Brassinolide-induced resistance enhances antioxidant defense and metabolic pathways against anthracnose in Camellia sinensis ‘Fuding Dabaicha’

• Anthracnose infection triggers oxidative stress and metabolic changes in tea plants. • Flavonoid and phenylpropanoid biosynthesis contribute to induced resistance in tea plants. • Brassinolide boosts peroxidase and glutathione-S-transferase activity after pathogen infection. • Differentially expressed genes are enriched in glutathione metabolism and flavonoid biosynthesis pathways. • Metabolomic analysis shows increased flavonoid and diterpenoid synthesis after brassinolide treatment. This study investigated the effect of exogenous brassinolide (BR) treatment on managing anthracnose in Fuding Dabaicha tea (FDT) plants following inoculation with Colletotrichum gloeosporioides ( Cg ). By analyzing changes in antioxidant enzyme activities, transcriptomic profiles, and metabolomic alterations, we evaluated the induced resistance of FDT to anthracnose after BR treatment and the associated physiological and biochemical responses. The results demonstrated that BR pretreatment before Cg inoculation effectively delayed disease progression and enhanced the activities of peroxidase (POD) and glutathione-S-transferase (GST). Transcriptomic analysis revealed that the comparison between Cg -inoculated control and BR-treated plants (CK-Cg vs. BR-Cg) showed significant enrichment in glutathione metabolism, plant hormone signaling, and phenylpropanoid biosynthesis pathways. Differentially expressed genes (DEGs) were particularly associated with phenylalanine metabolism and flavonoid biosynthesis. Metabolomic analysis further indicated that BR treatment may strengthen plant defense mechanisms by promoting the synthesis of flavonoids, flavonols, and diterpenoids. KEGG enrichment analysis of differentially expressed genes and metabolites highlighted significant enrichment in glutathione metabolism, flavonoid biosynthesis, phenylalanine metabolism, and various secondary metabolite biosynthesis pathways in both CK vs BR and CK-Cg vs BR-Cg comparisons.