Phylogeny, Diversity and Molecular Diagnostics of Ralstonia solanacearum

Abstract

R. solanacearum is a heterogeneous species consisting of several biovars, and distinct pathovars. The complexity of this species needs to be taken into account when considering issues such as quarantine and resistance breeding, as the properties of strains of R. solanacearum differ. The species may be separated into two divisions based upon RFLP data, division 1 consisting of biovars 3, 4, and 5, and division 2 biovars 1, 2, and N2. Phylogenetic analysis of R. solanacearum using 16S rDNA sequencing has revealed that the two divisions of R. solanacearum recognised by RFLP analysis have a phylogenetic basis. Furthermore, 16S rDNA sequencing has revealed a further subdivision of division 2. However, the conserved nature of the 16S rRNA gene makes conclusions on the phylogenetic relationship of strains difficult. Sequencing of other areas of the R. solanacearum genome has helped to clarify the relationship of strains of this very complex species. The variable regions identified within the sequences of the rRNA operon have been used to develop subgroup-specific primers for R. solanacearum. The ability of these primers to identify and subspeciate R. solanacearum will assist in quarantine and facilitate ecological studies on R. solanacearum.