Development of resistance to eCry3.1Ab-expressing transgenic maize in a laboratory-selected population of western corn rootworm (Coleoptera: Chrysomelidae)

Authors: FRANK, DANIEL - West Virginia University; ZUKOFF, ANTHONY - Kansas State University; Barry, Julie; HIGDON, MATTHEW - University Of Missouri; Hibbard, Bruce

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2013
Publication Date: 12/12/2013
Publication URL: http://handle.nal.usda.gov/10113/58148
Citation: Frank, D.L., Zukoff, A., Barry, J.M., Higdon, M.L., Hibbard, B.E. 2013. Development of resistance to eCry3.1Ab-expressing transgenic maize in a laboratory-selected population of western corn rootworm (Coleoptera: Chrysomelidae). Journal of Economic Entomology. 106(6):2506-2513.

Interpretive Summary: The study and development of colonies of corn rootworms resistant to transgenic corn that carry an insecticide can help us understand how such resistance occurs and help us to slow resistance in current and future control measures. The selected laboratory colony of the western corn rootworm was established by rearing larvae on transgenic corn expressing Cry3.1Ab (the insecticidal protein). The eCry3.1Ab protein is a partially modified insecticidal protein originally derived from a bacteria and engineered to be expressed in corn. Two colonies of corn rootworms were developed: a “selected” colony (from adults isolated and grown on transgenic corn) and a “control” colony (from adults isolated and grown on control corn). In laboratory and greenhouse experiments, there was no significant difference in the number of larvae recovered from transgenic and control corn for the selected colony, whereas this difference was significant for the control colony. Laboratory-selected resistance has developed in western corn rootworm populations to all insecticidal proteins currently registered for corn rootworm management, which emphasizes the importance of adhering to resistance management plans for maintaining product efficacy.

Technical Abstract: A laboratory colony of western corn rootworm, Diabrotica virgifera virgifera LeConte, was selected for resistance to transgenic maize expressing the eCry3.1ab protein. The selected colony was developed by rearing larvae on non-elite, non-commercial Bt maize expressing the eCry3.1Ab protein. After four generations of selection, selected and control colonies were screened on eCry3.1Ab-expressing and isoline maize using greenhouse experiments. There was a significant colony × maize pedigree interaction in terms of the number of larvae recovered. There was no significant difference in the number of larvae recovered from eCry3.1Ab-expressing and isoline maize for the selected colony, whereas this difference was significant for the control colony. There was not a significant colony × maize pedigree interaction in terms of root damage, or the number of beetles recovered, but the effect of maize pedigree was significant. After four and eight generations of selection, seedling bioassays were performed. Again, there was a significant colony × maize pedigree interaction in terms of the number of larvae recovered. Larvae of the selected colony, and offspring of reciprocal crosses of the control and selected colonies, had higher LC50 values than the control colony when exposed to increasing concentrations of the eCry3.1ab protein. Resistance ratios of the selected colony, selected female offspring colony, and selected male offspring colony were 2.58, 3.34, and 7.58, respectively. These data provide necessary information for understanding the potential for Bt resistance by western corn rootworm and will be useful for developing improved insect resistance management plans.