In vitro propagation of olive (Olea europaea L.) cv. Koroneiki

Single node explants of 'Koroneiki' olive trees were cultured for one month on a modified Driver-Kuniyuki for Walnut medium, lacking growth regulators. The explants were subcultured once a month on a medium supplemented with zeatin riboside, 6-(gamma-gamma-dimethylallylamino) purine, 6- benzyladenine or thidiazuron. Zeatin riboside proved to be superior to other cytokinins in inducing shoot proliferation. The combination of olive knot extract at 25 or 50 mg l(-1) with cytokinins suppressed shoot proliferation. After two months at the proliferation stage, the explants were cultured for one week in the dark in 1 ml liquid Woody Plant Medium supplemented with IBA, alpha-NAA or IBA+alpha-NAA. The explants were then transferred to the same solid medium lacking growth regulators, with a small layer of perlite on the surface. The combination of the two auxins at 1+1 mg l(-1) resulted in almost 76% rooting. The combination of olive knot extract at 50 mg l(-1) with auxins increased the rooting percentage up to almost 87%. Artificial infection of explants with the bacterium Pseudomonas savastanoi pv. savastanoi inhibited rhizogenesis, even in the presence of auxins. Rooted explants were successfully acclimatised under a mist system, with the survival rate reaching almost 75%.