Citric acid application alleviates endogenous salicylic acid levels in basil by modulating metabolism: The role of glycine, GABA, fructose, and glucose

This study aimed to investigate the potential marker metabolites in basil for stress-regulation. First, the effects of various concentrations of salicylic acid (SA) and citric acid (CA) on plant growth and metabolite profiles were examined, and based on these findings, stress-inducing and stress-alleviating conditions were established. Multivariate analyses (PCA and PLS-DA) and network analysis consistently separated treatment groups and revealed coordinated shifts in primary metabolism. Pathway enrichment analysis indicated that seven pathways were significantly affected (FDR < [0.002]), primarily involving amino acid metabolism, carbohydrate metabolism, and the tricarboxylic acid (TCA) cycle. Using complementary statistical criteria (volcano plot, VIP scores in PLS-DA, and correlation analysis), four marker metabolites, glycine, γ-aminobutyric acid (GABA), fructose, and glucose, were identified as the most discriminant features (VIP > [1.0], |log2FC| > [1.5], p < [0.05]). Collectively, these findings provide a metabolomics-based framework for diagnosing stress intensity and evaluating mitigation strategies in basil, with potential applications in stress-resilient cultivation and management.