OCCURRENCE OF A BACTERIAL WATERMELON FRUIT BLOTCH IN FLORIDA

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 disease 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.