Published on 08/27/24

Breakthrough discovery opens new doors in soybean cyst nematode management

By Julianne Johnston

A close-up of SCN females protruding from roots — Melissa Mitchum, CAES professor of nematology, and a multistate research team have identified the resistance-thwarting genes within soybean cyst nematodes, enabling new defenses and better resistance management. Pictured are female soybean cyst nematodes protruding from soybean roots. (Photo by Melissa Mitchum)

Researchers have made a major discovery in the fight against soybean cyst nematode (SCN) by focusing on the genetics of the parasitic roundworms. Extensive genetic sequencing coupled with genetic mapping helped them identify a handful of likely genes behind the tricky pests’ ability to skirt soybean genetic resistance.

“Out of the nine chromosomes and tens of thousands of genes in a nematode, we’ve mapped the areas involved in virulence (the nematode’s ability to reproduce on a resistant host) down to specific regions — in particular Chromosomes 3 and 6 — and a handful of genes,” said Melissa Mitchum, professor of nematology in the University of Georgia College of Agricultural and Environmental Sciences (CAES) and a member of the research team that made the discovery.

Mitchum, faculty in the CAES Department of Plant Pathology and Institute of Plant Breeding, Genetics and Genomics, is also an author of the related report published in Molecular Ecology.

Why is this discovery important? The identification of the resistance-thwarting genes within the nematodes lays the groundwork for:

Faster testing and identification of SCN populations in fields
Better resistance management using existing soybean varieties
New defenses against SCN
Similar efforts for other plant-parasitic nematodes

The SCN Coalition is thrilled by the news and strides made toward bringing farmers new strategies and tools for fighting SCN, a parasitic threat that costs farmers an estimated $1.5 billion each year.

Providing genetic resistance

“Our objective was to focus on the nematode and understand how SCN is adapting to reproduce on resistant soybean varieties,” Mitchum said.

The research team has also been working closely with soybean breeders on the soybean genes and gene combinations that provide genetic resistance. “We want to know which genes and gene combinations are most effective against which soybean cyst nematode populations,” Mitchum explains.

Knowing how these SCN genes and soybean genes interact and evolve will help the industry identify the virulence profile of SCN populations so farmers can make better use of the genetic resistance currently available for fighting SCN. It will also guide the development of future tools.

Putting discovery to work for farmers

“We’re trying to take it a step beyond whether a farmer has SCN. We want to give farmers the ability to choose which genetic resistance type will be most effective,” said Mitchum.

The next steps include focusing on high-priority candidates within those key regions to functionally confirm these genes have a role in nematode virulence on resistant plants.

“Once we prove which genes are contributing to virulence on specific genetic resistance like Peking or PI 88788, then we can develop a way to track this in a field population,” Mitchum said. She expects it will take a year or two to pinpoint the genes.

Proving a gene’s role in virulence is time-consuming and challenging, so parallel efforts will be underway to develop markers that correlate with virulence in field populations. That would give the industry what it needs to start developing tracking tools, fast-tracking the delivery of solutions for farmers.

“We’re trying to take it a step beyond whether a farmer has SCN. We want to give farmers the ability to choose which genetic resistance type will be most effective based on the SCN readout for their field,” Mitchum said. “It’s going to be very important that the breeders continually bring in those different resistant gene combinations.”

Paving the way for this breakthrough

“This breakthrough wouldn’t have happened without the investment of soybean farmers’ checkoff dollars in a collaborative, multistate North Central Soybean Research Program project involving nematologists, genome scientists and soybean breeders,” Mitchum said. Funds invested in the early stages of research for SCN genome sequencing laid the foundation that got us to where we are today.

To learn more about SCN and how to beat the pest, visit the coalition’s website. To learn more about plant pathology research at CAES, visit plantpath.caes.uga.edu.

Authors:

Julianne Johnston

Experts/Sources:

Melissa G Mitchum

As a University of Georgia Cooperative Extension specialist in the UGA College of Agricultural and Environmental Sciences, Bob Kemerait is well known for his devotion to the agricultural community of Georgia. He is also known for his international work with colleagues and small-scale farmers around the world. Recently, Kemerait took a team from UGA Extension to the Philippines, where he serves as a Fulbright specialist and works with the faculty at Mariano Marcos State University and farmers in the northern Philippines to improve disease management and other production practices.

