Radio-sensitivity of cowpea to ultra-violet radiation by pollen treatment

The technique of pollen irradiation for mutation induction technique has been successfully demonstrated in many crop species. Therefore, the mutagenic effects of UV irradiated pollen on cowpea accessions were investigated. Pollen grains of eight cowpea accessions were irradiated with 30,000µWs/cm2 UV for 60, 120, 180, 240, 300 and 360 minutes. Emasculated flowers of each accession were self-pollinated with irradiated pollen to evaluate the effects of pollen mutagenesis on seed setting in the M1 generation. Harvested seeds from M1 plants were advanced to M2 to evaluate the effects of UV radiation on seed germination, plant survival and for mutant selection in the M3 generation. Data were analyzed using descriptive statistics. Pollen irradiation with UV for a short period (60 min) increased seed setting in all the cowpea accessions at M1 except IB-Y-1 where it reduced seed setting by 28.6%. Observed LD50 of UV rays among the cowpea lines ranged from 142.6 to 210.1 minutes. No significant difference was observed in seed germination for all treatments at M2 except irradiation for 120 minutes in IT90K-284-2. A trend similar to seed germination was observed in seedling survival at M2. The three-primary leaf and four-primary leaf mutants selected at M3 generation reverted back to two-primary leaf seedlings at M4. Low mutation frequencies recorded in this study shows that cowpea is considered less amenable to the application of UV irradiation as a practical breeding method.   Key words: Cowpea mutagenesis, pollen irradiation, ultra-violet induced mutant, seed germination, seed setting.