Phylogenetic relationships among Flavescence doree strains and related phytoplasmas determined by heteroduplex mobility assay and sequence of ribosomal and nonribosomal DNA

Heteroduplex mobility assay (HMA) and DNA sequencing were performed on Flavescence doree (FD) phytoplasma strains and related phytoplasmas belonging to the elm yellows group. Part of the ribosomal RNA gene operon and a nonribosomal DNA region were utilized for phylogenetic analyses. Two FD strains, FD92 and FD-D, detected in France and Italy, respectively, were identical in both DNA fragments, confirming previous results. Other FD strains were all very similar and most closely resembled ALY, an Italian alder phytoplasma. Phytoplasmas associated with German Palatinate grapevine yellows were shown to form a distinct subcluster, also different from the elm yellows phytoplasma subcluster. Strain disparities revealed by HMA and sequence data were mostly in agreement, highlighting the utility of HMA in differentiation and classification of phytoplasmas belonging to the same ribosomal RNA group.