"Even some of the newer genes that haven't been deployed in cultivars weren't too effective," Cambron said.
That's because flies have likely interacted with, and adapted to, those genes already, said Brandi Schemerhorn, a USDA-ARS entomologist and Purdue assistant professor of entomology. She said it's possible that some of the genes were introduced to flies unintentionally in plots where wheat cultivars with those genes were being tested for suitability to Southeast climates. The resistance genes also could have come from other plants, such as rye, and the flies may already have started to overcome those genes.
Schemerhorn said she suspects a certain number of flies in any population have the ability to overcome any wheat resistance gene, which defends against the flies' ability to feed on the plant and starves the insect larvae. When a resistance gene kills off some of the flies, the survivors breed and eventually establish a population that renders the gene ineffective.
"We're creating a system in which the fly is becoming more virulent," Schemerhorn said. "What we have to do is slow down that adaptation or virulence."
Shukle and Schemerhorn suggest stacking genes in a wheat cultivar. There are only a few genes that haven't been deployed, and they believe combining two of those would be the best option.
"With a small number of identified resistance genes, we can't afford to release wheat lines with only one resistance gene," Shukle said. "If you deploy two different resistance genes, it's unlikely that a population of flies could overcome both of them."
Schemerhorn is working to combine two of the unreleased genes for testing with Hessian fly populations.
|Contact: Brian Wallheimer|