In the Mediterranean basin, Pinus pinaster (maritime pine) and P. pinea (stone pine) are highly economically important species of pine, namely as a source of raw material for various industries, such as wood, paper, resin, pine nuts (stone pine) and extraction of essential oils (EOs). Recently, these pine species have gained increased attention due to the identification of the pine wilt disease (PWD) for the first time in Europe, in Portugal. Stone pine is considered moderately tolerant to this pathology since there is no reported case in natural conditions. However, maritime pine is a particularly susceptible species and the PWD has caused grave economical losses. Research on these species, particularly on maritime pine, reports a large genetic and phenotypic intra-species variability that ultimately hinders the comparison between different studies. In consequence, this variability must also be present on pine tree chemical profiles. The present work reviews the available bibliography on P. pinaster and P. pinea EO composition and identifies the compounds responsible for the highest variation.

This study compiled the chemical profiling of EOs extracted from the aerial parts of these species, from a total of 25 publications. The EO components that showed the highest variations in relative amounts were limonene, α-pinene, β-pinene, trans-β-caryophyllene and β-myrcene for stone pine, and α-pinene, β-pinene, trans-β-caryophyllene, germacrene D and β-myrcene for maritime pine. Cluster analysis based on the quantitative composition of these compounds allowed to group the samples from each species into six chemically distinct groups. A considerable degree of chemical variability was detected for these species.

Variability on pine volatile metabolome may occur at the cellular and biochemical levels and can bias the results obtained for these species EOs. Research performed in the field or in greenhouse conditions should first ascertain chemical variability on P. pinea or P. pinaster.