The corn earworm is a widespread crop pest, particularly in the U.S. South, and adept at quickly developing resistance to genetically engineered crops. Over time, researchers looking at lab-selected strains of earworm have identified 20 genes that harbor mutations conferring resistance to pest-killing proteins in so-called Bt crops, which have been genetically engineered to produce bacteria that repel the earworm.
“We call these 20 genes ‘the usual suspects,'” said University of Arizona scientist Bruce Tabashnik. “Contrary to our expectations, in seeking the culprit for field-evolved resistance of corn earworm, none of the usual suspects were guilty.”
Instead, genetic sequencing by Tabashnik and other Arizona scientists found resistance was associated in a cluster of genes that was duplicated in some resistant earworm populations found in the wild. “But it remains a mystery as to how many of these genes contribute to resistance and how they confer resistance,” said Andrew Legan, a post-doctorate fellow at Arizona and lead author of a study to appear in the Proceedings of the National Academy of Sciences.
Although they did not track resistance to a specific gene, the researchers said the study showed the importance of developing tools to monitor resistance in the field and that the genetic basis of resistance can differ between the lab and the field.