In vitro multiple shoot regeneration from nodal explants of Stevia rebaudiana (Bert): an antidiabetic medicinal plant.

A simple, rapid and large scale in vitro propagation method for Stevia rebaudiana has been established. Shoots were induced from nodal explants of field grown Stevia plants on MS medium fortified with different concentrations of BAP (0.5-2.0 mg/l) alone or in combination with 0.5 mg/l Kinetin. After two weeks of culture, multiple shoots emerged directly from the nodal explants. The highest frequency of shoot bud regeneration was noticed on MS medium supplemented with 1.0 mg/l BAP. Microcuttings dissected out from the in vitro proliferated shoot clumps were cultured on half-strength MS medium containing different concentrations of NAA (0.1 to 0.5 mg/l) and full strength MS medium fortified with different concentrations of NAA and/or IAA (0.5-2.0 mg/l) for rooting. Of the two auxins used, NAA at 0.4 mg/l was found to be the best concentration for maximum percent of root initiation. The rooted plantlets were successfully transferred into plastic cups containing sand and soil in the ratio of 1:2 and subsequently established in the greenhouse. The protocol developed for plant regeneration from nodal explants of Stevia rebaudiana may be suitable for large scale in vitro propagation of this important antidiabetic medicinal plant. INTRODUCTION Medicinal plants are the most important source of life saving drugs for the majority of the world’s population. Medicinal plant research continues to explore Indian traditional medicines to develop the novel drugs. There is a great demand for herbal medicines in both developed and developing countries because of their wide biological activities, higher safety, than the synthetic drugs and lesser costs. India is next to China as the largest exporter of medicinal raw material equivalent to USD 60 million (Alok Sharma et al., 2008). Demand for medicinal plants is largely fulfilled from natural sources, particularly forests. The market has emerged great pressures on these resources and there has been a gross depletion of the natural population of a number of medicinal plant species. Diabetes mellitus is a chronic metabolic disorder characterized by high glucose concentration (hyperglycemia) due to insulin deficiency and/or insulin resistance. It is a metabolic disorder in which there is an inability to oxidize carbohydrate due to disturbances in insulin function (Ganong, 2003). The number of people suffering from the disease worldwide is increasing at an alarming rate with a projected 366 million people likely to be diabetic by the year 2030 as against 191 million estimated in 2000 (Wild et al., 2004). Developing countries are the most affected because of expensive and inadequate treatments coupled with the side effect associated with these drugs. Thus the search of a new drug with low cost, more potential and without adverse effect becomes inevitable. Several medicinal plants have been used in the treatment of diabetes in different parts of the world. Stevia rebaudiana is a valuable herbaceous perennial medicinal plant belongs to the Asteraceae family. It is a native of Paraguay, where it grows wild in sandy soil. This plant has been used traditionally for the treatment of diabetes. Stevioside is a diterpene glycoside present in Stevia rebaudiana (SR), and it is an abundant component of the leaf. Stevioside has become well known for its intense sweetness (250 to 300 times sweeter than sucrose), and it is used