Prager, Sean2024-01-1120232023-122024-01-11December 2https://hdl.handle.net/10388/15421Phytoplasmas are obligate parasites associated with several diseases in plants and can be transmitted by hemipteran groups such as psyllids, planthoppers, and leafhoppers. In the Canadian Prairies, phytoplasma group 16SrI is the causal agent of Aster Yellows (AY) disease and is primarily transmitted by populations of aster leafhoppers (Macrosteles quadrilineatus Forbes) (Hemiptera: Cicadellidae). Given the complexity of this pathosystem, domesticated and non-domesticated plant species (Poaceae, Brassicaceae, and Asteraceae) commonly found in this geographical region were used to address questions regarding the ecology of the insect vector and the epidemiology of AY. While cereals, Arabidopsis thaliana, and a few non-domesticated species from the Asteraceae family could sustain leafhopper reproduction and development, the opposite was observed in other plant species like canola. In the presence of a second host plant, however, aster leafhoppers preferred to settle on crops over wild species, including in those combinations containing canola. In other cases, some of the less suitable host plants were preferred for settling, oviposition, or probing, suggesting that host choice selection behavior of aster leafhoppers was context dependent. Moreover, there was a disassociation between the host suitability of aster leafhoppers and that of the phytoplasmas. Additional experiments with A. thaliana lines indicated that settling and oviposition behaviors of this insect species can be altered by plant-mediated responses involving the phytohormones salicylic acid and jasmonic acid, and that insect infection with phytoplasmas can also affect these behavioral responses. Finally, the probing behavior of aster leafhopper males and females was characterized using the electropenetrography technique in combination with plant histology. These insects produced a total of nine waveforms, with two groups of them associated with xylem and phloem activities. Comparison of the number of events and duration of different waveforms between males and females revealed that their probing behavior was similar.application/pdfenHemipteraCicadellidaeAster leafhoppersPhytoplasmasHost choice selectionElectropenetrographyPhytohormonesThesis2024-01-11