Grapevine leaf roll-associated viruses (GLRaVs) are a group of nine closely related viruses belonging to the Closteroviridae family that cause grapevine leaf roll disease in vineyards across the world (3). Within the continental United States, GLRaVs have been reported in the states of California, Michigan, Missouri, New York, Oregon, Washington, and Wisconsin, but not in Ohio (2,3). During 2012, grapevines with typical leaf roll symptoms were reported by owners of several Ohio vineyards. The symptoms included small, red leaves and downwardly rolled leaf margins, accompanied by tiny grape clusters with few fruits. A total of 20 symptomatic leaf samples were collected from two sites about 300 miles apart within Ohio, namely Valley Vineyards (cultivars Vidal Blanc and Fronterac) and South River Winery (cultivar Cabernet Franc). Total RNA was extracted from the samples using a previously reported procedure (1) and subjected to reverse transcription (RT)-PCR using specific primers for five known grapevine viruses including GLRaV-1 (1F: 5′-ACCTGGTTGAACGAGATCGCTT and 1R: 5′-GTAAACGGGTGTTCTTCAATTCTCT), GLRaV-2 [2F(FQ): 5′-GCTCCTAACGAGGGTATAGAAG and 2R(FQ): 5′-AGAGCGTACATACTCGCGAACAT], GLRaV-3 [3F(FQ): CAAGTGCTCTAGTTAAGGTCAG and 3R(FQ): 5′-CGGAACGTCGGTTCATTTAGA], Grapevine fan leaf virus (GFLVR1-F: 5′-TGAGATTAGTCATGGAGCAGCTT and GFLVR1-R: 5′-GGATAGACGTCTGGTTGATTTTG), and Tobacco ring spot virus (TRSVR1-1255F: 5′-GAGTGTTGTGCAATTATCT-GCATA and TRSVR1-1844R: 5′-CAAAGATGCCAAGAAAAGTTGCAAG). A 295-bp fragment of a grapevine actin cDNA (primers VvACT-F: 5′-ATCTCCATGTCAACCAAACTGAG and VvACT-R: 5′-GACAGAATGAGCAAGGAAATCAC) was used as a positive control for RT-PCR. The samples tested negative for GFLV, TRSV, or GLRaV-1 with our primer sets. However, four of the samples were positive for GLRaV-2, and 12 positive for GLRaV-3, as evidenced by the detection of PCR fragments of expected sizes (404 and 344 bp, respectively). All samples positive for GLRaV-2 were from a single field, whereas samples positive for GLRaV-3 were from both vineyards examined. The identities of GLRaV-2 and -3 were further confirmed by directly sequencing one GLRaV-2 and two GLRaV-3 (one from each location) PCR fragments from both ends. The 404 bp GLRaV-2-specific fragment shared 95 to 98% sequence identity with various GLRaV-2 isolates whose sequences were deposited at the GenBank. Similarly, the two 344-bp GLRaV-3 fragments share a 95 to 97% identity with known GLRaV-3 isolates. Notably, the sequences of the two GLRaV-3-specific fragments derived from two vineyards are not identical (97% identity), suggesting these two isolates might have different origins. As these viruses are known to be recalcitrant to mechanical transmission, we did not attempt to transmit these viruses to healthy plants. In summary, our results report for the first time the detection of GLRaV-2 and -3 in Ohio, suggesting that these two viruses are associated with the observed leaf roll symptoms, hence should be part of an effective management plan for grapevine viral diseases in the state.
References: (1) C. Louime et al. Eur. J. Sci. Res. 22:232, 2008. (2) S. Lunden and W. Qiu. Plant Dis. 96:462, 2012. (3) A. M. Sharma et al. PLoS One 6:e26227, 2011.
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