José de Barros França-Neto

Gene expression profiling of the green seed problem in Soybean

BackgroundDue to the climate change of the past few decades, some agricultural areas in the world are now experiencing new climatic extremes. For soybean, high temperatures and drought stress can potentially lead to the “green seed problem”, which is characterized by chlorophyll retention in mature seeds and is associated with lower oil and seed quality, thus negatively impacting the production of soybean seeds.ResultsHere we show that heat and drought stress result in a “mild” stay-green phenotype and impaired expression of the STAY-GREEN 1 and STAY-GREEN 2 (D1, D2), PHEOPHORBIDASE 2 (PPH2) and NON-YELLOW COLORING 1 (NYC1_1) genes in soybean seeds of a susceptible soybean cultivar. We suggest that the higher expression of these genes in fully mature seeds of a tolerant cultivar allows these seeds to cope with stressful conditions and complete chlorophyll degradation.ConclusionsThe gene expression results obtained in this study represent a significant advance in understanding chlorophyll retention in mature soybean seeds produced under stressful conditions. This will open new research possibilities towards finding molecular markers for breeding programs to produce cultivars which are less susceptible to chlorophyll retention under the hot and dry climate conditions which are increasingly common in the largest soybean production areas of the world.

Physiological quality of dynamically cooled and stored soybean seeds 1

Storage is an important step in the production of soybean seeds, mainly in tropical regions, where high temperatures can drastically reduce seed quality. The storage at cooler temperatures may be a feasible alternative to preserve seed quality during storage. The objective of this study was to evaluate the physiological quality of soybean seeds artificially cooled by a dynamic process and stored in an environment, with non controlled temperature and relativity humidity. Two seed lots of cultivars Monsoy 8757, TMG 115 RR and BRS Valiosa RR were used. After processing and during packaging the seeds were cooled to 18 o C by a dynamic process. Seed samples were collected after 0, 60 and 120 days of storage, using the following parameters germination, accelerated aging, seedling emergence in sand, speed of emergence index, electrical conductivity, tetrazolium and seed health. Although soybean seeds artificially cooled by the dynamic method may have slightly superior performance in maintaining physiological quality during storage in non-refrigerated warehouse, for lots of high physiological quality, these advantages are not observed.

Incidence of green soybean seeds as a function of environmental stresses during seed maturation.

Condicoes climaticas desfavoraveis, principalmente na regiao Central do Brasil, durante o periodo de maturacao da soja, tem ocasionado o aparecimento de semente de soja verde. Essa incidencia, em condicoes de campo, pode variar em funcao de aspectos como a epoca de ocorrencia ou o tipo de estresse a que as plantas sao submetidas. Os objetivos desta pesquisa foram: verificar em qual estadio de desenvolvimento da planta a imposicao de estresses de temperatura e deficiencia hidrica propicia maior ocorrencia de semente verde, e observar a variacao dessa ocorrencia em diferentes partes da planta e seus efeitos sobre a qualidade fisiologica de sementes de soja. Sementes da cultivar CD 206 foram produzidas em casa de vegetacao permanecendo ate o estadio de desenvolvimento R5.5. Na fase final de maturacao da soja, nos estadios R6 e R7.2, as plantas foram transferidas para câmaras de crescimento (fitotrons), para a inducao de estresse termico, com temperaturas elevadas (variacoes de 28oC a 36oC) e temperaturas amenas (variacoes de 19oC a 26oC). Para o estresse hidrico, a quantidade de agua nos vasos foi controlada nos seguintes niveis: testemunha (suprimento adequado de agua); 30% de umidade gravimetrica (Ug); 20% de Ug; e sem agua (corte total de irrigacao). A qualidade da semente, colhida no estadio R9, foi avaliada pelos testes de germinacao, tetrazolio e condutividade eletrica. Determinou-se, ainda, o peso de 100 sementes e a porcentagem de semente verde em diferentes posicoes na planta. A porcentagem de ocorrencia de semente verde variou de 9% a 86% em funcao da variacao de umidade e de temperatura. A imposicao de estresses de elevada temperatura e corte total de irrigacao, no estadio de desenvolvimento R6, propiciaram acentuada ocorrencia de sementes verdes. Estresse hidrico intenso (20% de Ug e corte total de irrigacao) em R6 e R7.2, quando associado com temperaturas amenas, nao resulta na ocorrencia de indices significativos de semente verde. Nao existem variacoes de ocorrencia de semente verde nas diferentes partes da planta, no que se refere a sua posicao nos tercos inferior, medio e superior. A qualidade fisiologica de sementes de soja e afetada negativamente pela incidencia de semente verde. Com base nos resultados do presente trabalho, foi desenvolvida metodologia em fitotron, visando a selecao de genotipos de soja quanto a sua tolerância ou suscetibilidade a producao de sementes esverdeadas.

