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Selective Medium for Xanthomonas campestris pv. pruni. E. L. Civerolo, Fruit Laboratory, Horticultural Science Institute, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705. M. Sasser, Department of Plant Science, University of Delaware, Newark 19711, C. Helkie, Fruit Laboratory, Horticultural Science Institute, and D. Burbage, Department of Plant Science, University of Delaware. Plant Dis. 66:39-43. Accepted for publication 1 April 1981. 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, 1982. DOI: 10.1094/PD-66-39.

A simple selective medium was developed for the detection and isolation of Xanthomonas campestris pv. pruni. The selectivity and sensitivity of X. c. pv. pruni selective medium (XPSM) were evaluated using 9 X. c. pv. pruni strains, 14 strains of eight other Xanthomonas nomen species, and one strain each of Agrobacterium tumefaciens, Corynebacterium michiganense, Erwinia stewartii, and Pseudomonas pseudoalcaligenes subsp. citrulli. The plating efficiencies of all X. c. pv. pruni strains were the same or higher on XPSM than on nutrient agar supplemented with glucose. Two strains of X. c. pv. begoniae and one strain of X. c. pv. pelargonii grew on XPSM. However, the plating efficiencies of these strains on XPSM were generally low, and the colony appearance of these strains was clearly distinct from that of X. c. pv. pruni. Colonies of two strains each of X. c. pv. phaseoli, X. c. pv. manihotis, X. c. pv. vesicatoria, and one strain of P. pseudoalcaligenes subsp. citrulli appeared on XPSM, but growth was suppressed. No colonies of any of the other strains developed on XPSM. X. c. pv. pruni virulence, sensitivity to lysis by two phages, and ability to produce characteristic yellow, mucoid colonies on nutrient agar supplemented with glucose were not detectably altered after growth on XPSM. Added X. c. pv. pruni was quantitatively recovered from soil containing about 102103 colony-forming units per gram and was recovered from leaf extracts containing less than 102103 colony-forming units per milliliter. X. c. pv. pruni was also readily detected in and isolated from extracts of lesions on naturally infected apricot leaves. Soil and leaf bacteria were generally suppressed on XPSM, and only an occasional fungal colony developed from soil samples on this medium.