Partial sequencing of the hrpB and endoglucanase genes confirms and expands the known diversity within the Ralstonia solanacearum species complex

We determined partial hrpB and endoglucanase genes sequences for 30 strains of Ralstonia solanacearum and one strain of the blood disease bacterium (B DB), a close relative of Ralstonia solanacearum. Sequence comparisons showe d high levels of variability within these two regions of the genome involve d in pathogenicity. Phylogenetic analysis based upon sequence comparisons o f these two regions revealed three major clusters comprising all Ralstonia solanacearium isolates, the BDB strain constituted a phylogenetically disti nct entity. Cluster 1 and cluster 2 corresponded to the previously defined divisions 1 and 2 of Ralstonia solanacearum. Moreover, two subclusters coul d be identified within cluster 2. The last cluster, designated cluster 3 in this study, included biovar 1 and N2 strains originating from Africa. This recently described group of strains was confirmed to be clearly different from the other strains suggesting a separate evolution from those of both d ivisions 1 and 2.