Fluorescence on Single-Carbon Sources for Separation of Pseudomonas syringae pv. syringae, P. syringae pv. tomato, and P. viridiflava on Tomato Transplants. J. B. Jones, Assistant Professor, Gulf Coast Research and Education Center, University of Florida, IFAS, Bradenton 34203. R. D. Gitaitis, Associate Professor, Coastal Plain Experiment Station, Tifton, GA 31793; and S. M. McCarter, Professor, Department of Plant Pathology, University of Georgia, Athens 30602. Plant Dis. 70:151-153. Accepted for publication 12 August 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-151.

Pseudomonas syringae pv. tomato (P. s. tomato), P. syringae pv. syringae (P. s. syringae), and P. viridiflava, three foliar pathogens of tomato, were readily separated by their differential capacity to fluoresce on iron-deficient Misaghi and Grogan’s medium containing sucrose, erythritol, and dl-lactate as single-carbon sources. P. s. syringae fluoresced on media containing sucrose, erythritol, or dl-lactate; P. s. tomato fluoresced on media containing sucrose but did not fluoresce on erythritol or dl-lactate; P. viridiflava fluoresced on media containing erythritol and dl-lactate but not on sucrose. Similar results were obtained when water suspensions from greenhouse-inoculated plants were streaked on the three media. When field samples were plated on media containing sucrose and erythritol, fluorescence occurred on media containing sucrose when P. s. tomato was present but occurred on erythritol medium when P. viridiflava was present. In a field where both P. s. tomato and P. viridiflava were present, water suspensions from individual lesions produced colonies that fluoresced on sucrose or erythritol but not on both. In two other fields where only P. s. tomato was present, fluorescence of colonies from similar suspensions occurred on media containing sucrose but not on media containing erythritol or dl-lactate. In separate tests in Georgia transplant fields where P. s. syringae and P. s. tomato were present, 91 and 0% of the lesions infected with P. s. syringae and P. s. tomato, respectively, produced fluorescent colonies on an iron-deficient medium that contained dl-lactate. Capacity to fluoresce on certain single-carbon media may be a rapid means for differentiating three foliar pathogens that occur on tomato.