Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Biology

Supervisor

Dr. Cam Donly

Abstract

The Colorado potato beetle, Leptinotarsa decemlineata, is a significant pest of potato, and its impact on agriculture is measured on a global scale. The beetle is mainly controlled by neonicotinoid insecticides, however, resistance development is a growing concern. Resistance to neonicotinoids is thought to involve elevated activity of detoxifying enzymes and xenobiotic transporters that break-down and excrete insecticide molecules. Here, using mRNA sequencing, I identified multiple detoxifying enzyme and xenobiotic transporter genes transcriptionally up-regulated in a neonicotinoid resistant strain of beetles. I then used RNA interference to knock down the transcript levels of the ten most promising genes in resistant beetles to test their possible roles in resistance. The silencing of two detoxifying enzyme genes, a cytochrome P450 (CYP4Q3) and a uridine 5'-diphospho-glycosyltransferase (UGT 2B5), significantly increased susceptibility of resistant beetles to the neonicotinoid insecticide imidacloprid. My results indicate that over-expression of these two genes contributes to neonicotinoid resistance.

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