Enhanced production of valepotriates by Agrobacterium rhizogenes induced hairy root cultures of Valeriana wallichii DC

Hairy roots of Valeriana wallichii DC were obtained following co-cultivation of detached leaf explants with Agrobacterium rhizogenes strains A(4) and LBA 9402. For V. wallichii the A(4) strain appeared to be better than the LBA 9402 strain in terms of both relative rate of hairy root formation and growth of the respective hairy root line. The optimal growth of both the hairy root lines occurred on half strength MS [1] salt medium with 40 gm/l sucrose. Valepotriate contents from the roots of 24 week old wild type field grown plants were compared with those of 12, 16 and 20 week old hairy root lines induced by the A(4) and LBA 9402 strains of A. rhizogenes. The homodidrovaltrate, didrovaltrate, IVHD and acevaltrate contents were quantified individually by HPLC. The valepotriates were localized only in the root tissues and were not detected in the culture medium. In terms of the production of total as well as individual valepotriates, the LBA 9402 induced hairy root line appeared to be a better performer than the A(4) induced one. The total valepotriate content was highest in the 20 week old LBA 9402 induced hairy root line (8.52% dw) followed by that of the A(4) induced line (5.10% dw) of the same age, which were 3.3 and 2 times higher, respectively than that of the control roots (2.58% dw). Rapid growth of the hairy roots of V. wallichii with in vitro valepotriates production potential may offer an attractive alternative to the exploitation of this endangered plant species. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.