Fig. 3

Flavonoids that contribute to tomato resistance to Fol. a Simplified phenylpropanoid and flavonoid pathway showing the branches including lignin, coniferin and flavonol metabolite synthesis. The significantly upregulated DEGs were enriched in the biosynthesis pathway based on KEGG analysis. b Antimicrobial activity of the synthetic metabolite candidates at concentrations of 125 µg/mL (left) and 62.5 μg/mL (right). The OD₆₀₀ was used to evaluate the antimicrobial activity. c Inhibition of Fol growth in the presence of galangin or quercetin. Mycelium-colonized agar plugs were cultured for 2 days on PDA media that included 62.5 μg/mL galangin or quercetin at 28°C. The diameter of Fol colonies was measured to evaluate growth inhibition. Statistical significance was determined by Student’s t-test; the P values are shown. d Resistance of tomato pretreated with galangin or quercetin prior to Fol infection. Inoculation assay was carried out 20 min after irrigation with 62.5 g/mL galangin or quercetin. Disease index of 10 plants was scored at 14 dpi. Statistical significance was determined by Student’s t-test; the P values are shown. e qRT-PCR validation of galangin- and quercetin-related genes in tomato root against Fol infection. The expression levels were normalized to those of SlActin. The data represent the means ± SEs of three technical repeats. The experiment was repeated twice with similar results. (Student’s t-test; ns, no significant difference; *P < 0.05; **P < 0.01; ***P < 0.001)