Genome sequences and structures of two biologically distinct strains of Grapevine leafroll-associated virus 2 and sequence analysis

• Author(s): Gonsalves, Dennis; Goszczynski, D.; Li, C.; Meng, Baozhong;
• Abstract: Grapevine leafroll-associated virus 2 (GLRaV-2), a member of the genus Closterovirus within Closteroviridae, is implicated in several important diseases of grapevines including leafroll, graft-incompatibility, and quick decline worldwide. Several GLRaV-2 isolates have been detected from different grapevine genotypes. However, the genomes of these isolates were not sequenced or only partially sequenced. Consequently, the relationship of these viral isolates at the molecular level has not been determined. Here, we group the various GLRaV-2 isolates into four strains based on their coat protein gene sequences. We show that isolates PN (originated from Vitis vinifera cv. Pinot noir), Sem (from V. vinifera cv. Semillon) and 94/970 (from V. vinifera cv. Muscat of Alexandria) belong to the same strain, 93/955 (from hybrid LN-33) and H4 (from V. rupestris St. George) each represents a distinct strain, while Grapevine rootstock stem lesion-associated virus (GRSLaV), a virus originally thought to be a new virus that is distinct from all known closteroviruses, should be considered a fourth strain of GLRaV-2. Through cloning the 5 terminal region of isolate 94/970, we determined the complete genome sequence for strain PN. Using an RT-PCR-based strategy, the entire genome of the severe strain 93/955 was also sequenced. The genomes of strains PN and 93/955 differ by 10.5% and the differences are unevenly distributed. Sequence analyses using multiple genomic regions confirm the proposition that GRSLaV is a strain of GLRaV-2 rather than a distinct virus. The possibility that GLRaV-2, either acting alone or together with a different virus, may actually cause other diseases totally different from the typical leafroll is discussed.
• Publication Date: Aug 2005
• Journal: Virus Genes