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United States Department of Agriculture

Agricultural Research Service


Location: Plant Genetics Research

2011 Annual Report

1a. Objectives (from AD-416)
Develop colonies with resistance to Cry34/35Ab1 and test the effectiveness of two refuge types to delay resistance. Test the dominance and fitness costs of resistance to Bt corn.

1b. Approach (from AD-416)
Western corn rootworm colonies will be selected for resistance to Cry34/35Ab1-expressing transgenic maize and resistance levels will be compared to control colonies and colonies designed to simulate a refuge. In addition, dominance of resistance will be tested by crossing resistant and susceptible colonies and evaluating progeny and fitness costs associated with resistance will also be evaluated.

3. Progress Report
This work is related to Sub-objective 1.A of the parent project: "Develop colonies with resistance to Cry34/35Ab1 and test the effectiveness of different refuge types to delay resistance." Transgenic corn is effective in rootworm management, but in order to maintain its effectiveness, "refuges" designed to delay resistance must be effective. Understanding which "refuge" types of non-transgenic corn are effective in delaying resistance can extend management options beyond that which would be otherwise possible. Colonies of the western corn rootworm aimed at evaluating "refuges" (planting of non-transgenic corn) for delaying resistance to Cry34/35Ab1 (Bt) transgenic corn (corn expressing the Cry34/35Ab1 insecticidal protein) which currently are in the fourth generation of selection in Ames, Iowa (an additional replication of similar colonies are being reared in Columbia, Missouri for project 3622-21220-007-04R). Two generations of backcrossing and one generation of selection have also been completed for Cry3Bb1 resistant western corn rootworm colonies and fitness costs measurements for this population have begun. Overall, these colonies should help us understand to what extent the mandatory planting of non-transgenic corn assists in the delay in the development of resistance to insecticidal transgenic corn targeted toward corn rootworms and whether or not fitness costs are associated with resistance. Monitoring activities included email exchange of information and results, telephone conference calls, and personal meetings at the Annual meeting of the Entomological Society of America.

4. Accomplishments

Last Modified: 10/17/2017
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