IN VITRO REGENERATION AND MICROPROPAGATION OF GF-677 HYBRID (PRUNUS AMYGDALUS × P. PERSICA) ROOTSTOCK

In this research a complete regeneration protocol was developed for GF-677, an important rootstock for almond. Nodal sections were cultured on MS (Murashige and Skoog, 1962) medium supplemented with various concentrations (0.5-2.0 mg/L) of BA (benzyladenine). The highest rate of adventitious shoot initiation and multiplication was recorded at concentration of 1 mg/L BA. The young expanding leaves were excised from in vitro shoots and cultured on MS medium supplemented with TDZ (thidiazuron) or BA alone, or in combination with NAA (naphthalene acetic acid) for 3 weeks in the dark and then transferred to a 16/8 hour of (light/dark) photoperiod. Callus formation occurred on the leaf explants within 3 weeks in the dark. The explants were subcultured in the same medium at 3-week intervals. After 4 subcultures no regeneration had been observed on the leaf explants. Callus formed at the bases of shoots on MS medium supplemented with 1 mg/l BA and the adventitious shoots differentiated from these calli. Regenerated shoots from callus were scored, excised, and transferred to elongation medium supplemented with 0.0, 0.1, or 0.5 mg/L BA. MS medium supplemented with 0.5 mg/L BA, 30 g/L sucrose, and 5.5 g/L agar provided the best shoot elongation. Elongated shoots of GF-677 were cultured on 1/2 MS medium supplemented with 0.05-2.0 mg/l IBA for rooting. On 1/2 MS medium containing 1.0 mg/L IBA, a maximum rooting efficiency of up to 84.2% was obtained. Rooted plantlets were successfully acclimatized and transferred to potting mix with 66.4% survival.