The soilborne beta-proteobacterium Ralstonia solanacearum is the causing agent of major plant diseases (bacterial wilt on several species, potato brown rot, Moko disease of banana) within tropical and subtropical areas, affecting both cash and subsistence crops. This species complex is constituted of four phylotypes, correlated with the geographical origin of strains (I, Asian; II, American; III, African; IV, Indonesian). Each phylotype is further subdivided in sequevars, on the basis of sequence divergence of the endoglucanase gene (egl); some of these sequevars have been associated to specific ecological features (host range, virulence at cool temperatures). Genomic structure and phylogeny of this species complex is now well understood, thank to recent CGH studies (2) and sequencing of several complete genomes. The subdivision in four phylotypes was clearly demonstrated, but the existence of different clades within each phylotype still had to be validated. The high genotypic and phenotypic plasticity of this organism has been illustrated by emergence of new pathogenic variants (3). It was demonstrated that this bacterium, naturally competent, is potentially subjected to recombination and horizontal genetic transfer (HGT). However, the real degrees of recombination occurring in natural populations, the dominant reproductive mode of this bacterium, the selection pressures structuring these populations, are still largely unknown. To clarify both phylogeny and evolutionary dynamics of the R. solanacearum species complex, we developed a MLSA-MLST scheme on a collection of 88 R.solanacearum strains classified in the four phylotypes and 51 sequevars described to date, and one strain of each of the close species R. syzygii, R. pickettii, R. mannitolylitica and R. insidiosa. Genes were chosen following previous MLSA approach (1) and reference studies; all were (i) evenly distributed across the two replicons, and distant of at least 100 kb, (ii) present in one