ABSTRACT Sowing arrangements composed of double-row spacing in corn can favor the interception of solar radiation by the canopy and, consequently, the yield performance of the crop. However, it is possible that the microclimate provided by this spacing, especially at high plant densities, favors the occurrence of leaf diseases. Thus, the objective was to evaluate the effect of 0.45 m and double-row spacing arrangements on the severity of foliar diseases and yield performance of corn grown in the first and second-crop seasons. Two independent experiments were conducted (with and without the fungicide fluxapyroxad + pyraclostrobin) in the first and second-crop seasons in a randomized block design arranged in a split-plot scheme with four repetitions. The plots consisted of spacing (0.45 m) and double-row (0.30 × 0.60 m), and the subplots, four plant densities (59,200, 74,000, 81,400, and 96,200 plants ha-1). In the plant density factor, in the second-crop season, there is a decrease in the severity of white spot as plant density is increased. Also, for the plant density factor, in the first-crop season, there may be a significant yield increase as the plant density is increased.

RESUMO Arranjos de plantas compostos pelo espaçamento fileira dupla no milho podem favorecer a interceptação da radiação solar pelo dossel e, consequentemente, o desempenho produtivo da lavoura. Entretanto, é possível que o microclima proporcionado por este espaçamento, sobretudo em altas densidades de plantas, favoreça a ocorrência de doenças foliares. Assim, objetivou-se avaliar o efeito de arranjos compostos pelos espaçamentos de 0,45 m e fileira dupla sobre a severidade de doenças foliares e o desempenho produtivo do milho cultivado em 1a e 2a safra. Foram conduzidos dois experimentos independentes (com e sem o fungicida fluxapiroxade + piraclostrobina) na 1a e 2a safra, em delineamento em blocos ao acaso com parcelas subdivididas, com quatro repetições. As parcelas consistiram nos espaçamentos (0,45 m) e fileira dupla (0,30 × 0,60 m), e as subparcelas, quatro densidades de plantas (59.200, 74.000, 81.400 e 96.200 plantas ha-1). No fator densidade de plantas, na 2a safra, há decréscimo na severidade da mancha branca conforme adensamento de plantas. Ainda, também para o fator densidade, na 1a safra, pode haver incremento significativo na produtividade em função do adensamento de plantas.

ABSTRACT The growth and yield performance of white oat cultivars may vary in response to doses of trinexapac-ethyl (TE) growth regulator. The objective of the work was to evaluate the lodging and productive performance of white oat cultivars under different doses of trinexapac-ethyl growth regulator. The experiments were carried out in a randomized complete block design with four replications, in a 4 x 2 factorial scheme, with four doses of trinexapac-ethyl (0, 50, 100 and 150 g ha-1) applied in the phenological stage between the 1st visible stalk node and the 2nd perceptible node in two white oat cultivars (URS Altiva and URS Corona). The following were evaluated: plant height, panicle length, panicles per m2, spikelets per panicle, grains per spikelet, number of grains per panicle, thousand grain weight, plant lodging and grain yield. The application of trinexapac-ethyl at doses 100 and 150 g ha-1 reduces plant height and panicle components: length, number of spikelets and grains per panicle of the two cultivars. TE doses above 100 g ha-1 provide a significant reduction in lodging with an increase in the number of panicles per m2 and in grain yield for the two white oat cultivars.

RESUMO Estresses abióticos associados causam efeitos e respostas diferentes da exposição a uma única fonte de estresse. Objetivou-se avaliar o efeito do estresse combinado de temperatura supraótima e déficit hídrico no processo germinativo de lotes de sementes de trigo com diferentes níveis de vigor. Sementes de trigo IPR Catuara de quatro lotes foram submetidas a germinação nos potenciais hídricos 0,000, - 0,075, - 0,223 e - 0,444 MPa, associados às temperaturas 20, 24, 28 e 32 ºC, totalizando 16 combinações de estresse. O delineamento experimental foi inteiramente casualizado, com quatro repetições, em esquema fatorial: quatro lotes x 16 combinações de estresse, e comparação de médias por Scott-Knott 5%. Avaliaram-se a germinação das plântulas normais aos quatro e oito dias, o conteúdo de proteína total e a atividade da catalase e ascorbato peroxidase (APX) na parte aérea e radicular das plântulas. As análises de componentes principais e de agrupamento hierárquico foram aplicadas à matriz original formada pelas 16 combinações, para a média dos quatro lotes. Sementes de trigo de maior vigor são mais tolerantes a combinação dos estresses hídrico e térmico. Não há prejuízo ao processo germinativo de trigo nas combinações sob temperaturas supraótimas até 28 °C e redução dos potenciais hídricos até -0,223 MPa. Independente da temperatura, o potencial hídrico -0,444 MPa diminui a porcentagem e a velocidade da germinação. A atividade da APX aumenta em condições de estresses hídrico e térmico atuando como defesa ao estresse oxidativo na germinação de trigo.

