In vitro propagation for conservation of the rare date palm (Phoenix dactylifera L.)'Amri' using immature inflorescence

Immature female inflorescence plays a significant role in date palm micropropagation because inflorescences are available with no practical limit as the source of explants. Moreover, using floral buds for propagation helps in the conservation of date palm biodiversity and the enhancement of socioeconomically valuable landraces. With the goal of avoiding undesirable genetic variability, the optimal combinations and concentrations of plant growth regulators and other medium compositions were investigated to achieve direct organogenesis and multiplication from the immature female inflorescence of date palm (Phoenix dactylifera L.) cultivar Amri. For the initiation stage, the best response was achieved using Murashige and Skoog (MS) medium containing 1.0 mg L-1 zeatin and 1.0 mg L-1 thidiazuron (TDZ) after 16 wk of culturing. For the multiplication stage, the best culture medium contained 0.5 mg L-1 TDZ solidified with Gelrite(TM), without activated charcoal for four subcultures, and then supplementing 30 mg L-1 glutathione to this medium composition for two additional subcultures. Plantlets were multiplied and grown for 12 wk on elongation medium and then transferred to the rooting stage in two steps. Compared with other treatments, foliar spraying and watering with 30 g L-1 sorbitol and 40 g L-1 salicylic acid twice a week yielded the best results in terms of survival percentage (95%), leaf width (2.9 cm), and growth vigor (4.4 lateral branch). This was the best combination of plant growth regulators and other medium compositions for micropropagation of date palm (Phoenix dactylifera L.) cultivar Amri without the need for callus formation to avoid undesirable genetic variability.