‘Candidatus Phytoplasma luffae’, a novel taxon associated with witches’ broom disease of loofah, Luffa aegyptica Mill

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’.