Effects of plant growth regulators and light intensity on the micropropagation of date palm (Phoenix dactylifera L.) cv. Mejhoul

Abstract

The present study aimed to determine the best combination of plant growth regulators (PGRs) and light intensity in order to improve organogenesis of date palm (Phoenix dactylifera L.) cultivar Mejhoul. Organogenic cultures obtained from shoot tip explants were cultured on half-strength Murashige and Skoog (MS/2) medium supplemented with various combinations of two auxins: 2-naphthoxyacetic acid (NOAA) and indole-3-acetic acid (IAA) at 0, 0.2, or 0.4 mg L−1and two cytokinins: kinetin and 6-(dimethylallylamino) purine (2iP) at 0, 0.4, or 0.8 mg L−1 under different light intensities. Our results revealed that after 3 months of culture, the combination of 0.2 mg L−1 NOAA, 0.2 mg L−1 IAA, 0.4 mg L−1 2iP, and 0.4 mg L−1 kinetin was the optimal for shoot proliferation (12.8 shoot buds per explant), with low levels of hyperhydricity (20.0%), tissue browning (20.0%), and precocious rooting (30.0%). The present study showed also that darkness and low light intensity (500 lux) significantly increased the incidence of precocious rooting while high light intensities (2,000 – 3,000 lux) decreased shoot bud proliferation and stimulated shoot elongation and greening. The optimal light intensity during the multiplication phase was 1,000 lux (13.2 shoot buds per explant, 15.0% greening, 25.0% precocious rooting). Shoot elongation and rooting occurred on PGR-free MS/2 medium then the plantlets were transferred to a greenhouse where 88.0% survived after 3 months. Our results are beneficial for the efficient and large-scale propagation of the elite and endangered date palm cultivar Mejhoul.