Sources of Variation in Maturation Soluble Solids ofThree White Grape Cultivars

Abstract

On vines of 'Vidal blanc', 'Seyval blanc' and Tinot Gris' exposed and shaded clusters were harvested and berry weight and soluble solids determined on individual berries of a random 30-berry sample from each cluster. Delaying harvest to optimum maturity of 'Vidal blanc' and 'Seyval blanc' decreased the variability and shifted the distribution of berries with higher soluble solids. There was little difference in range of concentration of soluble solids between early and mature harvests of 'Pinot Gris'. Berries from exposed clusters of all cultivars had higher soluble solid concentrations than shaded clusters. The sources in variation in soluble solids of 'Vidal blanc' were 31% due to berry to berry, clusters 28% and 41% vines. Soluble solids variation of 'Seyval blanc' were as follows: berries 22%, clusters 69%, and vines 9%. Variation in soluble solids for 'Pinot Gris' were as follows: berries 34%, clusters 18% and vines 48%. Based on these sources of variation, a table of sampling protocols is provided to insure 95% confidence in soluble solids half width intervals of 0.5,1.0 or 2.0% for each cultivar.