Fitness costs of Bt resistance in western corn rootworm

Resistance of insects to transgenic crops producing insecticidal toxins from Bacillus thuringiensis (Bt) has the potential to cut short the benefits these crops provide.  Bt corn provides effective control of western corn rootworm, Diabrotica virgifera virgifera Le Conte (WCR), which is a significant pest of corn.  Fitness costs arise in the absence of Bt toxin when insects that harbor Bt resistance alleles have lower fitness than Bt-susceptible insects.  Fitness costs are important because they can delay or prevent the evolution of Bt resistance.   We tested for the presence of fitness costs using a WCR strain that had been selected in the laboratory for Bt resistance on the Cry3Bb1 toxin.  We reared Bt-resistant and Bt-susceptible insects on three corn inbred lines, one that was susceptible to WCR and two that contained native resistance to WCR.  We measured survival to adulthood, longevity, fecundity, and developmental rate.  These data address the extent to which fitness costs of Bt resistance may be present in WCR and whether host-plant variety can affect fitness costs.