## 9 Summaries  
The current review represents an overview of the various advancements occurring in the elucidation of biosynthetic pathways and enhancement of SvGls production to meet the current demand. The natural sweetener steviol glycosides are chiefly produced from the leaves of _Stevia rebaudiana_. Stevia plants with a high leaf-to-stem ratio are highly desirable for achieving steviol's maximum extraction rate. SvGls are beneficial to human health, possessing anti-diabetic properties and high antioxidant activity, helping in lowering blood pressure, and foremost having a very similar sweet taste to sugar (sucrose). Developing methods to enhance steviol production is of high interest to the food and pharmaceutical industry. Stevia morphological behavior has set constraints in developing improved stevia variety by conventional breeding.  
Various conventional and biotechnological approaches have been applied to enhance the synthesis of SvGls. Several plant tissue culture methodologies have been suggested to micro propagate stevia cuttings and stems for large-scale production of stevia plants. Advanced biotechnology practices such as callus culture, adventitious root culture along with the use of elicitors, transformation techniques, and metabolic engineering (using bacterial strains) showed positive effects in increasing the production of SvGls. Studies by [PERSON] et al. (2015), [PERSON] et al. (2015) and [PERSON] et al. (2015) using nanoparticles with callus/nodal explant/root culture showed a significant increase of 60-70% in SvGls. Likewise, recent reports by [PERSON] et al. (2016) and [PERSON] et al. (2012) showed that overexpressing key genes _UGT76G1_, _SrDXS1_ and _SrKAH_ involved in the biosynthesis pathway of steviols enhanced the SvGls concentration in the transgenic stevia leaves. These methodologies offer some promising results and expand the way to manipulate the experiments to improve SvGls pro  
Figure 3: Fictorial representation of the various approaches employed to increase steviol glycosides synthesis. [PERSON] et al. (2012); [PERSON] et al. (2013); [PERSON] et al. (2014).  
duction. RNA-Seq methodology, utilized by some researchers to elucidate genes governing sweeter SvGIs and the development of SSR markers, shows the potential of transcriptomic for its utilization in genetic engineering and stevia breeding [84]. However, detailed studies need to be conducted to characterize and understand to role of enzymes involved in the pathway. Moreover, the function of these key enzymes in plant physiology is also an area that must be explored for better insight into gene regulation. Gene transformation and bulk production of SvGIs via metabolic engineering seem to be the future approaches that seem to be of particular importance.  
Conceptualization, A.R.; formal analysis, A.R. and S.-S.H.; original draft preparation, A.R.; writing-review and editing, A.R. and S.-S.H.; supervision, A.R. and S.-S.H.; funding acquisition, S.-S.H. All authors have read and agreed to the published version of the manuscript.  
S.S.H. acknowledges the support by the National Research Foundation of Korea (NRF) (Grant Nos. 2020R1A6A1A03044512, 2020R1A2C1012586) and the Korea Institute of Planning and Evaluation for Technology in Food, Agriculture and Forestry (IPET) through the High Value-added Food Technology Development Program, funded by Ministry of Agriculture, Food and Rural Affairs (MAFRA) (321027-5).  
Not applicable.  
The authors have no conflict of interest, financial or otherwise.