ABSTRACT Combined abiotic stresses have different effects and responses than exposure to a single source of stress. The objective of this study was to evaluate the effect of the combined stress of supra-optimal temperatures and water deficit on the germination of wheat seeds with different levels of vigor. Wheat seeds from four different lots of the IPR Catuara cultivar were germinated at water potentials of 0.000, -0.075, -0.223, and -0.444 MPa, associated with temperatures of 20 °C, 24 °C, 28 °C, and 32 °C, totaling 16 stress combinations. The experimental design was completely randomized in a factorial scheme with four replications (four seed lots × 16 stress combinations), and means were compared using Scott-Knott 5%. We evaluated the germination of normal seedlings at 4 and 8 d, the activity of catalase and ascorbate peroxidase (APX), and the protein content of the aerial and root parts of wheat seedlings. Principal components analysis and hierarchical clustering were applied to the original matrix formed by the 16 combinations for the average of the four lots. Wheat seeds with higher vigor were more tolerant to combined water and thermal stress. Temperatures up to 28 °C and reduction of water potentials down to -0.223 MPa did not prejudice the germination process of wheat seeds. Regardless of temperature, a water potential of -0.444 MPa decreased the percentage and rate of germination. APX activity increased under water stress and supra-optimal temperatures, acting as a defense mechanism against oxidative stress.

RESUMO As características agronômicas e físicas do milho são fundamentais para produtores e indústrias que utilizam este cereal como matéria-prima, pois, interferem nos processos de industrialização, rendimento e qualidade dos produtos finais. Desse modo, o objetivo com este estudo foi avaliar as características agronômicas e físicas do grão de híbridos de milho transgênicos e convencionais cultivados na primeira safra (verão) no Estado do Paraná. Foram instalados três experimentos, nas safras agrícolas 2017/18, 2018/19 e 2019/20. O delineamento experimental utilizado foi de blocos casualizados com oito híbridos: (Supremo Vip, Supremo, P30F53VYH, P30F53, P3456H, P3456, DKB290PRO3, DKB290) e três repetições. Foram avaliadas as características físicas dos grãos para fins industriais como a canjica, gérmen, vitreosidade, flutuação e peso hectolitro, e as características agronômicas como a porcentagem de grãos ardidos, peso de mil grãos e produtividade de grãos. A canjica e gérmen são influenciados pela escolha do híbrido e pela safra agrícola avaliada, em que os híbridos Supremo (convencional), Supremo Vip (transgênico) e P3456 (convencional) apresentaram os melhores resultados. As características físicas de flutuação, peso hectolitro e vitreosidade foram influenciadas pela escolha do híbrido e safra agrícola avaliada, destacando-se os híbridos Supremo (convencional), Supremo Vip (transgênico), P30F53 (convencional), P30F53 VYH (transgênico), P3456 (convencional), P3456 VYH (transgênico), com os melhores resultados. Os híbridos convencionais mostraram superioridade industrial comparados aos híbridos transgênicos para canjica, flutuação e vitreosidade.

