IN VITRO PROPAGATION OF P.S. B2 PEACH ROOTSTOCK.

Trials were carried out on the possibility of propagating P.S. B2 peach rootstock by in vitro culture. At the beginning of the trials a modified MS medium was used, adding BAP at 0.6, 1.2 and 2.4 mg/l. Apices, 10–12 mm in length, were taken from actively growing shoots developed on cuttings collected in winter and subsequently placed in a forcing chamber. During the initial 4 subcultures, explant growth was very poor: the apices developed only in length, with short internodes, large leaves and without axillary bud sprouting. Some of the explants were thus cultured on WPM medium to which 1.2 mg/l of BAP was added. Shoot growth was much improved; in fact, after the first 2 subcultures, shoot proliferation increased to a rate of 1:3.5, while on MS medium the explants still showed a lower growth rate. MS and WPM media were also tested for shoot elongation and rooting; best results (90% of rooting) were obtained by culturing the shoots on MS medium for the elongation phase and on WPM medium for rooting.