Priming of tomato plants by aboveground herbivores of different feeding guilds against root-knot nematodes

Plants are attacked by both above- and belowground herbivores which may indirectly interact with each other via herbivore-induced systemic changes in plant traits. Previous herbivory may also “prime” plants to more efficiently defend against subsequent herbivory. We examined whether tomato (Solanum lycopersicum) plants could be primed by aboveground chewing (Spodoptera exigua) and sucking (Myzus persicae) herbivores to be better defended against subsequent root herbivory by root-knot nematodes (Meloidogyne incognita). We hypothesized that potential priming effects would differ with respect to the feeding guild of the aboveground herbivores, because of the induction of different defense pathways. While we found no effects of the aboveground herbivory on the performance of the belowground herbivores, the herbivore treatments had significant effects on plant performance and resource allocation. Only plants primed with aphids showed compensatory growth in response to the nematode infestation and had higher C/N ratios in shoots and roots than those primed with S. exigua larvae. We will analyze phytohormone levels (SA, JA) of the treated plants to unravel the mechanisms underlying these feeding guild-specific effects. From the existing results it can be concluded that previous aboveground herbivory by aphids primes tomato plants for tolerance rather than defense against subsequent root herbivory by nematodes.