Inheritance and fitness costs of Bt resistance in field-derived strains of western corn rootworm (Diabrotica virgifera virgifera LeConte)

Resistance of western corn rootworm, Diabrotica virgifera virgifera LeConte, to transgenic corn producing Bt toxin Cry3Bb1, Zea mays L, has been appearing in fields in Iowa, USA since 2009. The current understanding of interactions between western corn rootworm and Bt corn is based primarily on computer modeling, interactions of susceptible insects with Bt corn, and experiments with strains developed through laboratory based selection. Furthermore, there are few data on the inheritance of the resistance and fitness costs for Bt resistance in western corn rootworm. This study seeks to examine the inheritance of resistance and fitness costs for western corn rootworm strains with field-derived resistance to Cry3Bb1 corn, which were originally collected from Iowa cornfields. Magnitudes of resistance were characterized with diet-based bioassays, and the genetic inheritance of resistance was measured via reciprocal crosses and seedling mat bioassays. Fitness costs were measured for numerous life-history parameters through growth chamber experiments. These data will aid in the development of more effective insect resistance management methods in light of the refuge strategy.