Regional Variation of Candidatus Liberibacter solanacearum Genomic Sequences Isolated from Carrot Psyllids in Scandinavia

New associations between Candidatus Liberibacter species and crop plants have been detected in different parts of the world, presenting concerns about the potential roles of these strains in causing disease. Plants infected with Liberibacter may experience significant yield losses and these plants also serve as potential reservoirs for Liberibacter to spread to other psyllid hosts with alternate crop feeding preferences, potentially introducing new epidemiological focal points among crops. Carrots (Daucus carota) showing damage from feeding of carrot psyllids (Trioza apicalis) were recently reported to also be infected with Candidatus Liberibacter solanacearum (Lso), known to occur in association with psyllids and crops in the Solanaceae family and associated with Zebra Chip disease of potato. We analyzed genome sequences of psyllids from Finland, Norway and Sweden that showed the presence or absence of Lso. Using Illumina high-throughput short-sequence methods, we generated sequence libraries for all six psyllid samples. To assess the diversity of microbial sequences commonly associated within psyllid microflora as well as to determine the extent of identity to Lso, we removed sequences from the dataset that were closely related to five other microbial reference genomes. Contigs with identity to the different bacterial genomes were assembled and differences between the putative Lso strain sequences were compared and identified. Differences between epidemiologically distinct strains may enable identification of infection sources and elucidate variation among regional populations.