Chemo-sensitive Responses of EMS and EBr on Physiological and Biochemical Traits of Cowpea [Vigna unguiculata (L) walp.]
Background: Cowpea [Vigna unguiculata (L) walp.] productivity is limited by soil and environmental factors, along with its narrow genetic base which collectively reduces the photosynthetic efficiency by reducing key photosynthetic components and nitrogen assimilation. Therefore, improving productivity requires developing stress-resilient and genetically diverse varieties. Induced mutagenesis offers an effective approach to create genetic variability and enhance crop performance for sustainable agriculture. Methods: The laboratory and pot culture experiments were conducted at Department of Genetics and Plant Breeding, SRM College of Agricultural Sciences, SRM Institute of Science and Technology, Chengalpattu, Tamil Nadu from August 2025 to December 2025aimed to study the effects of chemical mutagens, Ethyl Methane Sulfonate (EMS) and Ethidium Bromide (EtBr), on seedling growth, physiological and biochemical traits in the M1 generation of cowpea variety CO (CP) 7. Seeds were treated with five concentrations of EMS (20-40 mM) and EtBr (0.05-0.25 mM) along with a control and observations were recorded under a completely randomized design with three replications. Result: Results revealed significant variation among treatments. Moderate doses of EMS (20 and 25 mM) and EtBr (0.05 and 0.10 mM) enhanced germination, root length, shoot length and seedling height, indicating a stimulatory hermetic effect. In contrast, higher doses reduced growth parameters and increased seedling injury. Photosynthetic traits such as total chlorophyll, carotenoids and soluble protein improved at lower doses but declined sharply at higher concentrations. Nitrate reductase activity and total soluble sugars increased under mild treatments but decreased under severe mutagen stress. Proline accumulation showed a dose-dependent increase, reflecting stress response. The LD50 range was identified between EMS 30-35 mM and EtBr 0.15-0.20 mM. Principal component analysis revealed that PC1 explained 88.4% of the total variation. PC1 showed a positive association with growth and metabolic traits and a negative association with seedling injury and proline. Overall, moderate mutagen doses were optimal for inducing useful variability and can serve as effective selection criteria in cowpea breeding programs.