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Limitations of Tests Used to Detect Soft-Rotting Fluorescent Pseudomonads. I. J. Misaghi, Department of Plant Pathology, University of Arizona, Tucson 85721; C. R. Donndelinger, Department of Plant Pathology, University of Arizona, Tucson 85721. Phytopathology 73:1625-1628. Accepted for publication 16 June 1983. Copyright 1983 American Phytopathological Society. DOI: 10.1094/Phyto-73-1625.

Thirteen strains of soft-rotting, oxidase-positive, fluorescent pseudomonads were found to be highly variable in ability to macerate tissue slices of nine different plant species and to degrade polypectate and polygalacturonate. Some strains macerated tissue slices of only one or two plant species, while others exhibited a wider host range. Differences in macerating ability also were exhibited by some strains on three potato cultivars that were tested. In addition, some strains macerated stems, but not leaves, of head lettuce. All strains capable of causing moderate to extensive tissue maceration also degraded polypectate and polygalacturonate. However, the pattern and intensity of pectolytic activity of the strains varied in polypectate and polygalacturonate media. One strain that macerated potato and cucumber slightly (macerating index of 0.3- 0.4 on a 4-point scale) did not degrade polypectate or polygalacturonate. Implications of these findings on the interpretations of the results of tests used to detect soft-rotting fluorescent pseudomonads are discussed.

Additional keywords: polygalacturonase, Pseudomonas fluorescens, P. marginalis, Solanum tuberosum.