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Etiology

Characterization of Xanthomonas campestris Strains from Aroids Using Physiological, Pathological, and Fatty Acid Analyses. A. R. Chase, Professor of plant pathology, University of Florida, Central Florida Research and Education Center, Apopka, 32703; R. E. Stall(2), N. C. Hodge(3), and J. B. Jones(4). (2)(3)Professor and senior biological scientist, Department of Plant Pathology, University of Florida, Gainesville, 32611; and (4)Professor of plant pathology, University of Florida, Gulf Coast Research and Education Center, Bradenton, 34203. Phytopathology 82:754-759. Accepted for publication 23 March 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/Phyto-82-754.

One hundred and forty-nine strains of Xanthomonas campestris pv. syngonii and X. c. dieffenbachiae, obtained from ornamental and agronomic aroid plants, were characterized by pathogenic and physiologic reactions. Strains were originally isolated from plants in the following genera: Aglaonema, Anthurium, Colocasia, Dieffenbachia, Epipremnum, Philodendron, Syngonium, and Xanthosoma. In pathogenicity tests with Aglaonema, Anthurium, Dieffenbachia, Philodendron, and Syngonium, strain groups were more virulent on their host of origin than on other plants, but they were not host-specific. Similarly, multiplication of bacterial populations in leaf tissue for each strain was greatest, although strains grew to significant levels in other hosts as well. Although symptom expression varied from strain to strain, no correlation could be drawn between a strain group and symptom expression. Characteristics of strains from some host genera were different based on minimum pH for growth, pectolytic activity, and starch utilization on four media, although no combination of characteristics could be used to separate one host-strain group from the rest. Carbon source oxidation via the Biolog system showed that the majority of strains could be determined to their host of origin with the exception of strains from Anthurium and Dieffenbachia. Based on fatty acid profiles, strains from Anthurium, Colocasia, Epipremnum, Philodendron, and Syngonium had similar ratios (2:1) of the predominant fatty acids, 15:0 iso and 15:0 anteiso, and those from Aglaonema and Dieffenbachia had proportions of 1:1 and 3:1, respectively. Subgroups were based on quantitative differences among other unsaturated and hydroxy acids. None of the subgroups was consistently associated with strains from a particular host genus. The profiles of the strain group from Xanthosoma differed from all other strain groups by the unique 1:2 ratio of the 15:0 iso to 15:0 anteiso fatty acids. The degree of differences in pathogenic and physiologic reactions and the fatty acid profiles indicate the heterogeneous nature of X. c. dieffenbachiae, but do not support separation into different pathovars at this time.