Resin acids as inducible chemical defences of pine seedlings against chewing insects

PLoS One. 2020 May 1;15(5):e0232692. doi: 10.1371/journal.pone.0232692. eCollection 2020.

Abstract

Inducibility of defences in response to biotic stimuli is considered an important trait in plant resistance. In conifers, previous research has mostly focused on the inducibility of the volatile fraction of the oleoresin (mono- and sesquiterpenes), leaving the inducibility of the non-volatile resin acids largely unexplored, particularly in response to real herbivory. Here we investigated the differences in the inducibility of resin acids in two pine species, one native from Europe (Pinus pinaster Ait.) and another from North America (Pinus radiata D. Don), in response to wounding by two European insects: a bark chewer, the pine weevil (Hylobius abietis L.), and a defoliator, the pine processionary caterpillar (Thaumetopoea pityocampa Schiff.). We quantified the constitutive (control) and induced concentrations of resin acids in the stem and needles of both pine species by gas chromatography techniques. Both pine species strongly increased the concentration of resin acids in the stem after pine weevil feeding, although the response was greater in P. pinaster than in P. radiata. However, systemic defensive responses in the needles were negligible in both pine species after pine weevil feeding in the stem. On the other hand, P. radiata locally reduced the resin acid concentration in the needles after pine caterpillar feeding, whereas in P. pinaster resin acid concentration was apparently unaffected. Nevertheless, systemic induction of resin acids was only observed in the stem of P. pinaster in response to pine caterpillar feeding. In summary, pine induced responses were found highly compartmentalized, and specific to herbivore identity. Particularly, plant defence suppression mechanisms by the pine caterpillar, and ontogenetic factors might be potentially affecting the induced response of resin acids in both pine species.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acids / metabolism
  • Animals
  • Herbivory*
  • Moths / physiology*
  • Pinus / physiology*
  • Resins, Plant / metabolism*
  • Seedlings / physiology*
  • Weevils / physiology*

Substances

  • Acids
  • Resins, Plant

Grants and funding

This research was supported by the Ministerio de Ciencia, Innovación y Universidades, Agencia Estatal de Investigación and Fondo Europeo de Desarrollo Regional (MCIU/AEI/FEDER), UE grants (FUTURPIN, AGL2015-68274-C03-02-R; RESILPIN, RTI2018-094691-B-C33). XLG received financial support from Fundación Pedro Barrié de la Maza and FPI Grant programs from former Ministerio de Economía y Competitividad (MINECO, BES-2013-62663). LL received financial support for Ph.D. program from the Swedish Foundation of Strategic Research (Parasite Resistant Tree Project, grant number RBb08-0003). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.