Growth and Polyphenol Content of Ashwagandha (Withania somnifera L.Dunal) under Combined Moisture Stress and Salicylic Acid Treatment

Abstract

Ashwagandha is a medicinal herb that has very high demand in the global market. Root is the main part harvested from this plant because of its rejuvenating properties. This study investigates the effects of moisture stress and salicylic acid on the growth yield and polyphenol content of Ashwagandha. A polyhouse experiment was conducted where Ashwagandha plants were grown under four levels of soil moisture that included 50%, 60%, 80%, and 100% of field capacity (FC) and four Salicylic acid (SA) levels as 10 mM,1 mM,0.1 mM and control was applied as a foliar spray as treatments to induce the secondary metabolite production. Plant height, number of leaves, number of fruits, number of fallen leaves, SPAD value and leaf area, root dry of the root, free proline content and total polyphenol content were measured. The highest root dry weight (7.62g) and total polyphenol content (3.78 GAE mg/g d.w.b) was reported with the interaction effect of 50% of FC and 10^− 3M SA application. Under the combined application of 50% of FC and 1 mM SA the dry weight and total polyphenol content was increased by 2.7 folds and 12.49 folds respectively compared to control (100% FC and without SA). These findings suggest that a moisture stress level of 50% field capacity combined with a 1 mM SA foliar spray can significantly enhance the root yield and polyphenol content of Ashwagandha.