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

JORGE ALBERTO ZAVALA; PATRICIA CARINA FERNÁNDEZ; CAMILA DÁVILA

Ciudad de Mendoza

Congreso; X Congreso Argentino de Entomología; 2018

Egg deposition of insects on plants can induce defense responses, activating early mechanisms against 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 of the defense mechanisms against the upcoming hebivory. In other words, insect eggs are capable of induce defenses directed not against the eggs themselves, but against larvae that subsequently hatch from them. Here we studied how oviposition by the sawfly Nematus oligospilus on Salix spp foliage affects the plant?s defensive potential against sawfly larvae. This was performed in two willow genotypes that differ in their foliar content of phenolic glycosides (PGs, the most abundant secondary metabolite present in Salix spp). The species evaluated were S nigra (high PGs) and S babylonica (low PGs). We studied the performance of newborn larvae that initiated their development on Salix twigs on which they hatched from eggs in comparison to those fed on egg-free twigs. We also analyzed the phytohormone production and PGs content in plants after egg deposition. Our results showed that the only presence of sawfly?s egg on leaves decreased survival and size of the newborn larvae after 2 days in S nigra. We also found that the presence of eggs induced the production of Jasmonic acid (JA) in both willow varieties. PGs did change in any case. We conclude that egg deposition on the willow leaf would induce plant defense responses mediated by JA which constitutes a warning signal, decreasing larval performance and decreasing herbivory by the willow sawfly. Since JA changes protein inhibitor and volatiles production, we are currently evaluating these traits.