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

ABSTRACT: Drought stress significantly reduces cowpea yields in Africa,necessitating the development of drought-resilient genotypes. This studyevaluated the genetic variability and drought tolerance of nine ethidiumbromide (EtBr)-derived cowpea genotypes at the M7 generation undercontrol and drought stress conditions. The study was conducted in arandomized complete block design and assessed morphological and yieldtraits alongside ten drought tolerance indices (DTIs). Significant effects ofgenotype and genotype × treatment interactions were observed for mosttraits, except peduncle length and 100-seed weight. Genotypes G1 and G2demonstrated superior drought tolerance, reflected by high values for keyDTIs such as Geometric Mean Productivity (GMP), Stress Tolerance Index(STI), and Drought Resistance Index (DRI), and consistently maintainedhigher yields under stress. In contrast, G5 and G7 showed poorperformance under drought, with lower yields and DTI values. Broadsenseheritability was high for important traits, including plant height(84.41%) and seed yield per plant (60.08%), indicating strong geneticcontrol. High genotypic and phenotypic coefficients of variation,particularly for seed yield per plant (GCV: 71.54%, PCV: 92.29%), suggestconsiderable potential for selection-based improvement. The heatmapanalysis revealed that reproductive traits, particularly seed yield, number ofpods, and peduncle length, are strongly associated with key DTIs, makingthem valuable targets for selection under drought stress. These findingsunderscore the effectiveness of EtBr-induced mutagenesis in generatinggenetic variability and enhancing drought resilience in cowpea. Futurebreeding programs should prioritize genotypes like G1 and G2, integratingkey drought-related traits and indices to develop high-yielding, climate-resilientcowpea varieties suitable for drought-prone regions in sub-SaharanAfrica.