New insights for the production of medicinal plant materials: Ex vitro and in vitro propagation of valuable Lamiaceae species from northern Africa

The overuse of natural medicinal plants forces the search for alternative production techniques to meet the growing needs, compensate for habitat degradation and conserve natural populations of plants. This study investigated the macropropagation and micropropagation of four medicinal plants from the Lamiaceae family growing in Algeria: Thymus algeriensis Boiss & Reut., Rosmarinus officinalis L., Marrubium vulgare L. and Salvia officinalis L. This baseline study aimed to describe biotechnology techniques that will help in restoring these important species and the developed callus culture can be a source of pharmaceutically important metabolites. It included two experiments: In Experiment 1, macrocuttings of 10-15 cm were cultivated in plastic pots containing soil and submitted in open greenhouse conditions. The rates of developed cuttings into whole plants were estimated. Experiment 2: segments of 5 mm taken from young stems were washed, sterilized using 0.1 % HgCl(2)( )and then cultured on semi-solid Murashige and Skoog (MS) medium supplemented with various combined concentrations of plant growth regulators (PGRs): indole-3-acetic acid (IAA) and Kinetin or N-6-furfuryladenine (Kin). The explants were incubated in a photoperiod (16 h light/25 degrees C, 8 h dark/15 degrees C) in a phytotron. The rates of callogenesis and caulogenesis were evaluated for different IAA/Kin combinations. The obtained results from macropropagation experiment showed significant differences (P < 0.001) in regeneration rates between the plant species. Salvia officinalis presented the highest success rate of regeneration (100 %) compared to other plants that showed low success rates. The combinations between IAA and Kin exhibited significant effects (P < 0.05 and P < 0.001) on callogenesis and caulogenesis. The best results of callus formation in T. algeriensis were observed at the combination of (5 mg/L IAA, 5 mg/L Kin) and (5 mg/L IAA, 10 mg/L Kin) where regeneration rates reached 23.3 % and 20 % respectively. In R. officinalis, the greatest callus production was obtained at (2.5 mg/L IAA, 5 mg/L Kin) with a rate of 56.7 %. In M. vulgare, the highest callus formation was marked at (2.5 mg/L IAA, 2.5 mg/L Kin), (2.5 mg/L IAA, 5 mg/L Kin) and (5 mg/L IAA, 5 mg/L Kin) with success rates varied between 33.3 % and 36.7 %. While S. officinalis can be significantly regenerated through macrocutting, the application of IAA and Kin combinations influenced greatly callus and shoots proliferation in T. algeriensis, R. officinalis and M. vulgare in in vitro micropropagation. The caulogenesis scores were low in the three above plants. Whereas, S. officinalis did not show any organogenic changes with all PGR combinations.