ABSTRACT The agronomic and physical traits of corn are fundamental for producers and industries that use this cereal as a raw material since they interfere in the industrialization processes, yield, and quality of the final products. This study aimed to evaluate the agronomic and physical traits of the grain in transgenic and conventional corn hybrids grown in the first crop season (summer) in Paraná State. Three experiments were set up in 2017/18, 2018/19, and 2019/20 crop seasons. A randomized block design with three replications was used. Eight hybrids (Supremo Vip, Supremo, P30F53VYH, P30F53, P3456H, P3456, DKB290PRO3, DKB290) were evaluated. The physical traits of grains for industrial purposes, such as grits, germ, vitreousness, flotation, and hectoliter weight, and the agronomic traits (percentage of rot grains, 1000-grain weight, and grain yield) were evaluated. The hybrids and crop seasons influence the industrial physical traits of grits and germ. The hybrids Supremo (conventional), Supremo Vip (transgenic), and P3456 (conventional) had the best results. The hybrids and crop season influenced the flotation, hectoliter weight, and vitreousness, highlighting the hybrids Supremo (conventional), Supremo Vip (transgenic), P30F53 (conventional), P30F53 VYH (transgenic), P3456 (conventional), P3456 VYH (transgenic), with the best results. The conventional hybrids showed industrial superiority compared to transgenic hybrids for grits, flotation, and vitreousness.

ABSTRACT The identification of pod- and seed-related traits of soybean genotypes and their interaction with water uptake can be applied in breeding programs with a view to establishing cultivars developed for the production and maintenance of high-quality seeds. The objective was to evaluate the water uptake of pods and seeds of soybean cultivars with different lignin contents after different soaking periods. The experimental was arranged in a completely randomized, 7×10 factorial design, with four replications. The factors consisted of seven soybean cultivars and 10 soaking periods (1, 2, 3, 4, 5, 6, 7, 8, 24, 48 hours). The pods and seeds were grown in a greenhouse and harvested at the phenological growth stage R8 (at full maturation, when 95% of the pods had mature color). The following traits were evaluated: lignin content in pod and seed coat, moisture content, and rate of water uptake of pods and seeds. Soybean cultivars with pods with high lignin contents have a lower rate of water uptake. The lignin contents of the seed coats, within the chosen limits, did not affect the seed water uptake.

RESUMO Embora comprovados os efeitos isolados das cianobactérias Anabaena cylindrica bem como da bactéria Azospirillum brasilense, na fixação biológica de nitrogênio e na promoção de crescimento de plantas de milho, a co-inoculação de ambas pode ampliar outros benefícios às plantas. O objetivo foi avaliar o crescimento inicial e teores de pigmentos cloroplastídicos de híbridos de milho co-inoculados com A. brasilense e A. cylindrica. O experimento foi conduzido em condições de casa de vegetação sob o delineamento inteiramente casualizado, em esquema fatorial 2 × 4, com dois híbridos: Balu 184 e Balu 280 Pro e quatro tratamentos de inoculação: ausência de inoculação, inoculação de A. cylindrica, inoculação de A. brasilense e a co-inoculação de A. cylindrica + A. brasilense. A co-inoculação resultou no maior crescimento da raiz e massa seca da parte aérea nos dois híbridos, porém com maior responsividade para o híbrido Balu 280 Pro. A co-inoculação combinada de A. brasilense e A. cylindrica incrementou o crescimento inicial do milho, sem alterações nos teores dos pigmentos fotossintéticos.

ABSTRACT Although the isolated effects of the cyanobacteria Anabaena cylindrica and the bacteria Azospirillum brasilense are well-known, the co-inoculation of both can promote other benefits to corn plants’ biological nitrogen fixation and growth. The aim was to evaluate the initial growth and chloroplast pigment levels of corn hybrids co-inoculated with A. brasilense and A. cylindrica. The experiment was conducted in greenhouse conditions using the completely randomized design in a factorial scheme 2 × 4 with two hybrids, Balu 184 and Balu 280 Pro, and four inoculation treatments: no inoculation, inoculation of A. cylindrica, inoculation of A. brasilense, and the co-inoculation of A. cylindrica + A. brasilense. Co-inoculation resulted in higher root growth and dry mass of the aerial part in both hybrids; however, the hybrid Balu 280 Pro presented higher responsivity. The co-inoculation of A. brasilense and A. cylindrica increased initial corn growth without altering the photosynthetic pigment levels.

