Expression of selected tomato genes involved in plant defense following application of a systemic insecticide imidacloprid

The important environmental and economic benefits of imidacloprid such as its systemic nature, remarkably long residual toxicity, and high efficacy, have been offset by reports of secondary outbreaks of spider mites on plants that are treated with the insecticide in urban forests. In our previous studies we have explored if disruption of natural enemies and effect of imidacloprid on spider mite fecundity could explain the outbreaks on boxwood shrubs and elm trees. The focus of this research was to explore if changes in expression of genes involved in plant defense could contribute to increase in spider mite numbers. We used a model organism, tomato plant, to explore how imidacloprid affects expression of selected genes using reverse transcriptase PCR. We found 2 genes involved in the jasmonic acid pathway of plant defense to be expressed at lower levels when plants received imidacloprid application. We conclude that the increased performance of mites may be linked to a diminished ability of a plant to defend itself that renders it more vulnerable to mites.