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Molecular Plant Pathology

Identification of a Plasmid DNA Probe for Detection of Strains of Erwinia herbicola Pathogenic on Gypsophila paniculata. S. Manulis, Department of Plant Pathology, ARO, The Volcani Center, Bet Dagan 50250, Israel; Y. Gafni(2), E. Clark(3), D. Zutra(4), Y. Ophir(5), and I. Barash(6). (2)(3)(5)Department of Plant Genetics, ARO, The Volcani Center, Bet Dagan 50250, Israel; (4)Department of Plant Pathology, ARO, The Volcani Center, Bet Dagan 50250, Israel; (6)Department of Plant Pathology, ARO, The Volcani Center, Bet Dagan 50250, Israel, Department of Botany, Tel Aviv University. Phytopathology 81:54-57. Accepted for publication 8 May 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/Phyto-81-54.

Pathogenic strains of Erwinia herbicola incite crown and root galls in Gypsophila paniculata.Two serotypic groups were detected in the population of strains isolated from Gypsophila, each of which was composed of pathogens and nonpathogens. An additional isolate of pathogenic E. herbicola did not react with serotype I or II. Galls caused by pathogenic serotype I strains varied in morphological appearance from galls of other pathogenic strains. All strains secreted indoleacetic acid (IAA) in culture. No correlation was observed between gall size and the amount of IAA produced in vitro. All strains also contained one to four plasmids with sizes ranging between 10 and 100 MDa. A 7.5-kilobase (kb) DNA fragment was subcloned from a library constructed from plasmid DNA of a pathogenic strain. This DNA fragment cross-hybridized with the sequences encoding the IAA biosynthetic pathway in Pseudomonas savastanoi. The cloned 7.5-kb fragment was used to distinguish among pathogenic and nonpathogenic strains of each serotypic group by blot hybridization experiments. The probe hybridized to 78-MDa plasmids present in pathogenic strains of serotypes I and III and to 100-MDa plasmids present in pathogenic strains of serotype II. The relationship between IAA production and the specificity of the probe is discussed.