Pathotypes of Blumeria graminis (Dc. Ex Merat) Speer f. sp. tritici, the Causal Agent of Wheat Powdery Mildew from some Regions of Iran

Several samples of wheat leaves infected with powdery mildew were collected from Mazandarn, Golestan and Fars provinces in 2003 and 2004. After purification, 23 isolates of the pathogen were selected for pathotype determination. Seeds of 17 near-isogenic lines carrying the known Pm genes, were grown in pots in a greenhouse with 18-22 C, 95-100 RH and 12 hours light and darkness period. Each set of the isogenic lines were inoculated separately with pure condia of each isolate. Infection types of each line were recorded 12 and 16 days after inoculation. Twenty one different pathotypes were identified, having different virulence formula. Based on the results, 95% of the isolates were virulent on Pm3c and Pm5. Virulence for lines carrying Pm4b, Pm2,6, Pm1,2,9 and Pm2,4b,8 genes was rare among the isolates. This is the first report on the presence of virulence for Pm1,2,9 gene combination in Iran. Frequency of virulence for genes Pm4a, Pm8, Pm2,6, Pm1,2,9, Pm7 and Pm2,4b,8 was higher in 2004 than in 2003, but frequency of virulence for genes Pm1, Pm2, Pm3b, Pm3a, Pm6, Pm5, Pm3d and Pm9 was higher in 2003. No change in frequency of virulence for Pm3c was detected during two years. Pathotypes of Gharakhil in Mazandaran province, contained the highest number of virulence factors among the isolates.