Pre-harvest desiccation strategies in soybean genotypes with contrasting maturation: effects on seed physiological quality and longevity

ABSTRACT: Uneven maturation and green stem syndrome compromise harvest efficiency and the physiological quality of soybean seeds. Pre-harvest desiccation is a strategy to mitigate these problems, but its effectiveness depends on the interaction between herbicide, genotype, and environment. The objective of this study was to evaluate the impact of pre-harvest desiccation strategies on two soybean genotypes, NA 5909 RR (uniform maturity) and M 5947 IPRO (uneven maturity and green stem retention), in Paraguay, over two growing seasons. The strategies involved Photosystem I (PSI) inhibitors, Glutamine Synthetase (GSI) inhibitors, and Protoporphyrinogen Oxidase (PPO) inhibitors, applied alone or in combination. The PSI herbicides anticipated harvest by up to 10 days, resulting in seeds with greater germination and vigor, especially in the M 5947 IPRO genotype. Principal component analysis confirmed the superior efficacy of PSI, while Random Forest analysis highlighted that environmental factors, such as temperature and precipitation, were the main modulators of seed yield and quality, outweighing the effects of herbicides and genotypes. Rapid desiccation with contact herbicides proved to be the best strategy for advancing harvest and preserving seed quality, reducing exposure to environmental stresses. GSI showed intermediate performance, and their efficacy varied among genotypes, being less effective in preserving seed longevity due to the risk of sublethal phytotoxicity. It is concluded that herbicide selection should consider the genotype-environment interaction to optimize high-quality seed production, particularly in genotypes with uneven maturation.