Corteva Agronomy Manager Mary Gumz points to two predominant sources of resistance for soybean cyst nematode, PI 88788 and Peking. Most common is PI 88788, which about 90 to 95% of the commercial soybean varieties used today.
But the yield-robbing SCN has been exposed to PI 88788 for decades, and that’s led to some nematodes breaking resistance.
Pioneer now offers new sources of SCN resistance, including some outstanding varieties with the Peking gene, Gumz said.
“Pioneer is continuing to do research on other sources of cyst nematode resistance. And one of the things I'm most excited about as agronomy manager is that we've got a great selection of both Peking and 88788 varieties that really yield well,” Gumz said.
At Iowa State University, nematologist Greg Tylka says with SCN breaking resistance to PI 88788, farmers are losing the battle. “We are in a bit of a pickle,” he said.
That’s because almost everybody's breeding program has the PI 88788 resistance genes, he said. Industrywide, Peking varieties remain a tiny fraction of what farmers have to choose from, Tylka said.
“It's going to take a big effort and a lot of time and a lot of money to shift gears and really make a major effort to bring more varieties to market with the uncommon but more effective Peking resistance, and that's a hard thing, from a business perspective, to swallow and decide to do,” Tylka said.
“But we're seeing glimmers of hope. There's a very gradual increase over the years, a very slow increase in the number of varieties with the Peking resistance.”
Gumz notes that SCN tends to develop slowly, and knowing that we have decreased efficacy of 88788, we do have the opportunity to move to other resistance sources as we're going through our soybean crop rotation, Gumz says.
“So, for example, if you had a field or you knew you had increasing levels of cyst nematode, ideally, your crop rotation would be corn, 88788, soybeans, corn, Peking soybeans, corn, 88788, soybeans,” she explains.
“Rotating them in every couple of years to the soybean part of your rotation can really do a lot, and obviously, avoiding continuous soybeans in fields like that.”
She urges farmers and agronomists to also consider other sources of resistance. “One of the great tools we use is ILEVO seed treatment, which can gain three or four bushels, even under low cyst nematode pressure.”
Ken O’Brien, Corteva agronomy sciences leader, explains that different races of cyst nematodes respond to different resistance types in different ways. HG tests show different populations from your field and how they respond to different resistance genes.
“It's helping you understand if 88788 will still work for me in this field, or if this population seems to still reproduce highly on that resistance gene; I better try Peking or one of the other sources of resistance.”
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