Pruning effect on content of quercetin and catechin in berry skins of cv. Blaufränkisch (Vitis vinifera L.).

The effect of pruning severity on quercetin and catechin content in berry skins of cv. Blaufrankisch (Vitis vinifera L.) was studied over 3 years. Different crop levels and canopy structures were obtained by retaining 8, 16, and 24 nodes per vine at pruning. Canopy density, which is proportionate to the shoot number per canopy volume, directly affects the intensity of photosynthetically active radiation (PAR). The quercetin content has been shown to be highly dependent on the light exposure of the berries in which it accumulates. An increase in node number linearly decreased skin catechin, and it is suggested that the decrease was caused by increased yield per vine.