Selection of soybean genotypes exhibiting drought resistance by assessing morphological and yield traits

Abstract Drought stress significantly impacts soybean ( Glycine max L. Merr.) productivity, making selecting drought-resistant genotypes a critical focus for breeding programs. This study aims to select drought tolerance levels in various soybean genotypes by evaluating key morphological and yield factors. In this study, four different irrigation levels were applied in 2023 and 2024: irrigation stopped at the flowering stage (T1), pod-setting stage (T2), and pod-filling stage (T3), along with a control group (T0) that received regular irrigation. Through field experiments under controlled water stress conditions, we analyzed plant growth parameters and yield such as first pod height, plant height, number of branches, number of pods, seed yield, and 1000-seed weight. The first treatment (T1) at the flowering stage showed higher drought tolerance among the genotypes, likely because the plants had more time to activate their drought response mechanisms. However, the pod-setting stage (T2) was identified as the most sensitive to drought stress, leading to more significant yield reductions. The primary effect at the pod filling (T3) stage was the reduced seed size with wrinkles on the seed surface, which led to a decrease in 1000-seed weight and seed yield per plant despite having a slight difference in seed count per plant compared to control. These highlight the critical nature of the pod-setting stage in soybean cultivation under water-limited conditions. Despite facing a shorter drought than the flowering stage, sensitivity toward drought was the highest in the pod setting stage. Plant height and the number of branches had no significant impact on yield in this study. While T1 resulted in the shortest plants, seed yield and 1000-seed weight were lowest in T2 due to the high sensitivity of plants at that critical growth phase. A comprehensive analysis of data from both years showed that the G7 variety exhibited the highest level of tolerance under water-limited conditions. These findings highlight the importance of incorporating drought-tolerant traits in breeding programs to ensure the sustainability of soybean production in water-limited environments.