Anti-Xoo activity of PVD compounds on 1/2 TSA plates with different concentrations of exogenous iron. After spraying culture broth with Xoo, 10, 25, 50, and 100 μl of purified PVD were injected into the central hole of 1/2 TSA plates with increasing concentrations of exogenous iron (0, 10, 50, and 250 μM), respectively. Here, 50% methanol was used as the control. The diameters of the inhibitory zones were measured when Xoo covered the entire control plates containing increasing concentrations of exogenous iron.