Effects of culture medium and growth regulators on growth traits and secondary metabolites of Artemisia dracunculus L. under in vitro conditions

Considering the importance of medicinal properties of tarragon, and its propagation problems, tissue culture techniques can be used for its propagation. The aim of this study was to compare different culture media and chemical plant growth regulators on the growth traits and secondary metabolites of tarragon (Artemisia dracunculus L.). Treatments were culture medium at three levels of Murashige and Skoog (MS), Gamborg (B5) and Schenk & Hildebrandt (SH), and growth regulators at five levels of Kinetin (KIN), NAA, and 2,4-D alone (each with a concentration of 0.5 mg l-1), and two combinations of NAA+KIN and 2,4-D+KIN. The present study was conducted as a factorial based on completely randomized design with four replications. The results showed that culture media and growth regulators treatments had significant effects on callus characteristics, regenerated plantlets, callus secondary metabolites, and plant essential oil and its composition. MS medium caused a higher callus induction percentage and more increase in its fresh and dry weight. MS with NAA+KIN and 2,4-D+KIN caused the highest regeneration percentage (35.5), root length (1.28 cm), root (6.5 g) and stem (2.6 g) dry weight, the amount of callus phenolics, and also the amount of essential oil (2.42%) and ocimene (5.78%). Estragol percentage of essential oil increased by 2,4-D, while NAA enhanced ocimene, limonene, and linalool. The percentage of limonene in treatment with NAA alone and linalool in treatment with 2,4-D+ KIN was higher than those of other treatments. The results showed that the highest growth index, callus secondary metabolites, and plant essential oil were observed in MS medium containing growth regulators. Also, the application of kinetin with NAA and 2, 4-D resulted in improved callus growth, regeneration, essential oil, and some of its compounds production in tarragon.