Barcode identification of quarantine bacteria: strategy and results

Within QBOL, barcode sequences have been defined for a group of quarantine bacteria from the combined EU/EPPO lists, comprising the three Clavibacter michiganensis subspecies, Ralstonia solanacearum, Xylella fastidiosa and a selection of Xanthomonas pathogens.
Challenges were to compose a relevant collection of quarantine and closely related bacteria, to unravel their taxonomic and pathogenic identity, and to define representative barcode sequence regions.
A barcoding strategy had to be developed. For this we could not rely on other BOL programs, which study existing diversity of eukaryotes, but not of prokaryotes. Moreover, several Q-bacteria are named as pathovars, an infra-species division that refers to a pathological specialization and not necessarily correlates with a taxonomic unit. Barcode identification of the quarantine bacteria uses several gene sequences in a step-wise approach following different flows in a decision scheme. The barcoding principle and process will be illustrated for a set of Xanthomonas pathovars.