Ayres Abstracts

Lombardero, Maria J., Javier  Pereira-Espinel, and M.P. Ayres. 2013. Foliar terpene chemistry of Pinus pinaster and P. radiata responds differently to Methyl Jasmonate and feeding by larvae of the pine processionary moth. Forest Ecology and Management 310: 935-943. Link. Reprint available on request.

Abstract. Jasmonic acid and Methyl Jasmonate (MeJA) are important signaling molecules for plant defensive responses upon mechanical wounding, herbivory damage, or fungal inoculation. There is an increased interest in the use of exogenous chemical elicitors such as jasmonic acids to induce natural host defense mechanisms as an alternative to synthetic chemical pesticides. However few studies have compared the response caused by application of elicitors vs. real herbivores and few studies have analyzed the impact on particular pest species of plant responses induced by exogenous application of MeJA. We compared the defensive response of two pine species, one native to our study area (Pinus pinaster) and one introduced (P. radiata), after exogenous application of MeJA and after feeding of a regionally important indigenous pest (pine processionary moth, PPM). We analyzed variation in foliar terpenes, nitrogen and water. Additionally we assessed the consequences of plant responses to MeJA for the growth and mortality of PPM larvae. Because the defensive reaction may be influenced by resource availability, we also evaluated effects of site quality on plant responsiveness to MeJA and insect feeding. The exogenous application of MeJa had different effects in the two pine species. In P. radiata, there were no conspicuous increases from MeJA in any measured terpene, and on good sites, there were general decreases in overall concentrations of the three terpene classes. In P. pinaster, MeJA by itself had no detectable effect on overall concentrations of any class of terpenes, but there was a 6-fold increase in the concentration of one monoterpene, linalool. Feeding by PPM induced decreases in terpenes, especially monoterpenes, in both species. Foliar nitrogen contents were markedly higher in P. radiata than P. pinaster – especially on good sites. Foliar water content was similar between pine species and, in both species, was reduced relative to control trees in treatments that included PPM feeding. There were no differences in larval mortality between trees that were and were not exposed to exogenous MeJA. In summary, the exogenous application of MeJA had effects on the terpene chemistry of both pine species, but the effects were less general across species and compounds than expected under some models of MeJA biochemistry. It seems likely that operational manipulations of MeJA to manage pests in pine forestry will require further understanding of differences among pine species in their responses to MeJA.

Keywords: Methyl Jasmonate, Thaumetopoea pityocampa, Maritime pine, Monterery Pine, terpenes

 

Return to Publications