SCN Research Yields Real-World Results with Promise of More

Lurking beneath the soil, hungry nematodes eagerly await planting season and their lunch. Soybean cyst nematodes (SCN) are a particularly hungry pest, leading to an estimated $1 billion in yield loss each year.

As farmers begin, or prepare, for planting season it’s important to take a close look at what varieties hit the soil and nematode populations in fields.

The future of SCN resistance is on its way. Researchers, in partnership with the SCN Coalition, found two new forms of resistance that can be combined with Peking or PI 88788 resistances currently on the market. They’ve also identified how to make PI 88788 more efficacious.

“It’s kinda out of our hands [to get it on the market],” says Greg Tylka, nematologist at Iowa State University. “It’s in the hands of seed companies.”

The genetics have been released to anyone who wants to use them and feature a new form of resistance found in wild soybeans (Glycine soja), stacked with PI 88788 resistance. Researchers say they’re easy to backcross into current soybean varieties.

Research helps protect resistance available today.

“Nematodes are incredibly complex foes, and we need to find new solutions for soybean growers and protect current management tools,” says Melissa Mitchum, University of Missouri nematologist. Currently PI 88788 is under attack and more SCN populations are resistant, but new research reveals ways to protect the tool.

Nematologists have identified the two most important genes in soybeans to confer resistance. When the Rhg1 and Rhg 4 genes are repeated in the plant it’s resistant, and the greater number of copies of the genes means greater resistance.

“That’s why some SCN-resistance varieties with PI 88788 resistance are more effective than others,” according to Mitchum. “Some have higher copy numbers of those genes.”

Including more copies and stacking additional resistance mechanisms in soybeans can help protect PI 88788, which is used in 95% of SCN resistant varieties.

“In effect, over two decades we’ve selected more aggressive SCN populations that can overcome out main management tool,” Mitchum adds.

More research is being conducted to find additional forms of resistance and to get a handle on this pest. The SCN Coalition created a six-goal plan to promote education and outreach with the ultimate goal of maximizing profitability in spite of nematode threat:

  1. Nematode focus: research how nematodes are parasitic to plants and develop genomic and genetic tools.
  2. Soybean focus: enhance native nematode resistance in soybean by improving existing resources, finding new sources and developing multi-nematode resistant varieties.
  3. Trangenic focus: engineer new resistance using molecular tools.
  4. Management focus: confirm and improve today’s best management practices, identify new practices and find how they impact nematode populations and test seed treatment efficacy.
  5. Information focus: conduct nematode surveys to discover population densities and how big of an issue they are in different geographies.
  6. Audience focus: ensure researchers and extension are fostering education and outreach and provide personalized nematode management recommendations.

While SCN is a primary focus for researchers, they’re seeking solutions for other problematic pests such as root knot nematode, lance and others.