Soybean is the main oilseed crop cultivated worldwide and is important for human and animal nutrition. The duration of flowering, the reproductive period, and maturity is determined by genetic factors and influenced by environmental conditions, including temperature, photoperiod, precipitation, soil type, and crop management, which affect yield and regional adaptation. However, important gaps remain in understanding how soybean lines from different relative maturity groups respond to these conditions, particularly regarding the effects of temperature and precipitation on phenological development across growing seasons. Therefore, this study aimed to characterize the behavior of soybean populations and the environmental effect on the phenological cycle of the crop. Two populations were developed from biparental crosses with contrasting RMG values among the parental cultivars. The E2 population, comprising 150 lines, originated from the cross BMX Potência RR (RMG 6.7) × BMX Energia RR (RMG 5.3), whereas the E3 population, comprising 80 lines, originated from BRS 245 RR (RMG 7.3) × BRS 278 RR (RMG 9.4). The populations were evaluated over four growing seasons using an augmented block design, and the traits were analyzed using mixed models with environmental covariates. REML/BLUP methodology was used to estimate genetic parameters and predict genotypic values, enabling the selection of dual-purpose lines combining earliness and high yield. Higher temperatures and lower precipitation were associated with shorter phenological periods, whereas higher precipitation and lower temperatures were associated with longer periods. Population E2 showed more consistent associations with temperature and precipitation, whereas Population E3 showed weaker or nonsignificant associations for some traits, particularly NDM. These population-specific responses may be relevant for the selection of soybean lines in breeding programs.

Soybean is the main oilseed crop cultivated worldwide and is important for human and animal nutrition. The duration of flowering, reproductive period, and maturity is determined by genetic factors and influenced by environmental variables such as temperature, photoperiod, precipitation, soil type, and crop management, affecting yield and regional adaptation. However, gaps remain regarding the interaction between relative maturity groups (RMG) and the environment. Therefore, this study aimed to characterize the behavior of soybean populations and the environmental effect on the phenological cycle of the crop. Two populations were developed from biparental crosses with a narrow range in RMG among the parental cultivars. The E2 population originated from BMX Potência RR (RMG 6.7) × BMX Energia RR (RMG 5.3), and E3 from BRS 245 RR (RMG 7.3) × BRS 278 RR (RMG 9.4). The populations were evaluated over four growing seasons in an augmented block design, and traits were analyzed using mixed models with environmental covariates. Higher temperatures and lower precipitation were associated with shorter phenological periods, whereas higher precipitation and lower temperatures were associated with longer periods. Earlier lines were more environmentally sensitive, whereas later lines showed greater phenological stability.