Researchers discover new strains of clubroot

Researchers discover new strains of clubroot
Apr 12, 2021

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The discovery brings the total number of known pathotypes to 36

By Diego Flammini
Staff Writer

Western Canadian scientists have discovered nine new strains of a disease capable of nearly 100 per cent yield loss in canola fields.

Keisha Hollman, a University of Alberta researcher, led a team who tested canola fields across the Prairies for clubroot in 2017 and 2018.

Her work is published in the Canadian Journal of Plant Pathology.

“Before the 2017 and 2018 field seasons, we had 17 unique pathotypes,” she told “But then after those seasons we added nine more. It’s showing the difference in the virulence of this pathogen.”

Keisha Hollman

Hollman’s team’s research brings the total number of known clubroot pathotypes up to 36.

And more than half of them are “resistance-breaking,” she said.

“It means they overcome traditional first-generation resistance, which is the resistance that you see in most of the commercially available varieties,” she said. “19 of the 36 are able to overcome traditional first-generation resistance.”

With these new pathotypes and those able to withstand the resistance bred into them, the industry will need to shift the way it looks at clubroot management.

The approach needs to be more integrated, Hollman said.

“It means bringing in more management tools and not solely rely on genetics anymore,” she said.

Hollman provided tips for farmers to minimize the risk of clubroot outbreaks.

Thorough scouting and identifying a small patch of clubroot early can prevent it from spreading, Hollman said.

“You can mitigate the small patch easier than if it spreads to the whole field,” she said. “Rotations are huge. I know it’s a tough sell but if you do have clubroot, rotations are one of the most effective ways of controlling clubroot. We’re recommending a one-in-three or one-in-four rotation.”

Hollman and her team will continue pathotyping to identify where these resistance-breaking pathotypes are and where they are spreading to.

“Some of the more unique pathotypes are isolated right now and we want to keep it that way,” she said. has contacted members of the canola industry for comment.

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