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First Report of Bacterial Fruit Blotch of Watermelon in Oklahoma. J. L. Jacobs, Department of Plant Pathology, Oklahoma State University, Stillwater 74078-9947. J. P. Damicone, and B. D. McCraw. Department of Plant Pathology, and Department of Horticulture and Landscape Architecture, Oklahoma State University, Stillwater 74078-9947. Plant Dis. 76:1185. Accepted for publication 28 July 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-1185D.

Mature watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai 'Jubilee') from a field in Carter County, Oklahoma, in 1991 had large, irregular, olive green, water-soaked areas on the upper side of the fruit. Estimated yield losses in marketable fruit ranged from 10 to 15% in this field. Bacterial streaming was observed from rind sections cut from the blotch margins. A gram-negative, nonfluorescent, oxidasepositive, rod-shaped bacterium was isolated from diseased fruit tissues. The bacterium grew at 41 C and did not utilize glucose or sucrose as a sole carbon source. The characteristics of the bacterium were consistent with those described for the fruit blotch pathogen by Somodi et al (1). Pathogenicity of the bacterium on watermelon was verified after spray and stab inoculations of 2-wk-old watermelon seedlings (cv. Jubilee II) with a suspension of 1011 cfu/ml in 0.85% NaCI (saline). Inoculated seedlings were incubated in plastic bags. Water-soaked lesions developed on cotyledons, true leaves, and stems within 2 days. No lesions developed on control seedlings sprayed or stabbed with sterile saline. Koch's postulates were completed by reisolating the bacterium from inoculated plants.

Reference: (1) G. C. Somodi et al. Plant Dis. 75:1053,1991.