Influence of Gamma Rays on the Performance and Genetic Parameters for Grain Yield and Yield Attributes of Bread Wheat

PURE DRY seeds of two wheat cultivars; Sids 12 and Misr1 were subjected to gamma radiation doses at rates of 10, 15, and 20 KR. ⁶⁰Co used as a source of gamma rays at the Middle East Regional Radioisotope Center for Arab Countries at Dokki, Giza. Significant differences between irradiated and non-irradiated plants were detected for most of the studied characters in the M₁ and M₂ generations. The most beneficial dose was 10 KR. The impact of this dose was promising in grain yield and No. of spikes/ plant in both generations. High reduction in the mean values of plant height, spike weight and grain yield/ plant were obtained in response to higher does of gamma rays (20 KR) in M₁ generation. While it improved No. of spikes/ plant, spike weight and grain yield in M₂ generation, but grain yield was still less than that of the 10 KR. The two cultivars responded differently to different gamma radiation doses except grain yield in M₁ and heading date in M₂ generation as well as 1000-grain weight in the two generations. Maximum absolute value for No. of grains/ spike in M₁ generation was occurred at 10 Kr of gamma radiation for Sids 12. While, the same cultivar detected the heaviest spike weight under 15KR. Wheat grains of Misr 1 treated with either 10 or 15 KR recorded the highest No. of spikes/ plant in M₁ generation. The most desirable value for grain yield/ plant (30.4 g) was obtained when Misr1 wheat cultivar subjected to low gamma ray dose (10 KR) in the second mutagenic generation. In general, all the studied genetic parameters viz. σ²g, GCV, PCV, h²b.s as well as genetic advance from selection was higher and folded several times in case of irradiated plants compared with the control. These indicated that the efficiency of gamma radiation doses in inducing genetic variation allowing the wheat breeder to improve wheat yield and its attributes through this method. The desirable genetic advance was found to be associated with high heritability estimates in case of spike weight and No. of spikes/ plant. It is concluded from this study that mutation/ variability in wheat can be created through the three mutagenic treatments of gamma rays and various quantitative traits would be improved using gamma rays.