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). Specific detection of this important bacterial pathogen was possible using Southern hybridization with DNA-probes derived from plasmid-borne genes, celA encoding an endocellulase and pat-1 involved in pathogenicity. The celA probe differentiated the C. m. subsp. michiganensis, insidiosus, nebraskensis, tessellarius, and sepedonicus; moreover, the pat-1 probe distinguished virulent from avirulent strains of C. m. michiganensis. A polymerase chain reaction based on primers derived from the pat-1 region was developed. Virulent strains were detectable in homogenates prepared from infected tomato plants, naturally contaminated seeds, and healthy plant homogenates containing as few as 2 X 10(2) bacteria per milliliter.