Rosmarinus officinalis L.: micropropagation and callus induction for cell biomass development

Rosemary (Rosmarinus officinalis L.) is a typical Mediterranean shrub which belongs to the Lamiaceae family. Tissue culture techniques have been proved to be a useful tool for the yield of rosemary secondary metabolites (e.g., carnosic acid). In this paper, we have undertaken experiments addressed to point out a classical propagation protocol and we have investigated factors promoting the callus induction for the further establishment of cell culture. In vitro sowing provided seedlings which showed suitable multiplication rate when cultured on media deprived of growth regulators. Rooting at 50% occurred also in media lacking of growth regulators although higher rooting percentage was obtained in the presence of IAA (75 and 78.6 at 0.5 and 1 mg L^-1, respectively). The highest acclimatization percentage (64%) was achieved for plantlets rooted with 1 mg L^-1 IAA under greenhouse conditions with mist system. Apices and internodes of adult plants, grown in open field or in the greenhouse, showed, after disinfection, high percentage of mortality. Callus was induced from leaves taken from stock plants grown in open air. Callus development was observed after two months of culture. The biomass increased through 4-week subcultures on the same medium. The established and friable calli of R. officinalis were then transferred to liquid medium with the same hormonal composition, with the aim to scale-up the biomass production in vitro.