Investigation of resistance of Iranian bread wheat landraces to powdery mildew disease

A total of 17 wheat landraces were evaluated for resistance to powdery mildew in filed and greenhouse environments. The field experiment was performed at three disease hotspots in Sari, Gorgan and Moghan under natural disease incidence and the reaction of the genotypes was evaluated at adult plant stage. In order to evaluate the resistance of the genotypes at seedling stage, the isolates of the disease were collected from different regions and the pathotypes were identified by inoculation on the differential varieties. The results of field evaluation indicated that average reaction level of genotypes to the disease in Sari and Gorgan was similar and both lower than that of Moghan. A total of ten pathotypes were distinguished, all of which had virulence factors for Pm3a, Pm3c, Pm3g, Pm4a, Pm5, Pm6, Pm8 and Pm2. The varieties Shamrock (with unknown R gene), Normandie (Pm1+ Pm2+ Pm9), Axona (Pm2+Pm3d+Mld), Maris Dove (Mld+Pm2) and Wembley (Pm12) were resistant to all the pathotypes. The presence of Pm7 was postulated in genotype 7 as the resistance spectrum of this genotype was similar to that of Transfed. Genotypes 4 and 11 appeared resistant and moderately resistant at adult plant stage while they were susceptible to all pathotypes at seedling stage and therefore they were identified as genotypes with adult plant resistance. The total results of this research led to identification of seedling and adult plant resistance sources with different resistance gene combinations which could be exploited in breeding programs.