Genotype-specific radiosensitivity and mutagenic dose optimization in Ghanaian cowpea (Vigna unguiculata): a case study of cowpea cultivar Videza and Songotra

Purpose: Gamma irradiation is a potent mutagen, but its effectiveness depends on precise dose calibration and cultivar-specific responses. This study assessed the radiosensitivity of two Ghanaian cowpea cultivars (Videza and Songotra) exposed to ⁶⁰Co gamma radiation and determined the doses causing 50% reductions in germination, seedling survival, and seedling height. Materials and methods: Dry seeds were irradiated at doses of 0–1000 Gy (100-Gy increments) at 300 Gy h-1 and sown in a completely randomized design. Germination (day 10), seedling survival (days 14–21), and seedling height (day 21) were recorded. Dose-response data were analyzed using logistic regression in R Studio to estimate LD₅₀ for germination (LD₅₀^G) and survival (LD₅₀^S), and the 50% reduction dose for seedling height (RD₅₀^H). Results: Videza showed greater radiosensitivity than Songotra. Germination declined from 100% to 30% at 300 Gy in Videza compared with 96.6% to 53% in Songotra at the same doses. At 200 Gy dose, seedling survival for Videza dropped to 36.7%, whereas survival in Songotra remained at 60%. Seedling height was reduced to 36.8% at 200 Gy in Videza but remained 54.2% in Songotra. The LD₅₀^G and LD₅₀^S in Videza were 207.1 Gy and 168.6 Gy, respectively, compared with 347 Gy and 263 Gy in Songotra. Similarly, RD₅₀^H was lower in Videza (181 Gy) than in Songotra (222 Gy). These results demonstrate pronounced genotype-dependent differences and establish practical dose benchmarks. Conclusions: Our findings provide practical, cultivar-specific dose benchmarks for cowpea mutation breeding. Based on LD₅₀^G, LD₅₀^S, and RD₅₀^H values, we recommend gamma irradiation doses of 200–250 Gy for Videza and 250–300 Gy for Songotra to maximize mutation induction while maintaining seed viability. These guidelines support the development of improved cowpea varieties for enhanced food security and agricultural resilience.