Ecological risk assessment of transgenic conditional lethality systems for genetic biocontrol strategies
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Doctor of Philosophy (PhD)
Agriculture, Food and Environment
Dr. Nicholas Teets
Genetic strategies of insect pest control are receiving increased interest due to recent advances in genetic engineering. By introducing alleles that make males functionally sterile, genetically modified (GM) insects can be used in area-wide pest management programs similar to the Sterile Insect Technique (SIT). Genetic control strategies carry several potential benefits, including improved efficacy and specificity, lower operation costs, and reduced dependence on chemical insecticides, but their use is still controversial despite extensive technical documentation indicating their innocuity to humans and the environment. This hesitation is likely due to the novel nature of the approach.
While the first field applications of genetic biocontrol programs have provided promising evidence on the efficacy to suppress field pest populations, the limited number of studies leaves uncertainty about the potential environmental risks associated with the use of GM insects. Thus, prospective risk assessment studies provide the best evidence for understanding the potential hazards of these innovative strategies. In this dissertation, I use the common fruit fly Drosophila melanogaster as a model to assess the performance of conditional lethality (CL) expression systems under various ecologically relevant scenarios. Specifically, we examine the phenotypic variation of the CL system under variable abiotic conditions and the evolutionary response of experimental populations under sublethal exposure to GM male flies.
Our results indicate that the CL system in GM insects is robust under most abiotic conditions experienced directly or indirectly along their lifecycle, but stressful conditions may reduce their effectiveness. Additionally, our results indicate that exposure of experimental populations to sublethal ratios of GM insects carrying CL expression systems results in minimal changes in embryonic susceptibility, but in some cases, changes in susceptibility may arise due to prezygotic changes in adult mate preference that lead to assortative mating. Overall, our results provide evidence of the robustness of the CL expression systems in GM insects and highlight potential sources of evolutionary change that may impact the efficacy of genetic biocontrol strategies. In addition to these primary studies on conditional lethality, in a side project I applied my computational skills to develop a novel algorithm for automatically detecting motion in insects for behavioral and physiological studies
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This work was supported by Biotechnology Risk Assessment Grants Program grant 2017-33522-27068 from the United States Department of Agriculture National Institute of Food and Agriculture covering 2017-2022, Hatch Project 1010996 from the United States Department of Agriculture National Institute of Food covering 2016 to present, and Agriculture, and National Science Foundation grant OIA-1826689 from 2018-2023
Perez-Galvez, Fernan Rodrigo, "Ecological risk assessment of transgenic conditional lethality systems for genetic biocontrol strategies" (2023). Theses and Dissertations--Entomology. 73.
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