High frequency in vitro regeneration system for conservation of Coleus forskohlii: a threatened medicinal herb

Present study reports a high frequency regeneration system for in vitro propagation and conservation of an important and threatened medicinal herb Coleus forskohlii (Briq.). Shoot multiplication has been achieved through axillary bud development and direct adventitious shoot formation in nodal explants on Murashige and Skoog (MS) medium containing 6-benzyladenine (BA) (5 mu M). Further shoot multiplication was recorded up to third subculture on MS medium containing BA (5 mu M) in combination with 1-naphthleneacetic acid (NAA) (0.1 mu M). Excised microshoots on transfer to root induction medium consisting of half-strength MS medium (1/2 MS) alone as well as in combination with various auxins, resulted in varied rooting pattern in terms of number, length, and type of roots. Rooted microshoots were acclimatized successfully in earthen pots containing garden manure, garden soil, and sand (1:2:1) as potting mix with survival rate of 70 %. Acclimatized plantlets were studied for the amount of chlorophyll and carotenoid content as well as the net photosynthetic rate (P-N) during subsequent weeks of transfer to ex vitro condition. Histological studies revealed the direct origin and development of shoot buds from basal swollen cut end of nodal explants.