Plants that fight back: Washington State University researchers combat parasitic worm

By Seth Truscott

So small it can’t be seen with the naked eye, a parasitic worm called the root-knot nematode causes mammoth problems for Northwest farmers.

Potatoes, grapes and other crops could gain a new, nature-based way to fight back, thanks to Cynthia Gleason and Jennifer Watts, scientists at Washington State University.

Notorious thieves

Nematodes cause billions of dollars in crop losses nationwide every year. In Washington, they cause significant losses to crops such grapes, onions, garlic and the state’s $734 million potato industry.

“Root-knot nematodes are a huge problem for farmers,” said Gleason, plant pathologist with WSU’s College of Agricultural, Human and Natural Resource Sciences (CAHNRS). The soilborne parasites move into the roots of crops, “then just sit there and feed on the plant. They’re stealing nutrients and water.”

Nematodes don’t kill the plants, but they leave them stunted, wilted from lack of water, and more susceptible to other pathogens, ultimately reducing farmers’ yields.

Chemical-free weapon pursued

“Plants don’t have many natural resistances to root-knot nematodes, so we need a way to combat them,” Gleason said. Traditionally, farmers have used anti-nematode pesticides — nematicides — to eliminate the tiny worms.

“But there aren’t many chemical options left, and they’re very expensive,” she said. “I’m looking for new, chemical-free controls that help growers move on.”

Acid stops nematodes

To help, Gleason is using a new $47,400 Emerging Research Issues grant from the CAHNRS Office of Research to seek genetic defenses that help crops like potatoes and tomatoes fight back against the persistent pest.

“I’m developing plants that are basically toxic to nematodes,” she said.

Partnering with Jennifer Watts, researcher in the College of Veterinary Medicine’s School of Molecular Biosciences, Gleason is adding genes that tell plants to secrete a specific fatty acid that stops the nematode reproductive cycle.

Watts and her team of student researchers discovered that a certain fatty acid, referred to as DGLA (20:3n-6), stops egg production in a cousin species of the root-knot nematode.

“These fatty acids aren’t normally produced in plant tissue,” says Watts. “My team and I are working with Cynthia to introduce genes into plants so they can make them. If it works, it could be a new, chemical-free method to control nematodes.”

While the fatty acid is not known to be toxic to people or animals at low levels, the researchers plan to only express it in cover crops and plant tissues that aren’t normally eaten.

Future pest fighters

Farmers could one day plant a seed, Gleason said, that grows into a cover or cash crop with its own natural pest control. As nematodes feed on the plants, their populations will fall — leading to healthier plants, bigger crops and an improved food supply.

“Usually, the study of nematodes and the challenges they bring is about new chemicals and pesticide controls,” said Gleason. “This is a new and different approach, one that’s chemical free.

“By working across colleges, mine and Jennifer’s teams are discovering and accomplishing much more than we could individually,” she added. “We can use that information to fight parasites, help Washington farmers, and grow more food. It’s a collaboration that benefits everyone.”