Molecular mapping of a new gene for resistance to rice blast (Pyricularia grisea Sacc.)

A single dominant blast resistance gene conferring resistance to a Korean r ice blast isolate was identified in rice variety 'Suweon 365'. We report th e chromosomal localization and molecular mapping of this blast resistance g ene designated as Pi-18, which confers resistance to Korean isolate 'KI-313 ' of the blast pathogen. To know whether there is a relationship among gene s conditioning resistance to location-specific isolates of the blast pathog en and thereby to identify linked markers to resistance gene for isolate KI -313 collected in Korea, RFLP markers previously reported to be linked to m ajor blast resistance genes in different rice germplasm and other markers m apped to nearby regions were surveyed for polymorphism between a resistant ('Suweon 365') and a susceptible ('Chucheongbyeo') parent. Linkage associat ions of the RFLP markers with the resistance gene were verified using an F2 and F3 segregating population of known blast reaction. RFLP analysis showe d that Pi-18 was located near the end of chromosome 11, linked to a single copy clone RZ536 at a distance of 5.4 centiMorgans (cM) and that this gene was different from Pi-1(t). An allelism test revealed that this gene was al so different from Pi-k. Currently, a combination of RAPD and microsatellite primers is being employed to find additional markers in this region. Tight ly linked DNA markers will facilitate selection for resistant genotypes in breeding programs and provide the basis for map based cloning of this new b last resistance gene.