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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

Melissa Mitchum headshot among greenery outdoors
“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
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