Characterization of 'Candidatus Phytoplasma asteris' strains associated with periwinkle virescence in Southern Italy.

Phytoplasma symptomatology was observed in two periwinkle plants collected in a in commercial nursery in Campania Region (South Italy). The detected phytoplasmas were identified by RFLP analyses on amplicons and in silico as belonging to 16SrI-B subgroup (aster yellows). A multigene assays was performed to evaluate possible molecular diversity: the groEl gene characterization indicated that both strains are enclosed in subgroup groELI-III. The in silico RFLP analyses on tuf and rp genes allow to differentiate the two strains in periwinkle with Tsp509I endonuclease that produced unique profiles, clearly differentiating these from other phytoplasmas belonging to 16SrI-B subgroup. No differences were shown after RFLP analyses on SecY amplicons. Further work is in progress to evaluate the epidemiological relevance of these two aster yellows strains associated with virescence in periwinkle.