Location: Southern Insect Management Research
Project Number: 6066-22000-091-000-D
Project Type: In-House Appropriated
Start Date: Jul 7, 2020
End Date: Jul 6, 2025
Objective:
1. Determine ecological characteristics and insect-plant interactions, such as susceptibility and fitness, to help identify components that can be manipulated to minimize the evolution of resistance to Bt toxins in Helicoverpa zea.
1.A. Determine the status of Bt resistance in H. zea and develop methods to measure the subsequent fitness costs associated with survival on Bt crops relative to other wild and cultivated hosts.
1.B. Evaluate the impact of Bt corn as a primary host on subsequent H. zea damage and fitness on Bt cotton.
2. Characterize genomic, transcriptomic, and population genetic components of H. zea relative to their contribution to evolution of resistance to Bt toxins and develop computational methods for identifying interactions between gene co-regulatory networks that modulate resistance loci.
2.A. Develop computational methods to identify any gene regulatory networks that interact in responding to intoxication with Bt toxins in H. zea.
2.B. Characterize genomic, transcriptomic, and population genetic components of H. zea relative to their contribution to evolution of resistance to Bt toxins.
3. Develop and optimize early detection methods for invasive polyphagous pests of cotton.
Approach:
Recent failures of transgenic crops producing Bacillus thuringiensis (Bt) insecticidal toxins to control noctuid pests and reports of field-evolved resistance to Bt toxins indicate an increase in tolerance to certain Bt toxins in pest populations. To gain a better understanding of factors contributing to the evolution of resistance and to identify components that could be manipulated to minimize the development of resistance to Bt toxins, ecological characteristics of bollworm (BW), Helicoverpa zea, and its interactions with host plants will be investigated. The long-term objective of this project is to identify ecologically sustainable approaches and develop new strategies for the efficient management of BW resistance to Bt toxins. A large-scale Bt resistance survey will be conducted by collecting BW populations from a range of wild and crop hosts across the southern U.S. Progeny from these populations will be assayed using discriminating doses of Bt toxins that compare susceptibility of field insects with control insects from laboratory colonies. This survey will serve as a basis for quantifying the incidence of Bt resistant in BW in areas where Bt corn and cotton production coexists. The fitness parameters will examine the impacts of Bt crops on tolerant insects and fitness of their offspring. This information will assist in determining the status of susceptibility of BW to Bt crops in the southern US. Impacts of Bt corn as a primary host of BW on subsequent damage and fitness on Bt cotton will be assessed using correlations between Bt toxin levels in kernels and larval survival on Bt field corn. Toxin levels in kernels and larval survival on different Bt corn hybrids will facilitate the inference of selection pressure on BW by Bt corn, which will be vital for developing insect resistance management (IRM) strategies in Bt cotton. Contribution of genetic components to Bt toxin resistance evolution will be studied using empirical and computational methods. Genetic loci linked Bt resistance will be evaluated using computational methods such as weighted gene co-regulatory network analysis to predict interactions between gene co-regulatory networks that modulate resistance. Genetic loci predicted to have a high probability of participation in modulating mode of action of Bt toxins will be used in quantitative, comparative, and population genetic studies to evaluate their roles in to Bt toxin resistance. This approach is expected to identify novel genetic loci involved in the toxin mode of action and those contributing to resistance to Bt toxins. This project will also develop novel technologies or improve upon those currently available to facilitate rapid detection of invasive pests. Species-specific antibody-based lateral flow immune assays (LFIA) will be used for rapid identification of species. When LFIA is not possible due to lack of species-specific antigens (targets) in proteins to develop antibodies, isothermal recombinase polymerase amplification (RPA) technology that can amplify species-specific DNA tagged with artificial antigens will be used to detect invasive species.
