Comparison of methods for detection of Erwinia carotovora ssp atroseptica in progeny tubers derived from inoculated tubers of Solanum tuberosum L

Several techniques for detection of Erwinia carotovora ssp. atroseptica (Eca) on potato tubers were used to study the transmission of Eca from inoculated mother tubers into progeny tubers for 12 different potato cultivars. The sensitivity of the polymerase chain reaction (PCR) for a direct detection of Eca in crude peel extracts was only 10(7)-10(8) cells/ml, due to inhibition of PCR amplification by potato tuber-derived compounds. With dilution plating and ELISA, 10(5) and 10(7) cells/ml were detected, respectively. Immunofluorescence cell staining (IF), with a detection threshold of 10(4)-10(5) cells/ml, was shown to be most sensitive for direct detection, and transmission of Eca was found for six potato cultivars, whereas with the other techniques tested no transmission was found. After 48 h enrichment of peel extract in polypectate medium at 20 degrees C, IF and PCR detected an initial inoculum concentration of 10 Eca cells/ml, whereas 10(2), 10(4) and 10(4) cells/ml were detected in dilution plating, ELISA and conductimetry, respectively. With dilution plating, PCR and IF, performed after enrichment, transmission of Eca was found for, respectively, four, six and seven out of 12 potato cultivars tested. No transmission was found using ELISA and conductimetry, due to their lower sensitivity. Erwinia carotovora ssp. carotovora (Ecc) was only detected in the progeny tubers of control plants. No relation was found between the transmission of Eca to progeny tubers and blackleg incidence in the field.