Optimization of hairy root production for Stevia rebaudiana Bertoni through inoculation by Agrobacterium rhizogenes

Stevia rebaudiana Bertoni is a perennial shrub from the Asteraceae; native of Brazil and Paraguai. This Plant is containing sweet steviosides; rebaudioside and isostevol. This experiment was conducted to study the effects of diverse factors on induction and growth of hairy roots induced by Agrobacterium rhizogenes. The seeds were surface sterilized and then cultured on solid MS medium under 250C and 16:8 h photoperiod. After germination and development of seedlings, the root, stem and leaf explant of three different ages (30, 60 and 90 days) were placed on NYA and LB suspension media. Agrobacterium rhizogenes strains (ATTCC15834, R1000 and C58) and acetosyringone were treated on the plant sample by floating and spray method for 72 hrs at 270C. The incubated explants were treated to remove any bacteria and were transferred to 1/2MS media containing 400 mgl-1 cefotaxime. To optimize the growing media for hairy root induction and growth, 1/2 MS medium was enriched with 3% sucrose and 0.2 mgl-1 Indole-3-butyric acid. The results revealed that all the Agrobacterium strains were effective on hairy root induction from root and leaf explant. The highest hairy root induction was belonged to NYA suspension medium co-cultured with 1/2 MS. Furthermore, for the roots proliferation, 1/2MS medium containing 1/5% sucrose was the selected one. Leaf clone (C2LA) stevia lines obtained from ATCC15834 strain had the highest growth.