Modifying the expression of plant volatiles to affect the behaviour of greenhouse insect pests

Plant volatile organic compounds (VOCs) are known to attract insect herbivores and pollinators, as well as the predators and parasitoids of plant pests. Our recent findings have demonstrated how the feeding and oviposition habits of insect pests are affected by VOCs produced by the over-expression of genes in Arabidopsis thaliana and tomato Solanum lycopersicum. Micro-Tom cv. tomato plants were genetically modified to overexpress the carotenoid cleavage deoxygenase (CCD) gene (LeCCD1-1) that is involved in the carotenoid biosysnthesis pathway. Upregulation of LeCCD1-1 produced altered volatile profiles that made the transgenic tomato plant more attractive to herbivores. The overall project objectives were to determine whether the transgenic plants producing attractive or repellent volatiles can: 1) be applied as a trap crop for greenhouse whiteflies Trialeurodes vaporariorum (Westwood) and 2) be used as components in a “push-pull” strategy. The “push-pull” strategy employs one plant that releases volatiles to repel or “push” the pest insect away from the adjacent crop plant, while a second plant, more attractive to the pest insect than the crop, acts as the “pull”. Previous findings indicate the “push” plants for the whiteflies could be transgenic Arabidopsis plants that overexpress genes that lead to increased production of “repellent” apocarotenoid volatiles. In the present research the focus was on the attractive volatiles produced by transgenic tomatoes. Dual-choice trials determined a greater preference for transgenic tomato by the whitefly as a site for oviposition (OPI values of -0.35 to -0.63 for 3 LeCCD1-1 lines). Chromatographic analyses measured increased levels of specific monoterpenes and decreased levels of sesquiterpenes from the transgenic tomato believed to be responsible for the observed insect behaviour. The long term goal of this research is to allow us to manipulate natural plant volatiles as an environmentally sustainable pest control strategy that is compatible with other bio-based pest management tools such as parasitoids, predators and microbial control agents.