The role of cytokinins on in vitro shoot production in Salix tetrasperma Roxb.: a tree of ecological importance

A valuable tropical tree, Salix tetrasperma Roxb. commonly known as Indian willow has been investigated for its in vitro regeneration potential using nodal explants obtained from a 30-year-old elite tree. Agar-solidified Woody Plant Medium (WPM) containing different concentrations of Plant Growth Regulators (PGRs) was used in the study. Shoot induction response was best on WPM supplemented with 6-benzyladenine (5.0 μM) where 90% explants responded with an average shoot number (4.40 ± 0.50) and shoot length (0.92 ± 0.04) after 6 weeks of culture. However, multiplication and elongation was best recorded when BA (5.0 μM) treated shoot clusters were transferred to WPM containing BA (1.0 μM) + NAA (0.5 μM) where 18.40 ± 0.92 well-grown healthy shoots with an average shoot length of 5.30 ± 0.43 cm were obtained on completion of 12 weeks culture period. In vitro rooting of shoots was best achieved in half-strength WPM containing 0.5 μM IBA. Well-rooted plantlets were successfully hardened off and acclimatized in plastic cups containing sterile Soilrite. These plantlets were then transferred to pots containing normal garden soil followed by transfer to greenhouse and ultimately to field under full sun.