In the United States of America, the western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is commonly managed with transgenic corn (Zea mays L.) expressing insecticidal proteins from the bacteria Bacillus thuringiensis Berliner (Bt). Colonies of this pest have been selected in the laboratory on each commercially available transformation event and several resistant field populations have also been identified; some field populations are also resistant. In this study, progeny of a western corn rootworm population collected from a Minnesota corn field planted to SmartStax® corn were evaluated for resistance to corn hybrids expressing Cry3Bb1 (event MON88017) or Cry34/35Ab1 (event DAS-59122-7) and to the individual constituent proteins in diet-overlay bioassays. Results from these assays suggest that this population is resistant to Cry3Bb1 and is incompletely resistant to Cry34/35Ab1. In diet toxicity assays, larvae of the Minnesota (MN) population had resistance ratios of 4.71 and >13.22 for Cry34/35Ab1 and Cry3Bb1 proteins, respectively, compared with the control colonies. In all on-plant assays, the relative survival of the MN population on the DAS-59122-7 and MON88017 hybrids was significantly greater than the control colonies. Larvae of the MN population had inhibited development when reared on DAS-59122-7 compared with larvae reared on the non-Bt hybrid, indicating resistance was incomplete. Overall, these results document resistance to Cry3Bb1 and an incomplete resistance to Cry34/35Ab1 in a population of WCR from a SmartStax® performance problem field.
Bibliographical noteFunding Information:
We thank Monsanto Company and Dow AgroSciences, respectively, for Cry3Bb1 and Cry34/35Ab1 proteins and artificial diet for the diet toxicity studies. We also thank Monsanto Company and DuPont Pioneer for corn seed associated with plant bioassays. Collection of corn rootworm populations for this study was funded by the corn farmers of Minnesota through their corn check-off investment. A grant from Monsanto Company's Corn Rootworm Knowledge Research Program helped fund the analysis and writing of this manuscript. Also, we would like to thank Tom Clark (Monsanto Company), Miles Lepping and Nicholas Storer (Dow Agrosciences) and Clint Pilcher (DuPont Pioneer) for comments on an earlier draft. We also thank members of Dalton Ludwick's dissertation committee, Tom Coudron (USDA-ARS) and Debbie Finke and Mark Ellersieck (University of Missouri) for reviewing an earlier draft of this manuscript. Lastly, we thank two anonymous reviewers for their comments on this manuscript prior to publication.
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- Diabrotica virgifera virgifera
- resistance management