Optimization of auxin-cytokinin combination for rapid proliferation of adventitious buds of date palm cv. Aziza Bouzid

We evaluated the effects of various plant growth regulator (PGR) combinations on adventitious shoot bud multiplication of date palm cv. Aziza Bouzid. In the first experiment, we assessed the effect of four PGR combinations that have already shown good results in other date palm cultivars: half-strength Murashige and Skoog medium (MS/2) supplemented with 0.5 mg/L 2-naphthoxyacetic acid (NOA) and 0.5 mg/L kinetin (KIN); MS/2 supplemented with 0.2 mg/L NOA, 0.2 mg/L indole-3-acetic acid (IAA), 0.4 mg/L 6-(dimethylallylamino)purine (2iP) and 0.4 mg/L KIN; MS/2 supplemented with 0.5 mg/L 1-naphthaleneacetic acid (NAA) and 0.5 mg/L KIN and finally MS/2 supplemented with 0.5 mg/L indole-3-butyric acid (IBA) and 0.6 mg/L 6-benzylaminopurine (BAP). Our results showed no significant difference among the four culture media in terms of adventitious shoot bud multiplication (26.7-28.4 adventitious buds per explant). However, the medium containing 0.5 mg/L NOA and 0.5 mg/L KIN showed significantly lower rate of precocious rooting and thus this auxin-cytokinin combination was chosen for the second experiment. In the second experiment, we evaluated the effects of various NOA and KIN concentrations on adventitious shoot bud multiplication: 0, 0.25, 0.5 and 1 mg/L of each PGR, either alone or in combination. It was found that the combination of 0.5 mg/L NOA and 0.5 mg/L KIN is still the most appropriate for adventitious shoot bud multiplication. Shoot elongation and rooting were achieved on PGR-free MS/2 medium and a high acclimatization rate of 70% was observed in the greenhouse.