No abstract

Isolates of Potato virus Y (PVY), collected in Syria, induced vein necrosis in tobacco but reacted to PVYO monoclonal antibody, and were therefore classified as PVYNW (or PVYN:O). The possible recombinant points within the genome were checked using a previously reported multiplex RT‐PCR. These isolates were categorized in two groups according to recombinant points. Isolates with one recombinant point at the HC‐Pro/P3, identical to previously reported PVYNW (or PVYN:O), were designated as group 1. However, the majority of Syrian PVY isolates showed two recombinant points at both HC‐Pro/P3 and 6K2/NIa, revealing a new genomic recombination pattern that had never been reported for PVYNW (or PVYN:O), hereafter referred to as group 2. Further characterizations showed that isolates of group 2 had an additional recombinant point at the N‐terminal of the coat protein gene (CP) of their genome. Based on the bioassay on tobacco, serological and molecular studies, these isolates showed shared characteristics of both PVYNW and the recombinant PVYNTN, making it difficult to include them in any of these variants. We propose them as new isolates of PVYN strain, and label them PVYSYR (SYR is from Syria, the country of origin).

The biological and genetic diversity of Wheat yellow mosaic virus (WYMV) isolates in Japan was characterized. On the basis of wheat cultivar reactions, 14 WYMV isolates from various places were classified into pathotypes I, II, or III. These were distributed in central, northern, and southern areas of Japan, respectively. WYMV isolates comprised three genotypes (A, A' and B) based on amino acid differences in RNA1 and two genotypes (a and b) based on amino acid differences in RNA2. A correlation was found between the WYMV RNA1-based genotype and pathotype, suggesting that factors associated with pathogenicity map to RNA1. Genotype Aa and A'a were distributed mainly in the central to southern areas of Japan, and genotype Bb was found in northern areas of Japan, as shown by reverse-transcription polymerase chain reaction restriction fragment length polymorphism analysis. Chinese isolates YA and YZ were closely related to genotypes Bb and Aa, respectively. Wheat was introduced from China to Japan in the 4th and 5th centuries, and the two genotypes of WYMV might also have been introduced with the crop from China and later adapted to local wheat cultivars in Japan.

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.

A new filamentous virus