Abstract
A bacterial disease that affected production of seedlings and fruits of watermelon (Citrullus lanatus) occurred in Yamagata Prefecture, Japan, in the summer of 1998. The disease was characterized by necrosis and death of seedlings; irregular brown spots with halo on the true leaves; and fruit blotch. When seedlings of watermelon were inoculated with the bacterial isolates from the watermelon at Yamagata Prefecture in 1998, irregularly shaped lesions were expressed on cotyledons and true leaves. These isolates were also pathogenic to all cucurbits tested (cucumber, pumpkin, melon, bottle gourd, wax gourd, and oriental pickling melon), tomato, and eggplant. The most sensitive hosts among them were watermelon, cucumber, pumpkin and bottle gourd. The bacteriological characteristics of the present bacterial isolates coincided with those of the standard isolates of Acidovorax avenae subsp. avenae. On the basis of bacteriological characteristics and pathogenicity, the bacterium was identified as the Acidovorax avenae subsp. citrulli (Schaad, Sowell, Goth, Colwell & Webb 1978) Willems, Goor, Thielemans, Gillis, Kersters & De Ley 1992. This is the first report of watermelon bacterial fruit blotch disease in Japan.
