Microsatellite fingerprinting of barley scald pathogen, Rhynchosporium secalis, from the Hokuriku and Tohoku districts in Japan and genetic resources of barley breeding for resistance to its pathogen population

Variation in pathogenicity and microsatellite marker haplotype was investigated in 107 isolates of barley scald pathogen, Rhynchosporium secalis, collected from the Hokuriku and Tohoku districts in Japan during 2004 and 2005. By inoculation using 18 differential cultivars, 58 pathotypes were identified with complex variation in pathogenicity with no predominant pathotype. Among the 18 differential cultivars, Osiris exhibited highly stable resistance to all the isolates. As some differential cultivars with the same resistance gene(s) showed the different reaction pattern to the pathotypes, these differential cultivars may have unknown resistance gene(s) specific to Japanese isolates. DNA polymorphism was detected by 13 microsatellite markers to obtain 63 haplotypes that were classified into 6 clusters (I-VI). Two clusters (I and III) covered a broad region, and the remaining 4 covered a relatively limited region. Cluster VI was distributed only in Yamagata, and the isolates in this cluster showed higher pathogenicity than those in the other 5 clusters. Therefore, for resistance against the patholypes in cluster VI, some differential cultivars including Osiris were recommended as genetic resources for scald resistance in barley breeding. Finally, the possibility of monitoring using microsatellite markers was discussed.