Induction of Platycodon grandiflorum hairy roots through the mediation of four Agrobacterium rhizogenes strains

Balloon flower (Platycodon grandiflorum (Jacq.) A. DC.), the only species in Platycodon genus (Campanulaceae), is mainly distributed in East Asia. The rhizomes of P. grandiflorum, a traditional herbal medicine, have been widely used for the treatment of cough, sore throat, asthma, tuberculosis and other diseases. Recently, pharmacological researches identified important biological activities compounds in the rhizomes. Thus, to study and extract valuable compounds, a hairy root induced technique was achieved on P. grandiflorum for stable material with fast growth rates (in hormone-free media) and metabolites production. To achieve this, the “natural genetic tool” Agrobacterium rhizogenes, which can transfer DNA segments into genome of plant, was exploited. The results suggested two (A. rhizogenes ATCC 15834 and C34) of four A. rhizogenes strains could induce hairy roots. RolB and rolC genes, which are responsible for the induction of hairy roots, were inserted into the genome of hairy roots. Leaves had the highest infection frequency of hairy root induction 100 %. The optimization of protocol, including time of immersion and co-culture, had the best results with 10 and 15 mins (10 mins for A. rhizogenes ATCC 15834 and 15 mins for A. rhizogenes C34) and 72 hours, respectively. In the future, this protocol, which was described in this paper, should be useful for studying and isolating valuable compounds from P. grandiflorum hairy root cultures.