Impact of induced autotetraploidy on endogenous levels of alkaloids In Withania somnifera Dunal

Withania somnifera (L.) Dunal (family: Solanaceae), is an important medicinal plant. Roots and leaves of this plant are a valuable source of alkaloids like withaferin, and withanolides. The present investigation was undertaken with the objective of inducing autotetraploidy in this plant employing colchicine and assessing its impact on total alkaloid yield. Ten days old seedlings of Withania were treated with different concentrations of colchicine (0.05, 0.1, 0.2, 0.3 and 0.4%) for varying time intervals (1, 2, 3, 4, and 5 hrs). Later they were transferred to a polyhouse where they were allowed to grow along with their control diploid plants till the plants attained maturity. The total amount of alkaloids was estimated from the control and autotetraploid plants using gravimetric analysis. It was observed that the plants subjected to treatment with 0.3% colchicine for 2 hours showed doubled chromosome number (2N=4x=96) and exhibited morphological variations, viz., increase in height of the plant, larger leaves and increased number of berries per plant as compared to control plants. The autotetraploid plants yielded 1.5 times more alkaloids as compared to diploid plants.