A New Disease, Bacterial Leaf Spot of Rape, Caused by Atypical Pseudomonas viridiflava in South Korea

In March 2007, a bacterial leaf spot of rape (Brassica napus var. oleifera) was observed in fields near Seogwipo City, Jeju Province, South Korea. Symptoms on leaves included white and corky-brown spots and sometimes water-soaked spots on the lower leaf surface. Seven bacterial isolates (BC2495–BC2497 and BC2506–BC2509) were recovered on trypticase soy agar (TSA) from leaf spot lesions surface sterilized in 70% ethyl alcohol for 1 min. Isolates were gram-negative, aerobic rods with one to three flagella. Pathogenicity was evaluated on 2-week-old rape plants by spot and spray inoculation. Bacteria were grown on TSA for 48 h at 25°C. Five microliters of bacterial suspension in sterile distilled water (1 × 105 CFU/ml) were spot inoculated on pinpricked positions of five detached leaves for each isolate. The detached leaves were incubated in a plastic box with high humidity at 20°C. Spot-inoculated surfaces turned white 48 h after inoculation followed by a brownish discoloration. A bacterial suspension in ste...