News

New soybean cyst nematode resistance type to be released

There’s new hope in the fight against soybean cyst nematode (SCN). The seed company Syngenta is doing a limited release of a new soybean variety with the type of resistance known as PI 89772. Molecular nematologist Melissa Mitchum, at the University of Georgia, tells Brownfield Ag News she’s excited about that “primarily because we’re trying to diversify the genetic resistance on the market right now.”

Mitchum, formerly at the University of Missouri, says testing with the new variety, and with another resistance type called PI 90763, resulted in a drop in nematode populations. Many nematode populations have adapted to the only other known types of resistance, including the commonly planted PI 88788, said Mitchum.

“If a farmer rotates to one of these other sources (PI 89772 and PI 90763) that could significantly drop back the egg population densities in their fields,” said Mitchum, who is also a co-leader of the SCN Coalition.

Following this year’s limited release to researchers and a few farm cooperators, Syngenta says it’s doing a full commercial launch next year under two brand names: Golden Harvest GH2329X and NK Brand S23-G5X. It’s a Maturity Group 2.3 bean with SCN resistance, sudden death syndrome tolerance and the Roundup Ready 2 Xtend trait. USDA researchers originally discovered PI 89772 on an expedition in China back in 1930. “It takes time,” is how Mitchum summed up the amount of work and number of decades before that resistance type was ready for limited release. That’s a simplification of the reasons for the delay.

“Because the original source of PI 89772 was from USDA germplasm, we initially had agronomic issues we had to overcome,” said Jose Aponte, a soybean breeder with Syngenta, who has been working on that particular resistance type for nearly a quarter-century.

First it was necessary to breed performance and defensive packages into conventional soybean lines, according to Aponte, quoted in a news release.

“Then we have to transition it to herbicide-tolerant lines, first Roundup Ready 2 lines, then Xtend, Enlist E3 and ultimately XtendFlex,” Aponte added.

Findings of the research dovetail with research funded by the soybean checkoff via the North Central Soybean Research Program (NCSRP) and headed by Mitchum. In that project, Mitchum and other researchers are working to diversify the genetic base of SCN resistance in soybeans, identifying SCN virulence genes to better understand how the nematode adapts to reproduce on resistant varieties, and trying to determine what combinations of resistance genes would be beneficial in rotations to enhance the durability of SCN resistance.

Mitchum’s ultimate goal with the NCSRP project includes “marrying our knowledge of resistance with our knowledge of different SCN populations so we can offer farmers prescriptive SCN management,” she said.

Soybean cyst nematode lives in the soil, is highly reproductive and feeds on soybean roots, reducing yield by as much as 30 percent.

“We want to develop a rapid test to determine the SCN population in a soybean grower’s field that will help determine which genetic resistance to plant and which resistance rotation strategy to follow,” said Mitchum. “We hope to make this a reality.”