Colletotrichum sublineolum were sampled from hybrid mixtures cultivated in Sete Lagoas and Indianópolis (Brazil) as well as sorghum fields in Rio Verde and Paraúna (Brazil). The increase in the proportion of the resistant hybrid in the mixtures led to a reduction in anthracnose severity. The most effective proportions were those with 25% and 50% of the susceptible variety blended with the resistant variety. Complex breeds of C. sublineolum predominated in the populations and a reduction in phenotype diversity was observed. This reduction in diversity was attributed to deviations in the degree of polymorphism in relation to virulence. However, the increase in complex breeds did not imply lesser efficiency on the part of the resistant hybrid in conferring protection to the susceptible hybrid.

Resumo em Português:

Em três experimentos, avaliou-se o efeito de pulverizações de ácido jasmônico (AJ), etefon (ET) e acibenzolar-S-metil (Bion®) (ASM) a 0,1 mM, 0,5 mM e 0,3 g L-1, respectivamente, nos componentes de resistência do tomateiro (cv. Santa Clara) à pinta bacteriana, causada por Pseudomonas syringae pv. tomato e na atividade de peroxidases (POX), polifenoloxidases (PFO), β-1,3-glucanases (GLU) e lipoxigenases (LOX). Apenas no experimento 3, o período de incubação aumentou significativamente em um dia nas plantas pulverizadas com ASM, em comparação com as plantas pulverizadas com água (controle). O número de lesões por planta foi significativamente reduzido por AJ, ET e ASM nos três experimentos. Para algumas épocas de avaliação, a atividade de POX, PFO e GLU foram maiores para o AJ; de PFO, GLU e LOX, para o ASM; e de GLU e LOX, para o ET em comparação com o controle. Conclui-se que na presença de AJ, ET e ASM, os sintomas da pinta bacteriana foram reduzidos e a atividade das enzimas POX, PFO, GLU e LOX foram maiores.

Resumo em Inglês:

Three experiments were performed aimed to evaluate the effect of jasmonic acid (JA), ethephon (ET) and acibenzolar-S-methyl (Bion®) (ASM) sprayed at 0.1 mM, 0.5 mM and 0.3 g L-1, respectively, on the components of resistance of tomato plants (cv. Santa Clara) to bacterial speck caused by Pseudomonas syringae pv. tomato as well as on the activity of peroxidases (POX), polyphenoloxidases (PPO), β-1,3-glucanases (GLU) and lypoxigenases (LOX). Only for experiment 3, the incubation period significantly increased by one day for plants sprayed with ASM compared to plants sprayed with water (control). For all experiments, the number of lesions per plant was significantly reduced by JA, ET and ASM in comparison to the control. For some evaluation times, POX, PPO and GLU activities were higher for JA; PFO, GLU and LOX for ASM; and GLU and LOX for ET in comparison to the control. In conclusion, in the presence of AJ, ET and ASM, bacterial speck symptoms were reduced and the activity of the enzymes POX, PFO, GLU and LOX increased.

Resumo em Português:

A Sigatoka-negra (Mycosphaerella fijiensis) ameaça os bananais comerciais em todas as áreas produtoras do mundo e provoca danos quantitativos e qualitativos na produção, acarretando sérios prejuízos financeiros. Faz-se necessário o estudo da vulnerabilidade das plantas em diversos estádios de desenvolvimento e das condições climáticas favoráveis à ocorrência da doença. Objetivou-se com este trabalho desenvolver um modelo probabilístico baseado em funções polinomiais que represente o risco de ocorrência da Sigatokanegra em função da vulnerabilidade decorrente de fatores intrínsecos à planta e ao ambiente. Realizou-se um estudo de caso, em bananal comercial localizado em Jacupiranga, Vale do Ribeira, SP, considerando o monitoramento semanal do estado da evolução da doença, séries temporais de dados meteorológicos e dados de sensoriamento remoto. Foram gerados mapas georreferenciados do risco da Sigatoka-negra em diferentes épocas do ano. Um modelo para estimar a evolução da doença a partir de imagens de satélite foi obtido com coeficiente de determinação R² igual a 0,9. A metodologia foi desenvolvida para a detecção de épocas e locais que reúnem condições favoráveis à ocorrência da Sigatoka-negra e pode ser aplicada, com os devidos ajustes, em diferentes localidades, para avaliar o risco da ocorrência da doença em polos produtores de banana.

