Clubroot has evolved from a newly detected concern in Alberta to a Prairie-wide challenge for growers, agronomists and plant breeders.
Since the first case was reported in 2003, Dr. Stephen Strelkov has played a central role in understanding how the disease spreads, why early management tools were limited, and how resistance breeding has adapted in response.
His research has helped shape today’s approach to identifying pathotypes, developing resistance strategies and supporting canola growers across Western Canada.
From Tan Spot to Clubroot
It was August 2003, and Dr. Stephen Strelkov had just begun his plant pathology career at the University of Alberta with plans to focus on Tan Spot in wheat. One month later, the first canola clubroot case in Alberta changed his trajectory.
“When that happened, it caused me to reassess a little bit and think, ‘OK, this is an actual, practical problem that people are now facing, and maybe I need to devote more of my energy to this,’” he says.
At the time, little was known about how clubroot would affect canola in Alberta. Dr. Strelkov recalls feeling the need to pay close attention to the issue: “I felt I really needed to pay attention to it, and I’m glad I did because it became such a big issue.”
Although clubroot remains a growing concern across Western Canada, Dr. Strelkov notes that significant progress has been made in understanding and developing tools to manage the disease.
Clubroot Over the Years
Early Knowledge Gaps
“We didn’t know very much about clubroot at first, particularly how it behaved on canola.”
Early recommendations were limited. Growers were advised to avoid growing canola for extended periods if clubroot appeared on their farm, and there was little else to offer at that time.
Rapid Spread Across the Prairies
Since 2003, clubroot has moved outward from central Alberta into most canola-producing regions of the Prairies. Alberta continues to have the most affected fields — about 3,400 as of 2019 — while Saskatchewan and Manitoba continue to see rising case numbers.
Dr. Strelkov notes that the pace of spread has been unusually fast for a soil-borne disease.
“It’s definitely becoming a Prairie-wide issue, and it’s something anybody who’s growing canola should be aware of and keep an eye out for.”
Resistance Hybrids and Emerging Strains
The introduction of clubroot-resistant hybrids in 2009 was a major step forward, but new strains capable of overcoming first-generation resistance have since appeared in Western Canada. This has increased the need to characterize pathotypes and identify new sources of genetic resistance.
Developing the CCD Pathotype System
The Canadian Clubroot Differential (CCD) set, established in 2018 by Dr. Strelkov and collaborating scientists, modernized how pathotypes are identified and classified.
Unlike older systems, the CCD set incorporates newer Western Canadian strains and distinguishes between those that can and cannot overcome first-generation resistance.
Key CCD details include:
- 36 total pathotypes identified
- 19 capable of overcoming first-generation resistance
- High-impact strains 3A, 3D and 3H, which affect more fields across Western Canada
The CCD set provides essential guidance for breeders developing next-generation resistance traits.
Pathotypes and the Importance of Stacked Traits
Although new strains continue to emerge, first-generation resistance still matters. Some widespread pathotypes, such as 3H, may not be managed by next-generation genes alone.
Breeders have learned that combining next-generation resistance with forms of first-generation resistance produces more robust hybrids. DL Seeds — BrettYoung’s breeding partner — prioritizes stacked resistance, and all Clubroot DefendR® products include stacked traits for this reason.
“There are different sources of resistance, and not all resistance will work against all pathotypes. So, for the breeders, it’s very important for them to know essentially what pathotypes they have to breed against,” says Dr. Strelkov.
A Career Focused on Clubroot
Seventeen years into his university career, Dr. Strelkov still enjoys the balance of research, teaching and academic life.
“I definitely enjoy teaching, working and interacting with students as well.”
Although he continues to publish work on multiple diseases — including Tan Spot — clubroot remains his primary research focus. He values the opportunity to contribute to the industry’s long-term efforts to manage the disease.
FAQ
Why did Dr. Strelkov shift to Clubroot research?
When clubroot was first detected in Alberta in 2003, Dr. Strelkov refocused his work to address the practical challenges growers were already facing.
How has Clubroot spread across the Prairies?
The disease has expanded from central Alberta into other Prairie provinces, with thousands of confirmed cases in Alberta and rising numbers in Saskatchewan and Manitoba.
What early management options existed?
Initially, management strategies were extremely limited, and growers were often advised to avoid growing canola for a period of time.
How did resistant hybrids change management?
Resistance hybrids introduced in 2009 improved control, but emerging strains have since required breeders to pursue new resistance sources.
What is the CCD set?
The Canadian Clubroot Differential system classifies 36 pathotypes, including newer strains, and helps breeders target resistance strategies.
Why are stacked traits important?
Some widespread pathotypes are still only controlled by first-generation resistance, making stacked traits essential for broad protection.
