Effect of cluster thinning on berry skin anthocyanin composition of Vitis vinifera cv Nebbiolo

Cluster thinning (removal of 50 % of the cluster one month after bloom)
was tested for three consecutive years in a vineyard located in southern
Piedmont (Italy). At harvest, the concentrations of total anthocyanins
and flavonoids were assessed by spectrophotometry, and the
concentrations of individual anthocyanins determined by HPLC. Berry
weight and berry skin weight slightly increased following thinning.
Soluble solids and berry skin anthocyanins and flavonoids were more
concentrated in berries from cluster thinned plants. Cluster thinning
increased the concentrations of cyanidin-3-glucoside and
peonidin-3-glucoside and, to a lesser extent, petunidin-3-glucoside. The
concentrations of malvidin-3-glucoside and of acylated anthocyanins were
not affected by cluster thinning.