Variability in essential oil content and composition of Origanum hirtum L., Origanum onites L., Coridothymus capitatus (L.) and Satureja thymbra L. populations from the Greek island Ikaria

▶ Plants belonging to four “oregano” plant species (Origanum hirtum L., Origanum onites L., Coridothymus capitatus L., and Satureja thymbra L.) were collected during flowering from 33 sites located in the eastern part of the Greek island of Ikaria in the Eastern Aegean. The spatial distribution of all species was depicted on a GIS map. ▶ All four species exhibited essential oil concentrations higher than those reported in earlier literature, namely O. onites 3-4.3%, S. thymbra 4-6.5%, C. capitatus 3.7-5.6% and O. hirtum 5.5-10.0% (v/w). Carvacrol was the main constituent of the essential oils of all species, followed by γ-terpinene, p-cymene and caryophyllene, while no thymol was detected. ▶ All constituents varied remarkably among the four species, with carvacrol exhibiting the lowest variation. Carvacrol content varied between 72.3 and 89.2% in O. onites, 46.5 and 58.0% in S. thymbra, 82.9 and 90.9% in C. capitatus and 84.4 and 93.8% in O. hirtum. ▶ The carvacrol content was rather stable in the upper limits recorded in literature, while these high oil yields and carvacrol contents in this study merit further attention on understanding their genetic background, expression and heritability in the examined species.