The effect of IBA, NAA and 2, 4- D on callus production and growth in common yew (Taxus baccata L.) on in vitro conditions

Common yew (Taxus baccata L.) is one of the most valuable coniferous species in the northern forests of Iran which is shade tolerant and its distribution is from Astara to Ali Abad Katoul (Golestan province). This species additional to having genetic reservation, silvicultural and ecological values, has the special advantage in drug industry. As callus is a primary substance for cell cultures and secondary metabolite's production and indirect organogenesis, therefore, in order to suggest a suitable explant and definite concentration of growth regulators for callus production, the effect of Indole-3- butyric acid (IBA), α-Naphtaleneacetic acid (NAA) and 2, 4- Dichlorophenoxyacetic acid (2, 4- D) on callus production and growth in common yew under in vitro conditions were considered.
In this research, the explants were provided from different parts of the tree such as leaf, young stems and apical buds with 1.5 cm lengths. For sterilization of explants different methods were used. The explants were cultured in Murashige and Skoog medium after sterilization. For callus induction from IBA, NAA and 2, 4- D in 4 levels (0, 0.3, 3 and 6 mg L-1) were used. In order to prevention of auxins decomposition and their better absorption by explants texture, all of the explants were maintained in dark conditions for a week. For each explants of stem, leaf and bud callus growth curve were drawn. Data were analyzed with ANOVA and Duncan tests.
The results were shown that the best method for explants sterilization was ethanol 70% (for 1 min), HgCl2 0.2 % and CaCl2 0.2% (for 1 min). The maximum percentage of browning was observed in bud explants at concentration of 6 mg L-1 NAA. The leaf explants were better than other explants in the browning phenomenon, so that there was no evidence of browning in different concentration of IBA and 2, 4- D. The maximum wet and dry weight of callus was belonging to stem and bud explants under treatments of 2, 4- D and NAA at concentration of 3 mg L-1, respectively. In addition, the produced calluses had different texture and color. Most of bud explants at concentration of 0.3 mg L-1 NAA were normal conditions but at concentration of 6 mg L-1 IBA and 2, 4- D, they were converted to callus. The callus growth curves in different explants showed that initiation and callus production and its growth is having a relatively low rate.
2, 4- D at concentration of 3 mg L-1 for callus production from yew stem and leaf explants, NAA at concentration of 3 mg L-1 for callus production from apical bud and NAA at concentration of 0.3 mg L-1 for plantlet production from yew bud are suggested as suitable protocols.