ABSTRACT. Seed coat characteristics may be related to seed quality and longevity, attracting the interest of breeding programs. This study aimed to evaluate the relationship between the water absorption parameters and storage tolerance of soybean seeds with contrasting seed coat characteristics. For this purpose, seeds of five soybean cultivars with different seed coat colors and lignin contents were used. Before storage, the seed coat lignin content, moisture content, water absorption rate in 11 hydration periods (1, 2, 3, 4, 5, 6, 7, 8, 24, 32, and 48 hours), hydration speed index, germination, viability, and seed vigor were determined. After six months of storage in a dry and cold chamber (at 11ºC and 54% relative humidity [RH]) and uncontrolled environment (at 25ºC and 71% RH), the seeds were evaluated for germination, viability, and vigor to quantify changes in their physiological quality during storage and relate them to the seeds water absorption parameters for the different cultivars. The seed coat lignin content is negatively correlated with the seeds water absorption parameters. Soybean cultivars have different storage tolerance levels. Seeds that absorb larger amounts of water have lower tolerance to deterioration related to temperature and relative humidity fluctuations that occur in storage under uncontrolled conditions, negatively affecting the physiological potential of seeds.

Resumo: Os nutrientes minerais desempenham importante papel na composição das sementes, influenciando a taxa de germinação e a produção de plântulas vigorosas, o que é fundamental para o estabelecimento do estande de plantas e produtividade da cultura. O objetivo deste trabalho foi avaliar o efeito da adubação fosfatada sobre o teor de fósforo (P) e a qualidade fisiológica de sementes de cultivares de trigo. Foi utilizado delineamento em parcelas subdivididas 2 × 16, sendo duas doses de P (0 e 140 kg.ha-1) e 16 genótipos de trigo (cultivares BR 18, BR 23, BRS 208, BRS 254, BRS 264, BRS 404, BRS Graúna, BRS Pardela, BRS Sabiá, WT 15025, CD 118, IPR Catuara, Ocepar 14, Supera, TBIO Bandeirante e TBIO Iguaçu). Foram avaliados: primeira contagem, germinação, envelhecimento acelerado, emergência e comprimento de plântulas, condutividade elétrica, índice de velocidade de emergência, teor de P nas sementes e massa de mil sementes. Os dados de doses de P e genótipos de trigo foram submetidos à análise de variância e à comparação de médias pelo teste F e teste de Scott-Knott, respectivamente. As sementes da BR 18 e Ocepar 14 apresentaram maior qualidade fisiológica, enquanto as sementes da TBIO Iguaçu, CD 118 e BRS Sabiá apresentaram menor vigor. A adubação fosfatada proporciona a produção de sementes de trigo com maior teor de P e qualidade fisiológica, mas não influência a massa de mil sementes da maioria das cultivares de trigo.

Abstract: Mineral nutrients play an important role in the composition of seeds, influencing the germination rate and the production of vigorous seedlings, which is fundamental for the establishment of the plant stand and crop yield. This work aimed to evaluate the effect of phosphate fertilization on phosphorus (P) content and the physiological quality of seeds of wheat cultivars. A 2 × 16 split plot design was used, with two rates of P (0 and 140 kg.ha-1) and 16 wheat genotypes (cultivars BR 18, BR 23, BRS 208, BRS 254, BRS 264, BRS 404, BRS Graúna, BRS Pardela, BRS Sabiá, WT 15025, CD 118, IPR Catuara, Ocepar 14, Supera, TBIO Bandeirante and TBIO Iguaçu). The evaluation includes: first count, germination, accelerated aging, seedling emergence and length, electrical conductivity, emergence speed index, P content in seeds, and thousand-seed weight. The data of P rates and wheat genotypes were subject to analysis of variance and to the comparison of means by the F-test and Scott-Knott test, respectively. The seeds of BR 18 and Ocepar 14 showed higher physiological quality, whereas the seeds of TBIO Iguaçu, CD 118, and BRS Sabiá showed lower vigor. Phosphate fertilization provides the production of wheat seeds with higher P content and physiological quality, but it does not influence the thousand-seed weight of most wheat cultivars.

