REP-PCR-MEDIATED GENOMIC FINGERPRINTING - A RAPID AND EFFECTIVE METHOD TO IDENTIFY CLAVIBACTER-MICHIGANENSIS

The genomic DNA fingerprinting technique known as repetitive-sequence- based polymerase chain reaction (rep-PCR) was evaluated as a tool to d ifferentiate subspecies of Clavibacter michiganensis, with special emp hasis on C, michiganensis subsp. michiganensis, the pathogen responsib le for bacterial canker of tomato. DNA primers (REP, ERIC, and BOX), c orresponding to conserved repetitive element motifs in the genomes of diverse bacterial species, were used to generate genomic fingerprints of C. michiganensis subsp. michiganensis, C. michiganensis subsp. sepe donicus, C. michiganensis subsp. nebraskensis, C. michiganensis subsp. tessellarius, and C. michaganensis subsp. insidiosum. The rep-PCR-gen erated patterns of DNA fragments observed after agarose gel electropho resis support the current division of C. michiganensis into five subsp ecies. In addition, the rep-PCR fingerprints identified at least four types (A,B, C, and D) within C, michiganensis subsp, michiganensis bas ed on limited DNA polymorphisms; the ability to differentiate individu al strains may be of potential use in studies on the epidemiology and host-pathogen interactions of this organism. In addition, we have reco vered from diseased tomato plants a relatively large number of natural ly occurring avirulent C. michiganensis subsp. michiganensis strains w ith rep-PCR fingerprints identical to those of virulent C. michiganens is subsp, michiganensis strains.