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To tackle a pathogen, get the ID right first!

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Media Relations
Agriculture and Agri-Food Canada
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With more advanced equipment and technology, experts like Dr. Sarah Hambleton from Agriculture and Agri-Food Canada (AAFC) continue to refine our understanding and knowledge of different plants and fungi. In particular, correctly naming them can make a big difference when it comes to developing ways to protect crops from pests and breeding new varieties of crops.

Dr. Hambleton is an expert in identifying fungi, in particular rusts, a common disease on many crops. Most recently she worked with Dr. Miao Liu, also at AAFC, and researchers Dr. Lisa Castlebury and her postdoc Dr. Jill Demers from the United States Department of Agriculture in Beltsville, Maryland, to better understand rusts on switchgrass.

Switchgrass is an important forage, ornamental, and biofuel crop in Canada and the USA.

"Rust fungi cause diseases on switchgrass and I wanted to get a better understanding of what species of rust were affecting this grass and where they were found across the country. Historically, we had always believed that switchgrass was infected by one of two types of rust, but when I received a sample from Ontario for identification, it looked like neither one of them."

- Dr. Sarah Hambleton, Agriculture and Agri-Food Canada

Intrigued, Dr. Hambleton and Dr. Liu visited AAFC’s Canadian National Mycological Herbarium, a historical biological collection of fungi, to help them correctly identify the sample that was sent to them for identification. They looked for switchgrass, and closely related grasses, in the herbarium that had been infected by similar rust. At the same time, their American colleagues were doing similar investigations at the United States National Fungus Collections (BPI). Some of these grass samples dated back to the late 1800s.

The scientists compared the physical characteristics like the colour, texture and spores of the fungi found on the grasses and sequenced DNA to generate barcodes (taking very short segments of the fungi’s genetic material to identify it). They also looked at how others had described and identified these rusts and grasses in the past.

"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 Dr. Hambleton.

"You can’t accurately control rust if you don’t know exactly what you dealing with," explains Dr. Hambleton. "My research is really important to making sure that experts that breed new crops and develop ways to control pests have a good understanding of the challenges they are working to solve. Precise identification ensures that future research will be based on the best available information."

Dr. Hambleton and AAFC’s network of agriculture experts play a key role in helping scientists in various disciplines from around the world address the challenges facing modern agriculture.

Key facts

Photo gallery

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Dr. Sarah Hambleton, Agriculture and Agri-Food Canada mycologist looks at plant samples with rust on them from the 1800s at the Ottawa Research and Development Centre.
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Close-up of the rust fungus spores produced by the newly named species, Puccinia novopanici, on a switchgrass sample that was collected in 1922.
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Dr. Miao Liu, Agriculture and Agri-Food Canada mycologist works in her laboratory identifying fungi.

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