Detection and partial molecular characterization of atypical plum pox virus isolates from naturally infected sour cherry.

Atypical isolates of plum pox virus (PPV) were discovered in naturally infected sour cherry in urban ornamental plantings in Moscow, Russia. The isolates were detected by polyclonal double antibody sandwich ELISA and RT-PCR using universal primers specific for the 3'-non-coding and coat protein (CP) regions of the genome but failed to be recognized by triple antibody sandwich ELISA with the universal monoclonal antibody 5B and by RT-PCR using primers specific to for PPV strains D, M, C and W. Sequence analysis of the CP genes of nine isolates revealed 99.2-100 % within-group identity and 62-85 % identity to conventional PPV strains. Phylogenetic analysis showed that the atypical isolates represent a group that is distinct from the known PPV strains. Alignment of the N-terminal amino acid sequences of CP demonstrated their close similarity to those of a new tentative PPV strain, CR.