In vitro mass production of stevia rebaudiana bertoni (an antidiabetic endangered herb) and assessment of phytotoxicity of different heavy metals on stevioside synthesis

Diabetes is a major global epidemic currently affecting 50 million people across the world and is expected to rise to 300 million by 2025. However, the present pharmacological approach for the management of this serious disease is far from ideal, which behooves the exploration of newer and safer agents. Currently, there is an enormous increase in the use of herbal and other alternative medicines for the treatment of diabetes. Stevia rebaudiana, a member of Asteraceae has emerged as a natural sweetener against synthetic sugars and an alternative herbal cure for diabetes. This property of Stevia is attributed mainly due to the presence of major steviol glycosides e.g., steviosides, rebaudioside A, rebaudioside C and dulcoside A, besides, several other bioactive compounds. These compounds are known to stimulate the pancreatic cells to produce insulin in diabetic patients. It has, therefore, become imperative to undertake different biotechnological approaches such as its ex situ conservation and Agrobacterium rhizogenes-mediated genetic transformation for improved production of stevioside and related bioactive compounds. In light of the above, an in vitro technology has been developed for mass production of Stevia rebaudiana and optimization of stevioside production using various elicitors e.g., heavy metals, osmolytes, etc. Multiple shoots have been induced in the seedling derived node and leaf explants on MS medium augmented with different cytokinins. Of the various combinations tried, MS+1 µM BA proved optimum for differentiating an average of 12.05+/-0.31 and 10.40+/-1.02 shoots from nodal and leaf explants respectively, in 100% cultures after 30 days. Half-strength MS basal proved helpful in inducing rhizogenesis in 100% cultures. The plants were gradually hardened and subsequently transferred to garden soil where 97% plants survived and induced floral buds after 60 days. The impact of heavy metal stress on morphogenesis of nodal explants has also been studied.