Fig. 6

Effects of γ-PGA and its hydrolysates on triggering HR and ISR against Pst DC3000 infection in tobacco plants. a Effect of γ-PGA on triggering HR in tobacco leaves; b Effect of γ-PGA on triggering ISR against Pst DC3000 infection in tobacco plants. c SDS-PAGE analysis of γ-PGA hydrolysates. The pH of γ-PGA solution (5 g/L) was adjusted to 2.0, then hydrolyzed at 80 °C for 0, 1, 2, 3, 4, 5, 6, 7, and 8 h, respectively. d Effect of γ-PGA hydrolysates on triggering HR in tobacco plants. 5–1—5–10: 5 g/L γ-PGA hydrolysates produced by digestion at pH 2.0 and 80 °C for 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 h, respectively. e ISR triggered by 5 g/L γ-PGA hydrolysates produced by digestion at pH 2.0 and 80 °C for 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 h, respectively, to protect plants from Pst DC3000 infection. f Effect of γ-PGA hydrolysates (digestion at pH 2.0 and 80 °C for 5 h) at different concentrations on triggering ISR against Pst DC3000 infection. γ-PGA: the γ-PGA hydrolysates. *indicates significant difference from the control (CK, treated with water)