Effect of Liquid Media and In Vitro Pre-acclimatization Stage on Shoot Elongation and Acclimatization of Date Palm (Phoenix dactylifera L.) cv. Najda

The effect of stationary liquid media to improve shoots elongation in date palm cv. Najda and an in vitro pre-acclimatization stage to increase the survival percentage of plantlets in the greenhouse was investigated. Two basal liquid media were tested: full strength and half strength Murashige and Skoog medium (MS). Media were devoid of plant growth regulators (PGRs), containing 0.5 mg/L 6-benzylaminopurine (BAP) or 0.5 mg/L indole-3-butyric acid (IBA) and 0.5 mg/L BAP. After three months of culture, all liquid media were efficient and allowed to overcome slow growth problem. The maximum shoot elongation was 11.3 cm, obtained in MS supplemented with 0.5 mg/L BAP and 0.5 mg/L IBA. The shoots were isolated and transferred either to the greenhouse or to one month in vitro pre-acclimatization stage in a PGRs-free solid medium (MS or MS/2) then to the greenhouse. A higher surviving rate (ranging from 70 to 86 %) was obtained after one month pre-acclimatization compared with the direct transfer to the greenhouse (12–28 %).