Five microliters of culture filtrate obtained after centrifugation and filtration were applied to a paper disk (5 mm diameter) placed on NA agar inoculated with X. oryzae pv. oryzae or X. oryzae pv. oryzicola. Landy medium was used instead of culture supernatant as the control. The plates were incubated at 28 °C for 48 h and the inhibition zones (mm) included the paper disk diameter.