Analysis of Genetic Diversity of Russian Sour Cherry Plum pox virus Isolates Provides Evidence of a New Strain

Plum pox virus (PPV) exists as a complex of nine strains adapted to different Prunus hosts. Unusual PPV isolates that do not belong to the known cherry-adapted strains were discovered on sour cherry in Russia. Here, two complete genomes of isolates Tat-2 and Tat-4 were determined by sequencing on the Illumina HiSeq 2500 platform. Both were composed of 9,792 nucleotides, excluding the poly(A) tail, with the organization typical of PPV and had 99.4 and 99.7% identity between each other at the nucleotide and amino acid levels. The sequence identities between Tat-2/Tat-4 and known PPV strains ranged from 77.6 to 83.3% for genomic RNA and from 80.0 to 93.8% for polyprotein. Phylogenetic analysis placed Tat-2 and Tat-4 in a separate clade, distinct from the C and CR strains. Three more Tat-2/Tat-4-like isolates were detected in local cherry plantings using the newly developed, specific RT-PCR assay. Based on the phylogenetic analysis, sequence identities, and environmental distribution, Tat-2, Tat-4, and related isolates represent a new cherry-adapted PPV strain for which the name PPV-CV (Cherry Volga) is proposed.