Exogenous application of methyl jasmonate and salycilic acid in the leaves of pistachio (Pistachia vera cv fandoughi) trees and reduces the performance of the phloem-feeding psyliid Agonoscena pistaciae.

The phloem feeding psyllid Agonscena pistaciae is an important economic pest of Pistacia vera in several Asian countries. Plant response to this pest is regulated in part by the salicylate and/or jasmonate signalling pathways. Here the effects of exogenous methyl jasmonate (MeJa) and salicylic acid (SA) on P. vera leaves were assessed comparing the number of nymphs and eggs per leaflets. Consequently, the activities of selected antioxidant enzymes, hydrogen peroxide, phenolic content and protein content were evaluated. The effects of MeJa and SA were concentration and time dependent, with higher concentration of SA failing in inducing a more active response. Three days after hormonal spraying the egg number decreased by 79% and 56%, after SA and MeJa treatments, respectively and the nymph density by 73% and 64%. SA was found more efficient than MeJa. Both MeJa and SA increased antioxidant enzyme activities, whereas they decreased total protein content. Also SA negatively affected the total phenolic content. The levels of hydrogen peroxide were not changed by hormonal treatments. This is the first study investigating the potential role of MeJa and SA on the defensive responses and herbivory resistance in pistachio trees.