Resumo em Inglês:

Black Sigatoka (Mycosphaerella fijiensis) threatens the banana trade in most of world's producing areas, damaging the production and bringing significant financial loss. It is necessary to study the plant's susceptibility in the various developmental stages and climatic conditions that favor the disease occurrence. This paper presents a probabilistic model based on polynomial functions for estimating the risk of Black Sigatoka occurrence. A case study was developed in a commercial banana plantation located in Jacupiranga, Vale do Ribeira, SP, Brazil, considering the weekly monitoring of the disease's state evolution (EE), time series of meteorological data and remote sensing data. Georeferenced risk maps were prepared for different dates. We obtained a model to estimate the evolution of the disease from satellite imagery, with a coefficient of determination of 0.9. This methodology was developed for the detection of times and locations that have favorable conditions to the occurrence of Black Sigatoka and can be applied, with appropriate adjustments for different locations, to assess the risk of disease occurrence in other areas of banana production.

Resumo em Inglês:

The aim of this study was to evaluate the activity of elicitor, acibenzolar-S-methyl (ASM), in inducing resistance to Meloidogyne javanica in soybean and in enhancing plant development. Plantlets of the soybean susceptible cultivar BRSMT-Pintado and the resistant cultivar MG/BR 46 Conquista were treated with ASM (0.5 g/L) at three different times: seven days before, one day before and seven days after inoculation with 2000 eggs/plant. Untreated inoculated plants and untreated non-inoculated plants were used as controls. Sixty days after inoculation, the number of galls, eggs/g root and vegetative parameters (height, aerial part fresh and dry mass and root fresh mass) were evaluated. The experiments were conducted over two different periods (Experiments 1 and 2). Only in Experiment 2 treatment "seven days before inoculation" reduced the number of eggs/g root, irrespective of the cultivar evaluated, but the number of galls was not affected. Stronger plant development was observed in the susceptible soybean cultivar treated seven days before inoculation in Experiment 2.

Resumo em Inglês:

Cowpea mild mottle virus (CpMMV), the causal agent of stem necrosis disease, has drawn attention of soybean producers in recent years due to yield losses in the main producing regions of Brazil. Serological methods for viral detection require the use of an antiserum of good quality to achieve specificity and sensitivity. The entire coat protein gene of a Brazilian CpMMV isolate was cloned into a bacterial expression vector and transformed into Escherichia coli BL21::DE3 for in vitro expression. The coat protein, fused to a His-tag, was purified under denaturing conditions by affinity chromatography using a Ni-NTA resin. After renaturation, the integrity and identity of the purified recombinant protein was confirmed by SDS-Page and MALDI-ToF/ToF mass spectrometer analyses. A rabbit was immunized with increasing amounts of the recombinant protein. The specificity and sensitivity of the antiserum was demonstrated by Western blot and indirect ELISA assays. The polyclonal antisera raised against recombinant coat protein proved to be a reliable tool for CpMMV detection.

Resumo em Inglês:

The objective of this work was to evaluate the loss of sensitivity of Blumeria graminis f. sp. tritici (Bgt) to the fungicide triadimenol as seed treatment. The experiments were carried out in a growth chamber with temperature and photoperiod partially controlled. A mixture of four isolates of Bgt was used and maintained on potted wheat plants in the same environment. The treatments consisted of triadimenol fungicide (150 Baytan SC®) applied at three concentrations of 150, 250, 350 mL/100 kg of seeds. The inoculation was performed by placing pots with wheat plants heavily colonized by Bgt among the experimental units. After the onset of pathogen symptoms/signs, the evaluations of foliar incidence and severity were performed. The fungicide's efficiency in controlling Bgt was lower than that reported in the literature. The sensitivity of Bgt to triadimenol was not dependent on the fungicide dose, and was not significant when compared to the control treatment with no fungicide. Maximum control was 18.1% for incidence and 31.8% for severity with no significant effect between fungicide concentrations. It can be concluded that the sensitivity to the fungicide triadimenol of the tested populations of B. graminis f. sp. tritici was lost.

