Characterizing the inheritance of Cry2Ab2 resistance in a European corn borer (Lepidoptera: Crambidae) population from southern Minnesota

The European corn borer, Ostrinia nubilalis (Hübner), is a major corn insect pest, with larvae boring into the stalks of the plants. Transgenic corn expressing Bt proteins was developed in 1996 to target O. nubilalis and has successfully suppressed regional populations for the past three decades. However, long-term reliance on Bt technologies results in high selective pressure on O. nubilalis to evolve resistance, threatening the continual efficacy of Bt crop technology. In 2018, the first case of Bt resistance in O. nubilalis to Cry1F, was reported in Canada. More recently, field-evolved resistance to Cry1A.105 and Cry2Ab2 Bt sweetcorn was reported in Connecticut during 2023-2024. To delay insect resistance and ensure the sustainable use of Bt technologies, U.S. EPA has implemented an insect resistance management strategy, called ‘high dose/refuge’ strategy. This strategy’s effectiveness depends on resistance being recessive such that heterozygous progeny could be killed by the high dose Bt plants. On the contrary, when resistance is not recessive and heterozygous offspring could survive on Bt plants, durability of Bt technologies will be compromised. Consequently, determining the inheritance pattern of Bt resistance in a target insect is critical to understanding and managing resistance risks. In this study, we characterized the genetic basis of Cry2Ab2 resistance from an established resistant colony collected from southern Minnesota using F2 screens. The results of this study provide valuable information in understanding the inheritance patterns of field-evolved Cry2Ab2 resistance within O. nubilalis populations, which has significant implications in Bt resistance monitoring and management strategies.