Hairy root culture of Picrorhiza kurroa Royle ex Benth.: a promising approach for the production of picrotin and picrotoxinin

Picrorhiza kurroa Royle ex Benth. is an endangered plant producing various compounds of medicinal importance. Hairy roots of P. kurroa were obtained following cocultivation of shoot tip explants with Agrobacterium rhizogenes strains A 4 and PAT 405. Bacterial strain A 4 appeared to be better than the strain PAT 405 in terms of both growth of respective hairy root cultures and secondary metabolite production. The optimal growth of both the hairy root cultures occurred on half-strength semisolid medium with 3% sucrose. Picrotin and picrotoxinin from the roots of wild type field grown plants were compared with 8-week-old hairy root cultures induced by the A 4 and PAT 405 strains of A. rhizogenes. Picrotin and picrotoxinin content were evaluated in hairy root cultures as well as roots of field grown plant of P. kurroa. In terms of the production of picrotin and picrotoxinin, the A 4 induced hairy roots appeared to be a better performer than the PAT 405 induced hairy root cultures. The picrotin and picrotoxinin content was highest in 8-week-old A 4 induced hairy roots (8.8 μg/g DW and 47.1 μg/g DW, respectively). Rapid growth of the hairy roots of P. kurroa with in vitro secondary metabolite production potential may offer an attractive alternative to the exploitation of this endangered plant species.