Hibernation helps US corn pests cause billions in damage

Researchers at the University of Kentucky have identified the genetic mechanisms that regulate the diapause process, a strategy that allows corn pests to resist winter

by Matteo Cavallito

 

Corn is one of the most widely consumed grains in the world and, like all crops, faces each year the threat of pests. Two of them, in particular, have always been a significant concern for farmers in the United States: the Northern Corn Rootworm (Diabrotica barberi) and the Western Corn Rootworm (Diabrotica virgifera virgifera), so named in relation to the areas of greatest prevalence. Knowing their survival mechanisms, it goes without saying, is a key step in better understanding their dynamics and studying strategies to combat them.

Providing a contribution in this regard recently was a research from the University of Kentucky. Which, its authors claim, reveals a previously unknown issue: the genetic mechanisms that enable these pests to withstand the severity of winter.

Hibernation saves corn pests

The two pathogens, recalls a University of Kentucky statement, cause billions of dollars of damage each year in U.S. agricultural regions. Their most important weapon is what is known as diapause, a hibernation-like phenomenon that allows eggs to remain dormant in the soil for several months.

During this period, biological processes that require energy are minimized, while the protective functions that help them survive cold are strengthened.

Because of its hibernation, the embryo of the corn cockle can thus get through the most treacherous months and then hatch when the plant’s roots are available for attack. The pests, in other words, actually adapt to the timing of planting and thus become difficult to control. Hence the need to understand their dynamics at the genetic level to intervene early to protect crops.

Genetic mechanisms

“Rootworms undergo an obligate embryonic diapause to synchronize their life cycles with host plants,” says the research published in the journal Current Research in Insect Science. In the study, “we sequenced transcriptomes from both species at five time points (pre-diapause, diapause initiation, diapause maintenance, diapause termination, and post-diapause),” the authors explain. Results, they add, “indicate that transcriptional regulation is dynamic during diapause.”

At this stage, with cell cycle arrest, the activity of cyclin-related genes decreases while the activities of heat shock proteins, proteasome and immune-related genes increase.

With post-diapause recovery, the research continues, there is a strong activation of cellular respiration. Comparative transcriptomic analyses the two maize rootworm species, western and northern, finally, “indicated that while many gene expression changes were conserved across species, overall gene expression profiles were distinct.”

A step forward for crop defense

Although the results of this research do not yet translate into immediate solutions for agriculture, the information gathered represents an important step. “This study sheds light on the suite of mechanisms that allow some organisms to pause the symphony of cellular events that occur during embryonic development,” the authors further note.

“Further, the mechanisms identified here may contribute to further research and pest management efforts in this economically important pest group.”

The researchers hope that in the future experimental methods can be devised for laboratory development of parasite colonies capable of skipping the diapause period altogether or at least reducing it. Their study, therefore, would enable accelerated testing of insecticides and genetic control methods.