In vitro propagation of Helianthemum marminorense

A reliable protocol for the in vitro propagation of adult plants of Helianthemum marminorense from nodal segments was developed. A culture medium test revealed that Woody Plant Medium (WPM) was the most suitable for the in vitro establishment and growth of this species. A treatment with 0.5 mg l−1 2iP gave the best results in terms of number of nodes and shoots/explant. The appearance of callusing and hyperhydricity events in the explants after treatments with growth regulators was frequent regardless of the cytokinin employed. In the search for an improvement of the in vitro culture, we showed the suitability of a double-phase (DP) system consisting of a volume of liquid medium overlaying a free-hormone semisolid medium to promote elongation and node number in the explants and therefore the potential for their multiplication. The DP consisted of half-strength Knop solution supplemented with sucrose and activated charcoal (AC). The application of each DP component separately clarified a key role for both Knop solution and AC but identified no role for sucrose. Spontaneous rooting was close to 100% and acclimatization was successful with 97% surviving plants 8 weeks after removal from in vitro conditions.