QTL analysis of resistance to the rice blast pathogen in barley (Hordeum vulgare)

Barley is compatible with the rice blast pathogen (Pyricularia oryzae Cav.). Fiftyfour barley cultivars of diverse geographic origin and pedigree were inoculated with three isolates of the rice blast pathogen. All barley genotypes showed blast disease symptoms when inoculated at the seedling stage with each of the three isolates. However, one genotype showed quantitative resistance to all three isolates and three genotypes showed quantitative resistance to one or two of the isolates. By inoculating a set of doubled-haploid lines derived from the cross 'Harrington' (susceptible) and 'TR306' (resistant) with isolate Ken 54-20, we mapped quantitative trait loci (QTLs) determining seedling stage blast resistance. At all QTLs, TR306 contributed the resistance alleles. The four QTLs, when considered jointly, explained 43.6% of the phenotypic variation in blast symptom expression. A comparison of the blast resistance QTLs with other disease resistance QTLs reported in this population revealed a region on chromosome 4 (4H) with multiple disease resistance loci. It will be useful to capitalize on the syntenic relationship of rice and barley and to integrate information on species-specific resistance genes with information on the reaction of the two species to the same pathogen.