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Physiology and Biochemistry

Use of Quinate Metabolism as a Phenotypic Property to Identify Members of Xanthomonas campestris DNA Homology Group 6. Y. -A. Lee, Department of Plant Pathology, University of California, Berkeley 94720; D. C. Hildebrand, and M. N. Schroth. Department of Plant Pathology, University of California, Berkeley 94720. Phytopathology 82:971-973. Accepted for publication 1 June 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/Phyto-82-971.

Certain pathovars of Xanthomonas campestris that metabolize quinate were discovered. This discovery led to the development of a succinate-quinate (SQ) medium for the detection of quinate metabolism. Of five species of Xanthomonas and 77 pathovars of X. campestris, only members of five pathovars of X. campestris were positive in the SQ test. All tested strains of the four pathovars of DNA homology group 6 (i.e., X. c. celebensis, X. c. corylina, X. c. juglandis, and X. c. pruni) were positive, except for two strains of X. c. celebensis. Strains of X. c. carotae also were positive; this pathovar of DNA homology group 5 is most closely related to pathovars of DNA homology group 6. All 100 or more strains of X. c. juglandis isolated from different locations and walnut cultivars were positive, which indicated that this phenotypic property was stable in the population. Analysis of high-performance liquid chromatograms indicated that pathovars positive in the SQ test metabolized quinic acid to gallic acid, protocatechuic acid, pyrogallol, and several unknown compounds. However, most xanthomonads, positive or negative in the SQ tests, cannot utilize quinate as a sole carbon source for growth. These experiments indicated that quinate metabolism but not quinate utilization can be used as a phenotypic property in identifying members of Xanthomonas DNA homology group 6.

Additional keywords: taxonomy.