Evaluation of Resistance to Powdery Mildew Disease in some of Iranian Genotypes of Hordeum spontaneum

To study the resistance to powdery mildew and determine the resistance genes in Iranian germplasm of Hordeum spontaneum, a total of 29 genotypes belonging to wild barley collection of National Plant Gene Bank of Iran were investigated. For this purpose, the isolates of the causal agent of the disease were collected form infected fields of Karaj, Sari and Zarghan. The isolates were inoculated on seedlings of susceptible variety 'Afzal' and propagated as single clones. Five different pathotypes were distinguished by using 19 near isogenic lines. Evaluation of resistance of genotypes was performed by the pathotypes in greenhouse at seedling stage. The reaction of differential lines indicated that the isolate Karaj2 had higher pathogenisity than other isolates. The isolates lacked virulence factor for Mlal+Ml(A12), Mla3, Mla9, Mla13+Ml(Ru3) and mlo5 resistance genes. Hence, these genes were identified as having effective resistance in all three regions. The relationship among isolates was studied through biplot of multi-dimensional scaling method based on dissimilarity matrix. Among the studied genotypes, only genotype 314 was resistant to all isolates. The reaction patterns of genotypes 434, 1006, 451, 1040, 495 and 555 to the isolates were not consistent with any those of the differential lines indicating the probable presence of gene(s) different from those existing in the lines. The total results of this research demonstrated the existence of resistance sources to powdery mildew in Iranian germplasm of H. spontaneum and possibility of finding new resistance gene(s).