Protected grape cultivation develops rapidly because of huge economic benefits. However, adverse environmental conditions (insufficient sunlight, high temperature, etc.) in protected cultivation led to low-quality berries. This study aimed to evaluate the effects of berry thinning on the quality attributes of two table grape cultivars (Baoguang and Cuiguang) under linkage greenhouse conditions. Three treatments (L, light berry thinning; M, moderate berry thinning; H, heavy berry thinning) were compared with the control (C, no berry thinning). Berry thinning increased berry weight, total soluble solids (TSS), fructose, glucose, the ratio of TSS to titratable acidity (TA), anthocyanin contents, berry firmness, and mineral contents (Ca, Fe, Na, Mg). Conversely, TA and organic acid profiles were decreased by berry thinning. Cultivars showed significant effects on most of the berry quality parameters. The interaction of cultivars by berry-thinning treatments affected sugar and acid components, anthocyanin contents, and mineral elements.
Rain-shelter cultivation could protect grape berries from many diseases and affect grape berry quality. However, there have been few studies of the effects of rain-shelter cultivation on the accumulation of volatiles in Shuijing grapes grown in Yunnan Province. Therefore, the goal of this research was to explore the effects of rain-shelter cultivation on the accumulation of volatiles in Shuijing grape berries during development. The Shuijing grapes used during this study were grown in the Yunnan Province of southwest China in two consecutive vintages (2018 and 2019). The results showed that rain-shelter cultivation promoted grape ripening and inhibited volatiles synthesis in Shuijing grape berries. However, the application of rain shelters did not affect the accumulation patterns of volatiles; instead, it affected the concentrations of volatiles in Shuijing grape berries, especially during the maturation phase [12–15 weeks after flowering (WAF)]. The concentrations of isoprenoid-derived volatiles (2019), fatty acid-derived volatiles, and amino acid-derived benzenoids in Shuijing grape berries were decreased by rain-shelter cultivation during the maturation phase. The concentration of 2,5-dimethyl-4-methoxy-3(2H)-furanone (mesifurane) was also decreased by rain-shelter cultivation during the late maturation phase (14 and 15 WAF). A principal component analysis (PCA) indicated that the vintage had a much greater influence on the physicochemical parameters and volatiles of the Shuijing grape berries than the cultivation method. This work reveals the formation and accumulation patterns of volatiles of Shuijing grape berries under rain-shelter cultivation during development and has significance for exploring the potential of rain-shelter cultivation in grape-producing regions with excessive rainfall.