Fast Neutron Induced Genetic Variability in Cowpea [Vigna Unguiculata (L.) Walp.] Varieties

Cowpea ( Vigna unguiculata L. Walp.) is an important grain legume cultivated widely in sub-Saharan Africa, yet its productivity is constrained by narrow genetic diversity. This study was conducted to estimate genetic variability for agronomic traits in M₂ generation induced by fast neutron irradiation in two cowpea varieties (SAMPEA 21 and SAMPEA 20T). Seeds were irradiated with varying doses of fast neutron (0.85–11.1 µSv for SAMPEA 21; 0.70–16.40 µSv for SAMPEA 20T) at the Nigeria Research Reactor-1 (NIRR-1), Zaria. M₁ plants were raised in a randomized complete block design, and M₂ progenies were evaluated in an augmented design for ten agronomic traits. Analysis of variance revealed significant differences (p < 0.05 and p < 0.01) among M₂ progenies for most traits, including number of pods per plant, number of peduncles per plant, number of seeds per pod, pod length, hundred seed weight, and plant yield. Genotypic coefficient of variation (GCV) ranged from 1.39% to 60.81%, while phenotypic coefficient of variation (PCV) ranged from 3.37% to 69.15%. Broad-sense heritability estimates ranged from 17.09% to 93.42%, with number of pods per plant (76.45% in SAMPEA 21; 76.03% in SAMPEA 20T), hundred seed weight (90.01% in SAMPEA 21; 93.42% in SAMPEA 20T), and number of pods per peduncle (77.35% in SAMPEA 20T) recording high heritability coupled with moderate to high GCV. Substantial variability was observed among M₂ progenies for yield and yield-related traits, with several mutants outperforming parental lines. The study demonstrates that fast neutron irradiation effectively induces heritable genetic variability in cowpea, providing a useful foundation for selecting promising mutant lines for further breeding and cowpea improvement.