2012 Annual Report
1a.Objectives (from AD-416):
Evaluate the role of feeding behavior of WCR larvae that are resistant to Cry3Bb1 transgenic corn in their resistance.
1b.Approach (from AD-416):
A series of experiments will be conducted in order to support or refute the assertion that western corn rootworm feeding behavior plays a role in their survival on transgenic Cry3Bb1-expressing corn. Approaches will include direct observation, carbon isotope analysis of western corn rootworm larvae fed mixtures of Bt corn and cool season grasses for various lengths of time, cross sectioning Bt and isoline roots fed by resistant and susceptible rootworm larvae to see if they feed on different root tissue, and related follow-up experiments.
This work is related to Objective 1 of the parent project: “Develop lines of the western corn rootworm resistant to transgenic corn and investigate the biology, pest/host interactions, and fitness costs of resistant and control colonies as they relate to resistance management and rootworm biology” and contributes to Component IIa of the National Program 304 Action Plan by developing increased knowledge of the biology, ecology, behavior, and genetics of pests, and plant traits conferring pest resistance.
More hectares of cropland have traditionally received insecticide for Diabrotica than for any other agricultural pest in the United States. Because of recent changes in their distribution (now in Europe), biology (resistance to crop rotation), and cropping practices (more continuous corn), the impact of these pests is growing. Colonies of the western corn rootworm with resistance to transgenic corn have been developed, but the mechanism of resistance is unknown. It is possible that feeding behavior plays a role in this resistance. We are actively evaluating this possibility. Recently, we documented that the time to first feeding on transgenic corn lines targeting the western corn rootworm was significantly shorter for resistant insects than the time to first feeding on Bt corn in the paired western corn rootworm control strain. Although this was not the case for all resistant colonies and transgenic corn lines tested. We are following up on this data with additional behavioral bioassays to determine the mechanism, consistency, and impact of these feeding behavior differences.