Spatial and temporal volatile organic compound response of select tomato cultivars to herbivory and mechanical injury

Plants resist an insect or pathogen attack through a range of direct and indirect defense signals. Vegetable crop plants constitutively synthesize and store a battery of volatiles implicated in defense against herbivores. We examined the effect of herbivory (Spodoptera litura Fab.) and mechanical injury on the release of volatile organic compounds (VOCs) in five tomato (Solanum lycopersicum Mill.) cultivars followed by behavioral assays on Trichogramma chilonis Ishii. T. chilonis is an egg parasitoid widely used as biocontrol agent in integrated pest management practices. Our goal was to assess the VOC variability across cultivars under different induction regimes. The findings reveal variability among cultivars in the absolute quantity of VOCs emitted as well as qualitative composition of the blend. Herbivore and mechanical wounding caused a substantial quantitative shift in the emission profile of select cultivars. The uninduced and induced volatiles of the tomato cultivars predominantly constitute monoterpenes (65%) followed by sesquiterpenes (15%) and aldehydes (10%). These ubiquitous and induced signals triggered a distinct cultivar specific olfactory response in T. chilonis. The spatial and temporal variations in induced VOCs across tomato cultivars suggest that these unique metabolite profiles are largely intrinsic and genetically determined. This study highlights the genotype based volatile profile and indicates their potential role in host, pest and natural enemy interactions.