Vernonia brasiliana is a wild perennial shrub frequently found in pasture areas. Plants of this species have been observed displaying typical symptoms induced by phytoplasmas, which were characterized by shoot proliferation, deformed leaves and leaf chlorosis. The present study confirmed the presence of phytoplasmas in association with affected plants. Sequencing of the 16S rRNA gene, computer-simulated RFLP analysis and phylogenetic analysis revealed that one of the phytoplasmas identified was representative of novel subgroup. The sequence identity scores between the novel strain and those of previously described ‘Candidatus Phytoplasma fraxini’-related strains was 99 %, while similarity coefficient values were lower than 0.97. These findings provide support to delineate the phytoplasma found in vernonia plants as a reference phytoplasma for a novel subgroup designated 16SrVII-F. This representative of the novel subgroup was denominated VbSP phytoplasma (Vernonia brasiliana Shoot Proliferation; GenBank KX342018). The results of the present study revealed V. brasiliana to be a host of phytoplasmas, evidenced a novel phytoplasma associated with phytoplasmal disease in Brazil and extended the knowledge of the genetic diversity existing within the 16SrVII group.
The phytoplasma associated with witches’ broom disease of loofah [Luffa aegyptica Mill., syn. Luffa cylindrica (L.) M.J. Roem.] in Taiwan was classified in group 16SrVIII, subgroup A (16SrVIII-A), based on results from actual and in silico RFLP analysis of 16S rRNA gene sequences. Nucleotide sequencing of PCR-amplified, cloned DNA segments revealed rrn interoperon sequence heterogeneity in the loofah witches’ broom (LfWB) phytoplasma. Whereas the 16S–23S rRNA spacer region of rrnA contained a complete tRNA-Ile gene, the spacer of rrnB contained a nonfunctional remnant of a tRNA gene. Phylogenetic analysis of the rrnA and rrnB 16S rRNA genes revealed that the LfWB phytoplasma represented a distinct lineage within the phytoplasma clade, and the LfWB phytoplasma shared less than 97.5 % nucleotide sequence similarity of 16S rRNA genes with previously described ‘Candidatus Phytoplasma ’ taxa. Based on unique properties of DNA, we propose recognition of loofah witches’ broom phytoplasma strain LfWBR as representative of a novel taxon, ‘Candidatus Phytoplasma luffae’.