Characterisation of an Acidovorax sp. Associated with Geranium and Petunia

Since the late 1980s, a bacterium has been routinely isolated from leafspots on geranium (Pelargonium X hortorum L. H. Bailey) and more infrequently from petunia (Petunia hybrida). When inoculated on healthy geranium and petunia leaves, these bacteria caused leafspots identical to those observed on naturally infected geranium plants. Carbon substrate utilisation (BIOLOG) and fatty acid analysis (FAME) identified these isolates to the genus Acidovorax. According to BIOLOG, FAME, and pulsed-field gel electrophoresis (PFGE) data, the geranium and petunia strains formed a very tight phenotypic group that was distinct from other Acidovorax strains tested. In DNA:DNA hybridisation analyses, the geranium strains had greater than 90% homology to each other and to the petunia strain, but less than 50% homology to other Acidovorax species with the exception of A. konjaci (52%). Sequence analysis of the 16S rRNA revealed that the geranium and petunia strains had 99% homology with A. konjaci. Based on PFGE, BIOLOG, FAME, and DNA:DNA hybridisation results, the geranium petunia strains are very closely related to each other and are most closely related to A. konjaci.