• Grape and wine polyphenols vary significantly among different varieties and clones. • Malvidin derivatives cause major anthocyanin variations in grapes and wines. • Epicatechin causes non-color polyphenol variation in grapes and wines. • Berry anthocyanin content is positively related with the titratable acid content. • Polyphenols are more abundant in MBVCR6 grape and wine than in other genotypes.

Green leaf volatiles (GLVs) are important in giving grape a fresh and green aroma. But the changes in GLVs during the phenological development of grapevines are not well known. This study analyzed the GLVs and transcription levels of associated biosynthetic genes in six grape species from the Loess Plateau region at five stages of maturation. Thirteen GLVs were detected, showing unique patterns for each grape type at various growth phases. The primary components in six grapes were (E)-2-hexenal, (E)-2-hexen-1-ol, and hexanal. With the exception of Cabernet Franc in 2019, the overall GLV contents of the six types generally increased during growth and development, peaking or stabilizing at harvest. And Sauvignon Blanc, Cabernet Gernischt, and Cabernet Sauvignon exhibited higher total contents among the varieties. PLS-DA analysis revealed 3-hexenal’s high VIP scores across two years, underscoring its critical role in grape variety classification. Correlation analysis revealed a strong positive correlation between the levels of hexanal, 1-hexanol, (E)-2-hexen-1-ol, (Z)-3-hexenyl acetate, nonanal, and (E, E)-2,6-nonadienal and the expression of VvHPL and VvAAT genes in the LOX-HPL pathway. Specifically, VvHPL emerges as a potential candidate gene responsible for species–specific differences in GLV compounds. Comprehending the changing patterns in the biosynthesis and accumulation of GLVs offers viticulturists and enologists the opportunity to devise targeted strategies for improving the aromatic profile of grapes and wines.

Green leaf volatiles (GLVs) are important in giving grape a fresh and green aroma. But the changes in GLVs during the phenological development of grapevines are not well known. This study analysed the GLVs and transcription levels of associated biosynthetic genes in six grape species from the Loess Plateau region at five stages of maturation. Thirteen GLVs were detected, showing unique patterns for each grape type at various growth phases. The primary components in six grapes were (E)-2-Hexenal, (E)-2-Hexen-1-ol, and Hexanal. With the exception of Cabernet Franc in 2019, the overall GLV contents of the six types generally increased during growth and development, peaking or stabilizing at harvest. And Sauvignon Blanc, Cabernet Gernischt, and Cabernet Sauvignon exhibited higher total contents among the varieties. Correlation analysis revealed a strong positive correlation between the levels of Hexanal, 1-Hexanol, (E)-2-Hexen-1-ol, (Z)-3-Hexenyl acetate, Nonanal, and (E, E)-2,6-Nonadienal and the expression of VvHPL and VvAAT genes in the LOX-HPL pathway. Specifically, VvHPL emerges as a potential candidate gene responsible for species-specific differences in GLV compounds. Comprehending the changing patterns in the biosynthesis and accumulation of GLVs offers viticulturists and enologists the opportunity to devise targeted strategies for improving the aromatic profile of grapes and wines.

Global climate change poses a significant threat to viticulture, primarily due to high temperatures. This study examined temperature-induced changes in phenolic profiles in berries of three wine grape cultivars under 25, 35, and 45 °C for 0–48 h using HPLC-ESI-MS/MS. To investigate the molecular response to severe heat stress, transcriptomic analysis was conducted in Cabernet Sauvignon berries subjected to a 45 °C treatment. Results showed that the 45 °C treatment decreased the levels of anthocyanins (particularly delphinidin-3-O-glucoside and cyanidin-3-O-glucoside) in grape berries. Acylated anthocyanins, such as malvidin-3-O-(6-acetyl)-glucoside, exhibited enhanced stability at elevated temperatures. Additionally, high temperatures increased the levels of protocatechuic and gentisic acids and decreased those of rutin, ferulic acid, and p-coumaric acid. Transcriptomic and qRT-PCR analyses revealed that the expression of OMT, LDOX, GST, F3′5′H, and 3AT was positively correlated with changes in anthocyanin levels under high temperatures, suggesting their roles in the observed phenolic alterations. These findings highlight the molecular responses of winegrapes to heat stress, providing a foundation for future viticulture strategies under changing climatic conditions.