Title of dissertation: SYMBIONTS ASSOCIATED WITH THE SALIVARY GLANDS OF THE POTATO LEAFHOPPER, EMPOASCA FABAE, AND THEIR FUNCTION WHEN FEEDING ON LEGUMINOUS HOSTS

Many species of phloem feeding insects are host to symbiotic bacteria, which provide their hosts with nutrients lacking from phloem. The potato leafhopper, Empoasca fabae, feeds on the phloem and cell contents of a wide variety of plants. In this study, I identified two taxa of symbiotic bacteria present in the salivary glands, midgut, bacteriomes and saliva of the potato leafhopper: Sulcia muelleri and Wolbachia. Treatment of the leafhoppers with 0.01 % oxytetracycline-HCl resulted in the creation of aposymbiotic leafhoppers. Longevity and fecundity of aposymbiotic leafhoppers on alfalfa, Medicago sativa, and fava bean, Vicia faba, were significantly lower than that of symbiotic leafhoppers. In addition, aposymbiotic leafhoppers caused less of a decrease in photosynthesis rates on both alfalfa and fava bean in comparison to symbiotic leafhoppers. The salivary gland transcriptome of the potato leafhopper revealed the presence of potential salivary components, including lipase, pectin lyase and alkaline phosphatase, all of which were expressed at higher levels in salivary glands than in midgut or hind femur tissue. In addition, transcripts attributed to Wolbachia were discovered in the sialotranscriptome, providing more evidence that this bacterium i