engleski

Effects of partial defoliation at different phenological stages on yield and fruit composition of cv. Istrian malvasia

Partial defoliation is a common grapevine canopy manipulation practice in Istria (Croatia). Timing of partial defoliation varies considerably among grape growers, due to different opinions about the effects it has on yield components and fruit composition. The prevailing attitude in Istria is that early defoliation will lead to better fruit set and higher yield. However, recent researches proved that early defoliation limit assimilate availability at bloom with the consequence of lower degree of fruit set, lower number of berries per cluster and lower yield. Different timings of defoliation were investigated in this trial, performed in a commercial vineyard near Kaštelir (Istria, Croatia) in order to define the effects of timing of partial defoliation on yield components and fruit composition of Istrian Malvasia (Vitis vinifera L.). The defoliation was done at three different phenological stages: before bloom (BB), after bloom (AB) and at veraison (VE). It was done manually by removing all the basal leaves until the first cluster on the shoot, including the leave opposite to the first cluster. Control treatment without any defoliation was also included. BB treatment significantly reduced the number of berries per cluster, cluster weight and yield per shoot. Soluble solid concentration was slightly affected ; BB treatment and control treatment had lower values than VE treatment. Obtained results indicate that defoliation timing can be effectively used in order to regulate yield and grape quality of Istrian Malvasia.

defoliation; yield; fruit composition; Istrian Malvasia

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