High frequency regeneration protocol for Dendrobium nobile: A model tissue culture approach for propagation of medicinally important orchid species

• High frequency model regeneration protocol for medicinal orchids within a limited time span using meta topolin
• Higher yields of secondary metabolites in in vitro systems
• Clonal stability verified using targeted molecular marker systems like SCoT and IRAP

Low rates of shoot multiplication, clonal instability, poor rooting frequency and high cost of production are major impediments challenging the micropropagation of orchids and other ornamental plants. These problems can be solved with the proper usage of plant growth regulators (PGRs) in the medium. The highest shoot proliferation rate of 21 shoots/explant was recorded in Murashige and Skoog (MS) medium containing 1 mg/l meta-topolin and 0.8 mg/l Putrescine. To date, this is the best frequency of shoot induction for Dendrobium nobile and one of the highest among other orchids. Higher rooting frequency was also recorded with the highest rooting of 10.1 roots/shoot achieved in plants grown in half strength MS media supplemented with 2 mg/l of indole butyric acid and 0.5 mg/l of phloroglucinol. The plantlets were successfully acclimatized in the greenhouse with a survival rate of 82.3% exhibiting normal developmental patterns. The regenerated plantlets were assessed for genetic stability using the molecular markers namely SCoT and IRAP revealing high degree of genetic stability within the micropropagated plants of D. nobile. Being a highly medicinal orchid, the antioxidant potentials of the mother and the micropropagated plants were assessed using DPPH, FRAP and metal chelating assays which revealed a significantly higher antioxidant activity in the micropropagated plants. Rapid multiplication rate, higher genetic stability and significantly higher antioxidant power reported in the present study on D. nobile ensure the use of this micropropagation protocol for ex-situ conservation and commercial exploitation which could also be extended to other important orchid species.