Genetic variation, genotype × environment interaction, and correlation among drought tolerance indices in cowpea

Drought tolerance indices serve as valuable indicators for selecting cowpea genotypes with improved drought tolerance. However, there is a limited understanding of the variability and the impact of genotype (G) × environment (E) interaction (I) on these drought tolerance indices. Therefore, the objective of this study was to assess the extent of genetic variability and the influence of GEI on drought tolerance indices in cowpea. The experiment was conducted over two seasons under controlled conditions in a screen house. The results revealed that seed yield and all drought tolerance indices were significantly influenced by genotype, environment, and GEI. When the data from both years were combined, the yield under non-stress conditions ranged from 10.47 g in G2 to 17.27 g in G7, while under drought stress, it ranged from 2.19 g in G3 to 6.89 g in G1. Through mean rank analysis, principal component (PC) analysis, and clustering, highly tolerant accessions (G1 and G6) and highly susceptible ones (G2, G3, and G8) were identified. This study identified several indices, including geometric mean (GM), yield index (YI), mean productivity (MP), stress tolerance index (STI), modified stress tolerance index for non-stress (MST1), and stress (MST2), GMP, and HM, as effective in selecting high-yielding and drought-tolerant accessions under non-stress and drought conditions. Additionally, the drought resistance index (DRI) and yield stability index (YSI) were found to be reliable indicators under drought stress. Most of the indices exhibited moderate (≥ 30%) to high heritability (≥ 60%) and high genetic advance (≥ 20%), except for MST2, which had low heritability (12.73%).