In vitro propagation of a forest tree Paulownia tomentosa ( Thunb.) Steud. - A valuable medicinal tree species

The micropropagation of Paulownia tomentosa (Thunb.) Steud. was achieved by culturing nodal explants in MS medium through adding growth regulators: 6-benzylamino purine (BAP), indole-3-butyric acid (IBA) alone or combined in order to initiate shoot bud. Shoot proliferation was induced by the mean of MS medium containing different concentrations of BAP (1or 2 mg L-1) alone or in combination with IBA (0.25 or 0.5 mg L-1). Shoot buds were also placed on MS medium and added with IBA (0.25, 0.5 and 1 mg L-1). During rooting stage, grown shoots were placed in a medium containing IBA at different concentrations (0, 0.25, 0.5, 1 and 2 mg L-1). The results showed that supplementation of the culture medium by 1.0 mg L-1 of BAP exhibited the highest percent response (100%) for shoot bud initiation. During the multiplication stage, the medium containing (1 mg L-1) BA and (0.25 mg L-1) IBA was the most effective treatment to promote shoot multiplication. However, the number of shoots produced is relatively low represented by 1.4 shoot per nodal explants. For this reason, adding IBA only to MS medium was crucial to produce a single shoot with several nodes. Therefore, the supplementation of the culture medium by 1.0 mg L-1 of IBA induced the highest mean length of shoots per explants (3.75cm) and number of nodes per shoot (6). Concerning rooting potentiality, the addition of 0.5 mg L-1 IBA to MS medium showed 100% rooting percentage. Rooted plantlets were transferred and successfully acclimatized in greenhouse. The micro-propagated plantlets appeared morphologically similar with the mother plants.