Studies on growth, yield and chemical composition of Amukkara as affected by species and method of field establishment.

Abstract

Amukkara is one of the most important herbs used in Ayurvedic medicine. Sri Lanka imports about 30 metric tones of this commodity spending about Rs.2 million annually. Therefore, a proper program for cultivation of Amukkara at a commercial level is of prime importance. The imported Amukkara is scientifically known as Withania somnifera. Most of the Ayurvedic physicians use wild species of Amukkara (Ruellia tuberosa) as an alternative for Withania somnifera without knowing the chemical composition. Two separate experiments in pots and field were conducted to compare growth, yield and chemical composition of Amukkara as affected by species and method of field establishment. The pot experiment was laid out in a Completely Randomized Design (CRD) with five replicates. Data on growth and yield parameters were collected. As growth parameters, the number of leaves, number of branches, leaf area and plant height were taken at two weeks interval. As yield parameters, root length, root weight and root volume were taken three months after seed sowing and thereafter at two week intervals. Field experiment was laid out in a Randomized Complete Block Design (RCBD) with five replicates and consisted of four treatments, arranged in a factorial structure. Direct seeding and transplanting of both species of Withania somnifera and Ruellia tuberosa were done as assigned in different treatments. Root samples collected at 5 months were used for chemical analysis (Withanaloid and Withaferine A) by using High Performance Liquid Chromatography (HPLC). Data on growth parameters were collected starting at 4 weeks aftct planting and thereafter at two week intervals. Data were analyzed using Analysis of Variance (ANOVA) and means were separated using Duncan's Multiple Range Test (DMRT). In pot experiment, the growth parameters (plant height, number of leaves, number of branches and leaf area) were performed significantly better in Ruellia tuberosa than Withania somnifera. All yield parameters (root dry weight, root fresh weight, root length and root volume) were higher in Ruellia tuberosa than Withania somnifera. In field experiment, there was no combined effect of establishment method and species. Establishment method did not show a significant difference on plant height. But it significantly affected the number of leaves and number of branches, which were higher in Ruellia tuberosa than Withania somnifera. But plant height was higher in Withania somnifera. Direct seeding of these two species performed better than transplanting. Number of leaves, Number of branches and plant height were higher in direct seeding than transplanting. Considering growth and yield parameters in these experiments, Ruellia tuberosa is better than Withania somnifera and direct seeding is better than transplanting. Withanaloid and Withaferine A is the key ingredient found in Withania somnifera and according to the results of chemical analysis, those two chemicals also found in Ruellia tuberosa and amount of these compounds (Withanaloid and Withaferine A) are not significantly different in both species. Therefore Ruellia tuberosa appeared to be most promising species than the Withania somnifera for Ayurvedic preparations.