|Andow, D - UNIVERSITY OF MINNESOTA|
|Olson, D - UNIVERSITY OF MINNESOTA|
|Alstad, D - UNIVERSITY OF MINNESOTA|
|Hutchison, W - UNIVERSITY OF MINNESOTA|
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 31, 2000
Publication Date: N/A
Interpretive Summary: Several types of genetically-engineered (transgenic) plants have been produced that kill insects when they feed. Scientists and crop producers are excited about these plants because they offer an effective way to kill pests without conventional chemical insecticides. Reduced chemical usage translates into less surface and ground water contamination. Dramatic control of pests on these plants, however, has many scientists concerned about pests becoming resistant to these plants. In this study a breeding method is used to evaluate the frequency of resistance genes. Results suggest that current strategies for managing insect resistance to transgenic plants could be effective. This information will be useful for stakeholders (scientists, companies that produce these plants, producers, and consumers) interested in prolonging the value of transgenic plants.
Technical Abstract: The refuge plus high-dose strategy for resistance management assumes that the frequency of resistance alleles is low. We used an F2 screen to estimate the frequency of resistance to transgenic corn that produces Bacillus thuringiensis Cry1Ab toxin (Bt corn) in an Iowa population of European corn borer, Ostrinia nubilalis. We also proposed a modification and correction to the statistical analysis of the F2 screen that extends its application for non-uniform prior distributions and for repeated sampling of a single population. Based on a sample of 188 isofemale lines, we show that with 95% confidence that the frequency of resistance to Bt corn is <2.6 x 10-3 in this Iowa population. Using our modified formulae, we estimate with 95% confidence that resistance is <5.3 x 10-3 in the previously examined Minnesota population. These results provide weak evidence that the refuge plus high-dose strategy may be effective for managing resistance in O. nubilalis against Bt corn. Partial resistance to Cry1Ab toxin was found commonly in both populations. The 95% C.I.'s for the frequency of partial resistance were [1.7 x 10-3, 6.2 x 10-3] for the Iowa population and [1.8 x 10-3, 9.2 x 10-3] for the Minnesota population. Variable costs of the method were $14.90 per isofemale line, which was a reduction of 25% compared to our initial estimate.