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United States Department of Agriculture

Agricultural Research Service

Research Project: ECOLOGICALLY-BASED MANAGEMENT OF INSECT PESTS OF CORN, WITH EMPHASIS ON CORN BORERS, ROOTWORMS, AND CUTWORMS

Location: Corn Insects and Crop Genetics Research

Title: Effect of maize lines on larval fitness costs of Cry1F resistance in the European corn borer (Lepidoptera: Crambidae)

Authors
item Petzold-Maxwell, Jennifer -
item Siegfried, Blair -
item Hellmich, Richard
item Abel, Craig
item Coates, Brad
item Spencer, Terrence -
item Gassmann, Aaron -

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 6, 2014
Publication Date: April 1, 2014
Citation: Petzold-Maxwell, J.L., Siegfried, B.D., Hellmich II, R.L., Abel, C.A., Coates, B.S., Spencer, T.A., Gassmann, A.J. 2014. Effect of maize lines on larval fitness costs of Cry1F resistance in the European corn borer (Lepidoptera: Crambidae). Journal of Economic Entomology. 107:764-772.

Interpretive Summary: Genetically-engineered crops are widely planted to manage a number of insect pests; but there are concerns that insects will evolve resistance to these crops. Fitness costs associated with insect resistance are important to understand because, if they occur, they can delay the evolution of resistance. Ecological factors including host plant variety can affect the magnitude of fitness costs, and consequently, the degree to which fitness costs delay resistance. In this study, we measured fitness costs of resistance to Bacillus thuringiensis (Bt) toxin Cry1F in the important maize pest, European corn borer. Fitness costs were tested on three lines of maize by measuring larval survival, developmental rate and mass in two greenhouse experiments with plants in either the vegetative or reproductive stage. Maize lines significantly affected larval survival and developmental rate in both experiments. However, larval survival, mass and developmental time did not differ between the Cry1F-resistant and susceptible strains in either experiment, indicating an absence of fitness costs of Cry1F resistance. The absence of fitness costs increases the risk for Bt resistance in the field, although no resistance has been detected since Cry1F was commercialized in 2002. This information is valuable to maize growers and scientists interested in delaying insect resistance to Bt maize.

Technical Abstract: Crops producing insecticidal toxins from the bacterium Bacillus thuringiensis (Bt) are widely planted to manage a number of insect pests. The evolution of Bt resistance diminishes the capacity of Bt crops to manage insect pests. Fitness costs of Bt resistance occur in the absence of Bt toxins when insects with resistance alleles suffer a reduction in fitness relative to those that are susceptible. Ecological factors including host plant variety can increase the magnitude of fitness costs, and consequently delay the onset of resistance. In this study, we measured fitness costs of resistance to Bt toxin Cry1F in the European corn borer, Ostrinia nubilalis Hübner (Lepidoptera: Crambidae). A series of back-crosses and selections were used to generate Cry1F-resistant and Cry1F-susceptible strains that shared a similar genetic background. Fitness costs of each strain were tested on three lines of maize, Zea mays L., by measuring larval survival, developmental rate and mass in two greenhouse experiments with plants in either the vegetative or reproductive stage. Maize lines significantly affected larval survival and developmental rates in both experiments. However, larval survival, mass and developmental time did not differ between the Cry1F-resistant and susceptible strains in either experiment, indicating an absence of fitness costs of Cry1F resistance. The absence of fitness costs may increase the risk for Bt resistance in the field, although no resistance has been detected since Cry1F was commercialized in 2002. Future experiments should test for fitness costs of Cry1F resistance affecting survival to adulthood and adult life-history parameters.

Last Modified: 11/20/2014
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