Virulence analysis of wheat powdery mildew races during 2019–2020 seasons in Egypt.

Wheat powdery mildew (Blumeria graminis f. sp. tritici, Bgt) has become a principal disease occurring annually in Egypt followed by rusts which have been effectively controlled using resistance genes. Survey for fresh infected samples of powdery mildew was collected from fields of farmers and International Wheat Programs of five provinces, i.e., El-Gharbia, Kafr Sheikh, Dakahlia, Menoufia and Behera in Delta Egypt during 2019 and 2020 growing seasons. A total of 37 powdery mildew genes (Pm) including 16 known differentials were evaluated at the seedling stage for resistance and to identify the Bgt pathotypes prevailing in Delta Egypt. 84 isolates of powdery mildew, seven pathotypes were identified in the 2019 season, i.e., BIOE, FOOE, MOIE, MOOE, POEE, OOOE, POCE, while six pathotypes: MOOE, MMOE, COOE, CKKE, MOKE and HOOE were identified in the 2020 season. The pathotype MOOE showed the highest frequency of occurrence during the two seasons (62.16% and 62.18%), respectively. No virulence frequencies were detected in 27.02% of the tested Pm-genes, i.e., Pm11, Pm13, Pm16, Pm24, Pm25, Pm29, Pm32, Pm35, Pm36 and Pm37 during the two seasons of the study. Twenty-four of the 37 Pm-genes showed 5.56 up to 100% virulence frequencies during the two seasons of study, whereas three of the Pm-genes, i.e., Pm1b, Pm12 and Pm34 showed some fluctuations in virulence frequency with values of 16.67% in 2019 season, and 5.55%, 13.89% and 27.78% virulence frequencies in 2020, respectively. [ABSTRACT FROM AUTHOR]