Predicting the Adaptation of Colorado Potato Beetle (Coleoptera: Chrysomelidae) to Transgenic Eggplants Expressing CryIII Toxin: the Role of Gene Dominance, Migration, and Fitness Costs

Abstract

A simulation model was developed to predict the possible adaptation of Leptinotarsa decemlineata Say to CryIII toxin expressed in transgenic eggplant. Use of mixed fields of transgenic and susceptible isolines at a 90:10 ratio has been simulated. Beetle movement, a fundamental feature when studying plant mixtures, has been addressed with a 2-stage hypothesis. Biological and genetic characteristics of the beetles have been set to specifically address their possible interactions with resistant eggplant. The role of gene dominance, migration, and fitness costs associated with the resistant genotype have been examined. Using the hypothesis of partial dominance of the resistant gene, only a high level of migration (very likely, in most agricultural areas) or a sensible reduction of the fitness of resistant beetles, associated with the change in their genome, can guarantee a long-lasting efficacy of the germplasm. The simulations clearly indicate that the effect of resistance in transgenic clones expressing Bacillus thuringiensis-derived toxins can be optimized only in accordance with opportune agricultural practices.