Effects of the natural cytokinin meta-Topolin on in vitro shoot proliferation and acclimatization of Prunus spp.

Prunus shoots 'Ferdor' (P. insititia x domestica) and 'Torinel' (P. domestica) were in vitro multiplied on media containing either 2.1 mu M meta-Topolin (mT) or N-6-benzyladenine (BA) over three subcultures before facing the root induction and acclimatization phases. More than 90% 'Ferdor' and 'Torinel' plants survived after 8 months from acclimatization regardless of the cytokinin used during the multiplication cycle. However, shoots multiplied on medium supplemented with mT showed larger leaves and, in the case of 'Ferdor', plants were significantly higher with a marked increase of internodes length compared to the plants multiplied on BA-containing medium. In a further experiment, the effects of mT on in vitro multiplication were also evaluated for 'Penta' (P. domestica) and myrobalan '29C' (P. cerasifera) shoots grown on media containing either 1.78 mu M mT or BA. When mT was supplemented to the medium, 'Penta' and myrobalan '29C' cultures provided a lower multiplication efficiency and higher shoots compared to the cultures grown on the same medium with BA. These data confirm that the response of Prunus spp. to mT is species-dependent. These results represent a further contribution to the application of this growth regulator in micropropagation of Prunus spp.