Soybean cyst nematode (SCN) populations are adapting and raising questions about the effectiveness of PI 88788, one of the main sources of SCN resistance in soybean varieties.

University of Illinois research shows PI 88788 still does a good job of controlling nematodes, but new gene combinations derived from wild soybean may hold answers for the future.

"The bottom line is that PI 88788 resistance worked well in our tests," said Brian Diers, U of I professor of soybean breeding. "Our research showed a significant yield advantage with PI 88788 resistance across six locations compared to susceptible soybean."

However, researchers know SCN populations are adapting to overcome this resistance, and in some fields this resistance is already ineffective. More than 90 percent of SCN-resistant soybean varieties are derived from PI 88788, making discovery of alternative resistance genes a priority.

U of I Extension Nematologist Terry Niblack, said, "We need to find new alternatives to protect the profitability of soybean crops produced in SCN-infested fields. We also need to reduce the SCN populations in fields where the population has adapted to PI 88788. Host resistance is the best way to manage SCN because it's easy, inexpensive and not harmful to the environment."

Continuing to use one source of resistance will eventually become ineffective as this pest adapts, Niblack said.

In addition to measuring PI 88788's effectiveness, the research team also studied resistance genes from wild soybeans and found they did a good job of controlling nematodes.

"We're now combining genes from domestic and wild soybean varieties to create a more durable resistance," Diers said. "Greenhouse tests show we can get broad resistance through these gene combinations, but now we need to test them in fields this summer."

Diers' goal is to find gene combinations that will be useful to growers so when PI 88788 resistance is no longer working well, farmers will have other genes to utilize.

"We need to increase diversity of genes for resistance," he said. "By studying and identifying genes that are effective, but not currently in use, we will be able to develop better resistant varieties to protect future yields."

This research was presented at the Soybean Breeders' Workshop in St. Louis, Mo. Funding for this study was provided by the Illinois Soybean Association. The research team consisted of Brian Diers, Jake Delheimer and Terry Niblack of the U of I, Mike Schmidt of Southern Illinois University, and Grover Shannon of the University of Missouri.

SOURCE: University of Illinois.