Characterization of 'Candidatus phytoplasma solani' strains from grapevines, Hyalesthes obsoletus, reference strains in periwinkle and in colonies.

A multilocus typing (MLT) was performed on 72 phytoplasma strains from obtained from grapevine samples and Hyalesthes obsoletus specimens collected in different “bois noir” infected vineyards, and on a colony obtained from cultivation of a 'Candidatus Phytoplasma solani' strain from reference collection in periwinkle. The RFLP analyses on tuf, secY, groel and stamp genes allow to differentiate 8 lineages in the 72 field-collected samples resulted positive on the 4 genes employed, showing the presence of different ‘Ca. P. solani’ lineages in grapevine and/or in H. obsoletus samples. In some cases there was a good consistency in the MLT profiles of lineages detected in the grapevine and those identified in H. obsoletus indicating the presence of phytoplasma populations shared between the two hosts. On the other hand the lineages delineation on these genes in the six “stolbur” strains in collection in periwinkle were all different from those identified in the vineyard collected samples. The partial molecular characterization of the colonies obtained from the STOL strain after its isolation in a chemically defined medium shows gene congruence with those of the original strain maintained in micropropagation.