CAES News

UGA plant pathologist works to improve crop management and empower farmers across the globe 11/05/24 Robert C Kemerait Jr

As a University of Georgia Cooperative Extension specialist in the UGA College of Agricultural and Environmental Sciences, Bob Kemerait is well known for his devotion to the agricultural community of Georgia. He is also known for his international work with colleagues and small-scale farmers around the world. Recently, Kemerait took a team from UGA Extension to the Philippines, where he serves as a Fulbright specialist.

Seth McAllister and farmer Mark Daniel discuss crop production and agritourism.

CAES News

UGA Extension supports agritourism through expert advice and collaboration 10/24/24 Emily Cabrera

On a sunny day with bright-blue skies, I arrive at Mark’s Melon Patch in Sasser, Georgia, and immediately spot the familiar white University of Georgia Cooperative Extension pickup truck, the Terrell County Extension logo prominently displayed on the door. Seth McAllister, the Agriculture and Natural Resources agent for Terrell County, greets me with a broad grin and a firm handshake. Terrell County alone has 60,000 acres of row crops, half in cotton. But what McAllister loves most about his role as an Extension agent is the diversity of his work.

Combining data collection and analysis with plant pathology, precision agriculture and robotics, the UGA team will build a photographic library of the foliar symptoms caused by onion diseases and other physiological disorders, feed them into the AI software, and use machine learning to identify the diseases based on pattern and color recognition from the images.

CAES News

UGA uses AI, robotics to improve Georgia’s Vidalia sweet onion crop 10/23/24 Jordan Powers

A multidisciplinary team of UGA researchers aims to enhance the competitiveness of Vidalia onion growers in Georgia by providing them with the ability to confidently detect onion diseases early, enabling them to make management decisions on their crop at a critical time. These abilities, researchers say, should result in increased yield and quality of marketable onions and an overall increase in efficiency and productivity.

Scott Jackson first came to the university in 2011 as the GRA Eminent Scholar in Plant Functional Genomics in the College of Agricultural and Environmental Sciences. (Photo by Andrew Davis Tucker)

CAES News

Scott Jackson returns to UGA as GRA Eminent Scholar 09/10/24 Olivia Randall

Renowned plant genetics researcher Scott Jackson has returned to the University of Georgia College of Agricultural and Environmental Sciences as the inaugural Georgia Research Alliance (GRA) Eminent Scholar in Synthetic Biology. GRA Eminent Scholars are internationally renowned scientists recruited to Georgia’s leading research universities in collaboration with the Georgia Research Alliance. GRA Eminent Scholars are distinguished by the significance of their research discoveries and their potential for commercial application.

CAES News

Keep on the grass 08/29/24 Emily Cabrera, Scott Michaux

When the University of Georgia Bulldogs step between the hedges at Sanford Stadium, the grass on Dooley Field needs to look perfect. More importantly, though, it needs to help safeguard the health of athletes who compete on it. Gerald Henry plays a big role in the latter. The UGA Athletic Association’s endowed professor in environmental turfgrass leads a research team in the Department of Crop and Soil Sciences committed to creating sports fields that look good and perform well to limit the occurrence of injuries.

Cordyceps, the fungus behind The Last of Us, is real, and it actually does turn some species of ants into zombie-like creatures. The fungus penetrates the ant’s exoskeleton and begins to multiply. Eventually, the fungal cells take over the ant’s central nervous system. It causes the ant to fall from its primary habitat in the tree canopy to the forest floor. Then the fungus makes the zombified creature climb a tree to an ideal height of almost a foot off the ground. The ant bites onto the plant so forcefully that not even death can dislodge it. When the time is right, the fungus bursts from the ant’s body, scattering spores across the forest floor. And the cycle repeats.

CAES News

A New Public Health Enemy No. 1 08/26/24 Leigh Hataway

As antimicrobial resistance grows, the world faces a deadly adversary few predicted: fungus. The battle against pathogenic fungi is raging, and UGA researchers are on the frontlines. “The fungus starts to direct the ant’s behavior, telling it where to go, what to do, like a puppeteer with a marionette. And it gets worse,” Dr. Neuman begins. “The fungus needs food to live, so it begins to devour its host from within, replacing the ant’s flesh with its own. But it doesn’t let its victim die. No, it keeps its puppet alive.”