Influence of Different strains of Agrobacterium rhizogenes on Hairy roots Induction and phenolic acids content in Astragalus hamosus

Abstract

Different species of the genus Astragalus are sources of phenolic compounds, which are used in ancient Chinese medicine as antiperspirant, antihypertensive, diuretic, tonic and anticancer. In the last two decades there has been considerable interest in the production of the phenolics by genetically transformed root cultures because hairy root cultures display stable production of secondary metabolites which are often comparable to plant roots. In this study, hairy roots were induced using different explants of in vitro grown Astragalus hamosus L. seedlings following inoculation of Agrobacterium rhizogenes strains 15834, 2659 and WT. The 2659 proved to be more competent than other strains and the highest transformation rates were observed in leaf explants (67%). The transformed roots appeared after 14-24 d of incubation on hormone free MS (Murashige and Skooge) medium. Growth of hairy roots was assessed on the basis of total root elongation, lateral root density and biomass accumulation. Hairy root lines were further established in Gamborg (B₅) medium and the biomass increase was maximum from 17 to 30 d. PCR confirmed integration and expression of left and right termini-linked R_i T- DNA fragment of the R_i plasmid from 2659 into genome of Astragalus hamosus hairy roots. All the clones showed higher growth rate than non- transformed root. Phenolic acids were analysed quantitatively and qualitatively by gas-liquid chromatography.