PHYLOGENETIC CHARACTERIZATION OF THE BACTERIUM-LIKE ORGANISM ASSOCIATED WITH MARGINAL CHLOROSIS OF STRAWBERRY AND PROPOSITION OF A CANDIDATUS-TAXON FOR THE ORGANISM, CANDIDATUS PHLOMOBACTER FRAGARIAE

Marginal chlorosis is a new disease of strawberry which was first seen in France in 1988, A phloem-restricted bacterium-like organism was fo und associated with the disease, Even though the organism could not be cultured, and resembles in this way most other phloem-restricted path ogens, characterization was achieved from the sequence of its PCR-gene rated 16S rDNA, and comparison with other organisms. From these studie s, the strawberry agent was found to be a new bacterium within group 3 of the gamma subclass of Proteobacteria, a group of Gram-negative bac teria including, in particular, insect symbionts or parasites as well as enterobacteria. Its closest relative, Arsenophonus nasoniae, is the causal agent of the son-killer trait in wasps. The two bacteria share 92% 16S rDNA sequence identity. We propose a Candidatus taxon for the marginal-chlorosis-associated bacterium, 'Candidatus Phlomobacter fra gariae'.