Ralstonia solancearum belongs to rRNA homology group II (non- ﬂuorescent) within the pseudomonads.
Above: Colonies of Ralstonia
Ralstonia pickettii (a saprophyte or human facultative pathogen), Pseudomonas syzygii (causing Sumatra disease of cloves), and the so-called Blood Disease Bacterium (BDB, causing blood disease of banana in Indonesia) are closely related to R. solanacearum and may cross-react in serological and DNA-based detection methods.
Subclassiﬁcation of R. solanacearum, based on RFLP and other genetic ﬁngerprinting studies (Hayward, 2000), is into Division I (biovars 3, 4 and 5 originating in Asia) and II (biovars 1, 2A and 2T, originating in S. America).
Further taxonomic division is mainly based on nucleic sequence analysis into phyllovars and sequevars has been proposed (2004 OEPP/EPPO; Poussier et al. 2000; Taghavi et al. 1996).
The R. solanacearum race 4 falls in phylotype 1, we have not developed any sequevar typing yet for this pathogen.
However, using DNA gene sequencing, it groups with what were originally race 1 strains of R. solanacearum.