CLUSTER THINNING EFFECTS ON THE FRUIT AND WINE QUALITY OF 'DOONURI' GRAPE

Abstract

The quality of wine is influenced primarily by the quality of the raw material and secondly by fermentation technology. In general, important methods of cultivation for increasing the quality of the grape are shoot thinning, desuckering, shoot positioning and topping, basal leaf removal, girdling, cluster thinning and berry thinning. In this study the influence of cluster thinning was investigated to set standards for management for the grape cultivar ?Doonuri?. The ?Doonuri? grape was a cross of ?Schuyler? and ?Campbell Early? at the National Institute of Horticultural and Herbal Science in Korea in 2006. This red grape has a full fruit aroma, and it was used as a table and wine grape. In addition, this cultivar had a resistance to cold in winter as well as a downy mildew resistance. The fruit setting of grapes after cluster thinning was adjusted to 1.1 ton (1 cluster per shoot), 1.5 tons (1.5 clusters per shoot), and 2.1 tons (2 clusters per shoot) per 10 ares. As a result, ripening was faster when the yield was 1.5 t then 2.1 t per 10 are. Total acidity was reduced about 0.2% (w/v) at 1.5 t compared with 2.1 t. On the other hand, the sugar content was higher, about 2~3°Brix. The total acidity and sugar content for the 1.1 and 1.5 t levels were not significantly different. As cluster thinning increased, total polyphenol and total anthocyanin contents increased with early maturity. Also, the grapes with less 1.5 t per 10 acre were able to produce high quality wine.