Soybean Cyst Nematode (SCN) has shaped Missouri soybean production for generations. It rarely draws attention in a single season, but over time it reduces yield, stresses plants and forces farmers and researchers to keep adjusting.
“Much of the genetic discovery, pretty much started at the Delta Research Center in Southeast Missouri back in the early 1980s,” University of Missouri professor of plant genetics and biotechnology Henry Nguyen says.
That long history matters because SCN is not static. It adapts. And in Missouri, it has had decades to do so. 
The Resistance that Carried Farmers — and What’s Changing
For years, resistant soybean varieties built on a small number of genetic sources helped Missouri growers manage SCN pressure. But relying heavily on one resistance background has allowed the nematode to gradually adapt.
“SCN populations in Missouri have been exposed to the same resistance source for decades,” says University of Missouri research scientist Sushil Chhapekar. “That has allowed SCN populations to gradually adapt, with about 50% of Missouri SCN populations now showing high virulence on it.”
That adaptation often happens quietly.
“As a result, farmers may not always see obvious symptoms yet still experience steady and hidden yield losses year after year,” Chhapekar says. “With tight margins and increasing production costs, Missouri growers cannot afford these hidden yield losses.”
The issue is not that resistance has stopped working. It’s that the nematode has changed faster than the genetic toolbox has expanded.
“If you depend on one source, you find difficulty,” Nguyen says.
Missouri Researchers Helping Drive the Next Phase
A multi-institutional research effort is beginning to uncover additional sources of SCN resistance that have not been widely used in commercial soybean breeding. Scientists analyzing more than 1,100 soybean genomes — including cultivated varieties and wild relatives — have identified plants with resistance that functions differently from the genetics used in most current varieties.
University of Missouri researchers are part of that effort and are working to translate those findings into breeding pipelines.
“As SCN populations in Missouri continue to evolve, relying on a single resistance source is becoming increasingly risky,” Chhapekar says. “Our current research focuses on identifying and combining multiple resistance genes from diverse genetic sources beyond PI 88788 and Peking.”
Advanced genomic tools are helping researchers pinpoint where resistance exists and how it works.
“With advanced genomics and biotechnology tools, we can now pinpoint resistance regions more precisely and stack them more efficiently in elite breeding lines,” Nguyen says. “This approach helps slow nematode adaptation and creates varieties with durable, sustainable resistance.”
For farmers, the long-term impact could be meaningful.
“For Missouri growers, this means more stable yields and less risk from gradual resistance breakdown,” Chhapekar says.
What Farmers Can Do Right Now
While new resistance sources move through research and breeding pipelines, SCN management still depends on decisions farmers make today.
“SCN management still requires an integrated approach,” Nguyen says.
Rotation remains the foundation — both crops and genetics.
“Rotating resistance sources using crop rotation, including Peking-based varieties, non-host plants like corn, sorghum, and wheat, and PI 88788-based varieties, is essential,” Chhapekar says.
Seed selection should also be grounded in local performance.
“Selecting varieties based on local trial data is critical,” Nguyen says.
Additional tools can help manage pressure in high-risk fields.
“Regular soil testing and seed treatments can play a supplementary role,” Chhapekar says.
The message from researchers is consistent: breeding progress matters, but management still drives outcomes.
“Breeding provides the foundation, but long-term success depends on combining genetics with good management,” Nguyen says.
What the Breakthrough Means for Missouri Fields
The newly identified resistance sources will take time to move through breeding pipelines, but they represent an important shift. For the first time in years, researchers are working with resistance that appears independent of the genetics most widely used in commercial soybeans.
Future varieties are likely to combine multiple resistance sources rather than rely on just one.
“It’s always good to stack up along with the known source of resistance,” Nguyen says.
Emerging technologies and commercial developments will likely become part of that approach.
“For example, introduction of new SCN resistance technologies and varieties provides another tool, but they work best when combined with rotation and management,” Chhapekar says.
Missouri’s Role Continues
Missouri has been central to the SCN fight for decades, and that role continues. Public researchers, breeders and extension teams across the state remain deeply involved in testing genetics and refining strategies that eventually reach farmers.
SCN will keep adapting. That part is certain.
But Missouri farmers, and Missouri research, have been adapting right along with it. And the next generation of resistance is already beginning to take shape.
This article sponsored in part by the United Soybean Board and their checkoff.
