CHARACTERIZATION OF MONOCLONAL-ANTIBODIES SPECIFIC FOR ERWINIA-CAROTOVORA SUBSP ATROSEPTICA AND COMPARISON OF SEROLOGICAL METHODS FOR ITS SENSITIVE DETECTION ON POTATO-TUBERS

Seven monoclonal antibodies (MAbs) to Erwinia carotovora subsp. atrose ptica have been produced. One, called 4G4, reacted with high specifici ty for serogroup I of E. carotovora subsp. atroseptica, the most commo n serogroup on potato tubers in different serological assays. Eighty-s ix strains belonging to different E. carotovora subsp. atroseptica ser ogroups were assayed. Some strains of serogroup XXII also reacted posi tively. No cross-reactions were observed against other species of plan t pathogenic bacteria or 162 saprophytic bacteria from potato tubers. Only one strain of E. chrysanthemi from potato cross-reacted. A compar ison of several serological techniques to detect E. carotovora subsp. atroseptica on potato tubers was performed with MAb 4G4 or polyclonal antibodies. The organism was extracted directly from potato peels of a rtificially inoculated tubers by soaking or selective enrichment under anaerobiosis in a medium with polypectate. MAb 4G4 was able to detect specifically 240 E. carotovora subsp. atroseptica cells per mi by ind irect immunofluorescence and immunofluorescence colony staining and af ter soaking by ELISA-DAS (double-antibody sandwich enzyme-linked immun osorbent assay) after enrichment. The same amount of cells was detecte d by using immunolectrotransfer with polyclonal antibodies, and E. car otovora subsp. atroseptica and subsp. carotovora were distinguished by the latter technique. ELISA-DAS using MAb 4G4 with an enrichment step also efficiently detected E. carotovora subsp. atroseptica in natural ly infected tubers and plants.