Distinct rpsC single nucleotide polymorphism lineages of Flavescence dorée subgroup 16SrV-D phytoplasma co-infect Vitis vinifera L.

During a survey on grapevine yellows disease complex in vineyards of Lombardy region (northern Italy), phytoplasmas associated with Flavescence dorée disease were identified in symptomatic grapevines. Polymerase chain reaction and restriction fragment length polymorphism (RFLP) analyses of 16S rDNA revealed the prevalence of phytoplasmal subgroup 16SrV-D. Bioinformatic analyses of nucleotide sequences of rplV and rpsC genes, amplified from 16SrV-D phytoplasma infected grapevines and cloned, underscored the presence of five confirmed rpsC single nucleotide polymorphism (SNP) lineages, determined by different combination of SNPs at nucleotide positions 29, 365, 680, and 720 of rpsC gene. Virtual and actual RFLP analyses with the enzyme TaqI validated the presence of these SNPs. Co-infections by up to four distinct rpsC SNP lineages of 16SrV-D phytoplasma were found in grapevines. These results could open new perspectives for the study of the ecology and the epidemiology of Flavescence dorée.