Resumo em Inglês:

To date, seven species of viroids have been described infecting Citrus. However, only Citrus exocortis viroid (CEVd), Hop stunt viroid (HSVd) and Citrus dwarfing viroid (CDVd) have been reported in this crop in Brazil. The aim of our work was to identify and characterize viroids infecting plants of 'Navelina ISA 315' sweet orange cultivar grafted on 'Rangpur' lime from field experiments located in Bebedouro, SP, that showed gumming in the bark and wood symptoms. Biological indexing was done on the indicator host 'Clemelin 1120' tangor plants that reacted with typical gumming symptoms. Viroid infection was assessed by graft-inoculation of buds from the field trees on 'Etrog' citron plants grafted on 'Rangpur' lime, followed by RNA extraction and sPAGE analysis. RNAs were subjected to RT-PCR with primers for citrus viroids. The full-length amplified products were sequenced and compared to those available in the GenBank. The trees were found to be infected with cachexia (Ca) variants of HSVd-Ca or HSVd-Ca plus CDVd. The results indicate that efforts have to be made to increase and stimulate the indexing programs, to maintain plants healthy and to develop sanitary programs focused on reducing the spread of viroids and other graft-transmissible agents.

Resumo em Português:

O bolor azul (Penicillium expansum) e o mofo cinzento (Botrytis cinerea) causam perdas significativas em pós-colheita de frutos de maçã. Como alternativa de controle, avaliou-se o efeito da fumigação de ácido acético, acetaldeído, benzaldeído, d-limoneno, timol, metil jasmonato e álcool etílico nas concentrações de 8 e 15 µL/L de ar sobre a germinação de esporos e sobre a incidência e a severidade dessas podridões em maçãs 'Fuji'. A germinação de esporos foi avaliada em lâminas escavadas, dispostas no interior de caixas plásticas, onde um agente fumigante atuou durante 60 min. Com microscópio ótico, observou-se, 24 h depois, que o ácido acético a 8 µL/L de ar inibiu totalmente a germinação de esporos de P. expansum, enquanto limoneno, timol, benzaldeído e metil jasmonato reduziram-na parcialmente. Apenas ácido acético e benzaldeído apresentaram efeito inibitório sobre B. cinerea. Nos testes in vivo, a fumigação ocorreu em caixas plásticas contendo quatro frutos previamente inoculados por parcela. Ácido acético reduziu a incidência de bolor azul e de mofo cinzento em 44% e 100%, respectivamente, a 8 µL/L de ar, porém causou fitotoxidez nos frutos, mostrando potencial uso para a redução de inóculo de Penicillium e Botrytis, principalmente na desinfestação das câmaras.

Resumo em Inglês:

Blue mold (Penicillium expansum) and gray mold (Botrytis cinerea) cause significant post-harvest losses of apple fruit. As a control alternative, the effects of fumigation with acetic acid, acetaldehyde, benzaldehyde, d-limonene, thymol and methyl jasmonate, at 8 and 15 µL/L of air, on the germination of spores and the incidence and severity of blue and gray mold in 'Fuji' apples were evaluated. The germination of spores was evaluated in excavated slides arranged onto plastic boxes, where the fumigant agent acted for 60 min. With optical microscopy, it was observed after 24 h that acetic acid at 8 µL/L completely inhibited spore germination of P. expansum, while limonene, thymol, benzaldehyde and methyl jasmonate partially reduced it. Only acetic acid and benzaldehyde showed an inhibitory effect on B. cinerea. In in vivo tests, fumigation was conducted in plastic boxes containing four previously inoculated fruits per plot. Acetic acid reduced the incidence of blue mold and gray mold by 44% and 100%, respectively, at 8 µL/L of air. However, it caused phytotoxicity on fruits, indicating a potential use for reduction of inoculum of Botrytis and Penicillium in the disinfestation of chambers.

