Phytomorphological and essential-oil characterization in situ and ex situ of wild biotypes of oregano collected in the Campania region (Southern Italy)

Abstract

Oregano is an aromatic species of great interest, which spreads spontaneously over the Mediterranean area, but its genetic resources are not yet adequately developed. Moreover, the results of studies of wild strains of different origin - although quite numerous - are not always comparable, and, therefore, the influence of the environment and genotype on the variability cannot be distinguished. Hence, the plant morphology and the essential-oil composition of three wild, white-flowering biotypes of oregano collected in the Campania region (southern Italy) were characterized, and the effects of genotype and environment were assessed by comparison in situ and ex situ. This allowed deducing that the biotypes belonged to two different subspecies, i.e., Origanum vulgare ssp. virens and O. vulgare ssp. viridulum. The essential-oil yield was higher for the biotype belonging to ssp. virens, and it was significantly correlated with the glandular and stomatal density. The chemical composition of the oils obtained by hydrodistillation was found to be influenced by the genotype and the conditions of plant growth.

Keywords: Essential oils; Glandular trichomes; Origanum vulgare; Stomatal density.