Inheritance and stability of Cry2Ab2 resistance in an Ostrinia nubilalis strain originating from Wisconsin, U.S

Transgenic corn expressing insecticidal proteins from the bacterium Bacillus thuringiensis (Bt), including Cry1Ab, Cry1Fa and/or Cry1A.105/Cry2Ab2, has been used to control Ostrinia nubilalis since 1996. Extensive reliance on Bt corn has led to practical resistance of O. nubilalis to Cry1 Bt corn in Canada and at one location in the U.S. between 2018 and 2024. Understanding the inheritance and stability of insect resistance is essential for the sustainability of Bt technology. Here, we characterized the inheritance of Cry2Ab2 resistance in an O. nubilalis strain derived from insects collected in Wisconsin, USA and evaluated the stability of this resistance over 17 generations in the absence of Cry2Ab2 selection pressure.

Survival of Cry2Ab2-susceptible (SS), -resistant (RR), reciprocal cross and backcross strains in diet-overlay bioassays showed that Cry2Ab2 resistance in RR was not influenced by maternal effects or sex linkage. Both Stone's dominance D and effective dominance (D_ML) values indicated that the resistance is functionally recessive. χ² tests comparing expected and observed mortality in F₂ and backcross strains support a Mendelian monogenic mode of inheritance. Stability tests showed no significant differences in survival of RR at any Cry2Ab2 concentration in the first, sixth and seventeenth generations.

Results of this study indicate that resistance to Cry2Ab2 in O. nubilalis is autosomal, functionally recessive, controlled by a single gene, and stable. These findings will improve our understanding of the risks associated with Cry2Ab2 resistance and support the development of effective strategies for the proactive management of Bt resistance in O. nubilalis. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.