Identification of blast resistance genes in elite indica-type varieties of rice (Oryza sativa L.)

Seven blast resistance genes- Pi20, Pita, Pik (one of Pik alleles, Pik, Pik-h, Pik-m, and Pik-p), Pib, Pik-s, Piz-t, and Pia- were identified in International rice Research Institute (IRRI)- bred rice varieties through genetic analysed based on a differential system. Segregation analyses were performed using BCF populations derived from crosses of six varieties (IR34, IR36, IR60, IR74, IR46 and IR64) with a susceptible Indica-type variety C)39, and allelism tests using F populations derived from crossed of nine varieties (IR34, IR24, IR36, IR60, PSB Rcl, IR74, IR56, IR70, and IR64) with differential varieties carrying known blast resistance genes. Selected Philippine blast isolates of Pyricularia grisea (Cooke) Sacc. with known avirulence were used in the analyses. The genotype for blast resistance of each variety was identified based on a gene-for-gene relationship between resistance in rice and avirulence in the blast pathogen. Among the genes identified, Pib and Pik-s or Pik were detected in nearly all IRRI varieties used. Some genes that were not estimated from the reaction patterns of IRRI varieties in the previous analysis due to the masking effect of Pita, Pik, and Pi20 were also identified