SEROLOGICAL DETECTION OF NONMUCOID STRAINS OF CLAVIBACTER-MICHIGANENSIS SUBSP SEPEDONICUS IN POTATO

Serological detection of several strains of Clavibacter michiganensis subsp. sepedonicus was studied in vitro and in two potato cultivars grown in the field in 1989 and 1990. Colony morphology of these strains was categorized as mucoid, intermediate, or nonmucoid. Enzyme-linked immunosorbent assay (ELISA) detected mucoid and intermediate strains, but not nonmucoid strains, grown in culture. ELISA performed on infected potato stem samples using six combinations of anti-C. m. sepedonicus antibodies did not detect the three nonmucoid strains tested but did detect the other strains. Lack of sensitivity of ELISA to detect nonmucoid strains was not a function of bacterial population but may have resulted from lack of diffusible antigen recognizable by available antibody sources. In contrast, all strains were detected in infected potato stems using indirect fluorescent antibody staining.