Effects of Treatment Date, Width of Girdling, and Berry Number of Girdled Shoot on the Coloration of Grape Berries

Abstract

To clarify the effects of girdling on the coloration of berry skins, treatment date, width of girdling and berry number were investigated in ‘Aki Queen’ grapes’ (Vitis labrusca L. × V. vinifera L.). In Exp. 1, girdling treatment on bearing shoots was conducted 13 days after full bloom (DAFB) and 30 DAFB, and the berry number of the clusters was thinned to 13, 32, or 50 berries on each treatment date. Clusters with 13 berries were more sensitive to girdling treatment than clusters with 32 or 50 berries. In clusters of 13 berries, girdling on 13 DAFB increased berry weight, total soluble solids (TSS), and anthocyanin content; and girdling on 30 DAFB also increased TSS and anthocyanin content. Anthocyanin content of 30 DAFB treatment was even more than that of 13 DAFB treatment. In Exp. 2, girdling treatment was conducted on 5 dates (35, 42, 49, 56, and 63 DAFB) and 4 widths (3, 5, 10, and 20 mm). Girdling treatments on 35 DAFB increased TSS and anthocyanin content more than later girdling treatments, regardless of the width of the girdle. The width of the girdle had little effect on TSS or anthocyanin content. Anthocyanin accumulation by girdling was accompanied by sugar accumulation, hence sugar accumulation from 30 DAFB was thought to be critical for anthocyanin accumulation. Moreover, a narrow width of girdle such as 3 or 5 mm is sufficient to improve berry skin coloration.