New tools for an old pest: HiPlex targeted sequencing for Bt corn resistance screening in Ostrinia nubilalis (Lepidoptera: Crambidae) from Canada

For almost three decades, crystal (Cry) insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) have been used as plant-incorporated protectants (PIPs) in transgenic corn, resulting in areawide suppression of the European corn borer (Ostrinia nubilalis). Control of this once-considered most damaging pest of corn in North America is now threatened by the evolution of practical resistance to PIPs in Bt corn. Practical resistance to the Cry1F protein has been detected in eastern Canada, and cases of resistance to the other available Bt PIPs (Cry1Ab, Cry1A.105, and Cry2Ab) are starting to emerge in Canada and the USA. A proactive insect resistance management (IRM) plan greatly benefits from an effective resistance monitoring program. Accordingly, the development and implementation of high-throughput DNA-based resistance monitoring could bring substantial benefits to IRM for Bt corn. In this study, we report the development and testing of a highly multiplexed (HiPlex) targeted sequencing panel amplifying the ABC transporter subfamily C2 gene in O. nubilalis (OnABCC2), a proposed Cry1F receptor altered in resistant O. nubilalis. Using this molecular diagnostic tool, we identified polymorphisms associated with practical O. nubilalis resistance to Cry1F and examined their frequency in O. nubilalis populations collected in four Canadian provinces. The results identify disruptive mutations in OnABCC2 as closely associated with the Cry1F resistance phenotype and support the use of HiPlex targeted sequencing in monitoring for O. nubilalis resistance to Bt PIPs.