Callus-mediated organogenesis and effect of growth regulators on production of different valepotriates in Indian valerian (Valeriana jatamansi Jones.)

Abstract

A reproducible and efficient callus-mediated shoot regeneration system was developed for the large-scale production of Valeriana jatamansi Jones., a highly medicinal plant species of global pharmaceutical importance. Effect of Murashige and Skoog (MS) medium supplemented with different concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D), α-naphthaleneacetic acid (NAA) and indole-3-butyric acid (IBA) on callus induction and production of valepotriates accumulation was studied by using different explants. In V. jatamansi, the degree of callus induction varied significantly depending on explants type and the growth regulators used. Among different explants used, rhizomes have the highest callus induction potential followed by leaf. The callus induction frequency was found to be optimum in rhizome explants on media supplemented with 0.5 mg/l 2,4-D. The regenerative ability of proliferated compact calli was studied by the application of cytokinins alone and in combination with auxin. MS medium fortified with 0.75 mg/l thidiazuron in combination with 0.5 mg/l NAA showed the highest regeneration frequency (88.6 %) and produced the maximum number of shoot buds (15.20 ± 0.20) capable of growing into single plants. Vigorous callus obtained from MS medium supplemented with different concentrations of 2,4-D, NAA and IBA were used for industrially important valepotriates [acevaltrate (ACE), valtrate (VAL) and didrovaltrate (DID)] analysis. High performance liquid chromatography analysis of callus revealed that medium with 2,4-D (1 mg/l) was found responsible for increasing ACE and DID yield, whereas VAL production was higher in case of medium supplemented with NAA (1 mg/l). However, the accumulation of valepotriates in callus decreased in logarithmic phase after 8 weeks. IBA was not beneficial for the valepotriate synthesis, as it helped to accumulate significantly lower concentration of ACE, VAL and DID. Micropropagated plantlets with well-developed root system were successfully acclimatized in greenhouse condition, in root trainers containing garden soil with a survival frequency of 100 %. As Indian valerian is a highly traded medicinal plant due to extensive use of its industrially important secondary metabolites, the present system can be utilized to obtain mass multiplication of the species as well as for the stable biomass and continuous valepotriate production for the pharmaceutical industries.