Diversity of Dickeya and Pectobacterium spp. in potato in the Netherlands

Pectobacterium and Dickeya spp. that can cause blackleg and slow wilt, isolated from Dutch potato material from 1965 till 2012 were characterized with a variety of phenotypic and genetic techniques, including the use of species-specific TaqMan assays, whole genome sequence analysis and multilocus sequence analysis. It was shown that the diversity of strains of Pectobacterium carotovorum subsp. brasiliensis and Dickeya solani, pathogens recently introduced, was low compared to P. wasabiae, P. atrosepticum, and D. dianthicola that are already present in the Netherlands for decades. Field experiments with vacuum-infiltrated tubers demonstrated that all (sub)species are able to cause blackleg. Co-inoculations of tubers with two (sub)species can result in a decrease, but also in an increase of the blackleg incidence in comparison to inoculations with a single strain. The use of detection techniques in seed testing programs for this variety of blackleg causing organisms will be discussed.