Optimization of hairy root induction conditions in radish (Raphanus sativus L.) and evaluation of biosynthesis ability of secondary metabolites in hairy root cultures

 Agrobacterium rhizogenes results in the formation of hairy root phenotype in plants. The hairy roots have high growth rate and genetic stability and able to produce plant metabolites. In this study, the optimum parameters for induction and growth conditions of radish hairy roots has been investigated.   The effect of explant type (leaves, stems and cultures), co-culture medium (MS, ½MS, B5 and ½B5) and A. rhizogenes strains (A4, ATCC15834 and LBA9402) were evaluated based on factorial experiments in a CRD design with three replications. Transformation percentage was calculated based on the number of appearing hairy roots and was considered as an index for determining the optimum conditions. Transgenic nature of hairy roots was confirmed by PCR and specific primers for rolB and virD genes. The dry and fresh biomass and the amount of phenolic and flavonoid compounds of hairy roots were measured.   ATCC15834 had the highest ability to induce hairy roots in radish under different conditions. The ½B5 medium was the most suitable co-culture medium and the cotyledon explant was the best plant material for induction of radish hair roots. The growth rate among hairy root clones was significantly different based on dry and fresh biomass and the highest amount of phenolic and flavonoid compounds in hairy root cultures was 2.9 and 3.6 times more than normal plant, respectively.   The optimum conditions for induction of hairy roots must be determined in each plant and the hairy root cultures of radish have a high capability to produce secondary metabolites.