Location: Plant Genetics Research2012 Annual Report
1a. Objectives (from AD-416):
Characterize MIR604- and 5307-western corn rootworm resistant colonies.
1b. Approach (from AD-416):
1) Removal of selection experiments with the MIR604 resistant colony similar to Meihls et al. (2008). 2) Reciprocal crosses of the MIR604-selected colony and its control colony for calculation of heritability. We will do both similar studies to Meihls et al. (2008) and more detailed studies in which we will control for genetic divergence between selected and unselected colonies. 3) Evaluate for fitness costs of the MIR604 resistance. 4) Probe differences between the MIR604-selected colony and a split-off colony with a lower LC50 value that survived MIR604 in the field in 2009. We will focus on differences in feeding behavior and the potential role of feeding behavior in contributing to field resistance. 5) Provide Syngenta with up to 20,000 eggs each from the MIR604-selected and its paired control colony. 6) Removal of selection experiments with the 5307-selected colony similar to Meihls et al. (2008). 7) Reciprocal crosses of the 5307-selected colony and its control colony for calculation of heritability. We will do both similar studies to Meihls et al. (2008) and more detailed studies in which we will control for genetic divergence between selected and unselected colonies. 8) Evaluate fitness costs of 5307 resistance. 9) Provide Syngenta with up to 20,000 eggs each from the 5307-selected and its paired control colony. 10) Evaluate cross-resistance between 5307 and MIR604-selected colonies in the greenhouse and field (cross-resistance with Cry3Bb1 is also possible now and with Cry34/35Ab1 will also likely be possible within a year).
3. Progress Report:
The current project is related to parent project sub-objective 1.B “Evaluate our mCry3A-resistant colony for the heredity of this trait, whether the trait is maintained when selection is removed, and whether there are fitness costs associated with the trait.” and sub-objective 1.C. “Evaluate cross resistance in rootworm colonies selected for resistance to one rootworm product on other single and stacked trait products.” It also 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. Transgenic corn with resistance to corn rootworm larval feeding offers a viable alternative to insecticides for managing the most economically important insect pests of corn. Maintaining insect susceptibility to transgenic crops (resistance management) is in the interest of growers, the Environmental Protection Agency, and industry, but requires an understanding of corn rootworm biology that does not currently exist. A series of experiments conducted and data analyzed for this project included an evaluation of the potential for cross resistance between Syngenta’s transgenic events targeting rootworms. We also conducted experiments aimed at understanding heritability of resistance to Syngenta’s commercialized events and whether resistance is maintained when selection pressure is removed. Data that are important to seed companies and modelers in their attempts to optimize resistance management plans for transgenic corn may be required by the Environmental Protection Agency for commercialization, but are proprietary at this point.