Abstract
Basil, renowned for its aromatic properties, exhibits commendable drought tolerance and holds significant value as an edible and medicinal plant. Recognizing the scarcity of studies addressing basil's response to drought stress, we performed physiological experiments and omics analyses of sweet basil across four distinct levels of drought stress. During drought stress, basil showed increased activity of antioxidant enzymes and accumulated more osmoregulatory compounds. Our metabolic analysis meticulously identified a total of 830 metabolites, among which, 215 were differentially accumulated. The differentially accumulated metabolites under drought stress were predominantly esters and terpenes; however, none were identified as the primary volatile compounds of basil. Transcriptome analyses highlighted the pivotal roles of phenylpropanoid and flavonoid biosynthesis and lipid metabolism in fortifying the resistance of sweet basil against drought stress. α-linolenic acid, lignin, flavonoid, and flavonol contents significantly increased under stress; the essential genes involved in the production of these compounds were confirmed through quantitative real-time PCR (qRT-PCR), and their variations aligned with the outcomes from sequencing. This holistic approach not only enriches our understanding of the molecular intricacies underpinning basil's drought resistance but also furnishes valuable insights for the molecular breeding of basil varieties endowed with enhanced drought tolerance.