Author(s)

Festus Olakunle Olasupo^1,2*, Christopher Olumuyiwa Ilori¹, Brian Peter Forster³, Souleymane Bado⁴

¹Department of Crop Protection and Environmental Biology, University of Ibadan, Ibadan, Nigeria.
²Plant Breeding Section, Cocoa Research Institute of Nigeria, Ibadan, Nigeria.
³Biohybrids International Ltd., Reading, UK.
⁴Plant Breeding and Genetics Laboratory Joint FAO/IAEA Agriculture and Biotechnology Laboratory, International Atomic Energy Agency Laboratories, Seibersdorf, Austria.

Mutagenesis is used for creating new genetic variability in cultivar improvement. Optimal mutagenic treatment is required for effective mutation induction in crop species. Therefore, radio-sensitivity of cowpea accessions to gamma irradiation was investigated. Seeds of eight cowpea accessions were irradiated with ⁶⁰Co gamma radiation doses of 100, 200, 300, 400 and 500 Gy. The seeds were sown in pots to evaluate the treatment effects on seed germination (SG), seedling survival (SS) and growth habits of M1 generation. Data were analyzed using descriptive statistics. Low rates of SG (10% - 45%) were recorded at higher doses (500 - 400 Gy) in Ife Brown (IB) and its derivatives, whereas high SG rates (74% - 94%) were observed in IT90K-284-2 across all treatments. Percentage SS was inversely related to gamma dosage. A wide range of LD₅₀ for SG (329 - 1054 Gy) and SS (149 - 620 Gy) were observed across the cowpea accessions. Low LD₅₀ scores for SG (329 - 516 Gy) and SS (149 - 357 Gy) were observed among cowpea with rough seed coat, whereas cowpea with smooth seed coat recorded higher LD₅₀ for SG (521 and 1054 Gy) and SS (449 and 620 Gy). Seed germination LD₅₀ and SS LD₅₀ were highly correlated with mean coat thickness (0.899 and 0.937) than mean seed weight (0.621 and 0.678). Gamma irradiation of cowpea seed at low dosage (100 Gy) increased the vigor of M₁ seedlings with respect to primary leaf area, terminal leaflet area, seedling height and plant height at six weeks. Doses of 200 Gy and above resulted in a progressive reduction in vigor of plant and seed setting of cowpea. Radio-sensitivity varied with cowpea genotype and was associated with seed testa texture, thickness and seed weight. Low gamma irradiation treatment (100 Gy) may be used to enhance seedling vigor, vegetative growth and yield of cowpea at M₁ generation.

Cowpea, Mutagenesis, Radio-Sensitivity, Gamma Irradiation, Optimum Mutation Treatment

Olasupo, F. , Olumuyiwa Ilori, C. , Forster, B. and Bado, S. (2016) Mutagenic Effects of Gamma Radiation on Eight Accessions of Cowpea (Vigna unguiculata [L.] Walp.). American Journal of Plant Sciences, 7, 339-351. doi: 10.4236/ajps.2016.72034.