The effect of medium, carbon source and explant on regeneration and control of shoot-tip necrosis in Harpagophytum procumbens

Harpagophytum procumbens, an indigenous plant to southern Africa, has extensive pharmacological activity. It is traded internationally but is difficult to cultivate. In vitro propagation techniques are also problematic due to a high incidence of shoot-tip necrosis (STN). The effect of various culture conditions on regeneration and STN of H. procumbens were investigated. In this paper the effects of medium type and strength, sucrose concentration, sugar types, callus explant and sub-culturing were studied. Of the different media types tested, half-strength Murashige and Skoog (MS) medium reduced STN significantly without affecting shoot multiplication and growth. Sucrose at 0.086 M (3%) was the preferred carbon source both in terms of growth and preventing STN compared to glucose, maltose and fructose at equimolar concentrations. Indirect organogenesis of this species was possible via callus obtained from nodal explants with BA at 4.4 μM and IAA at 5.4 μM being the best hormone combination but the plants were hyperhydric. Transferring cultures to fresh medium at two-weekly intervals helped to reduce STN and enhanced growth.