ARS | Publication request: Adaptation by western corn rootworm to Bt corn: characterizing inheritance, fitness costs, and feeding preference

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 13, 2012
Publication Date: August 1, 2012
Citation: Petzold-Maxwell, J., Cibils-Steward, X., French, B.W., Gassmann, A.J. 2012. Adaptation by western corn rootworm to Bt corn: characterizing inheritance, fitness costs, and feeding preference. Journal of Economic Entomology. 105:1407-1418.

Interpretive Summary: Insect resistance to transgenic (Bt) crops compromises their efficacy. However, there may be fitness related costs associated with resistance, which would delay it thereby promoting crop efficacy. In this study, we used a laboratory-selected, Bt-resistant strain of western corn rootworm to characterize inheritance of resistance, feeding behavior, and fitness costs associated with Bt resistance to corn producing the protein toxin Cry3Bb1. The resistant strain developed faster and had increased survival on Bt corn relative to a susceptible strain. Results from reciprocal crosses of the resistant and susceptible strains indicated that inheritance of resistance was non-recessive, and there was evidence of sex-linkage. Fitness costs were not related to genes associated with Bt resistance in the presence of two parasitic nematode species. Larval feeding studies indicated that there were no differences in preference for Bt versus non-Bt root tissue for either susceptible or resistant strains in two-choice assays, except first instar Bt-resistant larvae preferentially fed on non-Bt roots when forced to enter through the outer corn root tissue. Our results suggest the western corn rootworm has the potential to adapt quickly to Bt corn. Understanding resistance evolution in pest insects could help develop better insect resistant management (IRM) programs.

Technical Abstract: In this study, we used a laboratory-selected, Bt-resistant strain of western corn rootworm, Diabrotica virgifera virgifera Le Conte, to characterize inheritance of resistance, feeding behavior, and fitness costs associated with resistance to maize producing the Bacillus thuringiensis (Bt) toxin Cry3Bb1. The resistant strain developed faster and had increased survival on Bt maize relative to a susceptible strain. Results from reciprocal crosses of the resistant and susceptible strains indicated that inheritance of resistance was non-recessive, and there was evidence of sex-linkage. No fitness costs were associated with resistance alleles in the presence of two entomopathogenic nematode species, Steinernema carpocapsae and Heterorhabditis bacteriophora. Larval feeding studies indicated that there were no differences in preference for Bt versus non-Bt root tissue for either susceptible or resistant strains in two-choice assays, with the exception of Bt-resistant neonate larvae preferentially feeding on non-Bt roots when forced to enter through epidermal tissue.