Using Gamma Rays for Genetic Improvement of Rice Resistance to Blast Disease

Abstract

Seeds of two blast susceptible Egyptian rice varieties; Sakha 101 and Sakha 104, were treated by four gamma rays' doses in order to establish genetic diversity and development of some desirable mutants for blast disease resistance. Sixty selected mutant lines for each variety were examined under an artificial infection for M3 seedlings using two different races of Pyricularia oryza; ID-15 and ID-16. Results revealed that almost all Sakha 101 mutants irradiated by 400 Gy gamma rays were resistant to blast disease for both races, although their original variety was susceptible. In addition, most mutants obtained from Sakha 104 variety; which was resistant to ID-15 and susceptible to ID-16, were resistant or moderately resistant to blast disease at different gamma rays' treatments. On the bases of blast disease scoring, 16 selected mutants, as well as the two original varieties, were characterized at the molecular level using three SSR markers (RM155, RM512, and RM541) linked to rice blast resistance genes; Pi genes. A total of 11 polymorphic alleles (average of 3.67 alleles per primer) with sizes varied from 151 to 260 bp were amplified for the 18 studied genotypes. The appearance of the highest number of resistance alleles in the two Sakha 101 mutants SK-400-1-3 and SK1-400-1-4 irradiated by 400 Gy gamma rays; in addition, Sakha 104 mutants irradiated by 400 and 500 Gy may be supporting our findings of blast disease scoring. Thus, the three SSR markers could be useful to evaluate resistance to blast disease of rice.