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Molecular Plant Pathology

Distribution Among Pseudomonads of Sequences Homologous to the Rutin Glycosidase and β-Glucosidase Genes of Pseudomonas viridiflava. M. Hendson, Assistant research plant pathologist, Department of Plant Pathology, University of California, Berkeley 94720; D. C. Hildebrand, and M. N. Schroth. Associate research plant pathologist, and professor, Department of Plant Pathology, University of California, Berkeley 94720. Phytopathology 82:1230-1233. Accepted for publication 16 June 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/Phyto-82-1230.

The rutin glycosidase and β-glucosidase genes of Pseudomonas viridiflava were cloned, and fragments internal to these two genes were used as probes to determine homology with some members of the rRNA homology I group of pseudomonads and other phytopathogenic bacteria. Sequences homologous to these two probes occurred in all fluorescent arginine dihydrolase-negative phytopathogenic pseudomonads tested, regardless of whether the phenotype was expressed. In contrast, the rutin glycosidase probe did not hybridize with any of the rutin glycosidase-negative nonfluorescent or fluorescent arginine dihydrolase-positive pseudomonads, with the exception of P. marginalis, which was weakly homologous with the probe. One strain of P. putida bv. B that expressed rutin glycosidase activity showed homology with the probe. The nonfluorescent, β-glucosidase-negative strain of P. alcaligenes hybridized weakly with the β-glucosidase probe. β-Glucosidase-positive strains belonging to other genera did not share any homology with the β-glucosidase probe. Pathogenicity tests were performed on tomato with a P. syringae pv. tomato strain and transposon mutants lacking β-glucosidase or rutin glycosidase to determine the possible function of these enzymes. No difference was observed between wild-type and β-glucosidase- and rutin glycosidase-negative strains with respect to numbers and morphology of lesions on tomato leaves.