In February 2009, grapevines (Vitis vinifera) in a commercial vineyard in Auckland were showing shortened, spindly canes with tiny leaves. Approximately 10% of the vines were affected. An RNeasy Plant Mini Kit (Qiagen, Valencia, CA) was used to isolate total RNA from leaves collected from six symptomatic (cvs. BAC0022A and Syrah) and eight symptomless vines (cvs. BAC0022A, Syrah, and Chardonnay). RNA was tested by reverse transcription-PCR for the presence of Australian grapevine viroid, Citrus exocortis viroid, Grapevine yellow speckle viroid 1 (GYSVd-1), Grapevine yellow speckle viroid 2, and Hop stunt viroid (HSVd). Four of the six symptomatic and all the symptomless vines tested positive for GYSVd-1 using primers 5′-TGTGGTTCCTGTGGTTTCAC-3′ and 5′-ACCACAAGCAAGAAGATCCG-3′, which amplify the complete genome (368 bp), and published primers PBCVd100C/194H (3), which amplify a 220-bp region of the genome. Amplicons from each PCR were transformed into a pCR 4-TOPO vector (Invitrogen, Carlsbad, CA), cloned, and sequenced. Sequence from both PCRs aligned identically to generate a consensus sequence (GenBank Accession No. HQ447056), which showed 99% nt identity to GYSVd-1 (GenBank No. X87906) by BLASTN analysis. All symptomatic and symptomless vines also tested positive for HSVd using primers C/H-HSVd (4) and HSVd-C60/H79 (1), which amplify the complete genome (298 bp). Amplicons from each isolate were cloned and sequenced. Sequence from both PCRs were aligned. Clones from all isolates, with the exception of one, aligned identically to create a consensus sequence (GenBank No. HQ447057) that showed 99% nt identity to Chinese HSVd isolates from grapevine (GenBank Nos. DQ371436–59) by BLASTN analysis. Sequence from the remaining isolate (GenBank No. HQ447056) was identical to a German Riesling grape isolate of HSVd (GenBank No. X06873). The presence of each viroid was further confirmed in PCR-positive plants by dot-blot hybridization with digoxigenin-labeled synthetic ssRNA probes specific to the full-length genomes of GYSVd-1 and HSVd (S. Harper and L. Ward, unpublished data). To our knowledge, this is the first report of GYSVd-1 and HSVd in V. vinifera in New Zealand. Since both viroids were detected in symptomatic and symptomless plants, the symptoms observed in the vineyard cannot be attributed to viroid infection. Symptoms described for GYSVd-1 include leaf spots and flecks, but no disease symptoms have been reported in grapes as a result of HSVd (2). Viruses found in the vines include Grapevine leaf roll virus-3, Grapevine viruses A and B, and Rupestris stem pitting associated virus, but these are not thought to be the cause of the symptoms. Two sequence types of HSVd were found, suggesting at least two separate introductions of HSVd into the vineyard. The vineyard is more than 40 years old so both viroids may have been present for some years. Export of wine from New Zealand was worth 1 billion dollars in 2009, so there is potential for these viroids to have an economic impact if symptoms are expressed. HSVd has been reported from China, Europe, Japan, Middle East, Pakistan, and the United States. GYSVd-1 has been reported from Australia, China, East Mediterranean, Europe, Japan, and the United States.
References: (1) A. Hadidi et al. Acta Hortic. 309:339, 1992. (2) A. Hadidi et al., eds. Viroids. CSIRO Publishing, Collingwood, Australia, 2003. (3) R. Nakaune and M. Nakano. J. Virol. Methods 134:244, 2006. (4) A. M. Shamoul et al. J. Virol. Methods 105:115, 2002.
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