Early Emergence of Revealed by Analysis of Diversity of Potato Blackleg and Soft Rot Causing Pathogens in Switzerland.

Blackleg and soft rot in potato caused by and enterobacteral genera are among the most destructive bacterial diseases in this crop worldwide. In Europe, over the last century, spp. were the predominant causal agents of these diseases. As for , before the large outbreak caused by in the 2000s, only was isolated in Europe. The population dynamics of potato blackleg causing soft rot was, however, different in Switzerland as compared to that in other European countries with a high incidence (60 up to 90%) of species (at the time called ) already in the 1980s. To pinpoint what may underlie this Swiss peculiarity, we analysed the diversity present in the Agroscope collection gathering potato isolates from 1985 to 2000s. Like elsewhere in Europe during this period, the majority of Swiss isolates belonged to . However, we also identified a few isolates, such as and , two species that have not yet been reported in potatoes in Europe. Interestingly, this study allowed the characterisation of two "early" isolated in the 1990s. Genomic comparison between these early 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.