Effect of different strains of Agrobacterium rhizogenes, type and age of explant on hairy root production in Valeriana officinalis L.

Valeriana officinalis from the valerianaceae is a precious medicinal plant has been employed for the treatment of mental ailments. The study was a factorial experiment in a CRD including bacterial strains (R1000, LBA9402, C58, A4, GM, and ATTCC15834), age of explants for inoculation (10, 20 and 30 days) and different explants of valerian (leaves and roots) in three replications. Solid Manitol Yest exteract Agar (MYA) medium was used for bacterial culture and MYA medium containing rifampicin antibiotic (50 mg/l) was used to prepare the bacterial suspension for inoculation. Two inoculation methods (floating and injection method) were evaluated on the percentage of rooting and the injection method was not effective in hairy root induction on explants. After determining the best strain and the best explants of the clones were cultured in MS, 1/2 MS and MS+0.2 mg/L NAA solid culture medium it was observed that the roots placed in MD medium were the most they had biomass. Strains of ATCC15834 and A4 on the MYA medium on 30 days old leaf explants was the best strain than others. The optimized root length and the top hairy root number were induced by A4 strain. The newly produced hairy root showed the highest growth on MS medium enriched with 3% sucrose at 25°C. Our results showed that the application of ATTCC15834, R1000, LBA9402 and A4 strains induced hairy roots in valerian and the other two strains were ineffective.