Detecting Satureja montana L. and Origanum majorana L. by means of SCAR–PCR in commercial samples of Mediterranean oregano

A recent pharmacognostic survey of the European market highlighted a high frequency of adulteration of commercial Mediterranean oregano with species of the Lamiaceae family (Satureja montana L. and Origanum majorana L.) having a similar appearance and a superimposing essential oil profile. When performed by skilled adulterators, this dilution can only be detected by pharmacognostic assays or phytochemical analyses, which can be either extremely laborious, expensive and time consuming when multiple batches of oregano have to be evaluated, or can produce inconclusive results. Sequence-Characterized Amplified Regions markers (SCARs) specific for these adulterants were developed from Random Amplified Polymorphic DNA (RAPD) markers, in order to support results of pharmacognostic or chemical analyses and/or to speed up the primary screening of oregano batches and allow the pre-emptive rejection of suspect samples, thus narrowing the number of samples to be subjected to further tests. The SCAR primers gave rise to the amplification of specific bands of expected sizes which allowed the detection of down to 0.5% of adulterating plants, despite the small genetic distance between the species involved. A specific protocol for DNA extraction was set up. In addiction, the relatively small size of these amplicons is suitable for the analysis of potentially degraded DNA obtained from dried and stored commercial material.