A Differential Medium for Semiselective Isolation of Xanthomonas campestris pv. vesicatoria and Other Cellulolytic Xanthomonads from Various Natural Sources. R. D. Gitaitis, Department of Plant Pathology, University of Georgia, Tifton 31793. C. J. Chang, K. Sijam, and C. C. Dowler. Department of Plant Pathology, University of Georgia, Griffin 30223; Department of Plant Protection, Universiti Pertanian Malaysia, 43400 Serdang, Selangor DE, Malaysia; and Agricultural Research Service, U.S. Department of Agriculture, Coastal Plain Experiment Station, Box 748, Tifton, GA 31793. Plant Dis. 75:1274-1278. Accepted for publication 20 June 1991. 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-75-1274.

A semiselective medium (CMC-E) was more effective than Tween medium B agar or nutrient agar for recovery of Xanthomonas campestris pv. vesicatoria from the environment or plant material. The selectivity of CMC-E medium was from the sodium salt of high-viscosity carboxymethyl cellulose as the primary carbon source and gelatin as the sole source of nitrogen. Additional selectivity was from the incorporation of eosin Y, methylene blue, bacitracin, cephalexin, cycloheximide, 5-fluorouracil, neomycin sulfate, and tobramycin. Colonies of cellulolytic Xanthomonas spp. on CMC-E were circular, flat, reddish purple, and distinct from those of most other bacterial species because they were in the center of saucer-shaped pits formed in the carboxymethyl cellulose-agar gel. Plating efficiencies for strains of Xanthomonas on CMC-E varied from 0 to 111%, but for most strains, the efficiencies were high enough to permit quantitative studies. By use of CMC-E, X. c. vesicatoria was recovered from pepper seed, irrigation water, and air samples.