Validação do zoneamento ecológico do estado do Paraná para produção de sementes de soja

This study was carried out to determine the ecological regions most suitable for soybean seed production in the State of Parana, Brazil. At harvest, 121 seed samples of the cultivars BR 16 and 119 samples of BRS 133 were collected from different regions in the state, from 1997 to 2002. Growing season seed quality evaluations were: standard germination and the tetrazolium test for field deterioration, mechanical damage and stink bug attack. Three regions were previously defined based upon mean temperature (MT) in February;:T1 region, with AT>24oC; T2, with AT between 22 and 24oC; and T3, with AT< 22oC. The region T3 produced the best quality seeds followed by regions T2 and T1. Mechanical damage during harvest significantly reduced seed quality, especially in regions T1 and T2. In general, region T3 was the most favorable area for production with high quality seed. Other factors, such as mechanical damage and stink bugs, were responsible for lowering seed quality of two soybean cultivars produced in the State of Parana. Based on the climatic chart of the State of Parana and the results obtained in this trial we can infer that the validation of ecological zoning is a solid alternative for seed producers in the State of Parana to search for suitable areas in which high quality soybean seed production is possible.

Épocas de tratamento de sementes no estabelecimento e desempenho produtivo da cultura da soja

The objective was to assess the early treatment effect of soybean seeds and pre-sowing with different combinations of chemicals on the establishment of plants and crop yield performance. The design was in randomized blocks in a 2x7 factorial arrangement, with two times for seed treatment and seven treatments (six chemical treatments and an untreated control). The treatments were: 1) fipronil + pyraclostrobin + thiophanate methyl; 2) imidacloprid + thiodicarb + carbendazin + thiram; 3) abamectin + thiamethoxam + fludioxonil + mefenoxam + thiabendazole; 4) carbendazin + thiram; 5) fludioxonil + mefenoxam + thiabendazole; 6) carboxin + thiram; and 7) untreated control (water only). The assessments were: seedling emergence, final stand, plant height and insertion of first pod, number of pods per plant, seeds per pod and per plant, thousand-seed weight and grain yield. Early treatment of soybean seeds (240 days prior to sowing) hinders the establishment of the crop, the thousand-seed weight and grain yield in relation to the pre-sowing treatment. Chemical treatments tested containing fungicides and insecticides associated favor the establishment of the crop, but do not alter the soybean yield performance.

Qualidade fisiológica de sementes de soja colhidas em duas épocas após dessecação com glyphosate

Pre-harvest desiccation of soybean plants with glyphosate has been routinely conducted by seed producers, although it is not recommended because it may reduce seed physiological quality. The objective of this study was to evaluate the effects of the pre-harvest desiccation of plants with glyphosate on the physiological quality of soybean seeds harvested at two different periods after application. The experimental design was completely randomized blocks, with four replications and subdivided plots. Main plots consisted of the presence and absence of a pre-harvest desiccation of soybean plants with glyphosate at the R7 stage, and subplots of seeds harvested 7 and 14 days after application. Moisture content, mechanical damage, viability, weight of 100 seeds, protein content and accumulation of glyphosate residues were determined after harvest. Physiological quality was evaluated by tests for germination, accelerated aging, electrical conductivity, seedling length and seedling dry matter. Pre-harvest desiccation of soybean plants with glyphosate reduces seed germination and seedling development. Delayed harvesting reduces the germination of soybean seeds produced by plants desiccated with glyphosate, but minimizes phytotoxicity in seedling development.

