SOUTHERN HYBRIDIZATION AND PCR FOR SPECIFIC DETECTION OF PHYTOPATHOGENIC CLAVIBACTER-MICHIGANENSIS SUBSP MICHIGANENSIS

Clavibacter michiganensis subsp. michiganensis is the causal agent of bacterial wilt and canker in tomato (Lycopersicon esculentum). Specifi c detection of this important bacterial pathogen was possible using So uthern hybridization with DNA-probes derived from plasmid-borne genes, celA encoding an endocellulase and pat-1 involved in pathogenicity. T he celA probe differentiated the C. m. subsp. michiganensis, insidiosu s, nebraskensis, tessellarius, and sepedonicus; moreover, the pat-1 pr obe distinguished virulent from avirulent strains of C. m. michiganens is. A polymerase chain reaction based on primers derived from the pat- 1 region was developed. Virulent strains were detectable in homogenate s prepared from infected tomato plants, naturally contaminated seeds, and healthy plant homogenates containing as few as 2 X 10(2) bacteria per milliliter.