Seed recommending committee tackles canola diseases

Changes to canola disease labeling systems, protocols and cultivar screening – which all work toward ensuring high quality canola can be produced with minimized disease pressure – are covered by the pathology sub-committee of the Western Canada Canola/Rapeseed Recommending Committee (WCC/RRC). A recent sub-committee meeting on February 2 included discussion and changes on:

Blackleg

Understanding blackleg resistance genes has been an industry priority. In 2017, the WCC/RRC introduced a blackleg major resistance gene (R-gene) identification system which provides more detail around a cultivar’s blackleg resistance rating. Blackleg major R-genes are classified based on interactions with Leptosphaeria maculans (blackleg causing species) avirulence genes. One change to the system has been the removal of resistance gene group H, and the addition of resistance gene LepR2 into resistance gene group G. Choosing cultivars based on their major resistance gene is most effective when the predominant L. maculans races are known in the field.

• RG A = Rlm1 or LepR3
• RG B = Rlm2
• RG C = Rlm3
• RG D = LepR1
• RG E1 = Rlm4
• RG E2= Rlm7
• RG F = Rlm9
• RG G = RlmS or LepR2
• RG X = unknown

Quantitative resistance is the other category of blackleg resistance. Due to its complexity, it is not as easily identified within a cultivar. The WCC/RRC pathology sub-committee has been reviewing protocols to be able to measure the quantitative resistance potential of a cultivar. Currently any claims of quantitative resistance are done through a standardized protocol. Cultivar promotions that use the terms Adult Plant Resistance (APR), minor genes, QTLs, or QR all refer to the cultivar’s quantitative resistance.

Verticillium stripe

To reduce the knowledge gap on verticillium stripe disease distribution and severity within Western Canada, a working group was assigned to develop a disease severity scale in time for use in the 2021 growing season.

Clubroot

The Clubroot Steering Committee presented new clubroot survey data and reviewed progress of the international initiative to harmonize nomenclature and curation of clubroot resistance (CR) genetics. This international initiative will improve communication and provide clarity for how clubroot resistance loci are named, and is expected to have a data table and a published manuscript available in the near future.

The CSC then proposed revisions for clubroot resistance screening guidelines, which will guide accurate CR screening for cultivar development and research. Because there are so many clubroot pathotypes, and those pathotypes exist in populations, there have been some unexpected outcomes when inoculum sources are maintained on different hosts. The revised clubroot resistance screening guidelines define new boundaries for trial design and were written by an impressive list of clubroot experts. These guidelines are being reviewed by the WCC/RRC pathology sub-committee and will be finalized/adopted by breeders and researchers for the 2021 growing season.