UNIVERSITY PARK, Pa. – Purple cauliflower, purple cabbage and Indian corn (also known as flint corn) get their color from compounds called anthocyanins. Anthocyanins are part of a group of compounds called flavonoids, which are now being studied to combat certain agricultural pests.

Surinder Chopra, a professor of maize genetics at Penn State University, said he first became interested in flavonoids as a postdoctoral researcher at Iowa State University. At the time, he and his advisers used pigmented lines of sorghum and maize to follow the genetics of the plants. Later, a colleague introduced him to the beneficial effects of flavonoids against fungi and bacteria.

When Chopra moved to Penn State as a faculty member, his interest in flavonoids continued and he began identifying plant lines of corn and sorghum that produce different types of flavonoids. Through breeding and genetically purifying those lines, he was able to create pure lines that contain one or two of the specific flavonoid compounds he identified.

“These (flavonoid) compounds in some of the pure lines will be present in the kernel or the seed or the grain, and in other pure lines, the compounds will be produced in other parts of the plant like the leaves and vegetative plant parts,” Chopra said. “It’s the vegetative plant parts that gave us the next direction to where we were able to purify those compounds and use them against fungi, bacteria, and insects in very specific lab-based experiments.”

Chopra and colleagues recently published research that demonstrated corn earworm larval feeding on flavonoid-rich maize tissues causes high mortality and reduces body weight of the insect, indicating slower growth of the insect. The same results were found when insects were fed a sorghum flavonoids supplemented diet. The study was spearheaded by Debamalya Chatterjee, a former postdoctoral scholar in the Chopra lab who is currently an assistant professor at Skidmore College.

The flavonoids appear to cause symptoms typical of leaky gut syndrome, a condition that has been observed in mammals. Leaky gut syndrome is a condition where the junctions between cells in the small intestine lining become weak or damaged. When these cells are damaged, undigested food, bacteria, and toxins leak into the bloodstream, triggering inflammation throughout the body.

Interestingly, it’s unclear why flavonoids are causing these symptoms in insects, leading to their decreased growth and death. Chopra said it’s known that flavonoids are potential antioxidants, or substances that can prevent or delay some types of cell damage. However, that doesn’t fully explain the effect observed in Chopra’s studies.

“We are still working on hypotheses and trying to figure out the actual mechanism behind why flavonoids cause leaky gut syndrome in the insect gut,” he said. “We don’t know exactly.”

Beyond understanding the mechanism of how flavonoids impact insect mortality, Chopra and his research group are moving forward to find the best breeding lines and make hybrids that are high yielding and have high flavonoid content. The group is interested in understanding how crops respond to the presence or absence of high flavonoids and if flavonoids cause yield loss.

“Flavonoids are basically carbon derivatives, so they’re taking the carbon source from sugars,” Chopra said. “Instead of giving you high yield in kernels, you may be getting a low yield at the expense of (a corn line) that is a little bit more tolerant to insects without the heavy use of pesticides.”

Additionally, Chopra said that there are hundreds of flavonoids to explore. Many plants produce flavonoids, so it’s possible that other types of flavonoids present in crops could also yield beneficial effects.

“Having an alternate source of insect tolerance in crops would be one way to reduce the usage of pesticides and improve sustainability and the health of environment,” he said. “We can work to develop alternate crops where there is a sort of biochemical tolerance coming from the plant itself to protect itself from insects or harmful fungi or bacteria.”

This research is being carried out by current student researchers in Chopra lab – Charlie Colvin, Tyler Lesko, Bryan Panek, Quinn Loudy, Gurkirat Singh, and Faith Mihalick in collaboration with entomologists Michelle Peiffer, Gary Felton and Jared Ali at Penn State University.

The USDA’s National Institute of Food and Agriculture financially supported the research.