Resumo: A combinação ótima entre densidade de semeadura e dose de nitrogênio (N) na adubação é um desafio para a produção de sementes de alta qualidade, considerando a diversidade de genótipos e ambientes. O objetivo deste trabalho foi avaliar o rendimento e a qualidade fisiológica de sementes de trigo em função da densidade de semeadura e dose de N, em diferentes condições edafoclimáticas. O experimento foi conduzido em três ambientes (Londrina, Cascavel e Ponta Grossa) em delineamento em blocos casualizados com quatro repetições, considerando um arranjo fatorial 2 × 3 × 4 composto por dois genótipos (BRS Anambé e WT 15-025), três densidades de semeadura (250, 350 e 450 sementes.m-2) e quatro doses de N (0, 40, 80 e 120 kg.ha-1). Foram avaliadas as seguintes características de sementes: rendimento, primeira contagem de germinação, germinação final de sementes, emergência de plântulas, índice de velocidade de emergência, comprimento de plântula e massa seca de plântula. O rendimento de sementes variou em função do ambiente e do genótipo. BRS Anambé produziu sementes com maior qualidade fisiológica. A combinação ótima entre densidade de semeadura e dose de N que proporcionou o rendimento econômico mais adequado, sem afetar a qualidade fisiológica de sementes de trigo, variou com o ambiente e foi estimada em 250 sementes.m-2 × 0 kg.ha-1 N para Londrina e Cascavel, e 350 sementes.m-2 × 18 kg.ha-1 N para Ponta Grossa.

Abstract: The optimal combination between sowing density and nitrogen (N) fertilization rate is a challenge for the production of high-quality seeds, considering the diversity of genotypes and environments. This study aimed to evaluate the yield and physiological quality of wheat seeds as a function of sowing density and N rate, under different edaphoclimatic conditions. The experiment was carried out in three environments (Londrina, Cascavel, and Ponta Grossa) in a randomized block design with four replications, considering a 2 × 3 × 4 factorial arrangement composed of two genotypes (BRS Anambé and WT 15-025), three sowing densities (250, 350, and 450 seeds.m−2), and four N rates (0, 40, 80, and 120 kg.ha−1). The following seed features were evaluated: yield, first germination count, final seed germination, seedling emergence, emergence speed index, seedling length, and seedling dry matter. Seed yield varied as a function of environment and genotype. BRS Anambé produced seeds with higher physiological quality. The optimal combination between sowing density and N rate that provided the more suitable economic yield, without affecting the physiological quality of wheat seeds, varied with the environment and was estimated in 250 seeds.m−2 × 0 kg.ha−1 N for Londrina and Cascavel, and 350 seeds.m−2 × 18 kg.ha−1 N for Ponta Grossa.

Resumo O objetivo deste trabalho foi analisar estruturalmente as vagens e os tegumentos de cultivares de soja (Glycine max), bem com determinar a qualidade das sementes quando submetidas à deterioração por umidade em pré-colheita. Utilizou-se arranjo fatorial 7×3 – sete cultivares e três volumes de precipitações pluviais simuladas (0, 54 e 162 mm). A exposição à chuva foi simulada no estádio fenológico R8. Em seguida, as plantas foram levadas à casa de vegetação, onde foram mantidas até a coleta das vagens e das sementes. Após a coleta, realizaram-se as seguintes avaliações: teste de tetrazólio, teor de lignina nas vagens e nos tegumentos, e análise estrutural de vagens (espessura do exocarpo, do mesocarpo e do endocarpo) e tegumentos (espessura da epiderme, da hipoderme e das células parenquimatosas). Precipitações de 54 e 162 mm em pré-colheita reduzem a qualidade das sementes de soja; entretanto, a resposta à deterioração por umidade difere de acordo com a cultivar. A tolerância a todas as precipitações pluviais simuladas foi maior para BRSMT Pintado, BRS Jiripoca e M8210IPRO e menor para BRS 1010IPRO. Vagens com maior espessura do exocarpo, do mesocarpo e do endocarpo e elevados teores de lignina apresentam maior tolerância à deterioração por umidade e sementes com maior vigor e viabilidade. A espessura da hipoderme da testa de tegumentos está relacionada à tolerância à deterioração por umidade e à obtenção de sementes de elevada qualidade.

