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Applications of Population Genomics to Integrated Pest Management in Cotton
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In this dissertation, we used a population genomics approach to improve the management of two insect cotton (Gossypium hirsutum L.) pests, the boll weevil, Anthonomus grandis Boheman (Coleoptera: Curculionidae), and the cotton fleahopper, Pseudatomoscelis seriatus (Reuter) (Hemiptera: Miridae). Despite the success of the United States (US) Boll Weevil Eradication Program, the boll weevil remains a threat to cotton production in the southern US, and is arguably the most important cotton pest in Central and South America. The cotton fleahopper is a secondary pest of cotton whose impact in the US has increased in the wake of improved management for other cotton pest species. Management efforts for both species are complicated by a lack of detailed knowledge of population genetic structure, and what little research there is has not taken advantage of high-throughput sequencing technology. Here, we used double digest restriction site-associated DNA sequencing (ddRADseq) to resolve the population genomic structure of the boll weevil in the southern US, northern Mexico, and Argentina, and of the cotton fleahopper in the Brazos Valley of Texas. Our boll weevil research supported a two-form hypothesis of geographic variants of boll weevil in North America wherein there is a western and eastern form, and suggested that the two variants occur due to geographic isolation rather than host plant association. Boll weevil collections from South America in Argentina were more closely related to the eastern North American boll weevil lineage, but with levels of genetic divergence consistent with isolation-by-distance. We also used a population genomics approach to identify probable source populations for weevils re-infesting previously eradicated areas in the US. Our work on the cotton fleahopper revealed high gene flow among populations collected from different host plants in the Brazos Valley. We identified one instance of yearly turnover of local genotypes and one instance of monthly turnover in cotton, indicating that population genomic structure may be labile to time. Our results also identified a probable natural refuge that promotes year-end gene flow between genotypes associated with cotton and those associated with alternative hosts.
insect resistance management
Raszick, Tyler Jay (2018). Applications of Population Genomics to Integrated Pest Management in Cotton. Doctoral dissertation, Texas A & M University. Available electronically from