Occurrence of a Bacterial Watermelon Fruit Blotch in Florida. G. Cameron Somodi, Institute of Food and Agricultural Sciences, University of Florida, Gulf Coast Research & Education Center, Bradenton 34203. J. B. Jones, D. L. Hopkins, R. E. Stall, T. A. Kucharek, N. C. Hodge, and J. C. Watterson. Institute of Food and Agricultural Sciences, University of Florida, Gulf Coast Research & Education Center, Bradenton 34203; Central Florida Research & Education Center, Leesburg 34748; Plant Pathology Department, University of Florida, Gainesville 32611; and Petoseed Company, Woodland, CA 95695. Plant Dis. 75:1053-1056. Accepted for publication 2 April 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-1053.

Mature watermelon fruit with large, firm, dark green, water-soaked lesions were observed in spring 1989. Losses of up to 50% in marketable fruit occurred in some fields in Florida. A gram-negative, aerobic, rod-shaped, nonfluorescent, oxidase-positive, arginine dihydrolase-negative bacterium was isolated from diseased tissues. In pathogenicity tests, the bacterium produced symptoms in foliage and fruit. Morphological, physiological, and biochemical properties of the bacterium related it to a previously described pathogen of watermelon, Pseudomonas pseudoalcaligenes subsp. citrulli. However, our strains from watermelon produced a hypersensitive response in tobacco and tomato, whereas the type strain of P. p. citrulli did not.