In vitro propagation of Lithodora rosmarinifolia (Ten.) Johnst., a rare endemic Sicilian shrub with potential as ornamental plant.

Lithodora rosmarinifolia is a rare shrub endemic to the Mediterranean island of Sicily and its minor islands. Propagation of Lithodora rosmarinifolia by standard methods is difficult due to erratic seed production and low percentage of rooted cuttings. As the plant is suited for domestication, the possibility of establishing an efficient in vitro technique for propagation and conservation of this threatened species was investigated. Nodal segments from shoot tips were used as primary explants to establish in vitro culture. A 2 X 5 factorial experiment with five concentrations (0 to 17.74 mM) of N6-benzyladenine (BA) and two concentrations (0 and 2.46 mM) of indole-3-butyric acid (IBA) was used to determine the optimum growth regulator combination for axillary shoot multiplication by nodal segments. In the subsequent experiment equal molar concentrations of three cytokinins [2-isopenthenyladenine (2iP), kinetin, and BA] in combination with equal molar concentrations of three auxins [indole-3-acetic acid (IAA), a-naphthaleneacetic acid (NAA) and IBA] were tested for ability to induce shoot proliferation. The highest rate of axillary shoot proliferation was induced on Murashige and Skoog (MS) agar medium to which 4.44 mM BA and either 2.46 mM IBA or 2.46 mM IAA were added. In vitro rooting was efficiently accomplished in a medium containing ½ MS salts and vitamins, 20 g l-1 sucrose, 8 g l-1 agar and augmented with IAA at 0.11 mM. Rooted plants, transferred into soil, grew vigorously and flowered profusely during winter.