Assessment of radio-sensitivity for three cowpea genotypes to gamma irradiation

Cowpea (Vigna unguiculata [L.] Walp) is an important food legume. However, production is limited by various biotic and abiotic constraints in sub-Saharan Africa and reduced genetic variability hinders crop improvement efforts. Gamma ray irradiation has been used as a mutagen to create variability but optimal dose determination is a prerequisite to maximize the recovery of mutant plants. In this study, three genotypes (KVx396-4-5-2D, Tiligre and Moussa local) from Burkina Faso were treated with four gamma irradiation doses (150, 200, 250 and 300 Gy) using a labelled cobalt source (60CO) and evaluated for seed germination and seedling survival. Results showed that germination and survival rates were severely decreased at treatments greater than 150 Gy and no germination was observed at the 300 Gy dose. The optimum dose (LD 50%) varied for the genotypes and ranged from 129 to 163 GY. Seed characteristic and quality were factors contributing to this variation.    Key words: Vigna unguiculata, γ-rays, mutagenesis, variability, radiosensibility.