'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 'CandidatusPhytoplasma' taxa. Based on unique properties of DNA, we propose recognition of loofah witches' broom phytoplasma strain LfWBR as representative of a novel taxon, 'CandidatusPhytoplasma luffae'.