Shoot regeneration from adventitious buds induced on juvenile and adult almond (Prunus dulcis Mill) explants

Adventitious shoot regeneration was achieved from almond leaves, cv. Boa Casta excised from in vitro cultures of juvenile and adult material. Murashige and Skoog (1962) medium (MS) was found to be more efficient for adventitious shoot induction than a modified medium of Quoirin et al. (1977) when using identical growth regulator supplements. Thidiazuron (TDZ) at 4.54, 5.90, 6.81, and 9.08 mu M was used in all induction media, together with indole-3-butyric acid (IBA), indole-3-acetic acid (IAA), or a combination of IAA and 2,4-dichlorophenoxyacetic acid (2,4-D). When N-6-benzyladenine (BA) was used instead of TDZ, no adventitious shoots were induced. Leaf explants of juvenile origin yielded the highest regeneration rates (40.0 and 38.2%) and required higher concentrations of TDZ for shoot induction than leaves of adult origin. An increase from 15.0 to 35.3% in the regeneration ability of adult leaf explants, tested on one of the induction media [modified medium of Quoirin et al. (1977) supplemented with 5.90 mu M TDZ and 2.85 mu M IAA], was achieved when donor shoots were subcultured twice on a medium with a low BA concentration of 1.33 mu M.