Fifty-five clubroot pathotypes and counting…so where do you begin with trying to tackle the diversity of clubroot pathotypes found in Canada?
The main challenge plant breeders face today is trying to incorporate traits that can battle clubroot while also maintaining high yield potential, meeting canola quality standards, and still including other disease resistance traits required for variety registration in Canada.
Diversity at the field level #
Of the 55 pathotypes identified in Canada, 35 of them can overcome some of the resistant canola hybrids in the marketplace. And as alarming as that may sound, many of those pathotypes have only been identified once or a couple times. The most predominant pathotypes in Western Canada continue to be 3A, 3D, and 3H, which make up 57% of the pathotypes identified through grower field surveying. Pathotypes 5L, 8A, and 9E round up the other relevant pathotypes – so what do we make of the other 49 pathotypes discovered?
BrettYoung’s Agronomic and Regulatory Services Manager, Justine Cornelsen, said when selecting a canola hybrid for the season, growers need to focus on the select few predominant pathotypes and not get overwhelmed with the diversity of clubroot pathotypes out there.
“We do see new relevant pathotypes emerging but for the most part a lot of the pathotypes discovered are one-offs, they’re never seen again”, says Cornelsen. “And from that comes a lot of marketing around resistance labelling to pathotypes that really aren’t relevant.”
Saskatchewan and Manitoba continue to have under 100 fields per province with confirmed clubroot infections, where Alberta has over 4,000 confirmed fields with the disease.
Labelling initiatives #
The Canola Council of Canada (CCC) is leading a cross-industry initiative to standardize a product labelling system that will help growers determine and compare resistant hybrids between seed companies. The labelling system’s focus is on the three predominant pathotypes (3A, 3D, & 3H) and will look to add others once they become more established.
Rigorous field and indoor screening of hybrids has always been a part of the BrettYoung Clubroot DefendR® designation. Through this new initiative and the use of a consistent clubroot inoculum source, there is now much more confidence in labelling hybrids for their resistance against specific pathotypes.
Stacking major clubroot resistance genes into a single hybrid is an important factor in how effective and durable resistance is in clubroot-resistant hybrids. This approach has proven to be very effective and targets a variety of relevant clubroot pathotypes.
Clubroot Best Management Practices #
Clubroot is to be managed using an integrated pest management approach and not by relying on a single practice to keep the disease at bay. Crop scouting and identifying clubroot patches in the field will help determine what other best management practices (BMPs) need to be adopted.
For clubroot positive fields, a focus on minimizing soil movement, controlling host weeds and volunteer canola, while practicing an effective crop rotation will help to reduce clubroot spore loads. For fields that want to grow canola in future years, a clubroot-resistant hybrid is a must, but Cornelsen also recommends using patch management techniques that limit susceptible host plants in areas with high spore loads.
“Selecting hybrids for clubroot resistance durability can only be achieved when other best management practices, mainly crop rotation, are followed to help alleviate the selection pressure,” she said.
