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POSTERS: Pathogenicity and host specificity

Pathotypes of Plasmodiophora brassicae, the causal agent of clubroot, in Manitoba and Ontario, Canada, and in North Dakota
Mary Ruth McDonald - University of Guelph. Travis Cranmer- Univ of Guelph, Meghan Moran- Ontario Ministry of Agriculture, Food and Rural Affairs, Afsaneh Sedaghatkish- University of Guelph, Fadi Al-Daoud- University of Guelph, Bruce Gossen- Agriculture and Agri-Food Canada

Plasmodiophora brassicae causes the disease, clubroot, on plants in the family Brassicace, including canola and many Brassica vegetable crops. The pathogen exists as several pathotypes that are determined by the reaction on differential hosts. Plasmodiophora brassicae has been present in many regions of North America for several decades, mostly on Brassica vegetables. The disease was identified on canola in Alberta, Canada, in 2003, and has been recently reported on this crop in other Canadian provinces including Ontario and Manitoba. Clubroot has also recently been reported in North Dakota on Brassica vegetables. Clubroot samples were obtained from field surveys and from researchers in these three regions and the pathotype was assessed using the Williams (1966) differential set. New pathotypes have recently been identified that can overcome the clubroot resistance of previously resistant canola. The resistant canola hybrid 45H29 was inoculated to determine if any of the collections were new virulent pathotypes. The pathotypes found in Ontario in surveys in 2016 and 2017 were 2 and 6, similar to what was found 50 years ago, and also 5 and 8. Two samples of pathotype 2 were able to overcome the resistance in 45H29, so have been temporarily named 2x. Pathotype 9 was found in Manitoba. The pathotypes from North Dakota were 2 and 8. The differences in pathotypes in these regions suggests independent introduction events, and not transport from region to region. This was especially important for Manitoba and North Dakota, as some of the agricultural areas share a border.