Proposed names for citrus greening bacterium and lime witches' broom phytoplasma
The greening disease of citrus (EPPO A1 quarantine pest) is caused by a phloem-restricted bacterium which has not been cultured. Characterization studies have been carried out on an Asian strain and an African strain of this bacterium and it was suggested that those two strains could belong to a new group of Proteobacteria, provisionally called 'Liberobacter'. Further genetic studies carried out on the African and Asian liberobacter indicated that they represent 2 different species in the proposed genus Liberobacter. Therefore the names 'Candidatus Liberobacter asiaticum' and 'Candidatus Liberobacter africanum' are proposed for the two forms of citrus greening.
Lime witches' broom phytoplasma (EU Annex II/A1) has been characterized by studying its genome size, the sequences of its 16S ribosomal DNA and the 16S-23S ribosomal DNA spacer region, and hybridization profiles obtained by using specific probes. The size of the phytoplasma genome is 720 kbp. Genomic similarities with the phytoplasmas of sunhemp (Crotalaria juncea), sesame and lucerne phyllody were demonstrated, and it was found that the lime witches' broom phytoplasma belongs to the sunhemp phyllody phylogenetic subgroup. A proposal has been made to designate the causal agent of lime witches' broom, as 'Candidatus Phytoplasma aurantifolia'. This name has an interim taxonomic status because 'Phytoplasma' has been approved only as a trivial name for MLOs, and not for a genus.
Sources
Jagoueix, S.; Bové, J.M.; Garnier, M. (1994) The phloem-limited bacterium of greening disease of citrus is a member of the alpha subdivision of the Proteobacteria.
International Journal of Systematic Bacteriology, 44(3), 379-386.
Planet, P.; Jagoueix, S.; Bové, J.M.; Garnier, M. (1995) Detection and characterization of the African citrus greening liberobacter by amplification, cloning and sequencing of the rlp KAJL - rpo BC operon.
Current Microbiology, 30(3), 137-141.
Zreik, L.; Carle, P.; Bové, J.M.; Garnier, M. (1995) Characterization of the mycoplasmalike organism associated with witches' broom disease of lime and proposition of a Candidatus taxon for the organism "Candidatus Phytoplasma aurantifolia".
International Journal of Systematic Bacteriology, 45(3), 449-453.