Evaluation of Resistance in Bt Maize Event DBN3601T Expressing Cry1Ab and Vip3Aa Proteins Against Athetis lepigone (Möschler) in North China

Athetis lepigone (Möschler) is an important pest of maize in North China, whose larvae feed mainly on maize leaves, stems, and roots during the seedling stage, with conventional maize lacking effective resistance to it. In recent years, transgenic Bt maize expressing Cry1Ab and Vip3Aa proteins has been commercialized in China; however, its resistance against A. lepigone has not yet been systematically evaluated. In this study, three Bt maize events, DBN3601T expressing Cry1Ab and Vip3Aa, DBN9936 expressing Cry1Ab, and DBN9501 expressing Vip3Aa, were used to comprehensively assess resistance against the pest based on Bt protein expression levels in different maize tissues, larval susceptibility across instars, and larval feeding behavior under controlled laboratory conditions. The results showed that Bt protein expression varied significantly among maize tissues commonly fed upon by the insect, following the general pattern: seedling leaf > stem > root. Bioassays using artificial diets incorporated with freeze-dried maize leaf powder indicated that larvae were significantly more susceptible to Cry1Ab than to Vip3Aa, with LC50 values of 1.05 and 2.65 μg·g−1, respectively. Maize co-expressing both proteins exhibited high insecticidal activity. First-instar larvae displayed feeding avoidance of Bt maize tissues, and early instars were more sensitive than later instars; however, stems and roots showed stronger toxicity to older larvae. In simulated field infestation assays, the control efficacies of DBN3601T, DBN9936, and DBN9501 reached 94.35%, 88.79%, and 10.56%, respectively, at five days post-infestation. Overall, DBN3601T maize exhibited a strong resistance performance against A. lepigone, indicating strong potential for pest management applications.