PVYNTN⁻NW, a novel recombinant strain of Potato virus Y predominating in potato fields in Syria

Detailed characterization of a number of isolates of PVYSYR, a novel recombinant strain of Potato virus Y (PVY) from Syria, was conducted to elucidate their origin, assess their significance and achieve a final classification of PVYSYR. Recombination analysis grouped isolates of PVYSYR into three recombination patterns, SYR-I, SYR-II and SYR-III, which varied in the first 700 nucleotides of their genomes, with the second recombination pattern, SYR-II, the most frequent. PVYSYR isolates shared highest genomic identity and close phylogenetic relationships with PVYNTN and PVYNW isolates from Syria, suggesting a common origin and local emergence of these isolates in Syria. All PVYSYR isolates (total of 20) induced tobacco veinal necrosis, but reacted to a PVYO monoclonal antibody, typical characteristics of the previously reported PVYNW (or PVYN:O). In potato, however, four isolates tested (one of SYR-I and three of SYR-II) induced potato tuber necrotic ringspot disease (PTNRD), which is the characteristic phenotype of PVYNTN. Given the shared properties of SYR-I and SYR-II isolates with PVYNTN and PVYNW, it was decided that they represent a new recombinant strain of the PVYN strain group, with the proposed name PVYNTN⁻NW. The classification of SYR-III will be possible only after testing the phenotype in potato. The high prevalence of PVYNTN⁻NW in potatoes and weeds, as well as its ability to induce PTNRD, demonstrates its importance and the necessity for its control.