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Cyst nematodes: molecular tools for population monitoring in fields

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Media Relations
Agriculture and Agri-Food Canada

Nematodes are microscopic worms that are usually beneficial to the soil. Research scientists use the presence of nematodes as an indicator of soil health. However, some nematodes can be harmful. In Quebec and Ontario, the presence of potato cyst nematodes (PCNs) and soybean cyst nematodes (SCNs) in fields is causing alarm among farmers. These nematodes attack the roots of certain crops and cause major economic damage. As these pests have emerged in Canada over the past few years, Agriculture and Agri-Food Canada (AAFC) research scientists have been studying their biology extensively and developing rapid screening and characterization methods.

"Finding soybean cyst nematodes in Quebec is certainly bad news, but it is fortunate that it was detected so early, before the populations got too high. This gives us time to talk to farmers and put strategies in place to limit the economic impact."

- Benjamin Mimee, PhD, Research Scientist and Nematologist, AAFC

Detecting cyst nematodes

Dr. Benjamin Mimee is exploring promising new methods for speeding up the detection and classification of virulent cyst nematode populations. For example, he is studying a sampling method known as piler dirt sampling that involves collecting soil samples from potato tubers as they are harvested, which means they can be analyzed more quickly than is possible with traditional sampling.

Dr. Mimee’s research focuses primarily on the genomics of cyst nematodes. Working with a team of experts from diverse fields (bioinformatics, molecular biology, nematology, etc.), he is developing new approaches for quickly decrypting the genomic data of cyst nematodes. His discoveries include the development of genetic markers to identify virulent pathotypes or to quantify the abundance and viability of nematode populations. Dr. Mimee and his team also use these data to understand the key stages in nematode development and to identify the genes that will be targeted by new control methods being developed. In addition, genomics is used to anticipate population trends in the context of climate change and to make recommendations to breeding programs. Within a few years, farmers should have access to cultivars that are resistant to cyst nematodes and better adapted to our climate conditions.

Prevention methods

Since it is not possible to eradicate cyst nematodes, crop rotation is the control method of choice. For PCN, the main host crops are potato, tomato and eggplant; for SCN, they are soybean, bean and pea. Alternating host crops with non-host crops (corn, cereals, canola, sunflower, alfalfa, etc.) stems the growth of nematode populations. The use of resistant host plant cultivars is also a highly effective control method, provided that the pathotype of the nematodes present is known.

Key discoveries (benefits)

Photo gallery

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The work of Benjamin Mimee and his team is aimed at maximizing the use of abstract data and transforming them into concrete applications to improve yields and reduce the environmental impact of agriculture.
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Each PCN cyst (yellow ball) contains hundreds of eggs that will lie dormant until they detect the presence of a host plant. They can survive this way for 30 years!
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Second-stage SCN larvae inside roots. After moulting three more times, they will form a giant cell and feed on the plant’s sap. Only the males will exit the root to fertilize the egg-filled females, which will attach themselves to the root and die. Each dried-out body will then become a cyst.

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