Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 12/1/1997
Publication Date: N/A
Technical Abstract: Blast resistance is one of the major objectives in rice breeding in tropical and temperate countries. Pyricularia grisea is known for its ability to overcome host-plant resistance, the resistance of some varieties have proven to be durable. RFLP analysis of DNA extracted from Lemont/Teqing F10 RILs provided a framework linkage map containing 185 marker loci. A subset of 245 of these RILs in the F8 generation were spray-inoculated to evaluate their reaction to five races of blast, IC-17, IB-49, IB-54, IG-1, and IE-1. Three replications of the 245 F8 RILs and controls were also planted in single-row field plots which were rated for field resistance. Greenhouse data on resistance/susceptibility to individual races were analyzed for association with the mapped marker loci. The chromosomal locations of three major resistance genes from Teqing and one major gene from Lemont were determined. Each of these dominant genes conferred resistance to at least two blast races. No gene provided resistance to all five races. Based on unique race reactions and map location, Pi-tq1 is a new gene. The other genes may be allelic with previously reported genes. Classical genetic analysis of F2 plants had indicated the presence of four major resistance genes in Teqing and two in Lemont. RFLP mapping located two of the six predicted genes plus two additional genes with unpredicted race specificities. The presence of unmapped resistance genes was further suggested by the fact that some RILs with susceptible alleles at all tagged loci showed significant resistance in the field. Pyramiding of major genes to improve a trait is based on the assumption that the genes will interact additively.