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Research reveals predominant races of Phytophthora root rot in Manitoba soybeans

MB Pulse

Carman, MB – November 21, 2016 – The most prevalent races of Phytophthora sojae (P. sojae) found in Manitoba soybean fields are Races 4, 25, 28 and 3, with Race 4 being most predominant, according to a groundbreaking study funded by the Government of Canada, the Province of Manitoba and Manitoba Pulse & Soybean Growers through the Pulse Science Cluster.

With this new information, farmers and agronomists can be strategic not only in choosing a variety with resistance, but they can choose what type of resistance genes may be most effective.

“This information is critical for our industry. We wanted to get this knowledge out so that pathologists, breeders and seed companies can work together to strategically develop varieties that provide genetic resistance to the Phytophthora races specifically found in Manitoba,” says Kristen Podolsky, Production Specialist with Manitoba Pulse & Soybean Growers.

Phytophthora is one of four pathogens that cause seedling blight and root rot in Manitoba soybeans. It was especially prevalent in the 2016 growing season with wet soil conditions and increased frequency of soybean in rotations.

From 2014 to 2016, approximately 184 soybean fields were surveyed for plants that were symptomatic for phytophthora root rot caused by P. sojae. This in-depth study of the race structure of Phytophthora is the first of its kind in Manitoba and has been led by Dr. Debra McLaren, Plant Pathologist at Agriculture and Agri-Food Canada in Brandon.

“The most effective method to reduce economic losses caused by phytophthora root rot is to use resistant cultivars, and therefore it is critical to know the races of P. sojae that are present in soybean-producing regions,” says Dr. McLaren. “Based on the research that we have completed to date, four races have been identified and this is very exciting because it provides farmers with an additional tool for variety selection. Knowledge of the race diversity in Manitoba is essential for breeding Phytophthora-resistant cultivars and for screening soybean cultivars and germplasm accessions against this pathogen.”

Variety selection is the top management practice to prevent and reduce Phytophthora, in addition to good crop rotation practices and fungicide seed treatment. Over half the soybean varieties tested in Manitoba Pulse & Soybean Growers Variety Evaluation trials contain genetic resistance to Phytophthora.

“We don’t have the technology yet to measure which races are present in individual fields, but I would suggest that choosing a variety with resistance to the most prevalent races is an excellent start at this point. For example, soybean varieties that contain resistance genes 1k or 6 will be resistant to Race 4, the most predominant race found in Manitoba thus far,” says Podolsky.

The 2016 Soybean Variety Evaluation Guide is available here: https://www.manitobapulse.ca/production/variety-evaluation-guide/

A description of the research project is available here: https://www.manitobapulse.ca/mpga-funded_projects/soybean-root-rot-investigation-and-integrated-management-strategies/

Manitoba Pulse & Soybean Growers has contributed $360,000 in addition to $323,909 provided by Agriculture and Agri-Food Canada through the AgriInnovation Program’s Pulse Science Cluster.

About MPSG

The Manitoba Pulse & Soybean Growers (MPSG) is a non-profit, member-based corporation representing more than 3,500 farmers in Manitoba who grow pulses, including edible beans, peas, lentils, chickpeas, faba beans, and soybeans. MPSG provides Manitoba pulse grower members with production knowledge and market development support, through focused research, advocacy, and linkages with industry partners. MPGA is funded by a 0.5% check off levy and is governed by a board of directors, including elected active producers and appointed industry representatives.

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For more information, please contact:

Toban Dyck
Director of Communications
204-227-8875
toban@manitobapulse.dev