Variation Among Strains of Xanthomonas campestris Causing Citrus Bacterial Spot. John S. Hartung, USDA-ARS, Plant Sciences Institute, Fruit Laboratory, BARC-West, Beltsville, MD 20705-2350. E. L. Civerolo, USDA-ARS, Plant Sciences Institute, Fruit Laboratory, BARC-West, Beltsville, MD 20705-2350. Plant Dis. 75:622-626. Accepted for publication 27 December 1990. 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, 1991. DOI: 10.1094/PD-75-0622.

A wide range of variation in restriction fragment length polymorphism (RFLP) and aggressiveness was observed among 45 strains of Xanthomonas campestris isolated from 20 outbreaks of citrus bacterial spot disease in Florida citrus nurseries. The most aggressive strains, based on an in vitro assay, belonged to a single RFLP type. Although apparently homogeneous in RFLP analyses, members of this group varied in carbon source oxidation. The less aggressive strains comprised a continuum of RFLP types and usually could be separated from the more aggressive group by carbon source oxidation profiles. Carbon source oxidation provided a convenient means for presumptive identification of strains isolated from citrus. Data from the in vitro aggressiveness assays, genomic DNA RFLP analyses, and carbon source oxidation profiles confirmed the separation of these bacteria into two distinct groups designated CBS-A and CBS-B. Based on carbon source oxidation, these strains may be related to some strains of X. campestris pv. dieffenbachiae.