Adaptation of oregano (Origanum vulgare L.) to cultivation in Elvas region, South Portugal

Origanum vulgare L. sustainable cultivation should be promoted in order to reduce genetic erosion risk caused by harvest in nature. The main goal of this study was to respond to the request of a farmer from Elvas region, focusing on the assessment of the adaptation to cultivation of six accessions, three spontaneous in Alto Alentejo (OV1, OV2, OV3) and three commercial (OVT1, OVT2, OVT3). Plant propagation was carried out from stem cuttings for the three spontaneous accessions and from seed for the three commercial accessions. Using material from OV2, a stem cutting vegetative propagation trial was carried out, using softwood (tip and intermediate) and semi-hardwood (basal) stem cuttings. Seed germination was tested using the 3 commercial seed accessions and the 3 spontaneous accessions (harvest in nature and after cultivation) at 20°C with 12-h photoperiod. The following descriptors were observed on the field characterization essay: flowering date, length, width and colour of the basal leaf, growth habit, width and height of the plant, length of the main stem, length and width of the terminal inflorescence, flowered portion of the stem length and width, plant biomass (fresh and dry). The softwood intermediate stem cuttings rooted better (83.8%) and rooting rate was significantly higher than basal semi-hardwood cuttings (56.8%). Seed germination varied from 69.5 to 92%, with significant differences between the commercial seeds and seeds of the spontaneous accessions after cultivation. On the characterization field essay, the flowering date was the only descriptor with significant differences between spontaneous accessions. The earliest-flowering accession was OV1 and the later-flowering accession was OV2. The difference between the flowering dates of these accessions was 13 days. The work provided useful information to the farmer for oregano growing, however, the study should be continued with a larger amount of accessions of broader geographical origin.