Effects of explant type and Agrobacterium rhizogenes strains on hairy root induction and alizarin production in madder (Rubia tinctorum Ardakan)

Hairy root culture of plants is a considerable way for the in vitro production of valuable metabolites because of genetic stability, rapid growth rate, biochemical stability, and high capacity in the synthesis of secondary metabolites. Alizarin is an anthraquinone derived from the roots of madder (Rubia tinctorum) and has been used since ancient times as a natural red dye and exhibits various pharmacological and biological activities including anticancer, antioxidant, and anti-microbial activity. The influence of two factors including explant (leaf, internode, cotyledon) and strains of A. rhizogenes (15834, 2656, MSU, R1000) was tested on hairy root production of madder. All explants produced hairy roots with acceptable frequencies but leaf explants produced the highest number of roots per explant followed by cotyledons. The highest root induction rate (100%) and the highest number of hairy roots per explant were obtained from leaf explants inoculated with 15834 and R 1000. Analysis of the PCR products showed the presence of a 403 bp amplicon related to the specific reproduction of rolA gene in transgenic roots. Anthraquinone production was documented in transgenic roots but there was a significant difference between roots from different bacterial strains. As a brief result, the use of suitable bacterial strains and explants were effective factors for hairy root induction in madder.