How Genetics, Amino Acids and Bacteria Combine to Fight Soybean Nematode

There is hope on the horizon for soybean growers battling nematodes, the tiny roundworms that damaged more than $95 million in soybean crops in Arkansas last year.

After several years of research, scientists at the Arkansas Agricultural Experiment Station and other land-grant institutions in California, Washington and Indiana have found a way to boost a plant’s natural defenses from soybean and reduce the reproduction of soybean cysts and root-knot nematodes with the help of special amino acids. acids called peptides.

“We saw that seed treatments with synthetic plant elicitor peptides were able to reduce infection by soybean cyst nematodes and root-knot nematodes,” Fiona Goggin, professor of entomology at the experimental station, the research branch of the U of A System Division of Agriculture, told a group of scientists at the Arkansas Biosciences Institute’s fall symposium. “And we have new results showing that rhizobacteria, or bacteria that colonize root systems, may represent a promising alternative approach to delivering these peptides for nematode management.”

Plant elicitor peptides (PEPs) are natural signaling molecules that initiate a defense response in plants when damaged by nematodes or disease. While there are a variety of nematode-resistant cultivars that Arkansas growers can choose from, none can control all strains of soybean cyst nematode and root-knot nematode at the same time, Goggin said. Nematodes cause similar damage to the plant, but they are genetically different.

“So we need additional control measures that are broad-spectrum and not just targeted at one species or another,” Goggin said.

In addition to coating soybeans with synthetic resistance-boosting peptides, the researchers also experimented with a common, non-pathogenic bacterium that was engineered to deliver plant elicitor peptides. An advantage of the bacteria delivery method over seed coating is longer protection throughout the plant’s growth cycle. Goggin said tests show the bacterial treatment reduces soybean cyst nematode reproduction. His team is currently conducting experiments to see if the method also works on the root-knot nematode.

Goggin said among the diseases that attack soybeans, the leading cause of yield loss in soybeans in the United States is soybean cyst nematode, and root-knot nematode is among the top five crop pests. Arkansas has a bigger problem with root-knot nematode. Economic losses to soybeans in Arkansas due to root-knot nematode have increased 180% from 2011 to 2021, according to data from the Crop Protection Network. Network data shows the root-knot nematode caused a 4% yield loss in soybeans in the state last year, or more than 6.6 million bushels worth over 84, $6 million. Soybean cyst nematode damaged about 10.5 million in Arkansas soybeans last year.

Scientists at the Arkansas Agricultural Experiment Station have several research projects aimed at improving soybean production. In terms of farm cash receipts, soybeans have the highest value among Arkansas row crops at $1.6 billion, according to the Arkansas Agriculture Profile 2022. Soybeans are the most common crop in Arkansas, with more than double the rice acreage, adds the agricultural profile.

Soybean meal is mainly used as a high-protein supplement in animal feed. The bean is about 20% oil and can also be used to produce biodiesel.

How the method works

The plant’s damage signaling process begins when short bioactive peptides are cleaved from longer propeptides — chains of amino acids that aren’t biologically active, Goggin explained.

Previous research in other labs has shown that a plant’s responses can be enhanced against pathogens and insects when supplied with excess propeptides or artificially fed with the bioactive peptide. Goggin collaborated with Alisa Huffaker of the University of California, San Diego, a researcher involved in the original discovery of plant elicitor peptides in Arabidopsis, a plant commonly used for experiments. Together, they showed that treating soybeans with soybean plant elicitor peptides could reduce soybean cyst nematode and root-knot nematode infection without suppressing root growth or seed development.

Since the effects of seed treatment may not carry over to later stages of the growing season, Goggin’s lab also experimented with using a bacteria delivery system for long-term impact and cost savings. potential. They collaborated with Cynthia Gleason from Washington State University and Lei Zhang from Purdue University, who had previously used bacteria to deliver peptides into potatoes. Early results are promising and suggest this approach can help limit soybean cyst nematode, Goggin said. The following researchers from Goggin’s lab have also been full partners in the research: Abeer Alnasrawi, Ph.D. candidate in the Cellular and Molecular Biology Program; Ashley Humphreys, graduate student; and postdoctoral fellows Min Woo Lee and Payal Sanadhya.

Some seed funding for this research came from the Arkansas Institute of Biosciences, Goggin said at the symposium. The U.S. Department of Agriculture’s National Institute of Food and Agriculture also awarded a $499,936 grant to Goggin and co-researchers John Rupe and Alejandro Rojas in 2021 to study methods of strengthening the defense response of soybeans against nematodes and soil pathogens.

Because alternative treatments boost the plant’s natural defenses, this could decrease the potential for pesticide resistance, Goggin noted. Some pesticides used for nematode management are used for other problems like fungus.

“The more these pesticides are used, the greater the potential for resistance to these pesticides, just like you see with antibiotic resistance,” Goggin said.

The science behind their findings may also be effective in other nematode-susceptible plants, she added.

“It’s possible that these peptides work on other soil-borne diseases, and we’re also interested in pyramiding these genetically engineered rhizobacteria with other biocontrol agents that are being explored for nematode or disease management. “, said Goggin.

With the positive results of using an engineered bacterium to introduce plant elicitor peptides into the roots of soybean plants and reduce nematode reproduction, the collaborative research effort could lead to the commercial development of an alternative system. pathogen management that has long-lasting effects and overcomes pesticide resistance. .

To learn more about Agriculture Division research, visit the Arkansas Agricultural Experiment Station website: https://aaes.uada.edu. Follow on Twitter at @ArkAgResearch. To learn more about the Division of Agriculture, visit https://uada.edu/. Follow us on Twitter at @AgInArk. To learn more about extension programs in Arkansas, contact your local Cooperative Extension Service agent or visit www.uaex.uada.edu.

About the Agriculture Division: The mission of the University of Arkansas Division of Agriculture System is to strengthen agriculture, communities, and families by connecting trusted research with the adoption of best practices. Through the Agricultural Experiment Station and the Cooperative Extension Service, the Division of Agriculture conducts research and extension work within the country’s historic land grant education system. The Division of Agriculture is one of 20 entities in the University of Arkansas system. It has offices in all 75 counties of Arkansas and faculty at five system campuses. The Agricultural System Division of the University of Arkansas offers all of its extension and research programs and services without regard to race, color, sex, gender identity, sexual orientation, national origin , religion, age, disability, marital or veteran status, genetic information, or other legally protected status, and is an Affirmative Action/Equal Opportunity Employer.