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Physiology and Biochemistry

Genomic Fingerprints of Xanthomonas campestris pv. citri Strains from Asia, South America, and Florida. John S. Hartung, U. S. Department of Agriculture, Agricultural Research Service, HSI, Fruit Laboratory, Beltsville, MD 20705; E. L. Civerolo, U. S. Department of Agriculture, Agricultural Research Service, HSI, Fruit Laboratory, Beltsville, MD 20705. Phytopathology 77:282-285. Accepted for publication 1 August 1986. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1987.. DOI: 10.1094/Phyto-77-282.

Genomic DNA was prepared from strains of Xanthomonas campestris pv. citri isolated in seven countries and in Florida. After the DNA was digested with restriction endonuclease Eco R1, the fragments were separated by polyacrylamide gel electrophoresis and the resulting genomic DNA fingerprints were compared. Nine Asiatic or A group strains were indistinguishable by this technique. Likewise, four cancrosis B group strains were also indistinguishable from each other. However, the A and B groups were clearly differentiated by this technique. The fingerprint of a single strain from Mexico, associated with citrus bacteriosis disease was, however, indistinguishable from that of the B group strains. In contrast to the apparently conserved genomic fingerprints observed with the A and B groups of strains, the strains isolated from diseased citrus in Florida (Group E) showed a wide variety of genomic fingerprints. These fingerprints varied not only among separate disease outbreaks but also within single outbreaks. These results are inconsistent with the idea that a new strain of X. c. pv. citri has been recently introduced into Florida but support the idea that the X. campestris strains isolated from Florida citrus are samples of an endemic flora.