Blackleg and soft rot in potato caused by Pectobacterium and Dickeya enterobacteral genera
are among the most destructive bacterial diseases in this crop worldwide. In Europe, over the last
century, Pectobacterium spp. were the predominant causal agents of these diseases. As for Dickeya,
before the large outbreak caused by D. solani in the 2000s, only D. dianthicola was isolated in Europe.
The population dynamics of potato blackleg causing soft rot Pectobacteriaceae was, however, different
in Switzerland as compared to that in other European countries with a high incidence (60 up to 90%)
of Dickeya species (at the time called Erwinia chrysanthemi) already in the 1980s. To pinpoint what may
underlie this Swiss peculiarity, we analysed the diversity present in the E. chrysanthemi Agroscope
collection gathering potato isolates from 1985 to 2000s. Like elsewhere in Europe during this period,
the majority of Swiss isolates belonged to D. dianthicola. However, we also identified a few isolates,
such as D. chrysanthemi and D. oryzeae, two species that have not yet been reported in potatoes in
Europe. Interestingly, this study allowed the characterisation of two “early” D. solani isolated in the
1990s. Genomic comparison between these early D. solani strains and strains isolated later during the
large outbreak in the 2000s in Europe revealed only a few SNP and gene content differences, none of
them affecting genes known to be important for virulence.