Detection of emerging resistance to Bacillus thuringiensis crystalline toxins with genomic monitoring

The evolution of pest resistance to agricultural management practices is a long-standing problem in food production systems, which results in crop failure and economic losses for growers. Detection of emerging resistance in pest populations would provide an opportunity to reduce its spread and improve the durability of management practices. Recently, there have been calls for studies to develop and test genomic monitoring approaches, which could identify subtle signatures of emerging resistance evolution in pest genomes. The phytophagous North American insect pest, Helicoverpa zea, has recently evolved high levels of resistance to corn and cotton expressing transgenes from the bacterium Bacillus thuringiensis (Bt). Our work examines the genome architecture of field-evolved Bt resistance in H. zea and tests whether genomic monitoring is a feasible approach for early resistance detection. Collections of H. zea adults made from the same field location over time, as well as simultaneous collections of H. zea larvae from plots of Bt-expressing and non-expressing corn revealed the impacts of selection by Bt on their genomes. Our work demonstrates the potential for genomic monitoring to detect emerging resistance years prior to crop failure, but also identifies challenges that must be overcome prior to its widespread adoption in pesticide resistance management programs.