Induction of organogenesis and callogenesis in Limbarda crithmoïdes L. (Asteraceae) explants cultured on MS media supplemented with various concentrations of Na⁺ and K⁺

The present work describes an efficient micropropagation and callus induction protocol of Limbarda crithmoïdes L. (Asteraceae), a halophyte species with medicinal and horticultural interests. The objective was to identify the culture media that support the best organogenesis and callogenic expressions of four types of aerial explants; nodal and internodal segments and leaf portions, by varying the mineral composition of twenty culture media by adding increasing concentrations of Na+ (from 0-100 mM) and K+ (from 0-50 mM). After two months of culture, parameters relating to the various expressions of organogenesis and callogenesis were measured. Results showed that the K+ and Na+ interactions affect the explants development. The combination of high concentrations of Na+ (50, 100 mM) and K+ (50 mM) ions allowed the most important regeneration of the axillary shoots (70.6-100%), root neoformation (82.6-96.1%) and callus induction (76.3-100%). Rooted plantlets with well-developed axillary shoots have been successfully acclimatized with a 93% of survival rate. The selected media would allow a large-scale multiplication of this medicinal species, without adding exogenous phytohormones, and could be used for the micropropagation of other threatened halophyte species or for the production of callus; rich in secondary metabolites.