Researchers' unusual discovery could help control soybean root rot

by DIANNE FETTERLY

An unusual discovery by a team of researchers at Agriculture and Agri-Food Canada's Southern Crop Protection and Food Research Centre may lead to better control of soybean root rot.

The scientists found that a pathogen responsible for soybean root rot breaks the genetic law that determines how characteristics are passed down through inheritance. The pathogen has figured out how to defeat most of the major resistance genes in the soybean plant therefore allowing the root rot, a fungus, to attack the plant.

 “We are pretty excited  because (the discovery) goes against the normal laws of genetics,” explained researcher Dr. Mark Gijzen. As a way to explain the discovery, he compared the pathogen's unusual behavior to that of human genetics, where in rare cases, both brown-eyed parents can produce a blue-eyed child.

While researchers still don't know how the pathogen manages to slip past the soybean plant's defenses, knowing that it behaves this way could lead to more options for growers battling the disease on their farms. “We are now trying to understand how the pathogen is able to beat soybean resistance and adapt. It could have broad implications for the industry in helping to create a better method of controlling root rot disease,” Gijzen said.

The pathogens responsible for root rot disease survive in the soil as spores. High moisture germinates the spores allowing them to affect the plant's roots. Root rot tends to thrive in soybeans grown in heavy clay or wet soils as well as heavily compacted soils and crops planted to no-till. Selecting seed varieties treated with fungicides will help combat the disease. Also, good management practices, such as crop rotation and reducing plant stress by avoiding low, wet fields can help keep root rot in check.

It took scientists at the centre about four years to make the discovery but Gijzen has spent nearly 20 years working on root rot research. He said this new knowledge can be used immediately by seed companies to help determine which fungicides work best in seed treatments; crop testing facilities; and other researchers to create more resistant varieties. It can even be applied to other crops, such as potatoes, since soybean root rot and potato blight organisms are fairly similar.

According to the Ontario Ministry of Agriculture, Food and Rural Affairs, root rot is considered to be one of the most destructive diseases of soybeans in Ontario. Agriculture Canada estimates national annual production losses from the disease at $40-$50 million.

Gijzen's research was recently published in the online journal, Nature Communications. BF