Old war against stem rust rages on

Tom Fetch, a stem rust specialist in cereal crops with Agriculture Canada, works with global partners to fight the spread of Ug99, a strain of stem rust spreading across Africa. |  Robert Arnason photo

MORDEN, Man. — Tom Fetch admits his job description makes little sense at first glance.

Fetch is an Agriculture Canada research scientist who specializes in stem rust in cereal crops, but Canada hasn’t had an outbreak of stem rust in decades.

“I’ve been working for Ag Canada for 15 years and when I was hired we hadn’t seen (stem) rust on the Prairies for probably 30 years,” Fetch said. “And (people) were wondering why I should be working here.”

Fetch explained the reasons for his study during an open house at the Agriculture Canada research centre in Morden.

Former Ag Canada scientists, current employees and residents of Morden celebrated 100 years of research at the centre Aug. 12.

Following the 2014 closure of the Cereal Research Centre in Winnipeg, Morden became home to more than 15 plant pathologists who study diseases in cereal, pulse and oilseed crops.

The federal government built a new building to accommodate the new staff and their work, and it is the only Level 3 lab in Canada where scientists study hazardous plant pathogens.

Stem rust hasn’t been an issue in North America since the 1950s because plant scientists developed varieties with resistance to the disease.

But in 1998, a new type of stem rust, Ug99, emerged in Uganda and has since spread across eastern Africa.

The Ug99 outbreak may be thousands of kilometres from Western Canada but it’s a threat to cereal crops here for several reasons:

  • Stem rust is a devastating disease in cereal crops and can destroy yields in infected fields.
  • Prevailing winds can transport fungal spores across countries or potentially oceans.
  • An estimated 90 percent of global wheat varieties are susceptible to Ug99.

“Our Canadian wheat, I’ve tested it to these strains,” Fetch said. “About 80 percent of it is susceptible, so I still have a job to do.”

He and his colleagues study Ug99 fungal spores at the Morden lab under highly controlled conditions.

The Level 3 lab operates under negative pressure so air cannot flow out of the room.

As well, the scientists work with Ug99 only in winter and do not wear laboratory clothes outside of the building.

“You do your work, then you shower out. So there’s no way you could bring the spores out,” Fetch said.

Pathologists in Fetch’s program have identified three wheat genes with resistance to Ug99, which will help plant breeders develop new resistant varieties.

In December 2014, the Canadian Food Inspection Agency registered AAC Tenacious, a red spring wheat suitable for Western Canada with resistance to Ug99.

Fetch and his team are also part of global efforts to fight the spread of Ug99. Wheat cultivars, bred in Canada, are sent to greenhouses in Kenya and Ethiopia to evaluate their stem rust resistance.

Complicating matters, a number of strains of Ug99 have emerged, partly because stem rust produces a large number of spores.

“I’ve done the math. In a one-acre field under moderate infection, it (stem rust) will release about one trillion spores per day,” he said. “Even if the mutation rates are low, there are so many spores it is going to change.”

If African farmers grow wheat with resistance to Ug99, it should reduce the number of spores and reduce the likelihood of mutations.

Fetch is part of the Durable Rust Resistance in Wheat project, a $40 million effort funded by the Bill & Melinda Gates Foundation and the United Kingdom, which is de-signed to help address poverty, hunger and disease in the developing world.

Fetch’s primary contribution to the initiative is tracking the movement of Ug99. So far the fungus hasn’t spread to western Africa. If it does, the fungal spores may drift across the Atlantic to South America.

“I’m doing some work with Brazil … to monitor Ug99,” he said.

Monitoring and vigilance is critical to stop the spread but it’s hard to prevent a random event.

“There are lots of possibles,” Fetch said. “If it came on somebody’s clothing (to North America)… basically that’s impossible to stop.”

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