New clubroot pathotype confirmed, can stump resistant canolas

A second round of tests on a clubroot pathotype found in the Edmonton area confirms it’s a new type that can beat canola varieties bred for clubroot resistance.

“This is a different pathotype that none of the commercially available clubroot-resistant varieties in Western Canada are effective at managing,” plant pathologist Stephen Strelkov of the University of Alberta said in a Canola Council of Canada release Tuesday.

Strelkov had collected samples from several fields in the area earlier this year, verifying higher levels of clubroot infection than would have been expected of clubroot-resistant canolas. [Related story]

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A “focused survey” is now being planned in the Edmonton region to help understand the new pathotype’s “prevalence and distribution,” the council said.

The council on Tuesday also advised canola growers and agronomists to scout fields seeded to clubroot-resistant varieties with “extra effort and vigilance” this summer. [Related]

Equipment sanitation remains the first line of defense against clubroot, new pathotype or not. “We are advising that growers practice good sanitation on their equipment, especially during spraying under wet conditions,” Curtis Rempel, the council’s vice-president for crop production, said in the council’s release Tuesday.

“This applies to equipment moving between all fields, not just those currently growing canola, since clubroot spores remain in the soil for years,” he added.

The level of sanitation should be based on the level of clubroot risk, the council said. It can range from knocking or scraping off soil lumps and sweeping off loose soil up to fine cleaning with a pressure washer and disinfection.

Other factors that may diminish the effectiveness of clubroot-resistant canola include canola rotations with less than a two-year break; lack of regular scouting in fields; seeding the same resistant canola variety in a rotation; or “any tillage that is more than zero-till.”

DuPont Pioneer, which launched the first clubroot-resistant canola for Prairie use in 2009, said in a separate release Wednesday that growers will also want to avoid use of straw, hay, green feed, silage and manure from “infested or suspect areas.”

Growers will also want to keep host weeds in check, and to avoid use of seed of any crop — for example, wheat seed — harvested from a known infected field, the company said.

“The tools we have”

Ian Grant, business manager for the company’s Canadian operations, said R+D staff are working on developing “longer-term” strategies.

“There is no immediate solution, but as an industry we need to do what we can to make the most of the tools that we have,” he said.

Clubroot, caused by the soil-borne Plasmodiophora brassicae pathogen, is established in Canada mainly in vegetable-producing regions of British Columbia, Quebec, Ontario and Atlantic Canada.

In canola, clubroot causes swollen galls to appear on the roots, cutting off the supply of water and nutrients to the plant, causing it to prematurely ripen and die. Typical yield losses run around 50 per cent but can run up to nearly 100 per cent in fields under severe clubroot pressure.

The disease’s first appearance in Canadian canola was in Quebec in 1997. Even given decades’ worth of large-scale canola production in Western Canada, it took until 2003 for clubroot to turn up on the Prairies, in spots near Edmonton. It’s since been advancing from that point in Alberta at a “fairly steady” 20 to 25 km per year.

Clubroot was confirmed in fields in Saskatchewan and Manitoba in 2011 and 2013 respectively. — Network


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