Psyllids can vector species of the Candidatus Liberibacter that pose a serious threat to the citrus, potato and carrot industries if introduced to Australia. The liberibacter genus was known to consist of seven phytopathogenic and endophytic species exotic to Australia; Liberibacter crescens (Lcr), ‘Candidatus Liberibacter africanus’ (CLaf), ‘Ca. Liberibacter americanus’ (CLam), ‘Ca. Liberibacter asiaticus’ (CLas), ‘Ca. Liberibacter caribbeanus’ (CLca), ‘Ca. Liberibacter solanacearum’ (CLso, synonymous to ‘Ca. Liberibacter psyllaurous’, CLps) and ‘Ca. Liberibacter europaeus’ (CLeu). Except for Lcr, species in the liberibacter genus are yet be grown as an axenic culture.
A novel species, ‘Candidatus Liberibacter brunswickensis’ (CLbr) has been detected in the native Australian eggplant psyllid, Acizzia solanicola. The identification of CLbr is based on nucleotide sequence of the 16S ribosomal ribonucleic acid (rRNA) region and seven additional genes using a multi locus sequence mapping approach, which phylogenetically separate CLbr into its unique branch in the liberibacter genus. CLbr has not been associated with plant disease and is yet to be grown in axenic culture. A. solanicola has broadened its host range to have plant-host crossover with Bactericera cockerelli, the tomato potato psyllid, a known vector of CLso. Additionally, the 16S rRNA region of CLbr is phylogenetically similar to, and can confound diagnostic tests, for two citrus phytopathogenic liberibacter species of concern to Australia, CLas and CLaf.
The biology of CLbr in A. solanicola feeding on eggplants and genomics of the liberibacter genus is explored. Understanding the microflora of Australian psyllids is important for both biosecurity preparedness and response management of exotic diseases.