Molecular diversity of 'flavescence dorée' phytoplasma strains in Slovenia

Abstract

The ‘flavescence doree’ (FD) phytoplasma is associated with the most devastating grapevine yellows disease ‘flavescence doree’. It belongs to the ribosomal group16SrV in which a high 16SrDNA identity among subgroup members exists. To investigate the genetic diversity of this phytoplasma in Slovenia a large analysis of strains in known and possible hosts and vectors was performed. The genotyping has revealed the occurrence of FD strains FD1, FD2 and FD3. Although isolates of FD2 and FD3 were detected in grapevines, those of FD2 prevailed. On the other hand, symptomatic as well as asymptomatic clematis (Clematis vitalba) plants were exclusively infected with FD3. Strains undistinguishable from FD1, FD2, FD3 and alder yellows were also detected in Alnus glutinosa and A. incana. In some alder samples mixed infections with different strain combinations were also demonstrated. FD2 strain was shown in the leafhopper vector of the disease Scaphoideus titanus. The FD1 strain was detected in the mosaic leafhopper Orientus ishidae. In addition, various specimens of this leafhopper were positive in PCR with a high presence of mixed infections.