Variability of the needle essential oils of Pinus heldreichii from different populations in Montenegro and Serbia.

The essential-oil compositions of Pinus heldreichii Christ. from Montenegro and Serbia are reported at the population level. Whitebark pine is a sub-endemic high-mountain Balkan pine relict of an anthropogenically reduced area, with large morphological diversity and insufficiently clear taxonomic position. In the pine-needle terpene profile from three populations from Montenegro, and one from Serbia, 101 compounds were detected, 72 of which could be identified (Table 3). The dominant constituents are limonene (26.3%), alpha-pinene (17.5%), germacrene D (13.5%), and beta-caryophyllene (10.4%), comprising ca. 67.7% of the essential oil. Medium-to-high contents (0.5-10%) of the following 16 additional components were found: beta-pinene, beta-myrcene, alpha-humulene, delta-cadinene, alpha-muurolene, (E)-hex-2-enal, beta-gurjunene, gamma-muurolene, isopimarol, camphene, gamma-cadinene, aromadendrene, beta-bisabolene, trans-beta-farnesene, alpha-cadinene, and (Z)-hex-3-en-1-ol. The similarity of the populations and the within-population variability was visualized by principle-component analysis (PCA) of eleven selected terpenes in 97 tree samples. Cluster and genetic analyses suggest closest connection between the two spatially most-distant populations I (Montenegro) and IV (Serbia). Based on the profile of the main sesquiterpene components, the studied populations from Montenegro and Serbia are more similar to the populations from Greece and the Central Balkan peninsula (Bosnia and Serbia-Kosovo) than to those on the furthest eastern margin of their natural range (Bulgaria).