F. C. Krzyzanowski

Qualidade fisiológica, física e sanitária de sementes de soja produzidas no Brasil

Nos ultimos anos, o Brasil tem apresentado desempenho crescente em termos de produtividade e producao de soja. Todavia, alguns estudos mostram que a falta de controle de qualidade tem comprometido a germinacao e o vigor de parte significativa de sementes de diferentes genotipos. Com base nessa realidade, foi conduzido um estudo, objetivando dimensionar e avaliar os aspectos da qualidade de sementes da soja em diferentes regioes produtoras do Brasil. Na safra agricola 1997/98, foram coletadas 331 amostras nos estados do Parana, Minas Gerais, Goias e Rio Grande do Sul. Para a analise da qualidade foram empregados os seguintes parâmetros: germinacao, vigor (TZ 1-3), viabilidade (TZ 6-8), deterioracao por umidade (TZ 6-8), lesoes de percevejos (TZ 6-8), sementes quebradas, ruptura de tegumento, dano mecânico (TZ 6-8) e sanidade (blotter test). A analise estatistica dos resultados mostrou reducao acentuada da germinacao e do vigor, em funcao dos altos niveis de deterioracao por umidade, de lesoes de percevejos, de quebras, de ruptura de tegumento e de injuria mecânica, no norte e oeste do Parana, Goias e Minas Gerais, quando comparados com o sul do Parana e Rio Grande do Sul. Estas ultimas regioes apresentaram baixos indices de deterioracao por umidade e de lesoes de percevejo. Ainda foi observado que a incidencia de certos patogenos, em sementes de algumas regioes, nao chegou a comprometer a germinacao e o vigor das diferentes cultivares avaliadas. De uma maneira geral, as sementes produzidas na regiao sul do Parana e no Rio Grande do Sul apresentaram um melhor padrao de qualidade quando comparadas com as demais regioes estudadas.

Accelerated ageing test for seed wheat evaluation

The wheat sown in southern Brazil has shown serious seed quality problems but standard procedures for determining the wheat seed vigor is missing from the literature. This project aimed to study the methodology of the accelerated ageing test to identify levels of vigor in wheat seed lots. Seeds of the wheat cultivars CD 104 and BRS 220 were used, each represented by five lots. The following tests were conducted: determination of moisture content (oven, 105 ± 3 oC, 24 h), standard germination (8x50 seeds, 20 oC) field seedling emergence, accelerated ageing (41 oC / 48, 60 and 72 hours, and 43 oC / 48 hours). Means were compared using the Tukey test at the 5% probability level; the Spearman rank correlation test was used for the study on the methodology of the accelerated ageing test, where a measure of the strength of the relationship between the test data and existing data on seedling emergence in the field was looked for. From the results, it was concluded that the accelerated ageing test at 43 °C for 48 h provides consistent information for differentiating between wheat seed lots.

AVALIAÇÃO DE METODOLOGIA ALTERNATIVA PARA O TESTE DE TETRAZÓLIO PARA SEMENTES DE SOJA

An alternative method of the tetrazolium test established that the preconditioning period of soybean seeds could be successfully shortened from the traditionally 16 hours at 25oC to 6 hours at 41oC. Since this alternative method has been tested so far with a limited number of soybean cultivars, it is imperative that it should be tested for additional cultivars. The applicability of this alternative procedure of seed preconditioning was tested in ten soybean cultivars: BR-13, EMBRAPA 4, EMBRAPA 48, FT-Abyara, FT-5, IAS 5, OCEPAR-13, OCEPAR-14, OCEPAR-16, and OCEPAR-17. Two imbibition periods (4 h and 6 h) at 41oC were tested and compared to the traditionally recommended period for preconditioning. The following tests were carried out: seed moisture content and tetrazolium through determinations of vigor, viability and level of mechanical damage, weathering and sting bug damage. From the results, the following conclusions can be drawn: a) seed preconditioninig for 6h at 41oC resulted in adequate staining patterns of the seeds, allowing accurate estimates of vigor and viability; b) seed preconditioning for 4 h at 41°C did not develop adequate staining of the seeds, to correctly evaluate vigor and viability of the seeds; however, this procedure was efficient to identify sting bug damage on seeds.

