Location: Southern Insect Management Research
Project Number: 6066-30400-002-000-D
Project Type: In-House Appropriated
Start Date: Jun 16, 2025
End Date: Jun 15, 2030
Objective:
Objective 1: Conduct research to understand the sublethal effects of Bt toxins on H. zea, determine their impacts on damage to Bt cotton, elucidate variability of the Bt toxin expression in transgenic crops, and examine its impact on H. zea survival in Bt cotton.
2: Develop novel cotton insect pest management methods to mitigate the impacts of Bt resistance in cotton and evaluate the effectiveness of integrative approaches in reducing resistance levels of crop insect pest populations, including impacts of endosymbionts on feeding behavior and chemical ecology.
3: Conduct research to determine population genomic characteristics of Helicoverpa zea and evaluate the extent of gene transfer from invasive H. armigera into native H. zea.
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.