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Conservation and characterization of oregano, Origanum vulgare L., wild populations in Europe

Within the genus Origanum biotypes exists a wide variability that influences some uncertain definitions at both the species and botanical levels. The number of different names reflects the extent of morphological variation the genus exhibits in nature. It has been reported that the pattern of variation follows the geographical distribution. Origanum vulgare L. has a very large distribution area, stretching not only across the Mediterranean, but in many areas falling within the Euro-Siberian and Irano-Turanian region. The main objectives of the ECPGR MAP WG project were to inventarize and to survey for native populations of wild oregano (Origanum vulgare L.), to characterize their genetic and chemical characteristics and to find out the distribution pattern of taxonomically defined populations in 19 South-Eastern European area (Albania, Bulgaria, Croatia, Czech Republic, Finland, Greece, Hungary, Israel, Italy, Latvia, Lithuania, Macedonia, Norway, Portugal, Serbia, Slovakia, Slovenia, Spain and Turkey). The above ground parts of individual plants of three Origanum vulgare L. (Lamiaceae) populations (habitats of wild oregano populations) were collected in each country at the beginning of flowering. Geographical coordinates (latitude, longitude and altitude) were recorded. The plants were dried at room temperature and leaves/flowers separated from stems. This fraction was used in genetic and chemical analyses. After DNA isolation, genetic variability within and among Origanum vulgare L. populations has been done with micro-satellite technique. Essential oil compounds were analysed by GC/MS and GC/FID. The dataset represented 51 populations from Origanum vulgare from almost all over Europe. From Turkey and Israel, O. vulgare was substituted by O. onites and O. syriacum, respectively, because O. vulgare is not present in this area. The results of the study showed that O. syriacum is far closer related to O. vulgare from the Iberian Peninsula than to the geographically closer O. onites from Turkey or O. vulgare from Greece. The populations from Scandinavia and the Baltic states are very closely related to populations from the West Balkan states and have their next relatives not - as we would expect - in populations form Central Europe. The oregano populations from the Iberian Peninsula are very closely related and all quite distant to the other European oreganos. The essential oil content presents the wide range of variability of oregano in Europe. The countries which are known for their high-quality essential oil oregano showed the highest essential oil content. These countries were Greece (39-46 mg/g), Israel (28-47 mg/g ; O. syriacum) and Turkey (36-42 mg/g ; O. onites). However, two populations from Italy (14 and 26 mg/g), two populations from Croatia (37 and 43 mg/g), two populations from Portugal (13 and 10 mg/g) and one population from Slovenia (16 mg/g) showed also interestingly high levels of essential oils. Qualitative analyses of essential oils showed that plant samples, coming form different countries, belong to three main chemotypes, i.e. carvacrol and/or thymol, linalool type and sesquiterpene type.

O. vulgare L. biodiversity; microsatellite markers; genetic structure; essential oil; chemotype

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