Drying peanut seed using air ambient temperature at low relative humidity

The moisture content of peanut kernel (Arachis hypogaea L.) at digging ranges from 30 to 50% on a wet basis (w.b.). The seed moisture content must be reduced to 10.5% or below before seeds can be graded and marketed. After digging, peanuts are cured on a window sill for two to five days then mechanically separated from the vine. Heated air is used to further dry the peanuts from approximately 18 to 10% moisture content w.b. Drying is required to maintain peanut seed and grain quality. Traditional dryers pass a high temperature and high humidity air stream through the seed mass. The drying time is long because the system is inefficient and the high temperature increases the risk of thermal damage to the kernels. New technology identified as heat pipe technology (HPT) is available and has the unique feature of removing the moisture from the air stream before it is heated and passed through the seed. A study was conducted to evaluate the performance of the HPT system in drying peanut seed. The seeds inside the shells were dried from 17.4 to 7.3% in 14 hours and 11 minutes, with a rate of moisture removal of 0.71% mc per hour. This drying process caused no reduction in seed quality as measured by the standard germination, accelerated ageing and field emergence tests. It was concluded that the HPT system is a promising technology for drying peanut seed when efficiency and maintenance of physiological quality are desired.

Perfil dos aspectos físicos, fisiológicos e químicos de sementes de soja produzidas em seis regiões do Brasil

A semente de soja, produzida em algumas regioes do Brasil, tem apresentado serios problemas de qualidade fisiologica. Essa situacao pode ser atribuida a ajustes inadequados do sistema de trilha das colhedoras, a ocorrencia de estresses climaticos na maturacao e, geralmente, a lesoes de percevejos, resultando em semente com baixos potenciais de germinacao e de vigor. O estudo teve como objetivo avaliar o comportamento da qualidade da semente produzida em diferentes regioes produtoras de soja e identificar locais com condicoes edafoclimaticas ideais para sua producao com melhor potencial qualitativo. Foram avaliadas 364 amostras de diferentes cultivares de soja, coletadas diretamente do tanque graneleiro das colhedoras, nos estados do Parana, Minas Gerais, Mato Grosso do Sul e Mato Grosso (regiao de Alto Garca). Para diagnosticar o desempenho da qualidade, empregaram-se os seguintes parâmetros: grau de umidade, germinacao, sementes quebradas e testes de hipoclorito e tetrazolio, este para estimar vigor, viabilidade, dano mecânico, deterioracao por umidade e lesoes de percevejos, alem de analise quimica. Os resultados indicaram que indices elevados de danos mecânicos, de quebra e de ruptura de tegumento, quando associados a percentuais acentuados de deterioracao por umidade e de ataque de percevejo afetaram, em maior intensidade, a qualidade da semente proveniente de Minas Gerais, do Mato Grosso do Sul e das regioes norte e oeste do Parana, quando comparados com aquelas oriundas do Estado do Mato Grosso e da regiao sul do Parana. Nos Estados do Mato Grosso e regiao sul do Parana, existem areas com potencial climatico, para producao de sementes de soja com elevada qualidade fisiologica. Existem regioes nos Estados de Minas Gerais, Parana e Mato Grosso que produzem sementes de soja com maiores teores de proteinas e oleo e com acidez relativamente baixa.

