Abstract
SummaryA novel candidate species of the liberibacter genus, ‘Candidatus Liberibacter brunswickensis’ (CLbr), was identified in the Australian eggplant psyllid, Acizzia solanicola. This is the first discovery of a species belonging to the liberibacter genus in Australia and the first report of a liberibacter species in the psyllid genus Acizzia. This new candidate liberibacter species has not been associated with plant disease, unlike other psyllid‐vectored species in the genus including ‘Candidatus Liberibacter asiaticus’ (CLas), ‘Candidatus Liberibacter africanus’ (CLaf) and ‘Ca. Liberibacter solanacearum’ (CLso). This study describes novel generic liberibacter genus primers, used to screen Australian psyllids for the presence of microflora that may confound diagnosis of exotic pathogens. CLbr forms a unique clade in the liberibacter genus based on phylogenetic analysis of the 16S ribosomal ribonucleic acid (rRNA) region and multilocus sequence analysis (MLSA) of seven highly conserved genes, dnaG, gyrB, mutS, nusG, rplA, rpoB and tufB. The MLSA mapping approach described in this article was able to discriminate between two ‘Ca. Liberibacter’ species within a metagenomic data set and represents a novel approach to detecting and differentiating unculturable species of liberibacter. Further, CLbr can confound the Li et al. (2006) quantitative PCR (qPCR) diagnostic tests for CLas and CLaf.
Highlights
The liberibacter genus includes species of Gramnegative alpha Proteobacteria that are known plant pathogens and endophytic species
There are currently seven species which are found in most regions of the world, excluding mainland 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) (Jagoueix et al, 1994; Duan et al, 2009; Liefting et al, 2009a,b; Munyaneza et al, 2010, 2014; Raddadi et al, 2011; Leonard et al, 2012; Phahladira et al, 2012; Tahzima et al, 2014; Keremane et al, 2015)
Acizzia solanicola DNA extracts from six additional sites tested from Victoria (VIC) and New South Wales (NSW) in south-eastern Australia were tested using the liberibacter generic primers, LG774F-LG1463R and universal 16S
Summary
The liberibacter genus includes species of Gramnegative alpha Proteobacteria that are known plant pathogens and endophytic species. With the exception of Lcr, species in the liberibacter genus are associated with psyllids (Hemiptera: Psylloidea). Lcr is the only liberibacter that can be grown as an axenic culture (Leonard et al, 2012). Due to the fastidious nature of the predominant liberibacter species, next-generation sequencing (NGS) approaches have played a large role in the investigation of this genus. NGS will aid the expansion of this genus and will continue to inform information on current species, their insect and plant host range
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