An efficient, rapid and improved in vitro plant regeneration protocol has been established for Withania somnifera L. using shoot tip and nodal explants, excised from 15 days old aseptic seedlings. A range of cytokinins were investigated for multiple shoot regeneration. Of the three cytokinins, 6-benzyladenine (BA), Kinetin (Kin) and 2-isopentenyl adenine (2-iP) evaluated as supplement to Murashige and Skoog (MS) medium, BA at an optimal concentration of 2.5 μM was most effective in proliferating apical and axillary buds. The highest regeneration frequency (95 %) and number of shoots (36.1 ± 0.33) were obtained on MS medium fortified with BA (2.5 μM) and NAA (0.5 μM) from nodal segments. High frequency of rooting (100 %) was obtained in in vitro raised shoots when transferred to half-strength MS medium supplemented with NAA (0.5 μM). Histological sections revealed that additional shoot bud primordia were differentiated within the explants just underneath the suberized cells which appeared to be arrested in their development. The presence of additional bud primordia within the explants is thereby helpful to maximize the potential of this system. The regenerated plantlets with well developed shoots and roots were hardened successfully, established in earthen pots containing garden soil and maintained in greenhouse with 95 % survival rate.
Keywords: Histology; Multiple shoots; Nodal explants; Plant growth regulators; Shoot tips; Withania somnifera.