INHERITANCE OF BLAST RESISTANCE IN NEAR-ISOGENIC LINES OF RICE

Resistance to blast disease is an important objective of most rice breeding programs. Genetic studies of resistance have been complicated by variability of the pathogen and lack of rice genotypes with single resistance genes. Near-isogenic lines (NILs) with single blast resistance genes were developed by backcrossing four donor cultivars to the recurrent parent CO39. Five pathogen isolates were used to screen the populations during backcrossing. The 22 NILs were classified into six groups by their reaction to a diverse set of blast isolates. Blast resistance was conferred by independent dominant genes in the NILs C101LAC, C101A51, and C104PKT, designated Pi-1(t), Pi-2(t), and Pi-3(t), respectively. Blast resistance in C101PKT and C105TTP-4 was conferred by dominant alleles at an additional locus, designated Pi-4a(t) and Pi-4b(t), respectively.