A new canola variety has shown some promising resistance to a new strain of clubroot that was found near Edmonton in 2013 and has since spread to nearly 30 fields.
But it won’t offer true resistance, says a plant pathologist from the University of Alberta.
“This variety had very, very strong resistance to the pathotypes that are prevalent, but only an intermediate reaction to this new pathotype — called 5X — from 2013,” Stephen Strelkov said about CS2000, Canterra Seeds’ new canola variety produced in partnership with DL Seeds.
“I think it’s a step in the right direction, and one that’s promising, but it’s certainly not a silver bullet.”
‘Intermediate resistance’ is a new concept for a lot of growers, he said.
Varieties that are susceptible to clubroot show disease severity that’s between 70 and 100 per cent, while resistant varieties show disease severity between zero and 30 per cent.
Varieties that have intermediate resistance — as CS2000 does — “fall somewhere in between,” said Strelkov.
“It’s significantly less susceptible than a variety that’s truly susceptible, but it’s not complete resistance.”
That terminology is important, said David Hansen, president of Canterra Seeds.
“Intermediate is a very, very sensitive word,” said Hansen.
CS2000 will offer some protection against 5X, he said, but not the complete resistance that it shows for the other “conventional clubroot pathotypes — 2, 3, 5, 6, and 8.”
A “limited amount” of CS2000 will hit the market this spring, enough to seed between 50,000 and 100,000 acres across Alberta, Saskatchewan, and Manitoba, he said.
“We’ve got a lot of demand for this, but we want to make sure we can put as much into as many hands as possible,” said Hansen.
In addition to its disease package, CS2000 is a “rock-solid variety from a yield and an agronomy perspective,” which is driving up demand, he said.
“It has a package of important attributes that are critically important for growers in Alberta.”
But because it’s not completely resistant, producers “need to be cautious,” said Strelkov. He suggests the new variety be used as a preventive measure rather than a management tool.
“The intermediate reaction to 5X may have some benefit in areas where clubroot is not established or present in very low levels,” he said. “Having that alternate source of resistance may reduce the probability of pathotype 5X if it’s not established, but in fields where there’s already heavy clubroot, we wouldn’t recommend it any more than any other clubroot-resistant varieties.”
The best prevention is still a four-year break between canola crops, he said.
“In fields where resistance has been overcome, we recommend that farmers avoid planting canola altogether in a short rotation,” said Strelkov. “A four-year rotation between canola crops is recommended on those fields.”
“Growers need to be not looking at these sorts of products as a silver bullet,” he said. “They need to also be taking into account rotations and cropping programs. You can’t be seeding canola back to back.”