Submitted to: Virus Genes
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/28/2004
Publication Date: 3/20/2005
Citation: Meng, B., Li, C., Goszczynski, D., Gonsalves, D. 2005. Genome sequences and structures of two biologically distinct strains of grapevine leafroll-associated virus 2 and sequence analysis. Virus Genes 31(1):31-41. Interpretive Summary: Grapevine leaf is one of the most important viral diseases of grapevines that are cause by different strains of grapevine leafroll virus (GLRaV). This work completed the genome sequence of the GLRaV 2 strain, and helps to clarify its potential in the leafroll complex. Particularly, the work presents evidence that a virus that is potentially the cause of rootstock incompatibility may be a strain of GLRaV 2. This work will help towards the understanding the properties of viruses that cause the important leafroll disease of grapevines.
Technical 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" in many grape-growing countries. Several GLRaV-2 isolates have been detected from different grapevine genotypes. However, the genomes of these isolates were only partially sequenced or not sequenced at all. 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 different 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 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.