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Soil bacteria may offer weapon against late blight in potatoes

Late blight has cost potato growers worldwide billions in damaged crops. (Scott Bauer photo courtesy ARS/USDA)

Potato producers may soon have a new ally in their battle against late blight, and it’s right under their feet.

Researchers have discovered bacterial strains in the soil that show promise as disease controls. Some bacteria suppress or inhibit late blight by over 90 per cent, according to an Agriculture and Agri-Food Canada (AAFC) release.

“The idea was to select the ‘best of the best’ bacteria from nature and put them through a rigorous screening program where the environmental conditions were favourable for the late blight pathogen,” said Dr. Sue Boyetchko, AAFC research scientist.

Boyetchko and Dr. Patrice Audy are leading the three-year study.

The research team has tested the bacteria in greenhouse and lab environments. Boyetchko said the best bacteria prevailed, with little or no optimization of their formulations or fermentation. “Dr. Audy and I were astounded by the amazing results.”

Those early results have piqued industry interest in creating a biopesticide containing the bacteria. Researchers are now narrowing the list of bacterial candidates that work on both potatoes and tomatoes, which are also affected by late blight.

Once the team has a good handle on how the bacteria control late blight, they’ll set their sights on how to commercialize the biocontrol.

To do so, they’ll need to increase shelf life and boost bacterial survival during storage, promote fermentation, and figure out the ideal formulation for field application, AAFC said.

Late blight is a serious threat to potato production, and can be a serious problem in Manitoba, Dr. Tracy Shinners-Carnelley wrote via email. Shinners-Carnelley is director of research and quality enhancement for Winnipeg vegetable supplier Peak of the Market.

As biopesticides’ availability increases, growers, researchers and agronomists are looking for ways to integrate them into disease management for plants, she said.

“If an effective biopesticide for late blight was developed it could have a significant impact on late blight management for both conventional and organically grown potatoes.”

Potato growers currently deal with late blight through management practices, Shinners-Carnelley said, including weather forecasting to determine disease risk, managing cull piles and eliminating other disease inoculum sources, using disease-free seed, scouting, removing volunteers, and using protectant fungicides.

How often producers apply fungicide depends on weather, pathogen presence, and maturity of the potato variety, she said. Under high disease pressure, they may apply fungicide 12 to 15 times, she added.

If weather and crop conditions favour late blight, it can defoliate a potato field in a matter of days, according to the Canadian Horticultural Council.

Each year the Canadian potato industry represents $1 billion in market value at the farm gate and $5.5 billion to food processing industry, according to AAFC — and potato producers in North America, Europe and developing countries lose between $3 billion and $5 billion annually to the disease.

Lisa Guenther is a field editor for Grainews and Country Guide at Livelong, Sask. Follow her at @LtoG on Twitter.

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