Powdery mildew in wheat caused by Blumeria graminis f.sp . tritici is one of the most important fungal diseases in Iran including Sistan province. During the years 1998 to 2001, wheat fields in the province were surveyed, powdery mildew infected samples collected from different areas, and transferred to the laboratory. In greenhouse, spores of the fungus were purified and then inoculated on susceptible wheat cultivars using single pustule as well as single spore procedures. Selected pure isolates were then inoculated on the first leaves in eight differential variaties for the identification of races. The results showed the presence of B.graminis f.sp. tritici races 66, 27, 11, 31, 50, 14, 28, 58, 21, 5, 19, 32, 24, 84, 53, 73 and 44 in Sistan province. These races were
new for Sistan Province as well as Iran. Among 17 races studied, races 11, 53 and 73 were the important dominant ones, constituting 40% of total population. Race 53 constituted 16% of all isolates and was the dominant race in the area with 62.5% pathogenicity. Therefore, this race was introduced as the most virulent one during the study period. This work indicated that the isolates were compatible with host plant genes pm8, pm3 and pm3b but incompatible with gene pm4b. Powdery mildew resistance was evaluated with race 11 on 70 wheat cultivars in seedling stages as well as adult plant under both greenhouse and field conditions during years 1999 to 2001.Among wheat lines tested for resistance against powdery mildew, cultivar Hirmand resembled the differential line Weihenst. M1 in that both probably Possess
gene pm4b, showing no symptoms under either the greenhouse or field conditions. Cultivar Chamran was found to be highly resistant whereas Sorkh tokhm susceptible. Other cultivars showed partial resistance against the disease.
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