Adaptation by Western Corn Rootworm (Coleoptera: Chrysomelidae) to Bt Maize: Inheritance, Fitness Costs, and Feeding Preference

Abstract

We examined inheritance of resistance, feeding behavior, and fitness costs for a laboratory-selected strain of western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), with resistance to maize (Zea maize L.) producing the Bacillus thuringiensisBerliner (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 nonrecessive. No fitness costs were associated with resistance alleles in the presence of two entomopathogenic nematode species, Steinernema carpocapsae Weiser and Heterorhabditis bacteriophora Poinar. Larval feeding studies indicated that the susceptible and resistant strains did not differ in preference for Bt and non-Bt root tissue in choice assays. KeywordsDiabrotica virgifera virgifera, feeding behavior, pest resistance, transgenic maize RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. ABSTRACT We examined inheritance of resistance, feeding behavior, and Þtness costs for a laboratory-selected strain of western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), with resistance to maize (Zea maize L.) producing the Bacillus thuringiensis Berliner (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 nonrecessive. No Þtness costs were associated with resistance alleles in the presence of two entomopathogenic nematode species, Steinernema carpocapsae Weiser and Heterorhabditis bacteriophora Poinar. Larval feeding studies indicated that the susceptible and resistant strains did not differ in preference for Bt and non-Bt root tissue in choice assays.KEY WORDS Diabrotica virgifera virgifera, feeding behavior, pest resistance, transgenic maize

Effects of Entomopathogens on Mortality of Western Corn Rootworm (Coleoptera: Chrysomelidae) and Fitness Costs of Resistance to Cry3Bb1 Maize

“…However, increased mortality of western corn rootworm larvae caused by entomopathogens was detected in six of the eight experiments conducted in this study (Table 3). These results parallel the work of Petzold-Maxwell et al (2012a), which also found that entomopathogens did not increase Þtness costs of resistance to Cry3Bb1 maize for western corn rootworm. Although signiÞcantly higher mortality was observed for the susceptible strain compared with resistant strain at some concentration of conidia in the seedling mat assay with B. bassiana, mortality in this assay was highly variable and did not differ signiÞcantly from zero ( Fig.…”

“…Both the results of this study and the results of Petzold-Maxwell et al (2012a), found an absence of Þtness costs in the presence of entomopathogens. In a study of Þve Cry3Bb1-resistant western corn rootworm strains (including the strain used here), Oswald et al (2012) did not detect Þtness costs for survival, fecundity, and egg viability, but did detect increased Þtness for resistant strains through faster developmental rate and higher fecundity.…”

“…Nematode solutions were made using DI water and added to soil to achieve the following four concentrations of nematodes within the soil: 50, 100, 150, and 200 nematodes per gram of dry soil. Concentrations were selected based on the results of Petzold-Maxwell et al (2012a). Each seedling mat with nematodes received 30 ml of nematode solution and each control seedling mat received 30 ml of DI water.…”

Effect of Maize Lines on Larval Fitness Costs of Cry1F Resistance in the European Corn Borer (Lepidoptera: Crambidae)

“…For example, Bt-resistant strains of P. xylostella had reduced survival and fecundity in one study (Groeters et al 1994), but no Þtness costs of resistance in other studies (Tang et al 1997, Ramachandran et al 1998. For the western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), an important pest of maize, no Þtness costs of Bt resistance were shown for a Cry3Bb1-resistant, nondiapausing strain in a study by Oswald et al (2012) and Petzold-Maxwell et al (2012); however, Meihls et al (2012) found evidence of Þtness costs. Gassmann et al (2009) found that the likelihood of a study detecting Þtness costs was positively correlated with the number of lifehistory characteristics measured.…”

Bt resistance in Australian insect pest species

“…While all cases of resistance to Bt cotton isolated in Australia have been recessive, at least two reported cases of practical resistance outside of Australia were partially dominant (reviewed in [6]; see also [23,24]). Therefore, concurrent with a shift in strategy, is a recognition that the highest priority in terms of novel resistance is detecting dominant resistance alleles.…”