Races and virulence of Puccinia graminis f. sp. tritici in some regions of Iran

Stem rust represents the major threat to wheat production in Iran. It has been present for many years and epidemics occur in different regions on both winter and spring wheat. The objective of this study was to characterize races of Puccinia graminis f. sp. tritici present in Khuzestan and Lorstan provinces of Iran in 2012. Using the international system of nomenclature for P. graminis f. sp. tritici, 20 races were identified. A total of 20 races were identified from 30 isolates, which included the most prevalent races TTKSK and TTJQC with a frequency of 36.4 and 33.3%, respectively. The second most frequent and dominant race was KTTSK with a frequency of 18.2%. The resistance genes Sr24 and Sr36 were found to confer resistance to most of the races prevalent from two provinces while genes Sr5, Sr9e, Sr7b, Sr6, Sr8a, Sr9g, Sr30, Sr9a, Sr9d, Sr10 and SrMcn were ineffective against most of the races detected. Among these genes, resistance genes, Sr11, Sr38 and SrTmp were found as low infection types (more effective resistance genes) against most of the races detected. The wide virulence diversity that was found in this study across regions and over time will undoubtedly render the task of breeding durably resistant materials more difficult.