ASSESSMENT OF SOURCE-SINK RELATIONSHIPS WITH SIMPLE INDICES IN GRAPEVINES

The balance between vegetative growth and yield was significantly affected by grapevine cultivar. Tocai vines had higher values for EVP and EV indexes than Sauvignon. In general, yield/pruning weight ratio (PL) did not show significative differences between cultivars, while L/EVP was 15.9 for Sauvignon and 12 for Tocai.

In Sauvignon vines PL index was statistically correlated with vine yield and, but negatively, with pruning weight. In Tocai vines PL was negatively correlated to pruning weight, but it had no statistical relationship with yield. For both cultivars yield and PL were negatively correlated with soluble sugar content. L/EVP index showed a positive correlation with must sugar.

Correlation between vine yield and must sugar resulted in significant negative correlations only within vines with similar EV values. Therefore an optimal soluble solids amount in grapes could be gained at increasing fruiting levels, if vines had the same growth potentials.

Crop load levels played a great role on sugar accumulation in grapes but, for some fruiting levels, Ravaz index (PL) was not statistically correlated with soluble solids in Sauvignon and Tocai grapes.

Significant relationships between L/EVP and must sugar contents were observed for both cultivars. A well defined amount of pruning weight over the total mass produced by the plant resulted to guarantee such a leaf area to gain high sugar content in grapes.

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