Effects of dicamba and casein hydrolysate on in vitro growthand shoot regeneration of date palm (Phoenix dactylifera L.) cv. Barhee

The investigation was carried out to evaluate the influence of the dicamba (3,6-Dichloro-2-methoxybenzoic acid) (DIC) and casein hydrolysate (CH) on the callus growth, shoot multiplication, and some biochemical constituents of date palm cv. Barhee cultured in vitro. Both DIC and CH were required for callus growth and shoots regeneration. The medium supplemented with 4.0 mg l⁻¹ DIC in combination with 1.0 g l⁻¹ CH gave the highest callus weight (287 mg), while the maximum response rate and the number of shoots per jar (86.67% and 15.07 shoots/jar) were found in MS media equipped with 4 mg l⁻¹ DIC and 0.5 mg l−1 CH combination. The total amount of phenolic compounds was significantly reduced to 0.82 and 0.79 mg GAE g^–1 in shoots cultured in the medium equipped with 4.0 mg l⁻¹ DIC with 0.5 and 1.0 g l−1 CH, which is reflected in the rate of browning. The results showed that the highest shoots content of endogenous IAA (3.71 and 3.50 μg g⁻¹), were obtained in response to 4 mg l⁻¹ DIC + 1.0 g l−1 CH and 4.0 mg l−1 DIC + 0.5 g l−1 CH, respectively. The macronutrient K, P, Ca, and free amino acids content significantly increased in the in vitro shoots regenerated on the media supplemented with 4.0 mg l⁻¹ DIC + 1.0 g l−1 CH. The genetic stability of this study was confirmed by the DNA-based fingerprinting method RAPD. The RAPD binding patterns indicated no variation among tissue culture-derived plants. The in vitro propagation protocol described herein can be introduced to the production of genetically stable date palm plants.