Abstract

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.