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Separation of Strains of Pseudomonas syringae pv. tomato into Serovars by Three Serological Methods. J. B. Jones, Postdoctoral associate, Department of Plant Pathology, University of Georgia, Athens 30602, Present address: Florida Agricultural Research and Education Center, 5007 - 60th Street East, Bradenton 33508-9324; D. L. Dawe(2), and S. M. McCarter(3). (2)Professor, Department of Medical Microbiology, University of Georgia, Athens 30602; (3)Professor, Department of Plant Pathology, University of Georgia, Athens 30602. Phytopathology 73:573-576. Accepted for publication 6 May 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-573.

Serological variation within Pseudomonas syringae pv. tomato was observed when 26 strains from widely separated areas of the United States and Canada were tested by Ouchterlony double diffusion (ODD), microagglutination (MA), and indirect immunofluorescence (IIF) methods. A strong correlation existed between two of the tests for placing the strains into two serovars. One serovar (designated serovar I) consisted of 20 strains, and serovar II contained five strains. One strain did not fit into either serovar. When the MA and IIF techniques were used, separation into serovars was only possible using cross absorbed antisera with other strains of P. syringae pv. tomato. ODD was not a definitive test for separation of the strains into two serovars. ODD was useful for identifying those strains in serovar 1; however, inconclusive results were obtained with strains we classified as serovar II. The existence of serovars should be considered in attempts to develop serological methods for rapid detection and identification of P. syringae pv. tomato.