Evaluation of lignin content of soybean seed coat stored in a controlled environment

Breeding soybean for high seed quality is an important approach for developing cultivars for tropical regions, and the lignin content in the seed coat is one of the screening parameters for this trait. Considering that many breeding lines are evaluated in each growing season using the presently recommended method for lignin determination, a long period is required for the evaluation of the whole breeding program. This time limitation may influence lignin content assessment, if lignin is degraded during storage. This research reported was designed to determine whether lignin was degraded in the seed coat of soybean seed cultivars stored for one year in a controlled environment (10°C temperature and 50% air relative humidity). Seeds of 12 selected soybean cultivars that had a range in seed coat lignin content were evaluated. Seeds were hand harvested just after physiological maturity and evaluated for seed coat lignin content at harvest and after one year of storage in a cold room (10°C and 50% RH). The lignin content in seed coats differed significantly among cultivars in both analyses, but for both results the sequence of cultivar classification and the lignin content values of each cultivar did not change. A regression analysis of lignin content at harvest and after one year of storage indicated a direct relationship between both lignin determinations suggesting no differences between the lignin content of each cultivar due to prolonged storage (r2 = 0.98***). This indicates that the lignin determination in the soybean seed coat can be performed over a long time period without any bias due to change in its content.

Lignin content and peroxidase activity in soybean seed coat susceptible and resistant to mechanical damage

Mechanical damage is one of the causes of great loss in the quality of soybean seeds during harvest and processing. Considerable interest exists in the lignin since its deposition in the seed coat tissue provides mechanical resistance and protects the cell against microorganisms. In addition, peroxidases might be involved in the oxidation of cinnamyl alcohols prior to their polymerization during lignin formation. Thus, the aim of the present work was to analyze the lignin contents and peroxidases activities of six Brazilian soybean cultivars (Savana, Paranagoiana, FT-10, Santa Rosa, Doko and Paraná) and their relationships with the mechanical damage. Results showed that the lignin content and peroxidase activity in the seed coat significantly differed among the soybean cultivars. Cultivars Doko and Paraná had the highest contents of lignin and peroxidases activities while the other cultivars had lowest lignin contents and enzyme activities. Lignin content and peroxidase activity may be reasonable indicators of resistance to mechanical damage in soybean seeds.

EFEITO DO BENEFICIAMENTO DE SEMENTES DE TREMOÇO AZUL SOBRE SUAS QUALIDADES FÍSICA, FISIOLÓGICA E SANITÁRIA

The evaluation of the effects of processing seeds of blue lupine on their physical, physiological and pathological quality was performed due to the lack of available information. Seeds of blue lupine cv. IAPAR 24 were processed using the air screen cleaner and the gravity table, individually or in sequence. The efficiency of the equipments was measured and the seed physical, physiological and pathological qualities were evaluated. The gravity table individually or in association with air screen cleaner contributed to improve the quality of blue lupine seeds.

Alternative procedure for the cold test for soybean seeds

The growing demand for high quality soybean [Glycine max (L.) Merrill] seeds requires a precise seed quality control system from the seed industry. One way to accomplish this is by improving vigor testing. Cold test has been traditionally employed for corn seeds. However, it has also been used for other seed crops such as cotton (Gossypium spp.), soybean (Glycine Max), dry bean (Phaseolus vulgaris) and pea (Pisum sativum). This study was carried out with the objective of adjusting an alternative procedure for the cold test to determine soybean seed vigor. Six commercial soybean seed lots of the cultivar BRS 133 were used. The physiological potential of the seed lots was evaluated by germination on paper towel and sand box, seedling field emergence, tetrazolium, accelerated aging and electrical conductivity tests. Seed moisture content was also determined. The temperature used for the cold test procedures was 10oC during five days. Four cold test procedures were evaluated: i) plastic boxes with soil; ii) rolled paper towel with soil; iii) rolled paper towel without soil, and iv) an alternative procedure, using rolled paper towel without soil under cold water. A completely randomized experimental design with eight replications was used and the means were compared by the Tukey test (p = 0.05). To verify the dependence between the alternative test and others single linear correlation was used. All cold test procedures had similar coefficients of variation (CV), highlighting that rolled paper towel with soil and the alternative procedure had the best performance, with an average of 94% and 93% normal seedlings and CV of 3.2% and 3.6%, respectively. The alternative procedure has satisfactory results for estimating soybean seed vigor, yielding consistent results compared to the traditional procedure.

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.