Induction of Genetic Variability for some Agronomic Traits and Blast Disease Resistance in Egyptian Rice Variety Sakha101

The present study was undertaken to assess the differential sensitivity of Egyptian rice variety Sakha101 to gamma radiation, to study the genetic variability induced and to get desirable phenotypic mutants especially of economic importance traits  and blast disease resistance. The study was conducted at the Experimental Farm of Sakha Agricultural Research Station, Kafr El-Sheikh, Egypt, during 2016 and 2017 rice growing seasons. Four gamma ray doses; 100, 200, 300  and 400 Gy were used to treat the seeds of the Egyptian rice variety Sakha 101. The results illustrated that heading date was early in all doses applied in M₁-generation, except in 400 Gy. Plant height was decreased by increasing gamma irradiation in both M₁ and M₂-generations. Number of panicles/plant were decreased by using the dose of gamma rays for 100 and 200Gy, while it increased for 300 and 400 Gy treatments in both of M₁ and M₂ generations. The doses of gamma rays increased the means of sterility % and 100-grain weight in both of M₁ and M₂-generations. For grain yield/plant, the mean values decreased by increasing the dose of gamma rays up to 300 Gy while, increased at 400 Gy, where the grain yield per plant increased by 47.7 grams as compared with the control (44.0 grams) in M₂-generation plants. All studied genetic parameters viz, genotypic variance (GV), genetic coefficient of variation (GCV), heritability in broad sense (h²bs) and genetic advance of mean (GS%) increased by increasing the dose of gamma rays in M₂-generation indicating individual plant selection for these characters should be effective and satisfactory for successful breeding purposes. A total of 101 M₂ mutant plants were found to be earlier in heading by 10-20 days than the mean value of the original variety Sakha 101; and 105 mutant plants were having grain yield/ plant more than 42 grams comparing with its original plants. About 591 plants from different irradiated treatments were found to be resistant to blast disease from M₂-generation plants. Hence, the induced genetic variability is consider important as it is a basic requisite for successful rice breeding program via direct selection or by crossing with the commercial cultivated varieties.