Quality control of commercial Mediterranean oregano: Development of SCAR markers for the detection of the adulterants Cistus incanus L., Rubus caesius L. and Rhus coriaria L.

A recent pharmacognostic survey showed a frequent adulteration of commercial Mediterranean oregano with dried plants having a similar silvery gray color (Rhus coriaria L., Cistus spp. and Rubus spp.). If performed by skilled adulterators, the detection of this practice relies almost completely on pharmacognostic assays which are extremely laborious and time consuming, especially when multiple batches of oregano have to be evaluated. Sequence-characterized amplified regions markers (SCARs) were developed from three RAPD markers specific for these adulterants, in order to speed up the primary screening of Origanum batches and allow the pre-emptive rejection of suspect samples, thus narrowing the number of samples to be subjected to more careful pharmacognostic analyses. The SCAR primers gave rise to the amplification of specific bands of expected sizes which allowed the detection up to 1% of adulterating plants. The relatively short dimension of these amplicons is suitable for the analysis of potentially degraded DNA obtained from dried and stored commercial material.