204 pages ; Supplemental file(s) description: Supplemental File 4.2 containing SNPs post genome-wide association and filtering, Supplemental File 4.1 containing Markers in retroelements and their coordinates. ; Huanglongbing (HLB), also known as citrus greening, poses a significant threat to the citrus industry worldwide, with devastating effects on tree health and fruit production. The disease is primarily spread by the Asian citrus psyllid, Diaphorina citri, which is the vector for the bacterium “Candidatus Liberibacter asiaticus” (CLas), the causal agent of HLB. Long term management of HLB hinges on sustainable control of the vector, reducing transmission of CLas to new, healthy trees. Understanding molecular interactions between D. citri and CLas is crucial for developing effective vector intervention methods. Vector competency, influenced by genetics, environment, and pathogen interactions, determines a vector's ability to transmit a pathogen. In D. citri, vector competency is likely regulated by distinct tissue barriers, which CLas must overcome to be successfully acquired and transmitted. However, understanding the direct barrier-CLas interactions that lead to either successful or failed acquisition and transmission has yet to be determined. In this dissertation, we conducted a comparative transcriptome analysis of healthy and CLas-infected D. citri, focusing on multiple organs including bacteriomes, salivary glands, and heads, in order to track CLas-D. citri interactions throughout the vector body. Using the latest D. citri genome assembly (v3.0), we integrated new transcriptome data with previously published datasets to elucidate the impact of CLas on the transcriptional landscape of D. citri organs involved in circulative, propagative transmission. In order to begin bridging the gap between laboratory-generated transcriptomic results and the reality of wild vector population diversity, we sampled four active citrus groves and assessed hundreds of psyllids for their individual vector competency via ...