Essential Oil Variability in the Genetically Depauperate Mediterranean Pine Pinus pinea L

The present paper deals with the variability in the composition of needle essential oil in the Mediterranean pine Pinus pinea L., a geographically widespread yet genetically depauperate species. The obtained results indicate that despite a lack of neutral genetic diversity, P. pinea exhibits significant variability in needle essential oil composition. In terms of the dominant terpene compounds, we distinguished essential oils with limonene dominance (20.4%-76.1%), an oil dominated by guaiol (12.7%) and limonene (11.4%) in approximately equal concentrations, and oils in which β-pinene (24.0% and 42.4%) or α-pinene (13.8%-37.0%) were dominant (with limonene either completely absent or present in very small amounts). Principal component analysis (PCA) suggests the presence of five phytochemical groups of P. pinea, whereas agglomerative hierarchical cluster analysis (AHC) confirms the existence of four distinct groups. Given the differing outcomes between phenotypic traits and molecular markers, we strongly recommend integrating both approaches when designing genetic resource conservation programs for P. pinea.