Clubroot (CR) is a costly canola disease that growers in Western Canada need to be aware of and understand the recommended management practices for. The latest research confirms continued spread of the disease throughout the canola-growing areas of Alberta, Manitoba, Saskatchewan and North Dakota. Many new pathotypes are present in the intensive CR areas of Alberta where the disease was first identified in Western Canada; however, new pathotypes have also been identified in Manitoba and North Dakota. Interestingly, surveys in these areas often show high levels of CR incidence on varieties with only first-generation CR resistance genes. This may be a result of too often relying on the protection provided by genetic resistance and ignoring the need for sufficient crop rotation. It has already been well documented in intensive CR areas that short canola rotations are a serious factor in aggravating disease incidence and are creating conditions for new CR pathotypes to emerge. New pathotypes quickly increase to serious levels because most canola hybrids being grown do not provide protection against them. Two levels of CR management are at the forefront of concern for growers, agronomists, and canola breeders: (1) CR is quickly becoming a concern for most areas of Western Canada and North Dakota and growers are heavily encouraged to include the CR resistance profile of a hybrid in their selection decisions; (2) Growers in intensive CR areas must consider the likelihood of encountering new pathotypes that will overcome first generation resistance. These fields require an integrated pest management approach and can include a variety of measures such as employing different genetics and extending the time between canola crops in rotation.
Pathotypes Capable of Overcoming First-Generation Resistance #
Certain newer pathotypes such as 3A, 3D and 8E are reportedly overcoming the first-generation resistance genes found in many commercial varieties. The 3A and 3D pathotypes, however, are by far the most frequently reported CR pathotypes where canola varieties are showing susceptibility. Thus far, these new pathotypes are primarily a concern only for growers around Edmonton, Alberta, and isolated areas of south-central Manitoba and north-central North Dakota. Adopting varieties with next-generation CR resistance genetics and adopting appropriate cultural practices will be key for growers in areas where risk of new CR pathotype emergence is high.
The Emerging Picture of Pathotype Diversity #
While Northern Alberta’s overall incidence rate of CR infestation is well ahead of other canola producing areas, recent CR surveys (fig. 1 below) suggest that the two regions mentioned previously are also seeing a much higher level of pathotype diversity than the Edmonton area. South-central Manitoba and north-central North Dakota are creating a far more complex situation for breeders who are working to screen and characterize new sources of CR resistance genes in their efforts to stay one step ahead. The stacking of major CR resistance genes into single varieties appears to be an important factor how effective and durable the resistance will be in next-generation CR resistant hybrids.
1st vs Next Generation Resistance #
First-Generation Resistance #
First-generation clubroot-resistant varieties tend to be varieties that can trace their resistance genetics to a resistance profile similar to the European-bred winter canola variety “Mendel”. These varieties are typically resistant to pathotypes 2, 3, 5, 6 and 8 (per the Williams’ Differential set, which are equivalent to pathotypes 2F, 3H, 5I, 6M and 8N on the CCD set).
Next-Generation Resistance #
There is no standard industry definition but in general, next-generation Clubroot-resistant varieties include first-generation resistance genes but should also contain additional resistance genes that may provide protection against newer pathotypes such as 3A, 2B, 3D, 8E, 5G, 5K, 3O and 5X. Consult the supplier of the variety for specific resistance profile information.
BrettYoung’s Clubroot DefendR: Broad Resistance with a Multi-genic Approach #
With the presence of new Clubroot (CR) pathotypes being found across the Western Canadian and Northern US prairies that can overcome first generation CR resistance it’s important to be aware of the ways to combat the evolving disease. Concurrent with the identification of new pathotypes, breeders have been identifying and incorporating new sources of resistance into the latest canola hybrids. This includes the stacking of multiple sources of resistance to CR in varieties like 6076 CR. This variety has resistance to the older pathotypes that were first identified on the Prairies (2F, 3H, 5I, 6M and 8N) and also to many newer pathotypes, including: 3A, 2B, 3D, 8E, 5G, 5K, 3O and 5X.
If you live in an area where CR is a concern, there are some best management practices you can follow in order to reduce your risk of infection and yield loss.
Recommended CR Management Practices: #
• Extend canola crop rotations to reduce spore load in soil
• In areas of higher risk, use first-generation resistant hybrids prior to infestation to delay the accumulation of CR spore loads that cause symptoms
• Use next-generation resistant hybrids with a minimum of three-year rotation in fields with high levels of infestation
• Scout fields to detect presence of disease symptoms
• Soil test to detect presence of pathogen spores
• Sanitize equipment properly
• Control canola volunteers and weeds that act as CR host plants
Growers in Manitoba, Saskatchewan and other areas not impacted by pathotype 3A can prevent the accumulation of spores for as long as possible by using resistant varieties such as 6090 RR, BY 6204TF and BY 5125CL. BY 6207TF and BY 6076 CR are recommended for areas where incidence of resistance breakdown is suspected.
Learn more about BrettYoung Clubroot resistant varieties by contacting your Regional Account Manager.
