FULL PAPER Essential-Oil Variability in Natural Populations of Pinus mugo Turra from the Julian Alps by Srdjan Bojovic ´* a ), Maja Jurc b ), Mihailo Ristic ´ c ), Zorica Popovic ´ a ), Rada Matic ´ a ), Vera Vidakovic ´ a ), Milena Stefanovic ´ a ) , and DuÐan Jurc d ) a ) Institute for Biological Research (SiniÐa Stankovic ´), University of Belgrade, Boulevard Despota Stefana 142, SR-11060 Belgrade (e-mail: bojovic@ibiss.bg.ac.rs, zorica.popovic@ibiss.bg.ac.rs, rmatic@ibiss.bg.ac.rs, vera.vidakovic@ibiss.bg.ac.rs, milena.stefanovic@ibiss.bg.ac.rs) b )Department of Forestry and Renewable Forest Resources, University of Ljubljana, Biotechnical Faculty, SI-1000 Ljubljana (e-mail: maja.jurc@bf.uni-lj.si) c ) Institute for Medicinal Plant Research (Dr Josif Panc ˇic ´), TadeuÐa KoÐc ´uÐka 1, SR-11000 Belgrade (e-mail: mristic@iplb.co.rs) d ) Slovenian Forestry Institute, Vec ˇna pot 2, SI-1000 Ljubljana (e-mail: dusan.jurc@gozdis.si) The composition and variability of the terpenes and their derivatives isolated from the needles of a representative pool of 114 adult trees originating from four natural populations of dwarf mountain pine ( Pinus mugo Turra ) from the Julian Alps were investigated by GC-FID and GC/MS analyses. In total, 54 of the 57 detected essential-oil components were identified. Among the different compound classes present in the essential oils, the chief constituents belonged to the monoterpenes, comprising an average content of 79.67% of the total oil composition (74.80% of monoterpene hydrocarbons and 4.87% of oxygenated monoterpenes). Sesquiterpenes were present in smaller amounts (average content of 19.02%), out of which 16.39% were sesquiterpene hydrocarbons and 2.62% oxygenated sesquiterpenes. The most abundant components in the needle essential oils were the monoterpenes d-car-3-ene, b-phellandrene, a-pinene, b-myrcene, and b-pinene and the sesquiterpene b-caryophyllene. From the total data set of 57 detected compounds, 40 were selected for principal-component analysis (PCA), discriminant analysis (DA) , and cluster analysis (CA) . The overlap tendency of the four populations suggested by PCA, was as well observed by DA. CA also demonstrated similarity among the populations, which was the highest between Populations I and II. Introduction. – Pinus mugo Turra (sensu stricto), dwarf mountain pine, belongs to the Pinus mugo Turra (sensu lato) or Pinus mugo complex, a very polymorphic species complex, with montane distribution in southern and central Europe, including the Julian Alps. Dwarf mountain pine has mostly multi-stem and shrub-shape forms and grows up to 3 – 5 m height. It is one of the most resistant tree species against strong winds, snow, avalanches, and low temperatures. Dwarf mountain pine covers an area not suitable for other tree or shrub species (high altitude and/or rocky and poor soils, slopes with frequent snowslides, sometimes peat bogs) from the Alps to the Carpathians and Rhodope Mts. Its branches are relatively thick and very elastic, resistant to storms, snow-pressure, freezing, and avalanches in high mountains. Growth is very slow, only 2 – 3 cm during the first years, which ranks it among the slowest-growing tree species in Europe. The bark is thin, grey-brown to dark grey and peels off in scuta on old individuals. Shoots are smooth, brown to grey-black, and buds are conical, red-brown, and strongly resinous. The needles occur in two per fascicle, are 2 – 5 cm in length and 1 – 2 mm in width, and are slightly tortuous, light to dark green in color. They remain on the tree for 4 – 10 years [1] [2]. The species is frequently used for landscape design in parks and gardens, where manifold horticultural vari- eties are found. According to the nomenclature proposed after an extensive research by Hamerník and Musil [3], which is followed here, the Pinus mugo complex comprises tree species (microspecies), i.e., P. mugo Turra, P. uncinata Ramond ex DC., and P. rotundata Link, their three hybrids, as well as the abovementioned species) three hybrids with P. sylvestris . The taxa included into the complex have been the object of many studies on the morphometric, genetic, (chemo)taxonomic, habitat condi- tion, and plant-disease and pest interaction levels [4 – 14]. The delimitation of taxa is difficult, because of a high variability in life forms and habitat conditions. Many researchers point out that the Pinus mugo complex is still not completely characterized, which is why more detailed morphological, genetic, and biochemical research is re- quired, not only within the defined taxa, but within single populations and individuals as well [1] [3] [5] [8] [15 – 17]. Research has been done into the chemical composition and essential-oil content of the dwarf mountain pine [18 – 20], but as far as we know, there has been no research into its chemodiversity at the intra- and inter-population level. Much more research of this type has been done for other Pinus species (e.g., P. peuce, P. nigra, and P. heldreichii ) [21 – 24]. To the best of our knowledge, this is the first report on the essential-oil variability of P. mugo from the Julian Alps at the population level. Chem. Biodiversity 2016, 13, 181 – 187 181 DOI: 10.1002/cbdv.201500029 # 2016 Verlag Helvetica Chimica Acta AG, Zürich