Synergism of m-topolin with auxin and cytokinin enhanced micropropagation of Maytenus emarginata

A synergistic effect of meta-topolin (mT) with auxin and cytokinin has been applied to stimulate large-scale shoot regeneration from Maytenus emarginata mature tree nodal explants. The efficacy of mT and BAP was compared during induction and multiplication stages of regeneration. At the shoot bud induction phase, BAP showed a greater response than mT. Shoots were multiplied when shoot clumps of four to five shoots were harvested from mother explants and subcultured on medium containing low concentrations of cytokinin-cytokinin or auxin-cytokinin combinations. Among all the plant growth regulator (PGR) types and concentrations evaluated, a combination of 0.5 mg L⁻¹ mT, 0.25 mg L⁻¹ Kin and 0.1 mg L⁻¹ IAA was found most effective for shoot proliferation with 80.20 ± 0.89 shoots. Synergistic effect of BAP, Kin and IAA was compared in combination with mT, Kin and IAA, and it was observed that the number of shoots (34.58 ± 3.68) regenerated on medium containing 0.5 mg L⁻¹ BAP; 0.25 mg L⁻¹ Kin was significantly lower than the combination of 0.5 mg L⁻¹ mT, 0.25 mg L⁻¹ Kin and 0.1 mg L⁻¹ IAA. The result of this study clearly indicates that mT alone is not effective but synergism of mT with Kin and IAA has a great impact on shoot proliferation. Shoots were able to induce root only when initially treated with higher concentration (200 mg L⁻¹) of IBA for 5 min and then transferred to PGR-free ¼ strength MS medium containing 100 mg L⁻¹ activated charcoal. About 74% of micropropagated shoots were rooted with an average number of 10.27 roots per shoot. About 80% rooted plantlets were acclimatised successfully under greenhouse condition. An improved plant propagation system developed by replacement of cytokinin BAP by mT in multiplication medium may be applicable for large-scale multiplication of the medicinal tree M. emarginata.