Anti-GLRaV-3 monoclonal antibody, clone 6B6/D3

Individual free amino acids, yeast assimilable amino acid (YAN) content, ammonia, organic acids, and simple sugars of berries from vines infected with GLRaV-2 or -3 were compared with paired vines free of these viruses. Samples were taken from two commercial vineyards during two growing seasons (2005 and 2006), with three different rootstock/scion combinations. Vines infected with GLRaV-2 did not differ significantly from their healthy counterparts in individual free amino acids, ammonia, or YAN content. Vines infected with GLRaV-3 were significantly lower in valine and methionine from Vitis riparia rootstock/'Pinot noir' clone 114 (VY2a) samples, and lower in glutamic acid from self-rooted/'Pinot noir' clone Pommard (VY2b) samples, compared to samples from their healthy counterparts. Samples from VY2b (self-rooted/'Pinot noir' clone Pommard) infected vines had significantly lower levels of malic acid and total organic acids compared to samples from their healthy counterparts. There were no significant differences between healthy and infected vines from all three rootstock/scion pairs in ammonia or free amino acids in samples taken during the weeks before ripening and at commercial harvest. This is the first study to report the influence of GLRaV-2 and -3 on 'Pinot noir' berries nitrogen (N) compounds significant to fermentation. Individual free amino acids may be inferior to phenolic compounds as indicators of GLRaV infection status. Published by Elsevier Ltd.

The effect of leaf removal treatments around vine cluster zones on must quality were tested during 2003 and 2004 in Rias Baixas (Spain) in two Albarino vineyards infected by GLRaV-3. As expected, the main virus damage was decreased sugar content (2.1 Brix in 2003 and 0.9 Brix in 2004) in the musts compared with leafroll-free plants. Leaf removal improved must quality by decreasing titratable acidity by between 0.5 and 1.9 g L-1 of tartaric acid, depending on the experiment; it also increased the grape sugar content an average of 1 Brix. In vineyards with high incidence of GLRaV-3, partial defoliation at veraison, or 2 to 3 weeks later, had an improved must quality, counteracting the negative impact of the virus. This process is recommended to avoid penalties in wineries during years with poor ripening conditions.