Canola growers could soon see clearer, more detailed information on seed labels when shopping for clubroot resistance.
Clubroot is a persistent and evolving soil-borne disease that affects canola and other cruciferous crops, causing swollen galls on roots that reduce nutrient uptake and stunt plant growth.
The Clubroot Steering Committee, an industry-led working group made up of seed companies, researchers and producer organizations, proposes a new voluntary labelling system that specifies the exact forms of clubroot to which a variety is resistant.
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Instead of the current blanket “resistant” or “susceptible” tags, the new system would indicate resistance to specific strains, or pathotypes, of the clubroot organism common in Prairie soils.
The goal is to help farmers choose and rotate varieties more effectively, reducing disease pressure and preserving the usefulness of resistance over time.
Currently, seed varieties are labelled as resistant if they show less than 30 per cent disease compared to a susceptible check. But it doesn’t tell growers which specific strains a variety resists. The proposed changes aim to address that limitation.
Newer forms of the clubroot pathogen are already overcoming resistance bred into popular canola varieties, threatening yields and long-term soil health.
“Pathotypes in a field can shift dramatically within just a few years,” the Canola Council of Canada notes. “We need a more nuanced approach to help farmers rotate resistance sources and reduce disease pressure.”
Under the new proposal, seed labels would identify resistance to the three most common clubroot pathotypes in Western Canada, designated 3A, 3D and 3H. These are among the most widespread and damaging strains found in Prairie soils.
While the proposal focuses on just three, more than 47 distinct clubroot pathotypes have been identified in Canada, with new ones appearing nearly every year. Multiple forms of the pathogen can sometimes be found within a single clubroot gall. So, researchers are working to isolate and characterize minor strains for future inclusion.
“Eventually we’re getting to testing some of the minor pathotypes in Western Canada as well,” says Curtis Rempel, vice-president for crop production and innovation with the Canola Council of Canada.
Dr. Stephen Strelkov, a University of Alberta plant pathologist who has tracked clubroot’s spread since it was first identified near Edmonton in 2003, is leading the development of single-spore isolates for the most widespread pathotypes.
Strelkov shared updates earlier this year at CropConnect in Winnipeg, highlighting the urgency of staying ahead of evolving pathogen types. Rempel reports that Strelkov’s work on the three isolates is progressing well.
“Stephen is on track to have them available late this year or early next year for developers to start testing,” he says, adding that within the next couple of years he expects them to show up on labels. “It doesn’t happen overnight.”
The proposed system would give seed developers a clear framework to describe resistance consistently and in a grower-friendly way, making it easier for farmers to compare varieties based on how they perform against specific clubroot strains.
Rempel emphasized the practical value of this system for long-term resistance planning. He says the new labels could help growers plan rotations that reduce selection pressure.
For example, after planting a variety resistant to pathotype 3H for three cycles — nine years in a typical rotation — a grower might switch to a variety with resistance to 3A to keep the pathogen population off balance.
“It’s going to tell the farmer that whatever gene is in the variety they’re buying and growing will be resistant to pathogen type 3H,” he said.
Though the new labels will be voluntary, Rempel expects strong uptake.
“I’ve looked historically at our canola industry in Canada — the companies are always trying to do right by the grower,” he says. “They’re looking to optimize yields. They’re looking to optimize profitability. So all of this adds up as favourable for the grower.”
Breeding resistance to specific pathogen strains using single-spore isolates is not a new concept. It mirrors what’s already done in wheat breeding for leaf and stem rust resistance.
“This is a model that’s working elsewhere,” Rempel notes. “You have to be able to characterize it to know that your resistance genes are of any value — or optimum value.”
The labelling system is still under discussion, and key details such as implementation timelines and seed industry participation have not been finalized.
