In vitro -studies in Plumbago zeylanica : rapid micropropagation and establishment of higher plumbagin yielding hairy root cultures

A protocol for rapid in vitro-multiplication of Plumbago zeylanica L. through axillary bud proliferation was developed as an essential prerequisite to conduct genetic transformation studies. A maximum of 3.5 ± 0.5 shoots were produced from a single nodal segment of a four year old field grown plant after 4 weeks of transfer to Murashige and Skoogʹs (MS) basal medium supplemented with 8.87 mmol/L BAP + 0.49 mmol/L IBA. Optimum root induction response was achieved upon transferring the individual regenerant to half strength MS medium containing 0.49 mmol/L IBA. Hairy roots initiated at 0.9 ± 0.05 relative transformation frequency with the A4 strain of Agrobacte riumrhizogenes exhibited optimum growth in half strength MS medium containing 4 % sucrose. Growth kinetic studies demonstrated a maximum 21 fold increase in biomass yield after 6 weeks of culture. The fresh hairy roots produced 2.5 times higher amounts of plumbagin than the fresh, untransformed control roots or the dry hairy roots of the same age. The present research findings revealed for the first time the potentialities of the hairy root cultures of P. zeylanica for the production of the important secondary metabolite plumbagin.