Polymorphism of rplF and tufB genes: expanding the MLST scheme for “flavescence dorée” phytoplasma typing in Croatia

In Croatia, major agents associated with grapevine yellows diseases (GY) are the “bois noir” (BN; ‘Candidatus Phytoplasma solani’) and the “flavescence dorée” (FD) phytoplasmas, with the latter emerging and spreading extensively in the last decade. The aim of this study was to perform genotyping of selected FD phytoplasma strains by analysis of the housekeeping genes rplF and tufB in order to expand the currently used multilocus sequence typing (MLST) scheme. The analysis included samples of grapevine, wild plants from the vicinity of vineyards and insect-vectors from continental Croatia and Istria county. Fragments of rplF and tufB genes were amplified by PCR and sequenced. The alignment and phylogenetic analysis revealed the presence of 5 and 6 genotypes, respectively. The gene rplF showed to be more conserved than the tufB gene, but both were proved as good candidates molecular markers in FD phytoplasma genotyping due to their variability. Implementation of data on rplF and tufB genotypes in the currently used MLST scheme for FD phytoplasma differentiation would give new possibilities for tracking and tracing this quarantine pathogen.