Select Corn Lines Contain Compounds That Sicken and Kill Major Crop Pest

By Jeff Mulhollem

The corn earworm causes the loss of more than 76,000 bushels of corn in the United States annually, and there is mounting evidence that increasingly extreme weather events and temperatures will exacerbate the damage done to agricultural output by insect pests.

Responding to the threat, a team of researchers at Penn State has demonstrated that genetic lines of corn have inherent compounds that serve as insecticides, protecting them from the larvae that feed on them.

In findings recently published online ahead of the March issue of Plant Stress, the researchers reported that corn earworm larvae feeding on the silks, husks and kernels of corn lines containing high levels of flavonoids—chemicals that play essential roles in many biological processes and responses to environmental factors in plants—grow much more slowly and many die, compared to larva feeding on corn lines without flavonoids.

In addition to increased mortality and reduced body weight, larvae feeding on high-flavonoid corn lines developed a leaky-gut-like syndrome, the researchers found, suggesting involvement of microbiome changes in the larval gut. Moreover, the expression of gut health-related genes was changed in larvae consuming the flavonoid-rich husks.

In the study, the researchers compared how corn earworm larvae survived on genetically identical strains, except for a few specific, known differences of corn—in this case, with some expressing high flavonoid content in silks, husks and kernels; some not.

The corn, grown at the agronomy farm at Penn State's Russell E. Larson Agricultural Research Center, included a line engineered to have a gene that triggers flavonoid production and a line that was conventionally bred to produce flavonoids, which was developed over the last two decades by Chopra's lab from cross-breeding a mutant line of corn.

Researchers pointed out that they noticed "a stark difference" in mortality and bodyweight between corn earworm larvae feeding on flavonoid-overproducing lines as compared to control lines. Both the genetically engineered line and the line bred from the mutant had similar effects on the larvae.

"This research is important because it may be an early step toward the development of corn lines resistant to insect pests ideal for organic production," said research team leader Surinder Chopra, professor of maize genetics. "These findings, which suggest a novel option for integrated pest management for corn earworm larvae, show that high-flavonoid maize has the potential to be used in a breeding program to develop specialty corn lines tolerant of multiple insect pests."