Abstract The objective of this work was to analyze structurally the pods and seed coats of soybean (Glycine max) cultivars, as well as to determine the quality of seeds when subjected to deterioration by weathering in pre-harvest. A 7×3 factorial arrangement was used – seven cultivars and three volumes of simulated rainfall (0, 54, and 162 mm). Exposure to rainfall was simulated in the R8 phenological stage. Then, the plants were taken to a greenhouse, where they were kept until the time of collection of pods and seeds. After collection, the following evaluations were carried out: tetrazolium test, lignin content in pods and seed coats, and structural analysis of pods (exocarp, mesocarp, and endocarp thickness) and seed coats (epidermis, hypodermis, and parenchymal-cell thickness). Pre-harvest rainfall of 54 and 162 mm reduces the quality of soybean seeds; however, the response to deterioration by weathering differs according to the cultivar. The tolerance to all simulated rainfall was greater for BRSMT Pintado, BRS Jiripoca, and M8210IPRO and lower for BRS 1010IPRO. Pods with a greater thickness of the exocarp, mesocarp, and endocarp and a high lignin content show greater resistance to weathering deterioration and seeds with greater vigor and viability. The thickness of the hypodermis of the testa is related to resistance to weathering deterioration and to the obtainment of high-quality seeds.

Resumo: Sementes de soja podem apresentar respostas diferenciadas à deterioração por umidade, em função das características intrínsecas do material genético e da intensidade e duração do período de precipitação pluvial. O objetivo foi avaliar o efeito da deterioração por umidade em pré-colheita sobre a qualidade e composição química de sementes de soja com diferentes teores de lignina na vagem e no tegumento. Foram avaliados a porcentagem de danos por umidade pelo teste de tetrazólio, teste de raios-X, teor de lignina na vagem e no tegumento, germinação, envelhecimento acelerado, emergência de plântulas, análise sanitária, teores de óleo, proteína e de clorofila. O delineamento experimental foi inteiramente casualizado, em esquema fatorial 7×3 (sete cultivares e três volumes de precipitações pluviais: 0, 54 e 162 mm; simuladas quando 95% das vagens apresentavam coloração madura). A qualidade fisiológica e sanitária das sementes reduz com o aumento das precipitações pluviais em pré-colheita. Sementes oriundas de cultivares com maiores teores de lignina na vagem apresentam maior tolerância à deterioração por umidade em pré-colheita e proporcionam sementes de melhor qualidade fisiológica. O teor de óleo e proteína das sementes é reduzido conforme se aumenta as precipitações pluviais, em algumas cultivares. Plantas com maiores teores de lignina nas vagens produzem sementes com menor incidência do fungo Cercospora kikuchii e menor teor de clorofila quando associado a precipitações pluviais em pré-colheita.

Abstract: Soybean seeds may show different responses to weathering deterioration depending on the intrinsic characteristics of the genetic material and the intensity and duration of the rainfall period. This study aimed to evaluate the effect of pre-harvest weathering deterioration on the quality and chemical composition of soybean seeds with different lignin contents in the pod and seed coat. The percentage of weathering damage was evaluated by the tetrazolium test, X-ray test, lignin content in the pod and seed coat, germination, accelerated aging, seedling emergence, seed health test, and oil, protein, and chlorophyll contents. The experimental design was completely randomized in a 7×3 factorial scheme, that is, seven cultivars and three rainfall volumes (0, 54, and 162 mm), simulated when 95% of the pods had a mature color. The physiological and sanitary quality of soybean seeds reduces with an increase in pre-harvest rainfall. Soybean seeds from cultivars with higher lignin contents in the pod present a higher tolerance to pre-harvest weathering deterioration and provide seeds of better physiological quality. Seed oil and protein content is reduced in some cultivars as rainfall increases. Plants with higher lignin contents in the pods produce seeds with a lower incidence of the fungus Cercospora kikuchii and lower chlorophyll content when associated with pre-harvest rainfall.

