Embryogenic cell suspension culture induction and plantlet regeneration of Rauvolfia serpentina (L.) Benth.: influence of different plant growth regulator concentrations and combinations

Establishment of embryogenic cell suspension culture from the embryogenic callus culture of Rauvolfia serpentina (L.) was attempted by transferring 4–6 weeks-old asynchronous embryogenic calli raised from mature embryo and cotyledon explants cultures in liquid media. The cultures obtained were inundated mostly with clumps of proliferating globular embryos with modest non-embryogenic tissues. The number and size of somatic embryos/clumps was recorded to calculate growth of embryogenic tissues under various conditions. Initiation and proliferation of embryogenic suspension culture was influenced by various exogenous plant growth regulators fortified to the culture medium at variable magnitude. For the establishment of suspension cultures, MS medium fortified with 2.0 mg l⁻¹2,4-D with 0.5 mg l⁻¹ BAP was found to be the most effective. For subsequent subculturing, the reduced level of 2,4-D (1.0 mg l⁻¹) in combination with 0.5 mg l⁻¹ BAP promoted somatic embryogenesis at a faster rate. Frequent and efficient plantlet regeneration occurred on MS medium supplemented with 0.5 mg l⁻¹, each of BAP, TDZ and NAA. Higher in vitro rooting response (root proliferating efficiency, number of roots and mean root length) was exhibited by MS rooting medium amended with 0.1 mg l⁻¹ IBA. A combination of 65% relative humidity and 28°C temperature regime exhibited higher survival of regenerated plantlets (∼95%) followed by 60% RH and 30°C (∼90%). Later approximately 85% plants survived after transplantation in the field.