Regeneration of Viola odorota plant from petiole callus

Sweet violet (Viola odorata) is a medicinal plant with immense medicinal value that over-exploitation of this medicinal plant led to decline its natural habitat. In vitro propagation delivers powerful methods for the mass multiplication of economically important species and germplasm conservation of endangered species. The present study has been carried out to establish an efficient protocol for in vitro callus induction and regeneration of Sweet violetby optimizing the various concentrations of plant growth regulators. For calli induction, different concentrations of 6-benzyladenine (BA) (0, 0.5, 1, 1.5, 2 and 2.5 mg/l) and 2, 4-dichlorophenoxyacetic acid (2,4-D) (0.5, 1, 1.5, 2 and 2.5 mg/l) and for indirect shoot regeneration different concentrations of BA (0.5, 1, 1.5, 2 and 2.5 mg/l) were used. The MS medium supplemented with 1.5 mg/l BA and 1.5 mg/l 2,4-D was found most suitable for callus induction from petiole explants after 30 days of incubation. The best growth response and the highest rate of shoot regeneration from callus were observed on MS medium containing 1.5 mg/l BAP. Shoots were rooted easily in the same regeneration medium after the second subculture and then successfully acclimatized in pitmoss:perlite substrate with 100% survival rate. This protocol could be successfully used for the mass multiplication and germplasm conservation of this valuable medicinal plant.