FIGURE 4.

Accumulation of hydrogen peroxide (H₂O₂) and callose in control and bacterized (PsJN) grapevine plantlets after infection with B. cinerea. (A) Dosage of H₂O₂ in non-bacterized and bacterized grapevine plantlets at 8 hpi. Data presented are the means ± SD from three independent experiments. Different letters above each bar indicate significant differences (P ≤ 0.05) as determined by Tukey’s analysis. (B) H₂O₂ accumulation visualized by DAB in grapevine leaves at 8 hpi. Detached leaves were stained with DAB 0,01% solution. Bars = 5 mm. (C) Microscopic observations of the DAB-stained leaves shows in (A). Bars = 100 μm. (D) Callose deposition in response to B. cinerea in leaves of control and bacterized plantlets. Chlorophylls were removed with ethanol to eliminate the auto-fluorescence background in callose visualization with the organic fluorophore aniline blue. Micrographs were taken by fluorescence microscopy using a 405 nm diode laser for aniline blue excitation. Distribution and amount of callose depositions in leaves stained with aniline blue at 24 h after pathogen challenge. Bars = 100 μm.