Multiplex detection and identification of bacterial pathogens causing potato blackleg and soft rot in Europe, using padlock probes

The objective of this study was to develop a multiplex detection and identification protocol for bacterial soft rot coliforms, namely Pectobacterium wasabiae (Pw), Pectobacterium atrosepticum (Pba) and Dickeya spp., responsible for potato blackleg and tuber soft rot. The procedures were derived from the phylogenetic relationships of these and other Enterobacteriaceae based on recA sequences. The group of Pw strains was highly homogeneous and could be distinguished from the other species. A ligation-based method for detection of Pw was developed. Five padlock probes (PLPs) were designed, targeting recA sequences to identify the Pw, Pba or Dickeya spp., whereas a sixth probe recognised recA sequences of all soft rot coliforms including Pectobacterium carotovorum subsp. carotovorum (Pcc). Two PLP-based applications were developed: one using real-time PCR and one using universal microarrays. Assay sensitivity and specificity were demonstrated using 71 strains of Pw, Pcc, Pba and Dickeya spp. Both multiplex methods can be potentially used for seed testing and in ecological studies, but further validation is required.