Comparative genomics of Ralstonia solanacearum ecotypes. Ralstonia solanacearum

Ralstonia solanacearum is a vascular soil-borne plant pathogen with an unusually broad host range. This economically destructive and globally distributed bacterium has thousands of distinct lineages within a heterogeneous and taxonomically disputed species complex. Some of those lineages include highly host-adapted strains (ecotypes) such as the banana Moko disease-causing strains, the cold-tolerant potato brown rot strains (also known as R3bv2) and the recently emerged Not Pathogenic to Banana (NPB) strains. These distinct ecotypes offer a robust model to study host adaptation and speciation because the polyphyletic Moko strains include lineages that are phylogenetically close to the monophyletic brown rot and NPB strains. Draft genomes of nine new strains belonging to these three model ecotypes were produced to complement the ten publicly available R. solanacearum genomes. Using a suite of bioinformatics methods, we looked for genetic and evolutionary features that discriminate among ecotypes. Surprisingly, there were relatively few divergent features that could explain host adaptation, yet several virulence factors were associated to Moko, NPB and brown rot speciation events.