Somaclonal variation in plants of oregano (Lippia palmeri, Wats) regenerated from calli (with 4 tables & 4 figures)

Plants regenerated from calli of oregano (Lippia palmeri, Wats.), cultured for 7 months on B5 medium were supplemented with 2,4-dichlorophenoxy acetic acid (2,4-D) and 6-benzyl adenine (BA). This treatment produced phenotypes that differed both morphologically and aromatically from the parent material. The most prominent variant, oregano somaclone-1 (osc-1), showed morphological and aromatic characteristics that resembled spearmint (Mentha spicata, L.). Gas chromatography-mass spectrophotometry was used to determine the composition of essential oils in the leaves and stems of oregano, osc-1, and spearmint. Osc-1 also showed morphological differences from oregano, the most significant being its change from a shrub to an herbaceous plant, the production of stolons, and variation in leaf shape and type and flower colour. These characteristics were maintained in clonally produced descendants, but sexual transmission has not yet been demonstrated. AFLP analysis shows that osc-1 and oregano are very different in each primer pair used in the analysis, percentage of homology ranging from 11 to 30 between mother and mutant plants. This new plant could be important in semiarid zones (where agriculture is limited) because it produces essential oils that can be used in the flavor, food, and perfume industries and, unlike traditional spearmint it, tolerates water scarcity.