Submitted to: Washington Association of Wine Grape Growers Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 1/16/2009
Publication Date: 2/4/2009
Citation: Lee, J., Martin, R.R. 2009. Impact of Grapevine leafroll associated virus-2 and -3 on fruit composition: commercial vineyard example. Washington Association of Wine Grape Growers Annual Meeting.
Technical Abstract: Some of the nine known Grapevine leafroll associated viruses (GLRaVs) have negative impacts upon vine productivity and grape quality, and these influences are dependant upon factors such as GLRaV strain, cultivar, clone, rootstock, and vine age. Fruit was collected from two commercially operating vineyards that had visual symptoms of GLRaV, which were later confirmed by RT-PCR. Grapes came from three rootstock / scion combinations. Samples were collected for two growing seasons and were examined for their content of phenolics, sugars, organic acids, free amino acids, ammonium, and YAN (yeast assimilable nitrogen). All vines were tested for GLRaV-1, -2, -3, and Rupestris stem pitting-associated virus (RSPaV). All vines were found infected with RSPaV. Vineyard one vines were GLRaV-2 positive or negative. Vineyard two (2 rootstock / scions) vines were GLRaV-3 positive or negative. The impact of GLRaV on phenolics was dependent upon the rootstock / scion combination. Only Vitis riparia rootstock / ‘Pinot noir’ clone 114 had significantly lower individual anthocyanins, total phenolics, and total tannins compared to its healthy counterpart. There were no clear trends in polyphenolic (phenolics other than anthocyanins) composition among the three rootstock / scion combinations. GLRaV-2 infected vines did not differ significantly from their healthy counterparts in individual free amino acids, ammonium, or YAN content. GLRaV-3 infected vines were significantly lower in valine and methionine from V. riparia rootstock / ‘Pinot noir’ clone 114 samples, and lower in glutamic acid from self-rooted / ‘Pinot noir’ clone Pommard samples compared to their healthy counterparts. Samples from self-rooted / ‘Pinot noir’ clone Pommard infected vines had significantly lower levels of malic acid and total organic acid compared to their healthy counterparts. GLRaV infection status did not alter sugar composition or content. No significant differences were found between healthy and infected vines from all three rootstock / scion pairs in ammonium or free amino acids during the weeks before ripening or at commercial harvest. The lack of magnitude seen in measured differences during this study may have been due to decreased vine stress imposed by Oregon vineyard practice of low crop load (average 2.8 tons per acre in Oregon for 2007). We are currently conducting a controlled study within an experimental vineyard to understand the direct impact of differing GLRaVs.