EXTRACTION OF CLAVIBACTER-MICHIGANENSIS SUBSP SEPEDONICUS FROM COMPOSITE SAMPLES OF POTATO-TUBERS

The presence of Clavibacter michiganensis subsp. sepedonicus was detec ted by immunofluorescence and ELISA in diluent in which cores from 200 potato tubers had been incubated on a rotary shaker. By this procedur e the ring rot pathogen was detected in composite samples from natural ly infected tubers and tuber samples ''spiked'' with infected tissue o r a pure culture of the pathogen. Populations of saprophytic bacteria increased about 100-fold in the diluent during 18 h of incubation but did not interfere with serological detection of C. m. sepedonicus. Som e of the results suggest that C. m. sepedonicus cells multiply during incubation of tuber samples. Extraction of ring rot bacteria from pota to tuber tissue by incubation on a rotary shaker requires little work and minimizes the amount of plant tissue in the extract compared to th e standard extraction procedure involving maceration and differential centrifugation.