Tragacanth, a Novel and Cheap Gelling Agent in Carnation and Miniature Rose Tissue Culture Media

The natural tragacanth gum, the sap of Astragalus gummifer, has been successfully used as a gelling agent in tissue culture media for in vitro shoot development and proliferation of miniature rose and carnation. Shoot development of nodal segments excised from greenhouse grown plants, was investigated on MS medium solidified with either 2.5, 3.0, 3.5 and 4.0% tragacanth or 0.8% agar as control. The media solidified with tragacanth were more transparent than the media solidified with agar. Viscosity of the tragacanth-gelled media was less than the agar-gelled media, and therefore, putting the explants on the media sometimes resulted in submersion of them into the media and some cases of development of hyperhydric shoots were observed. To increase the firmness of the media, the combinations of agar (0.2 and 0.3%) and tragacanth (2 and 3%) were used. The viscosity of the combinatory media was as good as the medium containing only 0.8% agar (control). Moreover, the explants productivity and growth obtained in these combinations were better than those recorded on the control medium. Being a plant product, biodegradable and environmental friendly, and 10 times cheaper than agar, tragacanth gum would definitely be useful for reducing costs, particularly in the plant tissue culture industry.