Effects of cross‐pollination among non‐Bt and pyramided Bt corn expressing cry proteins in seed mixtures on resistance development of dual‐gene resistant Helicoverpa zea

Abstract

BACKGROUND: Seed mixture strategy can guarantee the compliance of planting non-Bt crops to host the susceptible insects for resistance management. However, pollen movement between Bt and non-Bt corn in the mixed plantings could reduce the efficacy of this strategy for ear-feeding insects. Few studies have evaluated the effects of cross-pollination among non-Bt and pyramided Bt corn in seed mixtures on the resistance development of insects possessing multiple resistances. Here, we provided the first study to investigate whether cross-pollination in mixed plantings of pyramided Bt corn producing Cry1A.105 and Cry2Ab2 would increase the dominance of resistance of dual-gene resistant populations of Helicoverpa zea, a target of pyramided Bt corn and cotton in the USA. RESULTS: We compared the survival and development of susceptible, dual-gene resistant (resistance to both Cry1 and Cry2 proteins) and heterozygous genotypes of H. zea in the laboratory on non-Bt and pyramided Bt corn ears collected from mixed plantings and structured plantings in the field. We found higher fitness for F 1 heterozygous insects than for the susceptible insects of H. zea on both pyramided Bt corn and non-Bt corn in the mixed plantings.CONCLUSION: These results suggest that cross-pollination in mixed plantings will significantly increase the dominance of resistance by supporting survival of heterozygous insects for dual-gene resistant populations of H. zea, and therefore accelerate evolution of resistance to pyramided Bt crops.

Cross‐resistance and redundant killing of Vip3Aa resistant populations of Helicoverpa zea on purified Bt proteins and pyramided Bt crops

“…Any naturally occurring insects were removed from the ears and each ear was manually infested with three H. zea neonates. Infested ears were placed in 5.7‐L plastic containers with two pieces of paper towel underneath 15,30–33 . The containers were placed in an insect rearing room maintained at 26 ± 1 °C, ~50% RH, and a photoperiod of 16:8 h (L:D).…”

“…Infested ears were placed in 5.7-L plastic containers with two pieces of paper towel underneath. 15,[30][31][32][33] The containers were placed in an insect rearing room maintained at 26 ± 1 °C, ∼50% RH, and a photoperiod of 16:8 h (L:D). The survival and development of the insects were monitored until the pupal stage and corn ears were replaced as needed during the experiment.…”