SUMMARY
In vitro morphogenic response of mature seed embryo-derived callus cultures of Chonemorpha fragrans was studied using solid and liquid Murashige and Skoog medium amended with cytokinins or their combinations with naphthalene acetic acid at 0.5 mg L-1. The plant growth regulators (PGRs) combination and concentrations tested could not stimulate organogenesis after three subcultivations of the callus cultures on the same PGRs-amended solid medium and when cultivated in the liquid but, formation of morphogenic callus was observed. Evaluation of biomass and camptothecin production showed that the PGRs influenced biomass and CPT yield of the callus cultures. The alkaloid yield of various explants of 3-4 weeks old axenic seedlings was higher in roots (0.019% CPT) followed by mature seed embryos (0.0053%), cotyledons (0.0039%), hypocotyls (0.0024%) and leaves (0.0017%), and no significant difference was observed in yield of CPT from callus induced from the various explants. Camptothecin yield of morphogenic callus cultures cultivated in liquid medium was lower than that of solid due to extracellular leaching effect of the alkaloid. Amount of synthesized CPT in the callus cultures also varied with PGR type and concentration amended in the cultivation medium, and was association with biomass production. Results of the present study suggest that callus cultures offer alternative tissue source for in vitro CPT yield enhancement through biotechnological approaches, with application in the large-scale production of the alkaloid to conserve the ever-decimated natural population of the medicinal woody climber for CPT.