Overview of in-vitro regeneration on Stevia (Stevia rebaudiana bertoni)

Stevia (Stevia rebaudiana Bertoni) in abstract Stevioside and rebaudioside A, two natural, calorie-free sweetness agents that are significantly sweeter than sucrose, make bertoni an economically important medicinal herb. Stevia must be cultivated on a large and daily basis to meet the increasing market demand of the food, pharmaceutical, and nutraceutical industries. However, conventional approaches such as seed germination and stem cuttings are hampered due to low germination rates and genetic and biochemical variability. Within the aforementioned scenario, plant tissue culture techniques have proven to be an effective option for the rapid and disease-free micro propagation of plant materials truly representative of the parental type. This review article attempts to bring out a complete overview of the recent developments of the in vitro regeneration of Stevia rebaudiana plants. Several approaches related to explant materials such as nodal segments, shoot apices, leaves, petioles, and thin cell layers of Stevia plants have been studied. Of these, nodal segments and shoot tips have exhibited higher regeneration efficiencies and genetic stability on consistent basis. The MS medium with appropriate concentrations of cytokinins alone or in combination, such as BAP, kinetin, or TDZ, in addition to auxins like IAA, IBA, or NAA, has been widely reported as the most effective medium for shoot multiplication and rooting. Balance of growth regulator has also been emphasized as one of the critical factors for controlling morphogenic responses, rooting efficiency, and acclimatization success. Recent studies related to hardening and field establishment have also reported high survival rates when proper acclimatization protocols are followed. In the context of mass propagation, germplasm conservation, and genetic improvement of Stevia rebaudiana, the in vitro technique of regeneration is an environment-friendly and commercially workable approach. Further optimization of protocols with integration of molecular tools would improve propagation efficiency and quality assurance.