Ethidium Bromide-Induced Genetic Variability and Drought Tolerance in Cowpea (Vigna unguiculata L. Walp.) Under Field Conditions

Drought stress significantly reduces cowpea yields in Africa, necessitating the development of drought-resilient genotypes. This study evaluated the genetic variability and drought tolerance of nine ethidium bromide (EtBr)-derived cowpea genotypes at the M7 generation under control and drought stress conditions. The study was conducted in a randomized complete block design and assessed morphological and yield traits alongside ten drought tolerance indices (DTIs). Significant effects of genotype and genotype × treatment interactions were observed for most traits, except peduncle length and 100-seed weight. Genotypes G1 and G2 demonstrated superior drought tolerance, reflected by high values for key DTIs such as Geometric Mean Productivity (GMP), Stress Tolerance Index (STI), and Drought Resistance Index (DRI), and consistently maintained higher yields under stress. In contrast, G5 and G7 showed poor performance under drought, with lower yields and DTI values. Broad-sense heritability was high for important traits, including plant height (84.41%) and seed yield per plant (60.08%), indicating strong genetic control. High genotypic and phenotypic coefficients of variation, particularly for seed yield per plant (GCV: 71.54%, PCV: 92.29%), suggest considerable potential for selection-based improvement. The heatmap analysis revealed that reproductive traits, particularly seed yield, number of pods, and peduncle length, are strongly associated with key DTIs, making them valuable targets for selection under drought stress. These findings underscore the effectiveness of EtBr-induced mutagenesis in generating genetic variability and enhancing drought resilience in cowpea. Future breeding programs should prioritize genotypes like G1 and G2, integrating key drought-related traits and indices to develop high-yielding, climate-resilient cowpea varieties suitable for drought-prone regions in sub-Saharan Africa.