Resumo em Português:

O fungo Corynespora cassiicola, agente causal da mancha-alvo em soja, tem ocorrido com frequência na região Centro-Oeste do Brasil e pode, sob condições de alta temperatura e alta umidade, causar sérios danos à cultura. O uso de cultivares resistentes ao patógeno é recomendado, porém são poucas as disponíveis no mercado. Este trabalho foi realizado visando avaliar a reação de doze cultivares comerciais de soja inoculados com C. cassiicola, em casa de vegetação e no campo. A severidade foi avaliada utilizando escala diagramática de severidade da mancha-alvo. As cultivares menos suscetíveis ao patógeno na casa de vegetação foram BRSGO 7960 e BRS Sambaíba e as mais suscetíveis foram BMX Potência RR e M-SOY 7908 RR. No campo, as cultivares menos suscetíveis foram M-SOY 8866, M-SOY 7908 RR e BMX Potência RR e as mais suscetíveis foram BRSGO 8360 e BRS Tracajá.

Resumo em Inglês:

The fungus Corynespora cassiicola, the causal agent of soybean target spot, frequently occurs in the Brazilian midwestern region. Under favorable climate conditions it can cause serious damage to this crop. The use of resistant cultivars is recommended although there are only a few available in the market. This investigation was carried out to evaluate the reaction of twelve soybean commercial cultivars to C. cassiicola. Severity was evaluated using a diagrammatic scale of target spot. The less susceptible cultivars in greenhouse were BRSGO 7960 and BRS Sambaíba and the most susceptible were BMX Potencia RR and M-SOY 7908 RR. In the field, the less susceptible cultivars were M-SOY 8866, M-SOY 7908 RR and BMX Potência RR and the most susceptible were BRSGO 8360 and BRS Tracajá.

Resumo em Português:

O objetivo deste trabalho foi estudar diferentes fontes comerciais de fosfito e acibenzolar-S-metílico (ASM) seguidos de uma aplicação de fungicida no controle do míldio, do oídio e da ferrugem asiática, para reduzir o número de aplicações de fungicidas e aumentar o espectro de controle das doenças da soja. Foram conduzidos dois experimentos na região de Ponta Grossa, PR, nas safras 2006/07 e 2007/08. O delineamento experimental utilizado foi de blocos casualizados com quatro repetições. Os tratamentos foram cinco fontes comerciais de fosfitos de potássio e uma de manganês (450 g P2O5 ha-1) e ASM (12,5 g i.a. ha-1), aplicados nos estádios V7 e R2. Os tratamentos com fosfito e ASM receberam uma aplicação do fungicida piraclostrobina + epoxiconazole (66,5 + 25 g i.a. ha-1) no estádio R3 e foram comparados com uma em R2 e duas aplicações do mesmo fungicida, aplicados em R2 e R5.1, e a testemunha. O uso de fosfito e ASM reduziram significativamente a área abaixo da curva de progresso do míldio e não tiveram efeito sobre o oídio e a ferrugem asiática. O maior número de aplicações do fungicida aumentou o controle dos patógenos biotróficos sob maior pressão das doenças.

Resumo em Inglês:

The goal of this study was to evaluate commercial sources of phosphite and acibenzolar-S-methyl (ASM) followed by one fungicide application on the control of downy mildew, powdery mildew and asian soybean rust, reducing the number of fungicide applications and increasing the control spectrum of these soybean diseases. Two field experiments were carried out in Ponta Grossa, Paraná state, Brazil, during the 2006/07 and 2007/08 growing seasons. The experimental design was of randomized blocks with four replications. Treatments consisted on five sources of potassium phosphite and one of manganese (450 g P2O5 ha-1) and ASM (12.5 g a.i. ha-1) sprayed at the V7 and R2 stages. Phosphite- and ASM-treated plants received one application of the fungicide piraclostrobine + epoxiconazol (66.5 + 25 g i.a. ha-1) at the R3 stage and were compared to plants which received two fungicide applications at the R2 and R5.1 stages, as well as to untreated plants. The use of phosphite and ASM significantly reduced the AUDPC for downy mildew. No effects were observed for powdery mildew and Asian rust. The higher number of fungicide application increased the control of biotrophic fungi under higher disease pressure.