More than 10 years after commercialization, Vip3A-expressing MIR162 remains highly efficacious in controlling major Lepidopteran maize pests: laboratory resistance selection versus field reality

Authors: WEN, ZHIMOU - Syngenta Crop Protection; CONVILLE, JARED - Syngenta Crop Protection; MATTHEWS, PHILLIP - Syngenta Crop Protection; HOOTMAN, TRAVIS - Syngenta Crop Protection; HIMES, JO - Syngenta Crop Protection; WONG, SARAH - Syngenta Crop Protection; HUANG, FANGNENG - Louisiana State University; Ni, Xinzhi; CHEN, JENG SHONG - Syngenta Crop Protection; BRAMLETT, MATTHEW - Syngenta Crop Protection

Submitted to: Pesticide Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/2023
Publication Date: 3/17/2023
Citation: Wen, Z., Conville, J., Matthews, P., Hootman, T., Himes, J., Wong, S., Huang, F., Ni, X., Chen, J., Bramlett, M. 2023. More than 10 years after commercialization, Vip3A-expressing MIR162 remains highly efficacious in controlling major Lepidopteran maize pests: laboratory resistance selection versus field reality. Pesticide Biochemistry and Physiology. 192:105385. https://doi.org/10.1016/j.pestbp.2023.105385.
DOI: https://doi.org/10.1016/j.pestbp.2023.105385

Interpretive Summary: The introduction of genetically modified crops that express insecticidal Bt proteins from in the mid-1990s revolutionized crop protection practice. Corn hybrids with event MIR162 (expresses insecticidal protein Vip3Aa) was approved for commercial cultivation in major corn producing countries including Brazil in 2009 and the USA in 2010. The MIR162 corn is highly efficacious against the fall armyworm, an important corn pest in the Americas including Brazil and the USA, as well as an important invasive pest worldwide. Furthermore, MIR162 corn upholds its high efficacy against laboratory-selected fall armyworm strains that are resistant to other Bt toxins. With the aim to preserve the value of MIR162 for insect control, we report the selection and establishment of a Vip3Aa-resistant fall armyworm strain. Resistant strains selected in the laboratory will not only help us to understand mode of action and mechanisms of Bt resistance, but also serve as valuable tools for screening new insect control leads with new mode of action. We also report the assessment of MIR162 efficacy against field populations of three major corn pests, that is, the fall armyworm, the corn earworm, and the western bean cutworm from different geographic locations. Our results indicate that the MIR162 event is efficacious against the field derived populations of these three pests.

Technical Abstract: MIR162, a maize event that expresses Vip3Aa20 (Vip3A) approved for commercial cultivation around 2010, has been excellent for control of major Lepidopteran pests. However, development of fall armyworm (FAW) resistance to Vip3A is a serious concern. Resistant colonies selected in the laboratory can serve as valuable tools not only for better understanding of Vip3A’s mode of action (MOA) and mechanism of resistance (MOR) but also for screening novel leads of new MOA that will help control FAW in case resistance to Vip3A in the field becomes a reality. We selected a Vip3A-resistant FAW strain, FAWVip3AR, by subjecting a FAW founder population containing field genetics to Vip3A exposure. FAWVip3AR had >9,800-fold resistance to Vip3A by diet surface overlay bioassays and resistance was stable. Feeding bioassays using detached leaf tissues or whole plants indicated that FAWVip3AR larvae readily fed and completed the full life cycle on Vip3A-expressing MIR162 maize plants and leaf tissues that killed 100% of susceptible larvae. Yet, FAWVip3AR faced at least two challenges. First, FAWVip3AR suffered an apparent disadvantage (incomplete resistance) when feeding on MIR162 in comparison to FAWVip3AR feeding on Vip3A-free isoline AX5707 maize; and second, FAWVip3AR showed a fitness costs in comparison to a Vip3A-susceptible strain when both fed on AX5707. We also demonstrated that, more than 10 years after commercialization, MIR162 and Vip3A remain highly efficacious against field populations of three major Lepidopteran pests from different geographic locations and FAW strains resistant to other Bacillus thuringiensis (Bt) toxins that are currently on the market.