Effect of Growth Regulators on In Vitro Organogenesis and Long Term Storage of Plectranthus barbatus Andr. (Syn.: Coleus forskohlii (Wild.) Briq.)

This report describes a large scale micropropagation protocol for Plectranthus barbatus Andr. (Syn.: Coleus forskohlii (Wild.) Briq.) an important medicinal herb belonging to the family Lamiaceae. Multiple shoots were obtained from nodal explants on MS medium fortified with varying concentrations of different cytokinins in combination and with auxins. Profound proliferation of multiple shoots was noticed on the medium with cytokinins used in combination. The medium supplemented with BAP (0.25mg/l) and KN (0.25mg/l) resulted with an average of 41 multiple shoots. The shoots were very healthy with broad leaves. Individual shoots were excised and rooted in vitro on half strength MS medium without growth regulators. The rooted shoots were hardened in growth chamber with 90% humidity and later transferred to the field with 95% of survival rate. In vitro slow growth for the conservation of the plant is maintained by elimination of cytokinin for two to three passages for long-term maintenance. The root biomass of in vitro raised plants was compared with vegetatively propagated plants, which were raised from the same selected mother plants. The regenerated plantlets did not show detectable phenotypic variation. The protocol can be successfully applied for the production of plants suitable for field cultivation and can be conserved from over exploitation of the natural resources of the species.