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Physiology and Biochemistry

Isozyme Analysis of Xanthomonas campestris pv. citri. Q. B. Kubicek, Research plant pathologist, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705; E. L. Civerolo(2), M. R. Bonde(3), J. S. Hartung(4), and G. L. Peterson(5). (2)(4)Research plant pathologists, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705; (3)(5)Research plant pathologist and biological laboratory technician, Foreign Disease-Weed Science Research, Agricultural Research Service, U.S. Department of Agriculture, Ft. Detrick, Bldg. 1301, Frederick, MD 21701. Phytopathology 79:297-300. Accepted for publication 13 September 1988. 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, 1989. DOI: 10.1094/Phyto-79-297.

Isozyme analysis of 14 putative isozymic loci by horizontal starch gel electrophoresis was conducted on 36 strains of Xanthomonas campestris pv. citri representing four pathogenic variants associated with different forms of citrus bacterial canker disease in eight countries. An additional 80 strains of X. campestris associated with citrus bacterial spot disease, primarily in Florida citrus nurseries, also were analyzed. Four enzymes were monomorphic in all 116 strains. The number of isomorphs for the 10 remaining polymorphic loci ranged from two to five. Generally, all strains of X. c. citri were isozymically similar, but not identical in all cases, to the neopathotype strain. No isozymes were found in the citrus canker groups of strains that distinguished any of the forms of citrus canker. As a subgroup, the Asiatic citrus canker strains exhibited relatively little isozymic polymorphism despite their varied origins worldwide. In contrast, several isozymic alleles were present only in the set of citrus bacterial spot strains isolated from Florida citrus nurseries. These strains also exhibited extensive isozymic polymorphism. Isozyme analysis may be a useful technique in epidemiological studies of phytopathogenic bacteria.