Pre-harvest desiccation with glyphosate and quality of stored soybean seeds

Abstract

Seeds from non-genetically modified soybean cultivars harvested after chemical desiccation of plants with glyphosate may produce abnormal seedlings; these may show phytotoxicity symptoms that could persist even after some time of storage due to accumulation of toxic residues. This study aimed to evaluate the quality of stored soybean seeds harvested after chemical desiccation of plants with glyphosate at R7 stage. Seeds from soybean cultivar 'Conquista' were produced with and without desiccation with glyphosate, at the dose 2.0 L ha -1 , applied at physiological maturity stage. Seed quality was evaluated right after harvest and after eight months of storage by tests of moisture content, mass, germination and vigor. The experimental design was the completely randomized block with four replications. Data was submitted to variance analysis and means were compared by the Tukey test (p ≤ 0.05) as a 2 x 2 factorial. The results show deleterious effects of glyphosate used as desiccant for early harvest of soybean seeds from conventional cultivars. Accelerating plant senescence leads to production of seeds with lower germination and decreased seedling development, although the percentage of abnormal seedlings is reduced after 8 months of storage possibly due to degradation of toxic residues of glyphosate and/or derivates. Key words: Glycine max, phytotoxicity, physiological maturity, germination, seedling development ResumoSementes de cultivares convencionais de soja colhidas após dessecação química das plantas com glifosato podem produzir plântulas anormais, com sintomas de fitotoxicidade que podem persistir mesmo após o armazenamento devido ao acúmulo de resíduos tóxicos. Este trabalho objetivou avaliar a qualidade de sementes armazenadas de soja colhidas após dessecação química das plantas com glifosato no estádio R7. Sementes de soja da cultivar Conquista foram produzidas com e sem dessecação das plantas com glifosato, na dose de 2,0 L ha -1 , no estádio de maturidade fisiológica. A qualidade das sementes foi avaliada logo após a colheita e aos oito meses de armazenamento quanto ao teor de água, massa, germinação e vigor. O delineamento experimental foi o inteiramente casualizado, com quatro repetições. Os dados foram submetidos à análise de variância e as médias comparadas pelo teste de Tukey (p≤0,05), em esquema fatorial 2 x 2. Os resultados mostram efeitos deletérios da aplicação de glifosato utilizado como dessecante para antecipação da colheita de sementes de soja de cultivares 1 Prof a Dr

Qualidade de sementes de feijão-azuki dessecadas com saflufenacil e submetidas ao armazenamento

“…Os efeitos negativos nessas variáveis (PN e PNEA) ocorreram após o armazenamento das sementes por seis meses quando houve redução no vigor (Tabela 1). O nível de vigor das sementes afeta o estabelecimento da cultura, o desenvolvimento das plantas, a uniformidade da lavoura e a sua produtividade (Toledo et al, 2014).…”

“…A utilização de dessecantes para antecipação da colheita de sementes tem sido empregada nas culturas, sobretudo na soja (Toledo et al, 2014) e no feijão-comum (Franco et al, 2013) logo após atingirem a maturidade fisiológica buscando facilitar a colheita, diminuir injúrias mecânicas, ataque de pragas e microrganismos após o período de maturidade fisiológica (Toledo et al, 2014).…”

“…O conhecimento do produto e da dose de aplicação evita perdas no rendimento e no vigor das plântulas (Toledo et al, 2014). O saflufenacil é um herbicida usado em pré-emergência, pré-plantio incorporado ou pós-emergência para o controle sobremaneira de plantas daninhas dicotiledôneas.…”

Physiological quality of seeds of crambe desiccated at pre-harvest with glyphosate

“…Desiccants have been used to uniformize maturation and promote early harvest of seeds in various crops, such as soybean (Daltro et al, 2010;Marcandalli et al, 2011;Toledo et al, 2014), canola (Silva et al, 2011) and common beans (Kappes et al, 2012;Franco et al, 2013). However, Daltro et al (2010) observed that glyphosate negatively interfered with germination and initial development of soybean seedlings, particularly hampering their roots due to the phytotoxic effect caused by the desiccant.…”

“…Moisture content (A) and germination (B) of crambe (Crambe abyssinica Hoechst) seeds with and without plant desiccation at pre-harvest with glyphosate, at different times of application *Significant at 5% probability level by t-test Ns Not significant at 5% probability level by t-test Times of application (days) different times of glyphosate application, maintaining a mean value of 58%. Toledo et al (2014) observed that the germination of soybean seeds, after accelerated aging, was reduced with the desiccation of the plants at pre-harvest, due to the increase in the percentage of abnormal seedlings. Defining the desiccant application time is indispensable for the efficiency of the product, because applications performed far away from the period of seed physiological maturity or under unfavorable conditions of climate, especially rainy periods, can compromise seed quality (Santos et al, 2005).…”