The market’s interest in aromatic plants is growing dramatically, in particular for oregano, one of the most popular, which is traditionally used for many food preparations. Yet, great confusion about the correct taxonomic classification of oregano still remains due to the many species marketed under this name. Most species, collected or cultivated to produce oregano, are characterised by a composition of essential oils rich in carvacrol, the component to which the characteristic taste and aroma of this spice is attributable. This work reports on studies focused on the morphological, chemical, and agronomic traits of some clones obtained from wild populations in different environments of southern Italy. INTRODUCTION The markets interest in aromatic plants is growing dramatically, not only for fresh consumption, but also for the new needs of agri-food sector. Oregano is among the most important of them, since it is largely used as a spice, condiment, and flavoring (Lawrence and Reynolds, 1984). The genus Origanum is characterised by a high variability of morphological and technological traits which has resulted in confusion in the correct taxonomic identification of oregano, due to the many species marketed under this name, and the opportunity to select, according to the final use of the product, the peculiarities characterizing different species and within each species, the different wild biotypes (Bernath, 1997). The purpose of this work is to test the morphological, chemical and agronomic traits of the collected accessions with a view to contribute to their assessment and characterisation, targeted to the present and new prospective uses. MATERIALS AND METHODS Plant Material Twenty-three biotypes belonging to the genus Origanum, selected from wild populations in different locations of southern Italy (Apulia, Basilicata and Calabria) (Table 1) have been collected since 1998. Experimental Design The germplasm is kept in a collection field at the Agricultural Faculty of Bari (Italy). The field was fertilized with 120 kg ha N, 100 kg ha P2O5, 100 K2O kg ha. The experimental design was a randomised complete-block design with three replications. The planting distance was 0.75 m between rows and 0.35 m within rows. Harvest and Processing The herb of the experimental material was harvested in the early flowering stage (20% of opened flowers). Shortly before harvest the date of flowering and the plant height were recorded. The material to be harvested was cut for each single plant at 10 cm above the ground to ensure the re-growth. Plant samples were tested for morphological traits, based on the indications provided by Ietswaart (1980). Measurements included the number of glandular hairs on the leaves, the indumentum of stems and leaves, and the color and shape of corolla that are considered as very influential for the characterisation Proc. XXVI IHC Future for Medicinal and Aromatic Plants Eds. L.E. Craker et al. Acta Hort. 629, ISHS 2004 Publication supported by Can. Int. Dev. Agency (CIDA) 356 of different botanical forms of oregano (Kokkini et al.1991, Tucker and Maciarella, 1994). The measurement of the number of glandular hairs per cm was made on the upper blade of six leaves taken from the fourth node starting from the first inflorescence; images were taken by a stereo-microscope equipped with a video camera and analysed, after an appropriate calibration using an image analysis program (Scion image). At harvest samples of 20 leaves per plant were taken for the determination of the mean leaf area, whereas the fresh biomass for each single plant was weighed and ovendried at 35 °C. Leaves and flowers were then separated from the stems, and single samples of leaves-flowers and stems (10 g for each) were oven-dried at 105 °C for the dry matter content determination. Content of Essential Oil A 5 g air-dried leaf-flower fraction of each single plant was submitted to water distillation in a Clevenger type-apparatus with a flask of 500 ml and 200 ml water for 60 minutes. Composition of Essential Oil The distilled essential oil was analysed using gas chromatography/mass spectrometry on a HP 6890 coupled with a HP 5972 MSD and fitted with a HP 30 m x 0.25 mm capillary column coated with HP-5MS (0.25 μm film thickness). Analytical conditions were: helium as carrier gas, injector temperature 250 °C, split ratio 50:1, temperature program 60-110 °C with 2 °C/min rise and 110-220 °C with 10 °C/min rise. The analysed components were then identified by the system HP Enhanced ChemStation G1701BA Version B.00.00 (Hewlett Packard) by comparing their mass spectra with the data in the literature (John Wiley & Sons) and confirmed by their gas chromatographic retention indices (Adams, 1995). Statistical Analysis The percentage concentrations of the components in the different oils were used as matrix elements to perform the hierarchical cluster analysis. All PC analyses were carried out using SAS software (SAS Institute Inc., Cary, NC) procedures.