A reproducible and high frequency plant regeneration from mature axillary node explants of Gymnema sylvestre (Gurmur)-An important antidiabetic endangered medicinal plant

Gymnema sylvestre is an important medicinal plant used in different systems of medicine as a remedy for the treatment of diabetes. The present study describes an efficient and rapid protocol for large scale in vitro plant regeneration from mature axillary node explants of G. sylvestre. The axillary node explants were cultured on MS medium supplemented with different concentrations of BAP and KIN (0.5-3.0 mg/l) for shoot bud induction. In order to enhance the shoot bud multiplication, regenerated shoot buds were further subcultured onto MS medium fortified with different concentrations of BAP (0.5-3.0 mg/l) in combination with 0.5 mg/l of NAA/IBA/IAA/KIN. The highest frequency (84.22%) of multiple shoot bud regeneration with maximum number of shoots (14.20 shoots/explant) was noticed on MS medium supplemented with 1.0 mg/l BAP and 0.5 mg/l KIN combination. In another experiment, in vitro derived shoot buds were cultured on different concentrations of GA3 (0.5-2.0 mg/l) and various concentrations of BAP (0.5-3.0 mg/l) in combination with KIN (0.5 mg/l) and GA3 (1.0 mg/l) for shoot bud multiplications as well as elongation. For large scale plant production, in vitro derived axillary buds were cultured on MS medium fortified with BAP (1.0 mg/l) + KIN (0.5 mg/l) + GA3 (1.0 mg/l) combination, in which about 418.72 shoots/explant were obtained after five subcultures on the same media composition. Elongated shoots (>2 cm) were dissected out from the in vitro proliferated shoot clumps and were cultured on half-strength MS medium containing different concentrations of various auxins (IAA, IBA and NAA) (0.5-2.0 mg/l) for root induction. Highest frequency of rooting (78%) was noticed on half-strength MS medium augmented with 2.0 mg/l IBA. The rooted plantlets were successfully transferred into plastic cups containing sand and soil in the ratio of 1:2 and subsequently they were established in the greenhouse. The present in vitro regeneration protocol would facilitate an alternative method for fast and large scale propagation of this endangered antidiabetic medicinal plant.