Abstract: In this research, a HPLC analysis, along with transcriptomics tools, was applied to evaluate chitosan and water stress for the prediction of phenolic flavonoids patterns and terpenoid components accumulation in Salvia abrotanoides Karel and S. yangii. The results indicated that the tanshinone contents under drought stress conditions increased 4.2-fold with increasing drought stress intensity in both species. The rosmarinic acid content in the leaves varied from 0.038 to 11.43 mg/g DW. In addition, the flavonoid content was increased (1.8 and 1.4-fold) under mild water deficit conditions with a moderate concentration of chitosan (100 mg L????1). The application of foliar chitosan at 100 and 200 mg L????1 under well-watered and mild stress conditions led to increases in hydroxyl cryptotanshinone (OH-CT) and cryptotanshinone (CT) contents as the major terpenoid components in both species. The expressions of the studied genes (DXS2, HMGR, KSL, 4CL, and TAT) were also noticeably induced by water deficit and variably modulated by the treatment with chitosan. According to our findings, both the drought stress and the application of foliar chitosan altered the expression levels of certain genes. Specifically, we observed changes in the expression levels of DXS and HMGR, which are upstream genes in the MEP and MVA pathways, respectively. Additionally, the expression level of KSL, a downstream gene involved in diterpenoid synthesis, was also affected. Finally, the present investigation confirmed that chitosan treatments and water stress were affected in both the methylerythritol phosphate pathway (MEP) and mevalonate (MVA) pathways, but their commitment to the production of other isoprenoids has to be considered and discussed

Keywords