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Abstract
Rice diseases are one of the major limiting factors of rice production worldwide specially, blast (Magnaporthae grisea) and bakanae or foot rot (Fusarium moniliforme) diseases. Therefore, this study was conducted to improve rice for resistance to blast and bakanae diseases as well as yield and yield related traits using gamma rays and Simple Sequence Repeats (SSR) technique. where grains of three local rice cultivars Giza 177, Sakha 101 and Sakha 104 were irradiated with different doses of gamma rays (0, 150, 200, 250 and 300 Gy). Eleven rice mutants were selected and evaluated for resistance to blast and bakanae diseases under natural and artificial infection conditions in M₃and M₄ generations. Molecular screening and genetic diversity of resistance (R) genes to blast and bakanae diseases were performed for the selected mutants and its parents using 22 SSR and 3 specific markers. Results of both natural and artificial infection showed that out of the eleven selected mutants only nine mutants were resistant; four mutants were highly resistant to blast and bakanae diseases at seedling and adult stages under natural infection in permanent field and artificial infection in greenhouse while, five mutants were resistant to blast disease and susceptible to bakanae disease. Results of SSR analysis revealed that all markers produced a total of 72 alleles with 13 unique bands. The genetic similarity between 11 rice mutants and its parents ranged from 5% between mutant SK4151 and Sakha 101 to 73% between mutant SK4201 and its parent Sakha 104. Molecular screening of R genes to blast showed that blast resistant mutants have a combination of some partial resistance genes, Pi40(t), Pi20(t), Pi35(t); and complete resistance genes (Pib, Pik, Pik-h, Pita, Piz) that confer durable resistance to all blast races