Identification of DNA markers linked to resistance genes to rice blast (Pyricularia grisea Sacc.)

Abstract

Resistance genes to the blast pathogen (Pyricularia grisea Sacc.) were mapped using a recombinant inbred populationconsisting of 231 lines derived from a cross between the japonica parents, Suwon365 and Chucheongbyeo. Phenotypic analysisshowed that Suwon365 carries two loci each conferring complete resistance to two Korean races KI-197 and KI-313, respectively.To know whether there is a relationship among genes conditioning resistance to location-specific isolates of the blast pathogen andthereby to identify linked markers to resistance gene for isolates, SSR markers previously reported to be linked to major blast resis-tance genes in diferent rice germplasm and other markers mapped to nearby regions were surveyed for polymorphism between theparents. AFLP analysis was employed to identify AFLP markers linked to genes conferring resistance to KI-313 and KI-197 races.Linkage associations of the DNA markers with the resistance gene were verified using the RIL population of known blast reaction.Linkage analysis showed that the resistance gene to KI-197, tentatively designated as Pi-25(t) was located on chromosome 12,linked to several SSR and AFLP markers. Inoculation test revealed that this gene was diferent from Pi-21(t) identified inSuwon365. Also, AFLP markers linked to Pi-18 conditioning resistance to KI-313 were found. Tightly linked DNA markers wilfacilitate selection for resistant genotypes in breeding programs and provide the basis for map-based cloning of this new blast resis-tance gene.