Chemical and genetic differentiation of two Mediterranean subspecies of Teucrium scorodonia L.

Chemical and genetic diversity of Teucrium scorodonia L. subsp. scorodonia from Corsica and T. scorodonia L. subsp. baeticum from western Algeria were investigated. Diversity within and among the two populations of subspecies was assessed according to the chemical composition of their essential oils, and genetic diversity was evaluated using three polymorphic genetic markers. Chemical analysis was performed using a combination of capillary GC-RI and GC/MS after fractionation using column chromatography. Genetic structures were mapped using two chloroplast markers (RPL32-TRNL and TRNL-F) and ribosomal nuclear markers (ITS region). The statistical analysis showed that the two subspecies were clearly distinguished by these chemical and genetic markers. The chemical composition of oil differed qualitatively and quantitatively between the subspecies. Corsican oil samples contained germacrene B (4.2-8.8%) and γ-elemene (2.6-5.7%), which were not detected in Algerian oil samples. The oils of the scorodonia and baeticum subspecies were dominated by sesquiterpene hydrocarbon compounds (75.6-82.9% and 69.6-79.4%, respectively), but they differed in oxygenated sesquiterpene content (3.1-8.9% and 8.4-20.3%, respectively). Neighbor-joining trees constructed from chloroplast DNA and ITS region sequences showed the existence of two groups associated with taxonomic and chemical characteristics. One group consisted of T. scorodonia subsp. scorodonia and the other of T. scorodonia subsp. baeticum, indicating that variation in the essential oil composition of T. scorodonia subspecies depends more on genetic background than environmental characteristics.