Optimizing Tissue Culture Protocol for In Vitro Shoot and Root Development and Acclimatization of Date Palm (Phoenix dactylifera L.) Plantlets

The current study aims to optimize in vitro elongation and rooting protocol and successful acclimatization of two elite date palm cultivars of Pakistan. The differentiated repeated embryos (RE) and non-repeated embryos (NRE) of date palm cvs. Aseel and Dhakki were harvested and transferred on germination medium containing different combinations of NAA + Kin (mg L−1), full strength MS nutrients and 30 g L−1 sucrose. The maximum somatic embryos germination and plantlet formation was achieved on the medium comprising 0.05 NAA + 1.0 Kin (mg L−1). Whereas improved elongation and rooting was obtained on the MS medium comprising 0.1 NAA + 0.1 BA (mg L−1). Addition of activated charcoal (3 g L−1) and trimming of roots (prior to proper rooting stage on rooting medium) were found vital to enhance leaf and root length, in addition helped secondary and tertiary root formation. The in vitro hardening was observed as helpful to bring gradual physiological changes from heterotrophic to autotrophic mode of plant nutrition. In vitro plantlets with 2–4 leaves (avg. 20 cm long) and healthy roots (avg. 8–12 cm long) were acclimatized in greenhouse on different soil mixtures. The best soil medium for acclimatization of plantlets was peat moss + river sand mixture at ratio of 3:1 (v/v) which resulted in 92% survival of plantlets in the greenhouse during first month of transferring. The current micropropagation protocol may support for commercial scale production of other elite date palm cultivars worldwide.