Identification of adaptive traits and mechanisms in tropical soybean lines under drought stress from flowering to pod formation1
ABSTRACT Drought stress reduces soybean [Glycine max (L.)] yield stability in tropical environments, particularly from flowering to pod formation. This study aimed to identify adaptive traits and underlying mechanisms of tropical soybean lines under water-limited conditions, as well as to assess the selection potential under non-stress environments. Twenty-five high-yield soybean genotypes carrying the long juvenile (lj) and pod dehiscence1 (pdh1) genes were selected and evaluated under normal (± 80 % of the field capacity - FC) and water-deficit (± 50 % FC) conditions. Two potentially tolerant (which demonstrated a higher capacity to maintain physiological performance and metabolic stability under water deficit) and two susceptible genotypes were identified for further in-depth evaluation. Proline and malondialdehyde (MDA) were negatively and significantly correlated with grain yield under normal and water-deficit conditions. Both characters showed high broad-sense heritability across the environments, indicating strong genetic control and stable phenotypic expression. The simultaneous increase of proline and MDA is associated with reduced grain yield, indicating a stress-induced metabolic trade-off in which carbon and energy are redirected from reproductive development toward cellular protection mechanisms in the soybean genotypes.