Micropropagation of <i>Genista aetnensis</i> [(Raf. ex Biv.)DC

Abstract

Genista aetnensis [(Raf. ex Biv.)DC] is a large deciduous shrub or small tree native to the Italian islands of Sardinia and Sicily. Being winter hardy and characterized by high plasticity in altitude and ecology, the species is grown in gardens and landscaping, both for flower and for its attractive shape. Genista species are generally propagate by seed or semi-hardwood cuttings. In this report an efficient in vitro technique for propagation of G. aetnensis was investigated. Multiple shoots were induced on nodal segments of a mature plant of Genista aetnensis. The Murashige and Skoog medium, augmented with different concentrations of N-6-benzyladenine either singly or in combination with indole-3-acetic acid, as potential medium for shoot multiplication by nodal segments was tested. In the following experiment equal molar concentrations of four cytokinins (2-isopenthenyladenine, kinetin, zeatin and N-6-benzyladenine) were tested for ability to induce axillary shoot development from single node stem segments. The highest rate of axillary shoot proliferation was induced on the medium supplemented with 0.44 µM BA. Growth regulator requirements for shoot proliferation in G. aetnensis were satisfied by BA alone. Explants were divided, subcultured and continued to proliferate shoots. A proliferation rate of 3.5 shoots per single node explants every four weeks occurred. Seven indole-3-acetic acid concentrations (0, 0.23, 0.45, 0.91, 1.82, 3.64 or 7.29 µM) were tested to determine the optimum conditions for in vitro rooting of microshoots. The highest rooting percentage was obtained with indole-3-acetic acid at 3.64 mM (57%). Eighty percent of the in vitro rooted plantlets were successfully established in soil. This micropropagation system of G. aetnensis based on axillary shoot development from nodal segments followed by in vitro rooting should be preferred for rapid and efficient mass propagation of selected clones and could represent an alternative method to sexual and conventional asexual propagation.