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This chapter describes an efficient protocol for large-scale micropropagation of date palm. Somatic embryo-derived plants are regenerated from highly proliferating suspension cultures. Friable embryogenic callus is initiated from juvenile leaves using slightly modified Murashige and Skoog (MS) medium supplemented with 0.1 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D). Suspension cultures consisting of proembryonic masses are established from highly competent callus for somatic embryogenesis using half-strength MS medium enriched with 0.1 mg/L 2,4-D and 300 mg/L activated charcoal. The productivity of cultures increased 20-fold when embryogenic cell suspensions were used instead of standard protocols on solidified media. The overall production of somatic embryos mostly exceeds 10,000 units per liter per month. Partial desiccation of mature somatic embryos, corresponding to a decrease in water content from 90 down to 75%, significantly improved germination rates.

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Objectives The present study aimed at exploring the eliciting effects of increasing concentrations (50, 100, and 200 µM) of MeJA. We cultivated actively proliferating buds of Phoenix dactylifera L. cv. Barhee in a temporary immersion system and we monitored the bioactive compounds accumulation after 7 days of culture. Methods Total phenolic (TPC) and flavonoid (TFC) contents were determined by high-performance liquid chromatography (HPLC), Fourier-transform infrared (FTIR), and radical scavenging activity using DPPH and ABTS assays. We also explored the activity of phenylpropanoid pathway enzymes, namely phenylalanine ammonia-lyase (PAL), tyrosine ammonia-lyase (TAL) and polyphenol oxidase (PPO). Results Our results revealed that high MeJA concentrations induced an increase in the PAL, TAL and PPO activities. Several stress markers such as Hydrogen peroxide (H2O2), Nitric oxide (NO), Malondialdehyde (MDA), Superoxide dismutase (SOD), Catalase (CAT) and Guaiacol peroxidase (GPOD) were also found to rise. Beside, MeJA caused subsequent elevations in the amount of catechin, 4-Hydroxybenzoic acid, caffeic acid and p-Coumaric acid and antioxidant capacity with the lowest DPPH and ABTS IC50 values. Microscopic observations using fluorescence probes such as fluorescein diacetate (FDA) and acridine orange/ethidium bromide demonstrated that the supplementation of MeJA to culture media induced cells death in a dose dependent manner. Conclusion The findings suggest that in vitro cultures elicited by MeJA of Phoenix dactylifera L. have the capacity to produce secondary metabolites.

The present study is a part of a program designed at improving the date palm, Phoenix dactylifera L. cv. Barhee, through induced somaclonal variation. In this work, caulogenic cultures were subcultured on MS media supplemented with 0, 1, 5, 10, 20 and 40 mg L− 1 2,4-D in order to induce genetic and epigenetic variations. The highest doses of 2,4-D were found to induce severe negative effects on in vitro cultures, although some tissues were able to survive and to produce calli with high morphogenetic capacities. Our analysis showed some significant effect of 2,4-D on several physiological parameters. Indeed, chlorophyll and growth rates were found to drastically decrease while proline content increased from 535 nmol g− 1 to 2973 nmol g− 1 FW when 40 mg L− 1 2,4-D were used. In vitro cultures showed several signs of oxidative stress, such as high levels of hydrogen peroxide (H2O2) and malondialdehyde (MDA); likewise, the specific activity of several antioxidant enzyme was found to increase. Plant regeneration from in vitro cultures treated with 2,4-D was obtained after subculturing explants onto PGR-free media. The ISSR analysis of 2,4-D-treated material showed that this plant growth regulator (PGR) induced measurable genetic variations. The global DNA methylation rates (GMR) as estimated through the HPLC analysis of nucleosides also confirmed the presence of epigenetic changes caused by 2,4-D as GMRs increased from 13.8–18.93%.