To tackle a plant pathogen, get the ID right first

Forages: News Roundup from the May 2018 issue of Canadian Cattlemen

With more advanced equipment and technology, experts like Dr. Sarah Hambleton from Agriculture and Agri-Food Canada (AAFC) continue to refine our understanding of different plants and fungi.

A recent case in point occurred when Hambleton, whose specialty is identifying fungi, and in particular rust, was sent a sample of contaminated switchgrass from Ontario to identify the rust involved. Historically only two rusts were known to infect switchgrass but this new rust didn’t look like either one of those.

That sent Hambleton and fellow AAFC researcher Miao Liu first to the department’s Canadian National Mycological Herbarium, which holds 350,000 fungal and fungal plant disease specimens, the largest collection in Canada. They searched the switchgrass and closely related grasses in the herbarium looking for a similar rust.

American researchers were simultaneously going through the same hunt at the United States National Fungus Collections (BPI) which houses some grass samples dating back to the late 1800s.

They not only compared colour, texture and spores of the mystery rust but sequenced short segments of its DNA to identify it.

“What we found was that five species of rust infect switchgrass, rather than only two as previously believed. Even more interesting is that none of them were the species that had been most commonly reported, which we found attacks a different grass called witchgrass,” explained Hambleton.

This may seem like a minor victory but eventually Hambleton’s discovery will be passed on to plant breeders and plant disease researchers to guide their future work.

“You can’t accurately control rust if you don’t know exactly what you’re dealing with,” says Hambleton.

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