Effects of plant growth regulators and carbon source on shoot proliferation and regeneration in date palm (Phoenix dactylifera L.) '16-bis'

The aim of this study was to optimise in vitro culture conditions for the date palm (Phoenix dactylifera L.) cultivar '16-bis'. The effects of various combinations of plant growth regulators (PGRs) and sources of carbon in the growth medium on shoot proliferation and growth were evaluated. The PGRs used were indole-3-butyric acid (IBA), 2-naphthoxyacetic acid (NOA), 6-benzylaminopurine (BAP), and kinetin (KIN), each at 0, 2.5, or 5.0 mu M. The carbon sources used were sucrose, sorbitol, or mannitol, each at 10, 20, 30, 40, or 50 g l(-1). Explants cultured on 1.0x Murashige and Skoog (MS) medium supplemented with 2.5 mu M IBA plus 2.5 mu M BAP and 20 g l(-1) sucrose showed the highest rate of shoot proliferation (22.3 shoots per organogenic cluster). Higher concentrations of PGRs increased the frequencies of hyperhydricity and precocious rooting. Carbon source and its concentration affected almost all of the parameters measured. The highest rate of shoot proliferation was on 1.0x MS medium containing 20 g l(-1) sucrose. The frequency of precocious rooting increased with higher concentrations of carbon source. The proliferated shoots were transferred onto PGR-free 1.0x MS medium supplemented with 10, 20, 30, 40, or 50 g l(-1) sucrose, sorbitol, or mannitol for elongation and rooting. Those grown on 1.0x MS medium containing 40 g l(-1) sucrose showed the strongest growth and development, and the highest rate of survival (92.5%) after the plantlets were transferred to a glasshouse. These results will be useful for producing large numbers of '16-bis' date palm plants to restore Moroccan palm groves decimated by bayoud disease.