Solving the Pest Resistance Riddle

UMD researchers offer the possibility of whole genomic monitoring as a viable strategy to save crops and prevent economic losses

A corn earworm larva feeding on an ear of sweet corn

Image Credit: David Owens, University of Delaware Cooperative Extension

December 21, 2021 Graham Binder

Pests are inherently pesky. Over time they find ways to become resistant to pesticides that once prevented them from damaging a farmer’s yield, posing a daunting economic threat to the agricultural community. In recent years, the scientific community has introduced Bt crops, which produce bacterial proteins to protect the plants from insect feeding damage. They are a safe and environmentally friendly way to manage insect pests, but the effectiveness of these crops has eroded as pests continue to adapt.  Solutions for resistance management are badly needed for these and other pest control measures. To help recognize early warning signs and provide time to mitigate resistance issues, University of Maryland researchers tested a novel approach called genomic monitoring, to help track molecular signals of emerging pest resistance. Highlighted in a paper published in Proceedings of the National Academy of Sciences (PNAS), the findings demonstrate an underlying potential for genomic monitoring to slow or even prevent widespread pest resistance, and offer a promising path forward in the fight against pests and the subsequent crop damage they impose.

Drs Katherine Taylor, Kelly Hamby and Megan Fritz from UMD’s Department of Entomology tested this new approach by monitoring how the genome of the corn earworm - a major crop pest - changed between 2002 and 2017, a 15-year period during which both Bt crops and pest resistance increased in North America.

“While previous work has focused on monitoring small numbers of genes for resistance, for this study we took a gene agnostic approach and analyzed changes across the entire genome,” explains Taylor.

Through a series of genomic scans on wild corn earworm, paired with a process called quantitative trait locus mapping, which links genetic traits with molecular markers, Taylor, Hamby and Fritz found that Bt resistance in corn earworm is influenced by more than one gene, or polygenic. “According to our findings, the traditional model that assumes that one or few genes underlie traits like Bt resistance can be misleading,” says Taylor.

Throughout their analysis, Taylor, Hamby and Fritz identified an important timing component suggesting that changes in the genome associated with resistance would have been detectable several years prior to widespread, yield-reducing resistance to Bt crops. “This strengthens our case that genomic monitoring has the potential to detect resistance early, before it becomes problematic,” says Taylor. Many regions of the genome changed significantly as resistance was evolving and were associated with resistance to Bt proteins. However, not all changes they detected were linked to resistance, suggesting that for genomic monitoring to work, pest biology, sampling, and cropping system considerations must be carefully addressed.

“Our findings suggest that genomic monitoring is a promising new approach for slowing or preventing widespread pest resistance to any management strategy, not just Bt crops,” says Fritz. “The evolution of pest resistance threatens crop production and results in significant economic losses. Managing pest resistance evolution will be key to feeding the world population.”

This paper, titled “Genome evolution in an agricultural pest following adoption of transgenic crops” is published in PNAS.