Abstract: In this study, the spine grape cultivar Tianputao (Vitis davidii Foex.) from Huaihua, Hunan province was used as the experimental material. Three loading levels were set as follows: 1 300 kg/667 m2 (L1), 1 900 kg/667 m2 (L2) and 2 500 kg/667 m2 (L3). The main quality indicators of mature grapes such as total acid, reducing sugar, anthocyanins and non-anthocyanin monomeric phenolics were determined. Principal component analysis (PCA) was carried out on the fruit quality attributes. The results showed that: (1) total acid content increased with loading level for the two crop years 2014 and 2015, while the reducing sugar content decreased; (2) total anthocyanin content was the highest at L1 and L2 for 2014 and 2015, respectively, and the total content of basic anthocyanins was the lowest at L3 for both years; (3) for the two years, the total content of non-anthocyanin monomeric phenolic compounds and total flavonol content were both the highest at L2, followed by those at L1, and L3 gave the lowest values. Furthermore, principal component analysis (PCA) showed that the distribution of Tianputao under the three loading levels was consistent but there was clear discrimination in fruit quality between the two years. For both years, the content of phenols was the highest at L2.

Key words: Tianputao; loading level; anthocyanins; non-anthocyanin monomeric phenolic compounds