Chemical ecological protection of tomato by synergising plant priming and pest deterrence

When tomato plants, Lycopersicum esculentum, are infested with whitefly, Trialeurodes vaporariorum, they emit herbivore-induced plant volatiles (HIPVs). These volatiles are able to induce an elevated herbivore defence in nearby tomatoes, a concept termed 'priming'. My project aims to develop a non-toxic ecological whitefly pest management system for tomato plants based on the exploitation of this natural plant signalling mechanism. I aim to identify the specific herbivore induced plant volatiles (HIPVs), emitted by whitefly infested tomato plants, which can prime the defence of un-infested tomato plants against future herbivore challenge and allow them to mount a stronger and faster defence. In order to determine the chemicals responsible for priming, air entrainment and GCMS will be used to collect and analyse volatiles from whitefly infested and control tomato plants. Since priming is time-dependent, a comparison of HIPVs collected before, during and after whitefly infestation by a time-series of air entrainments will facilitate identification of chemical signals by GCMS. The priming response will be determined by subsequent infestation and whitefly performance data, as well as by post-colonisation induced volatile defence chemistry (analysed by air entrainment and GCMS). Candidate chemicals will be trialled individually for their ability to reproduce the priming response and efficacy in pest control.

As well as using HIPVs from tomato, I will identify non-host volatile chemical cues from unrelated plant taxonomy to deter initial whitefly infestation. Literature searches of T. vaporariorum non-hosts will be used to select several separate plant families, and the volatile chemistry of these families tested for behavioural activity with whitefly. Following this, three non-host plant volatiles will be used for further analysis. Candidate non-host and priming volatiles will be tested in a commercial glasshouse setting at Stockbridge, where the compounds will be applied in a standard spray medium onto un-infested tomato plants. This will allow confirmation that laboratory results are applicable to a commercial setting for growing. Settling and egg lay of whiteflies in glasshouse mixed culture will be used as measures of efficacy for the priming compounds identified from HIPVs. The most deterrent non-host compounds will also be determined, as well as the concentrations at which they work most effectively.

Finally, the blending of priming and deterrent material will be trialled. By combining these two chemical ecological mechanisms I aim to prevent successful whitefly colonisation through a novel pest management strategy. The strategy will not rely on stress-induced chemistry, which could have adverse effects on the performance of tomato crops, and will employ cheap, non-toxic chemistry, consequently eliminating biochemical resistance. Using a multi-component strategy will also reduce the development of behavioural resistance in T. vaporariorum and maximise the effectiveness of this pest control strategy.