Organogenesis of Phoenix dactylifera L. cv. Mejhoul: Influences of natural and synthetic compounds on tissue browning, and analysis of protein concentrations and peroxidase activity in explants

• An efficient regeneration system for Phoenix dactylifera cv. Mejhoul is reported.
• Chemical and natural additives showed different effects on tissue browning.
• Date stone-based activated carbon has a powerful effect against tissue browning.
• A positive correlation was found between tissue browning and peroxidase activity.

The effect of some chemical and natural antioxidants on date palm organogenesis was evaluated. Shoot tip explants of Phoenix dactylifera L. cv. Mejhoul were cultured on half-strength Murashige and Skoog (1/2MS) medium supplemented with various concentrations (1.5, 3 or 4.5 g l−1) of activated charcoal (AC), polyvinylpyrrolidone (PVP) or date stone-based activated carbon (DSAC); or with the methanolic extracts of Rosmarinus officinalis and Thymus satureioides, either alone (0.16-0.48 g l−1) or in combination (0.08-0.24 g l−1). The use of PVP at 1.5 g l−1 provided the optimal conditions during the initiation stage with an organogenesis frequency of 52.5% and a tissue browning frequency of 30.0%. During the multiplication stage, 1.5 g l−1 DSAC showed significantly better results in terms of shoot bud proliferation (13.9 shoot buds per explant) and tissue browning (7.5%). The total protein concentration and peroxidase activity varied significantly depending on the anti-browning additive, and positive correlations were revealed between protein concentration and bud proliferation and morphology, and between peroxidase activity and tissue browning. Shoot elongation and rooting were achieved in plant growth regulator-free 1/2MS medium and up to 97.5% of plantlets survived after acclimatization. It has been revealed that DSAC is an efficient natural anti-browning compound for date palm organogenesis.