Identification of new -J and -K 16SrXII subgroups and distinct single nucleotide polymorphism genetic lineages among 'Candidatus Phytoplasma solani' strains associated with Bois noir in central Italy

Bois noir of grapevines is attributed to infection by ‘Candidatus Phytoplasma solani’ strains, taxonomic subgroups 16SrXII-A, -F, and -G. Plant-to-plant transmission by polyphagous leafhoppers determined that ‘Ca. Phytoplasma solani’ strains exist in diverse plant hosts in varied ecosystems, where selection conceivably influences intra-species strain diversity. In this study, virtual restriction fragment length polymorphism (RFLP) and single nucleotide polymorphism (SNP) analyses of 16S rDNA nucleotide sequences, amplified from grapevines and bindweeds in central-eastern Italy, revealed the presence of two new subgroups (16SrXII-J and 16SrXII-K) in the 16SrXII group, and of genetically distinct SNP lineages. Findings from the present and related works report the extensive intra-species diversity among ‘Ca. Phytoplasma solani’ strains in vineyards, underscoring the need for further studies to investigate relationships between diverse phytoplasma strains and dynamics of bois noir epidemiology.