Exogenous application of methyl jasmonate and salicylic acid increases antioxidant activity in the leaves of pistachio (Pistacia vera L. cv. Fandoughi) trees and reduces the performance of the phloem-feeding psyllid Agonoscena pistaciae

The phloem-feeding psyllid, Agonoscena pistaciae, is an important key pest of Pistacia vera in several Asian countries. Plant response to this pest is regulated in part by the salicylate and/or jasmonate signaling pathways. Here, the effects of exogenous methyl jasmonate (MeJa) and salicylic acid (SA) application on P. vera leaves were assessed comparing the number of nymphs and eggs per leaflets. Also, the activities of selected antioxidant enzymes, hydrogen peroxide, phenolic content and protein content were evaluated. The effects of MeJa and SA were concentration dependent, with higher concentration of SA failing to induce a more active response. SA was found more efficient than MeJa, as 3 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 %. Both MeJa and SA increased antioxidant enzyme activities, whereas they decreased total protein content. SA affected negatively also the total phenolic content. The levels of hydrogen peroxide were not changed by hormonal treatments.