The promise and pitfalls of genomic resistance monitoring: Genome evolution in Helicoverpa zea following release of transgenic crops

Emergence of insect resistance to new management technologies is a significant and ongoing challenge in agricultural ecosystems. Early detection of resistance may allow for regulatory changes which limit its spread. Monitoring pest genomes for characteristic signals of selection and adaptation following the release of new technologies could provide an early warning before irreversible and damaging resistance is widespread. We tracked genome-wide changes in a major agricultural pest, the corn earworm (Helicoverpa zea), in the years following deployment of Bt-expressing transgenic crops. We identified regions of the genome that underwent significant changes as damaging levels of resistance to Bt crystalline (Cry) toxins evolved in H. zea and the use of transgenic corn became widespread. We then identified genomic regions functionally linked to Cry resistance using quantitative trait locus mapping for laboratory crosses between resistant and susceptible populations. Our findings highlight both the promise and challenges associated with use of genomic monitoring due to the complex nature of resistance evolution in H. zea.