Virulence structure of Blumeria graminis f. sp. tritici, the causal agent of wheat powdery mildew, in Ontario in 2018 and 2019

Authors: XUE, ALLEN - Agriculture And Agri-Food Canada; LIM, SEARA - Agriculture And Agri-Food Canada; CHEN, YUANHONG - Agriculture And Agri-Food Canada; HUMPHREYS, GAVIN - Agriculture And Agri-Food Canada; CAO, WENGUANG - Agriculture And Agri-Food Canada; MENZIES, JIM - Agriculture And Agri-Food Canada; Cowger, Christina; LI, HONGJIE - Chinese Academy Of Agricultural Sciences; SERAJAZARI, MITRA - University Of Guelph

Submitted to: Canadian Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2021
Publication Date: 5/12/2021
Citation: Xue, A.G., Lim, S., Chen, Y., Humphreys, G., Cao, W., Menzies, J., Cowger, C., Li, H., Serajazari, M. 2021. Virulence structure of Blumeria graminis f. sp. tritici, the causal agent of wheat powdery mildew, in Ontario in 2018 and 2019. Canadian Journal of Plant Pathology. https://doi.org/10.1080/07060661.2021.1915876.
DOI: https://doi.org/10.1080/07060661.2021.1915876

Interpretive Summary: The virulence profile of the fungus that causes wheat powdery mildew on wheat in Ontario, Canada, was studied in 2018 and 2019. Powdery mildew isolates were collected from greenhouses and commercial fields, and 40 different virulence profiles were identified. They were inoculated on a set of 24 wheat lines each carrying a single powdery mildew resistance gene. Eight of the genes were effective against all of the powdery mildew isolates: Pm1a, Pm1b, Pm1c, Pm12, Pm16, Pm21, Pm37, and MlAG12. Four other resistance genes were effective against at least 80% of the isolates: Pm29, Pm3d, Pm34, and NCAG13. Results suggested that the Bgt population of Ontario was relatively stable and the effective genes identified in this study could be used in wheat breeding programs for developing powdery mildew resistant cultivars in Ontario.

Technical Abstract: The virulence structure of Blumeria graminis f. sp. tritici (Bgt), the causal agent of powdery mildew in wheat (Triticum aestivum) in Ontario, was examined in 2018 and 2019. Of the 42 single colony isolates collected in Ontario greenhouses and commercial fields, 40 virulence phenotypes, assigned VP1 to VP40, were identified on a set of 24 single-gene differential genotypes. Of the 24 resistance genes possessed by the differential genotypes, eight genes including Pm1a, Pm1b, Pm1c, Pm12, Pm16, Pm21, Pm37, and MlAG12 were effective against all of the 42 Bgt isolates. Four genes including Pm29, Pm3d, Pm34, and NCAG13 were mostly effective with resistance reactions to more than 80% of the isolates. There were no significant differences in numbers of virulence genes per isolate between the two years, or between the greenhouse and field origins. The virulence frequencies of Bgt isolates for these effective and mostly effective genes were also not significantly affected by the year of collection and their origins, suggesting that the Bgt population is relatively stable and the effective genes identified in this study may be deployed or used for gene pyramiding in wheat breeding programs for developing powdery mildew resistant cultivars in Ontario.