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Research keeping up the fight against Aphanomyces

A decade after its first appearance in Alberta, this causal agent of root rot in peas has slowly given up its secrets. This scientist believes collaboration will be key to future progress.

Back in 2011, many pea growers in Alberta noticed a high degree of yellowing in their crops that had a devastating impact on yield. This disease threat was clearly serious, but what exactly was it?

“When you don’t know what you’re facing, there needs to be a journey of discovery,” said Dr. Syama Chatterton, Lethbridge-based Plant Pathologist with Agriculture and Agri-Food Canada. “We started from there.”

Over the next decade, Chatterton led the effort to get to the bottom of this disease threat. Looking back, it offers a playbook for how research can deal with emerging diseases and provides lessons to learn from.

What is it? After an intensive survey where the pathogen was first found, comparison with known pathogens confirmed that this was Aphanomyces root rot. “Aphanomyces can be quite challenging to detect and culture,” Chatterton noted. “We tested a molecular technique and that established that we had it.”

How widespread? The news here was not good. Surveys found that, rather than being a pathogen that could be contained locally, Aphanomyces was present all across the prairies.

How about resistant cultivars and fungicides? Do some pea varieties show at least partial resistance when in the presence of Aphanomyces? Chatterton found none. Over the past 10 years, she’s also examined both registered fungicides and products in the pipeline to see if there was anything promising. So far, this doesn’t look like a viable solution.

How can we help growers? Chatterton wanted to develop a test to allow growers to determine what level of Aphanomyces is in their fields. If it’s high, they need to refrain from growing peas on that land for years. “It worked great in wetter years like 2014 and 2016 but we stalled out in some dry years, which made it challenging to offer a test to growers.”

Despite both wins and setbacks to this point, Chatterton sees exciting developments on the horizon. With funding from the Canadian Agricultural Partnership AgriScience Program, she’s broadened the Aphanomyces research team to include experts in genomics, genetics and chemistry.

“One of the lessons we’ve learned with Aphanomyces is to try to put together a team with diverse experience as early as possible,” Chatterton said. “There’s an Aphanomyces community in Canada, the U.S. and France that’s small but very open to collaboration.”

The COVID-19 pandemic caused about a 20% decrease in Aphanomyces work in 2020, due in part to diminished lab capacity. Chatterton’s program returned to near-normal in 2021. She and her colleagues expect to be at full strength as they continue this critically important work in 2022.

While farmers are understandably frustrated by the impact of Aphanomyces on their production and livelihood, it’s comforting to know that Chatterton and her diverse team are going hard on the case. Professionally speaking, there’s nowhere she’d rather be.

“It’s a pathologist’s dream to work on a project like this,” Chatterton said. “We still don’t have immediate solutions, so that means we’re going to have to think outside the box. It’s been 10 years already but I expect to be working on Aphanomyces for the next 25.”

Funded in part by the Government of Canada under the Canadian Agricultural Partnership’s AgriScience Program, a federal, provincial, territorial initiative.