Foliar Spraying of Salicylic Acid Enhances Growth, Yield, and Curcuminoid Biosynthesis Gene Expression as Well as Curcuminoid Accumulation in Curcuma longa

The application of exogenously applied salicylic acid plays important roles in improving the growth, yield, and bioactive compound compositions of different plant species. Curcuma longa is a medicinal plant that is commonly used as a spice and food additive, and has antioxidant potential. In this study, an innovative strategy for enhancing active compound production was investigated by applying a natural plant growth enhancer-namely, salicylic acid (SA)-to C. longa plants. The experiment was conducted using a complete randomized block design. The effects of SA on the growth, yield, and chemical compound contents of C. longa were recorded. Our findings demonstrated that SA significantly improved C. longa growth, yield, and curcuminoid content when compared to control treatment, with SA at 10(-3) M having the greatest effect. The study also indicated that the increase in the curcuminoid content was accompanied by the overexpression of the curcumin synthase 1 (CURS1), 2 (CURS2), and 3 (CURS3) genes, as well as the diketide-CoA synthase (DCS) gene, which have been implicated in the synthesis of curcuminoids.