Only P. pinaster yielded enough oleoresin from feeding wounds to be sampled for analysis of volatiles, although some oleoresin exudation was also seen from P. pinea after feeding by M. galloprovincialis.

The volatiles collected by SPME from each P. pinaster oleoresin sample were complex mixtures in which 53 components were identified, representing ≥92% of the total volatiles. The identified components are listed in Table 4 in order of their elution on the DB-1 column, arranged according to the lowest and the highest percentages found for each component in the seven samples, or to the samples grouped by EO chemotypes.

The monoterpene fraction was dominant in all analysed samples (68–96%), while the sesquiterpene fraction ranged from 4 to 26%. In all cases the relative amount of monoterpene hydrocarbons (62–95%) was higher than that of oxygen-containing monoterpenes (0.1–10%).

When considering the volatiles from all oleoresins, α-pinene was a major component (18–80%), although the oleoresin volatiles from C1 trees were dominated by δ-3-carene (20–30%) and/or β-pinene (20–26%), because this group showed the lowest percentages of α-pinene (18–19%). On the other hand, α-pinene (26–80%) was the main component from C2 trees, followed by β-pinene (5–35%).

The chemical composition of oleoresin from Pinus species has been extensively studied, mainly from solvent extracts, to the extent that specific monoterpenes, sesquiterpenes, and resin acids can be used as chemotaxonomic markers (Arrabal et al., 2005 and refs. cited therein). Nevertheless, we found only one study on the volatiles of maritime pine oleoresin. Adsorbent headspace analysis of the oleoresin volatiles from P. pinaster pruning wounds showed α- and β-pinene to be major components, with lesser proportions of camphene, myrcene, limonene, and linalool, along with traces of δ-3-carene, terpinolene, longifolene and β-caryophyllene. According to the authors, linalool was an artefact resulting from the adsorbent used in the headspace analysis (Kleinhentz et al., 1999).