Role of cytokinins and physical state of the culture medium to improve in vitro shoot multiplication, rooting and acclimatization of date palm (Phoenix dactylifera L.) cv. Boufeggous

We investigated the effects of cytokinins and the physical state of the culture medium on in vitro shoot multiplication of date palm (Phoenix dactylifera L.) cv. Boufeggous. Organogenic cultures obtained from shoot tip explants were cultured on stationary liquid or semi-solid half-strength Murashige and Skoog medium (MS/2) supplemented with 3 mu M indole-3-butyric acid (IBA) and with either N-6-[2-isopentenyl] adenine (2iP), 6-benzylaminopurine (BAP), kinetin (KIN), or thidiazuron (TDZ) at 1, 2, 3, or 4 mu M. After 3 months of culture, shoot multiplication, hyperhydricity, browning, and precocious rooting were significantly influenced by the type and level of cytokinins and the physical state of the culture medium. Generally, BAP and KIN stimulated shoot multiplication better than 2iP and TDZ, while semi-solid media supported morphologically superior shoots than stationary liquid media. The optimal medium for shoot multiplication was semi-solid MS/2 supplemented with 3 mu M IBA and 3 mu M BAP. The shoot multiplication rate increased with increasing BAP concentration, but more hyperhydricity was observed. Regenerated shoots were elongated and rooted on plant growth regulator-free MS/2 medium. After plantlets were transferred to a glasshouse, those that were previously cultured on semi-solid media showed higher survival rates, reaching 92.5 %. The protocol reported here will be useful for the rapid and efficient propagation of cv. Boufeggous, an elite date palm cultivar.