Evaluation of EMS-induced phenotypic variation in the M1 generation of cowpea (Vigna unguiculata L. Walp.)

Ethyl methane sulfonate (EMS) is widely used in mutation breeding to induce variation and broaden the phenotypic diversity available for crop improvement. This study evaluated the effects of different EMS concentrations on germination, survival, and phenotypic variation in the M 1 generation of cowpea ( Vigna unguiculata L. Walp. var. Wankae). Twenty-five seeds of the Wankae variety were treated with each EMS concentration (0, 20, 60, and 80 mM) and evaluated for germination, survival, quantitative traits, and qualitative characteristics. EMS significantly influenced germination, survival, and trait expression, with responses varying across concentrations. Germination declined from 100% in the control to 88% at 80 mM EMS, while survival remained high (95.45–100%) across treatments. The mean days to 50% germination increased from 2.60 days in the control to 4.14 days at 80 mM EMS. Moderate EMS treatment (20 mM) enhanced several agronomically important traits, including mean plant height (34.66 cm), number of main branches (5.46), peduncle length (15.12 cm), number of pods per plant (14.39), number of locules per pod (12.09), and average seed weight (5.01 g), while maintaining relatively higher vigor and survival. Higher EMS concentrations (60 and 80 mM) generated additional phenotypic variation in growth habit, pod pigmentation, seed morphology, and other qualitative traits. Still, they were associated with reduced germination, survival, and overall plant performance. Distinct qualitative variants were also observed, including the appearance of brown seed coat colour at 20 mM EMS and black seed coat colour and dark purple mature pod colour at 80 mM EMS. GLM contrast analysis identified putative mutants across developmental, reproductive, yield-related, and seed traits, demonstrating the effectiveness of EMS in generating phenotypic diversity. The results indicate that moderate EMS doses are effective for inducing useful variation while minimizing adverse effects on plant growth. In contrast, higher doses increase phenotypic variability at the expense of plant vigor. This study provides an initial evaluation of EMS-induced phenotypic variation in the M 1 generation of cowpea. It identifies putative mutant materials for further evaluation in subsequent generations to determine their stability, heritability, and potential breeding value.