Defense induction on leaves of Salix spp after egg deposition of the willow sawfly Nematus Oligospilus.

DAVILA CAMILA; JORGE A ZAVALA; FERNANDEZ PATRICIA CARINA

Congreso; X Congreso Argentino de Entomologia; 2018

Egg deposition of insects on plants can induce defense responses, activating early mechanismsagainst the herbivore eggs. In addition, in the last years it was demonstrated that, in a few systems,these activations leads also to a primed state of the plant that allows a more efficient activation ofthe defense mechanisms against the upcoming hebivory. In other words, insect eggs are capableof induce defenses directed not against the eggs themselves, but against larvae that subsequentlyhatch from them. Here we studied how oviposition by the sawfly Nematus oligospilus on Salix sppfoliage affects the plant?s defensive potential against sawfly larvae. This was performed in two willowgenotypes that differ in their foliar content of phenolic glycosides (PGs, the most abundant secondarymetabolite present in Salix spp). The species evaluated were S nigra (high PGs) and S babylonica (lowPGs). We studied the performance of newborn larvae that initiated their development on Salix twigson which they hatched from eggs in comparison to those fed on egg-free twigs. We also analyzedthe phytohormone production and PGs content in plants after egg deposition. Our results showedthat the only presence of sawfly?s egg on leaves decreased survival and size of the newborn larvaeafter 2 days in S nigra. We also found that the presence of eggs induced the production of Jasmonicacid (JA) in both willow varieties. PGs did change in any case. We conclude that egg deposition onthe willow leaf would induce plant defense responses mediated by JA which constitutes a warningsignal, decreasing larval performance and decreasing herbivory by the willow sawfly. Since JAchanges protein inhibitor and volatiles production, we are currently evaluating these traits.