Relação entre a permeabilidade da vagem e a qualidade da semente de soja

The aim of this study was to evaluate the influence of pod wall permeability on the physiological quality of soybean seed. The cultivars studied were Sant’Ana, FT-2, FT-10, Bossier, Davis and the breeding line F 84-7-30, with a black seed coat. Pods were collected from plants at the R4, R5, R6, R7 and R8 development stages, which composed the treatments in regard to time of harvest. The parameters of permeability and the lignin content of the pods and the seeds within the pods were evaluated. The seeds were collected just after full maturity (R8), and the following tests were performed: germination, electrical conductivity, and tetrazolium, which determined seed viability and vigor. A randomized complete block design in a split-plot in time arrangement was used, with four replications per treatment. The soybean genotypes (six) composed the plots, and the split-plots consisted of the development stages (R4, R5, R6, R7 and R8). In seed evaluation, the same design was used, reducing the number of treatments to three in the split-plots (R6, R7 and R8). Pod permeability varied with the genotype and stage of development; this affected seed vigor, but not the viability of newly-harvested seeds. The pod lignin content did not show any influence on pod permeability.

Adaptação do teste de tetrazólio para avaliação da viabilidade e do vigor de sementes de girassol

The objective of this work was to evaluate methodologies for performing the tetrazolium test in the evaluation of the viability and vigor of sunflower seeds, and to establish seed quality classes for test interpretation. Different methodologies were evaluated for extracting the pericarp and seed coat, besides water priming for 16 and 18 hours (25°C), and staining with tetrazolium solution (30oC) at the concentrations of 0.1 and 0.5%, for 2, 3, and 4 hours; and of 1.0%, for 1, 2, and 3 hours. After the definition of the most adequate methodology for performing the test, vigor classes were established according to seedling emergence on field. Five vigor classes were established, which had perfect correlation with seedling emergence. For the viability assessment of sunflower seeds, the pericarp and the seed coat should be removed after a lengthwise cut of up to 1/3 seed length, water priming should be carried out for 16 hours, and staining should be done with tetrazolium solution at 0.1%, during 3 hours.

Effects of phosphine fumigation on the quality of soybean seeds 1

Fumigation is a technique employed to eliminate insect pests in stored seeds by using gas. The aim of the experiment was to evaluate the effect of the gas phosphine on germination and on vigor (accelerated aging and seedling length) of soybean seeds. Soybean seeds of two cultivars with two vigor levels were used. Each treatment was replicated four times and each experimental unit consisted of two kilograms of seeds, which were placed in individual 1 m 3 gas-tight capacity chambers with phosphine. The concentrations used were 1.0; 2.0 and 3.0 g PH 3. m -3 , achieved by applying 3.0; 6.0 and 9.0 g of Fertox® commercial formulation. During seven days, the phosphine gas concentration within each chamber was monitored using the Silochek® gas meter. After this period, the chambers were opened, the seeds were removed and the quality analyses were performed. Throughout the experiment, PH 3 concentrations in the chambers remained at the concentrations required for the elimination of all life stages of insect pests of stored seed. Even in the lowest dosage, the gas concentration remained above 400 ppm that is considered the minimum concentration for eliminating insect pests. No detrimental effects were detected on the physiological quality of the fumigated seeds. Efeito do expurgo com fosfina sobre a qualidade de sementes de soja RESUMO - O expurgo e uma tecnica empregada para eliminar pragas infestantes em sementes armazenadas mediante uso de gas. O objetivo do experimento foi avaliar o efeito da fosfina na germinacao e no vigor (envelhecimento acelerado e comprimento de plântula) da semente de soja. Foram usadas sementes de soja de duas cultivares com dois niveis de vigor. Cada unidade experimental composta por dois quilogramas de sementes de cada repeticao foi colocada em câmaras individuais de expurgo. Foram usadas concentracoes de 1,0; 2,0 e 3,0 g de PH 3. m -3 , conseguidas pela aplicacao de 3,0; 6,0 e 9,0 g do produto comercial Fertox®. Diariamente, durante sete dias, foi monitorada a concentracao do gas fosfina no interior de cada câmara atraves do medidor Silochek®. Apos este periodo, as câmaras foram abertas, retiradas as sementes e realizadas as analises de qualidade. As concentracoes de fosfina se mantiveram nas concentracoes necessarias para a eliminacao de todas as fases das pragas de sementes armazenadas. Mesmo a dose mais baixa manteve a concentracao superior aos 400 ppm que e a referencia tecnica de concentracao minima para eliminar os insetos praga. Nao foram detectados efeitos adversos dos tratamentos na qualidade fisiologica das sementes de soja.