Abstract
Roots of Ophiorrhiza prostrata D. Don serve as a rich source of camptothecin (CPT), an anticancer drug. Because of the large-scale collection of its roots, the plant has become a threatened species. The present study accomplishes the induction of adventitious roots as a means for the production of CPT as well as for the large-scale propagation of this anticancer drug plant using leaf and internode explants. The biomass yield and CPT content of adventitious roots induced from different explants were compared to roots developed on ex vitro rooted stem cuttings. Adventitious roots were produced on half-strength Murashige and Skoog (MS) medium supplemented with $10.74{\mu}M$ ${\alpha}-naphthaleneacetic$ acid and $2.32{\mu}M$ kinetin at mean fresh weights of 0.753, 0.739 and 0.748 g roots from leaf, internode and shoot, respectively. CPT yield from in vitro derived roots after 50, 80 and 120 days of incubation (0.028, 0.06 and 0.1% dry weight, respectively) was not significantly different from those harvested at the same age from ex vitro rooted (0.03, 0.06 and 0.13%, respectively) stem cuttings. CPT from subcultured roots derived from solid (0.08%) medium was lower than from suspension culture medium (0.12%). Subsequent cultures of the adventitious roots showed a stable production of CPT (0.16%). The yield of CPT from 360-day-old plant-derived roots was 0.19%. Elicitation using methyl jasmonate and acetyl salicylic acid exhibited no enhancement in CPT yield. In vitro propagation through direct shoot regeneration was achieved from the adventitious roots upon transfer to MS medium with $8.87{\mu}M$ $N^6-benzyladenine$ (BA) and $2.46{\mu}M$ indole-3-butyric acid (IBA) with a mean of 21.2 shoots per culture in 50 days. The shoots upon subculture on medium having the same level of BA and IBA underwent rapid proliferation. The shoots transferred to field conditions after in vitro rooting exhibited 95% survival. Adventitious root induction, from leaf and internode explants, enables the feasible production of CPT as well as the large-scale rapid propagation of this species which can safeguard it from extinction.