'Candidatus Phytoplasma vignae’, assigning a species description to a long-known phytoplasma occurring in northern Australia

Abstract

Gene- and genome-based approaches were used to determine whether Vigna little leaf (ViLL) phytoplasma, which occurs in northern Australia, is a distinct ‘Candidatus Phytoplasma’ species. The ViLL 16S rRNA gene sequences exhibited the highest known similarity to species in the 16SrXXIX-A and 16SrIX-D subgroups, namely ‘Candidatus Phytoplasma omanense’ (98.03–98.10%) and ‘Candidatus Phytoplasma phoenicium’ (96.87–97.20%), respectively. A total of 48 single-copy orthologue genes were identified to be shared among the two draft ViLL phytoplasma genomes, 30 publicly available phytoplasma genomes, and one Acholeplasma laidlawii genome as the outgroup taxon. Phylogenomic assessments using the 48 shared single-copy orthologue genes supported that ViLL and ‘Ca. Phytoplasma phoenicium’ were closely related yet distinct species. The 16S rRNA gene sequence analysis and phylogenomic assessment indicate that ViLL phytoplasmas are a distinct taxon. As such, a novel species, ‘Candidatus Phytoplasma vignae’, is proposed. Strain BAWM-336 (genome accession number JAUZLI000000000) detected in Momordica charantia (bitter melon) serves as the reference strain of this species, with infected plant material deposited in the Victorian Plant Pathology Herbarium (VPRI) as VPRI 44369.