Survival of Softrot Bacteria during the Storage of Witloof Chicory Roots

During the cold storage of witloof chicory roots, changes in the populations of the softrot bacteria Erwinia carotovora ssp. carotovora (Ecc), Erwinia carotovora ssp. atroseptica (Eca) and Pseudomonas marginalis (Pm) were investigated from October (directly after harvest) until March of the next year. Colonization incidence of Ecc and Pm changed during the early weeks of storage in each of the 3 years of the experiment and increased significantly after December, approximately 6 to 8 weeks after the roots had been placed in storage. After inoculation, during storage in 1996, populations of Eca decreased continuously from 5.8 × 105 CFU/ml to 103 CFU/ml 4 weeks later in mid-November without any further statistically significant increase during the rest of the storage period. Timecourse analysis of the monthly colonization incidence of Ecc and Pm over the 3 years revealed that the incidence was significantly dependent on the incidence 2 weeks earlier. Also, high colonization incidences during storage coincided with high disease incidence during the following forcing period of the roots. Therefore, a forecast of disease incidence during forcing of the witloof chicory heads may be envisaged.