SUMMERLAND, B.C., RALEIGH, N.C. — What has been called the most destructive pest affecting soybean yields in the United States has a new nemesis — the enemy within.
In effect, genetic material from the nematode is being turned against itself.
Scientists at Kansas State University in Manhattan, Kan., have used a gene targeting method known as RNAi that stops soybean cyst nematodes from reproducing.
The research could have wide-reaching effects in Canada, especially in Ontario, where the pest is most prevalent.
In the U.S., the nematode costs the soybean industry billions of dollars in yield losses.
The University of Illinois’ crop sciences estimated that 125.15 million bushels of soybeans were lost because of the parasite in 2014. At a current soybean price of about US$10 per bushel, that’s a loss worth about $1.25 billion.
Doug Fatheringham of Syngenta said the pest is well established in Ontario and has reached nearly to Manitoba’s southern border.
“This isn’t a pest you turn your back on. It will cost you, as a farmer a lot of money. So far Western Canada hasn’t suffered from it, but very soon that will end,” he said about its movement north.
The Kansas State process uses RNAi to extract the gene from the nematode and add it to the soybean plant.
Harold Trick, who led the RNAi process side of the research, said in an email that the technology involves specific genes from the soybean cyst nematode that are important for nematode reproduction or development and genetically modified soybean plants that are designed to express it as a double-stranded RNA (dsRNA) molecule.
The soybean does not normally contain this genetic sequence, so it does not affect the plant. However, when a nematode feeds on the soybean roots, it ingests the dsRNA, recognizes it as “foreign” and silences the targeted gene, ultimately killing or weakening the nematode.
“We are targeting the soybean cyst nematode, but some of our sequences are also found in the root knot nematode, so it has the potential to target both species,” he said.
Timothy Todd, plant nematology researcher at Kansas State, said the process essentially stops or inhibits the nematode’s reproductive cycle.
He said the new trait should be heritable once researchers are able to get it into a stable plant line.
“It is still a way off getting it to the point where we’ll use it in the field,” he said, adding it was difficult to pin down a timeline because a lot of other parties are working on it and he’s not sure of their progress.
He also said he is not certain how the public will greet the research, although he pointed out that RNAi technology is much more precise than traditional methods of genetic modification.
“It targets one gene and one organism specifically, so it’s different than other transgenic processes,” he said.
People don’t have to worry about the RNAi process causing damage beyond stopping the parasite, he added.
Mario Tenuta, a soil ecology expert at the University of Manitoba, said research there is focusing on surveys, which are carried out every second year, and developing soil tests to help detection.
No positive soil tests have been found for the parasite there yet, but that doesn’t mean western provinces will escape it forever.
The next survey is scheduled for 2017.
Tenuta said he’s aware of the research at Kansas State and looks forward to seeing it made available to farmers.
“Yes, for sure, because our traditional resistance now that we have in our soybean varieties is breaking down.”
Harold Wright of Syngenta said his company’s Clariva, which contains a biological product that is being used on American farms, is working, but that company has soybean cyst nematode resistant genes in its pipeline of new products.
The biological element of that product is an endospore-forming bacterium and natural obligate parasite of SCN. It delivers a direct mode of action that reduces SCN feeding and reproduction, eventually killing the nematodes.
He said the biological is highly targeted at the SCN and when combined with resistance will help maintain resistance genetics in the crop.
Todd is hopeful the Kansas research will go as planned.
“I know there are some companies that believe in it and are chasing it,” he said.
“With any kind of technology like this, it isn’t easy to achieve success, but … it has good promise.”
Soybean cyst nematode has been moving northward from the U.S. and westward from Ontario for decades. It will move into new areas as soybeans become more popular and seeded acreage increases on the Prairies as it has in recent years.
Tenuta said sometimes the parasite strikes crops even harder because it pairs well with other diseases, such as sudden death, another major yield killer in soybeans.
Growers can manage the parasite by using resistant varieties, proper rotations and early identification.
Not all nematodes are bad, but soybean cyst nematodes feed on roots. Females attach their eggs to plant roots, which eventually are released into the soil and become juvenile worms.
The parasite restricts plant nutrients and water, disrupts normal nodulation and damages roots.
From above ground, infected fields may appear similar to drowned-out crops or as a field with iron chlorosis problems.
Plants can appear yellow, stunted and have fewer pods with uneven maturity.
Below ground, symptoms include stunted or discoloured roots with few nodules. Farmers may find white-to-yellowish, egg-shaped cysts smaller than a pinhead on plant roots.
Farmers should dig out plants with a shovel to avoid breaking off plant roots.
The Ontario government has created a chart that shows potential yield losses based on egg populations found in the soil.
It can be found at www.omafra.gov.on.ca/english/crops/pub 811/14soybean.htm.
Growers who have found the infection in their fields are advised to avoid plants that are good hosts for the disease, such as dry beans, especially kidney beans and peas. They must also control weeds, many of which also serve as good hosts.
As well, farmers should thoroughly wash equipment before moving it to a new field and should not drive pick-up trucks through different fields.
Using nematode resistant varieties is also critical in slowing the parasite’s progress.