To explore the effect of postharvest dehydration on grape berries and wine quality, we determined physicochemical properties, polyphenols, antioxidant activities, volatile compounds and sensory characteristics for wines brewed by ‘Marselan’ (Vitis vinifera L.) grapes with 0%, 10%, 15%, 20%, and 25% of water loss. The result showed that postharvest dehydration improved the alcohol content, residual sugar and titratable acidity of Marselan wine. Phenolic compounds and antioxidant activities in wines with a dehydration of 20% have significantly increased. Postharvest dehydration increased the contents of isobutanol, isoamyl alcohol, phenylethyl alcohol, ethyl acetate, isoamyl acetate and ethyl butyrate in Marselan wines, and enhanced the floral, fruity and sweet taste of wines. Marselan wine had the lowest acceptability score under the condition of severe dehydration (25% dehydration), which was related to the significant increase of tannins content. In summary, postharvest dehydration was beneficial in improving the quality of Marselan wine.

Grapes are one of the widely cultivated fruits, with high nutritional value and economic value. The widespread occurrence of grape virus diseases has seriously affected the development of the grape industry. The grapevine varieties “Merlot”, “Cabernet Sauvignon”, “Syrah”, “Chardonnay”, “Welsch Riesling ”, and “Riesling Weiss” were used as materials for screening grapevines carrying the viroid GYSVd1 by RT-PCR. Principal component analysis (PCA) was employed to systematically assess the physicochemical indexes of both grape berries and wine in order to determine the extent of the influence of GYSVd1 on the quality of grape berries and wine. The results demonstrated that GYSVd1 infection significantly compromised both berries and wine quality across the tested cultivars, albeit with distinct varietal susceptibility patterns. Regarding berries’ quality, the negative impact of GYSVd1 followed this decreasing order: Merlot > Chardonnay > Welsch Riesling > Syrah > Riesling Weiss > Cabernet Sauvignon. Similarly, for wine quality, the negative impact exhibited the following gradient: Welsch Riesling > Riesling Weiss > Chardonnay > Cabernet Sauvignon > Syrah > Merlot. There were significant differences in the amount of sugar, acid and phenolic substances between GYSVd1-infected and -uninfected grapevines, but no significant differences in berry weight, berry shape index, and alcohol content. GYSVd1 affected the quality of berries and wine mainly by regulating the contents of sugar, acid, and phenolic substances.

Grapevines in cold regions are prone to frost damage in winter. Due to its adverse effects on soil structure, plant damage, high operational costs, and limited mechanization feasibility, buried soil overwintering has been gradually replaced by no-burial overwintering techniques, which are now the primary focus for mitigating frost damage in wine grapes. While current research focuses on the selection of thermal insulation materials, less attention has been paid to the insulation mechanism of covering materials and covering methods. In this study, we investigated the insulation performance of two covering materials (tarpaulin and insulation blanket) combined with six height treatments (5–30 cm) to analyze the effect of insulation space volume on no-buried-soil overwintering. The results show that the thermal insulation performance of the insulation blanket is significantly better than that of the tarpaulin. The 5 cm height treatment under the tarpaulin cover and the 25 cm height treatment under the insulation blanket cover exhibited the best thermal insulation performance. Using a neural network machine learning approach, we constructed a model related to the height of the insulation material and facilitate the model’s accurate predictions, in which tarpaulin R²_branches = 0.92, R²_{20 cm} = 0.99, and R²_{40 cm} = 0.99 and insulation blanket R²_branches = 0.89, R²_{20 cm} = 0.98, and R²_{40 cm} = 0.99. The model predicted optimal insulation heights of 6 cm for the tarpaulin and 22 cm for the insulation blanket. Factors like solar radiation within the insulation space, ground radiation, airflow, and material thermal conductivity affect the optimal insulation height for different materials. This study used a neural network model to predict the optimal insulation heights for different materials, providing systematic theoretical guidance for the overwintering cultivation of wine grapes and aiding the safe development of the wine grape industry in cold regions.

To investigate the effect of mountain-basin system on wine quality, four different regions were selected according to altitude and latitude. This work analyzed the differences in physicochemical properties, organic acids, monomeric phenols, antioxidant activity and volatile compounds of Cabernet Sauvignon wine between four regions. Comparative analysis revealed that there were significant differences in alcohol content and pH, respectively. Malic acid in organic acids was the main acid to distinguish the four regions. Correlation analysis showed that there was a significant correlation between physicochemical properties and climatic conditions in the four regions. There were significant differences in most of the monomeric phenols, and the antioxidant capacity was also significantly different. A total of 60 volatile compounds were detected, including 11 key volatile compounds, and there were significant differences in the composition of wines in the four regions. Methyl salicylate, ethyl caprate and ethyl hexanoate were the characteristic aromas in mountain front (MF) and intermontane basin (IB) regions, decanal was the characteristic aroma in sloping field (SF) region, and ethyl butyrate was the characteristic aroma in near desert (ND) region. This study further clarified the influence of climate and terrain on wine quality, and provided a better theoretical basis for the fine management of small producing areas.

Overwintering frost damage is a major challenge for the wine grape industry in northern China. This study investigates overwintering treatments to improve survival rates and mitigate frost damage in the wine grape production area of the northern foothills of the Tianshan Mountains. Seven overwintering treatments were tested: soil-covered striped cloth, striped cloth, sandwiched striped cloth, thickened striped cloth, double-layered striped cloth, heat-insulating striped cloth, and heat-insulating sandwich striped cloth. Temperature and humidity were continuously monitored during the overwintering period, both aboveground and at depths of 20 and 40 cm underground. By analyzing temperature trends, the duration of low temperatures, and temperature fluctuations, comprehensive overwintering indices were derived through principal component analysis to assess heat retention, moisture preservation, and the impact on grapevine survival. The results showed that the sandwiched striped cloth treatment provided the best insulation, with a 4.4 °C higher minimum daily temperature and a 356% increase in overwintering indices compared to striped cloth alone. The double-layer striped cloth treatment also improved safety, with a 130% increase in overwintering indices. Other treatments, including the soil-covered and the heat-insulating striped cloth, showed reduced performance. The sandwiched striped cloth and double-layer striped cloth treatments are recommended for northern China’s wine grape regions, with further research needed to evaluate their economic viability.

This study investigates the roles of grapevine berry inner necrosis virus (GINV) and grapevine yellow speckle viroid 1 (GYSVd1) in regulating the soluble sugar and organic acid metabolism of grape berries and wine. The contents of soluble sugar and organic acid components and the activity and expression levels of critical enzymes of the soluble sugar acid metabolism pathway were measured in ‘Welschriesling’ grape berries and wine carrying the virus GINV, the viroid GYSVd1, and a mixed infection of both GINV and GYSVd1 (GINV + GYSVd1), respectively. The results show that the virus GINV and the viroid GYSVd1 decreased the soluble sugar and increased the organic acid in berries and wine. GINV decreased glucose content and increased malic acid content by regulating AI, NADP-IDH, PEPC, and NAD-MDH activity, as well as VvHT4, VvSWEET10, VvPEPC, and VvMDH expression levels. GYSVd1 decreased glucose content and increased malic acid content by regulating AI and CS activity and VvHT4, VvSWEET15, and VvPEPC expression. The results suggest that the viroid GYSVd1 negatively impacts berries and wine more than the virus GINV. Moreover, in the mixed infection with GINV + GYSVd1, the negative effects of GINV and GYSVd1 on soluble sugars do not seem to be observed.