Estimation of resistance allele frequencies to Cry1A.105 and Cry2Ab2 in the corn earworm (Lepidoptera: Noctuidae) with F2 isolines generated from a mass-mating method

The corn earworm/bollworm, Helicoverpa zea (Boddie), in the United States is targeted by transgenic and cotton expressing Bacillus thuringiensis (Bt) proteins. Previous studies have shown that resistance to Cry1A/Cry2A Bt has occurred field. In this study, we established 103 F2 isolines mass-mating of H. populations collected during 2018 2019 four southeastern U.S. states: Louisiana, Mississippi, Georgia, South Carolina. Dissection mated females showed at least 92.7% were originated from single matings, suggesting applied method a suitable approach establish isolines. screen allele frequencies these high two proteins expressed MON 89034 hybrids, averaging 0.405 for Cry1A.105 0.330 Cry2Ab2. observed confirm insect common region. addition, (0.490 0.541 Cry2Ab2) significantly greater than (0.312 0.081 2018, indicating selection Cry was likely still ongoing Information generated study useful assess risk, refine modeling, improve IRM programs mitigate sustainable use crop technology States.