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Specific Detection of Clavibacter michiganense subsp. michiganense by a Homologous DNA Probe. E. Thompson, Department of Plant Pathology, University of California, Riverside 92521; J. V. Leary, and W. W. C. Chun. Department of Plant Pathology, University of California, Riverside 92521. Phytopathology 79:311-314. Accepted for publication 15 September 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-311.

A chromosomal DNA library for strain 23 of Clavibacter michiganense subsp. michiganense was constructed in the cosmid vector pLAFR5 and transduced into strain HB101 of Escherichia coli. Random clones were selected and screened against several strains of C. m. michiganense: C. michiganense subsp. insidiosum, C. rathayi, Curtobacterium flaccumfaciens pv. poinsettiae, Rhodococcus fascians, Pseudomonas corrugata, P. syringae pv. tomato, and a variety of other bacteria, including saprophytes isolated from field-grown tomato plants and surrounding weeds. Several clones were identified that hybridized with C. m. michiganense, C. m. insidiosum, and C. f. poinsettiae but not to other bacteria tested. One cosmid clone (pTLC1-44), after digestion with the restriction endo-nucleases EcoRI and HindIII, yielded fragments of approximately 13, 11, and 5 kilobases. When the 5-kb fragment was used as a probe, it specifically distinguished C. m. michiganense from an avirulent strain and all other bacteria tested. The 5-kb fragment was subcloned into pDSK519 and demonstrated the same specificity.

Additional keywords: bacterial canker, DNA probes.