ABSTRACT. Precrops have different growth patterns, nitrogen (N) requirements, and production of residues varying in amounts and quality that may affect the N-clycling and the soybean (Glycine max L. Merrill) cropped in succession. This study aimed to evaluate the effect of precrops and N fertilization on soybean performance. An experiment was conducted in Londrina, Paraná State, Brazil, with six precrops treatments: fallow, ruzigrass (Urochloa ruziziensis), showy rattlebox (Crotalaria spectabilis), corn (Zea mays) without or with 80 kg ha−1 of N at topdressing as urea, and wheat (Triticum aestivum). Subplots consisted of two levels of N fertilization at soybean sowing: 0 and 30 kg ha−1 of N as ammonium nitrate at sowing. Urochloa ruziziensis as precrops increased the soybean yield (5,171 kg ha-1) when compared with corn (4,346 kg ha-1) and fallow (4,467 kg ha-1). In 2016/17, N fertilization of soybean with 30 kg ha−1 of N at sowing, although increasing the initial plant growth (745 kg ha-1 with vs. 662 kg ha-1 without), impairs nodulation (100 mg pl-1 with vs. 130 g pl-1 without) and does not increase grain yield. Oil and protein concentrations in soybean grains are not influenced by precrops and N fertilization at sowing. We found that the use Urochloa ruziziensis as cover crop in soybean precrops is a good recommendation option in tropical regions of Brazil, because increasing the yield of soybean grown in succession. N fertilization at in soybean sowing it should not be recommended even in the presence of a large amount of straw.

ABSTRACT Differences in seed storage tolerance between soybean cultivars have been frequently observed. Thus, identifying compounds found in them that may be related to these differences is necessary to support the selection of cultivars with seeds with better storage potential. Therefore, this study aimed to evaluate changes in viability and vigor of soybean seeds during storage in two environments, relating them to antioxidant activity, production of reactive oxygen species, and metabolites of the phenylpropanoid pathway. The experimental design was completely randomized in a 4 × 5 factorial scheme (storage periods × cultivars). Cultivars with contrasting characteristics of lignin content, seed coat color, and isoflavone content in the seed were used, stored for six months in a cold and dry chamber and an uncontrolled environment. Every two months, viability and vigor, enzymatic activity (superoxide dismutase and catalase), and hydrogen peroxide content were evaluated. Storage in a cold and dry chamber maintains seed viability of cultivars A, C, and D; it is reduced in all cultivars in an uncontrolled environment. Seed vigor is reduced during storage. There is no association between the seeds’ physiological quality and the superoxide dismutase and catalase activities. The increase in the hydrogen peroxide content in the seed coat is an indicator of the reduction in the seed physiological quality when stored in an uncontrolled environment. The difference in deterioration tolerance during storage is associated with the lignin content in the seed coat.

ABSTRACT Increases in plant density associated with the use of plant growth regulators, aside from modifying the plant architecture, can also change the maize yield performance. This study aims to investigate the yield components and grain yield of maize hybrids with contrasting leaf architecture, in response to different plant populations and trinexapac-ethyl rates (TE). Field experiments were conducted in two growing seasons, in a (5 x 5) factorial randomized block design. The treatments consisted of: five plant population (40, 60, 80, 100, and 120 thousand plants ha-1) and five TE rates (0, 100, 200, 300, and 400 g a.i. ha-1), with four replications, using the hybrids 2B710 HX and Status TL. We evaluated the number of rows per ear, ear length, number of grains per row, 1000-grain mass, and yield. An increased plant density reduces ear length, number of grains per row and 1000-grain mass, without changing the number of grain rows per ear. TE rates increases ear length and number of grains per row and reduces 1000-grain mass, mainly under favorable cultivation conditions. TE interacts with the plant density, changing the maize yield components with increases in grain yield, but these gains variy, according to the environment and genotype characteristics.

ABSTRACT Nitrogen fertilization, besides increasing productivity, can favor the production of well-formed, large, and heavy grains, which are traits valued by the oat processing industry. However, high nitrogen (N) doses may lead to plant lodging, which could be solved by using growth retardant. This study aimed to evaluate the industrial quality of white oat grains cultivated under different nitrogen doses and associated with the growth retardant trinexapac-ethyl in two growing environments. Experiments were conducted in Londrina and Mauá da Serra, PR, Brazil, using the cultivar IPR Afrodite in a randomized block design in a 4 × 2 factorial scheme and four replications. Treatments consisted of four topdressing N doses (0, 30, 60, and 90 kg ha−1) and the application or not of growth retardant. Thousand-grain weight, hectoliter weight, grain index greater than two millimeters, peeling index, and industrial grain yield were evaluated. The effect of N fertilization and growth retardant on the industrial quality of white oat grains depends on the characteristics of the growing environment. The trinexapac-ethyl application reduces grain quality in Londrina and Mauá da Serra. However, the industrial quality of grains is high in both growing environments when the growth retardant is associated with nitrogen doses.