Methoxypyrazines (MPs) are a unique class of volatile compounds containing nitrogenous heterocyclics that impart green bell, vegetal and herbal odors to red grape berries and wines. In this study, the quality and MPs levels of grape berries from six representative red wine grape varieties were determined in the two consecutive years. The results showed that, at maturity, the highest total soluble solid was observed in Petit Verdot grape berries in the two consecutive years. While the anthocyanin content showed the highest in Marselan berries in 2018, in 2019, Petit Verdot berries had the highest anthocyanin content. Moreover, 2-methoxypyrazine (MOMP), 3-methyl-2-methoxypyrazine (MEMP) and 3-ethyl-2-methoxypyrazine (ETMP) levels were relatively lower, with almost no detectable in berries at maturity. The relative higher 3-isobutyl-2-methoxypyrazine (IBMP) content was observed in Cabernet Sauvignon, Marselan, Merlot, and Malbec berries. However, 3-sec-butyl-2-methoxypyrazine (SBMP) and IBMP were only detected in six wines, and their levels were higher than those in the grape berries. Furthermore, correlation analysis showed that there was a statistically positive correlation between the expression levels of VvOMT1 and VvOMT3 and MPs content in grape berries, while the lowest association was found in the VvOMT2. These findings provide a basis for selecting the most suitable grape varieties to improve wine quality.

The eastern foot of Helan Mountains in Ningxia belongs to the semiarid area and has been identified as the best wine grape producing area in China. In order to solve the problems of a high sugar content, organic acid falling too fast and severe shortage of acidity in the berries during ripening, which lead to lack of wine harmony, this study took Vitis. vinifera L. cv. ‘Cabernet Sauvignon’ as the experimental material and expanded nine treatments from setting to harvest. Nine rows were selected and divided into three groups, treated with mild (–0.20 MPa ≥ Ψb ≥ –0.40 MPa), moderate (–0.40 MPa ≥ Ψb ≥ –0.60 MPa), severe (Ψb ≥ –0.60 MPa) water stress from setting to veraison separately. From veraison to harvest, within each group, the mild, moderate, severe water stress were set, forming light-light (CK), light-medium (T1), light-heavy (T2), medium-light (T3), medium-medium (T4), medium-heavy (T5), heavy-light (T6), heavy-medium (T7), heavy-heavy (T8) treatments. The results showed that when the medium treatment was used from setting to veraison and the medium or severe treatment was used during post-veraison to harvest, it would facilitate the transportation and accumulation of sugar and improve the fruit quality.

No abstract

Soil burial is a survival strategy for grapevines that can safely overwinter in north-western regions of China. A suitable training system was beneficial for soil burial to provide winter protection. Moreover, the training system can also significantly affect fruit quality during the development of grape berries, such as primary and secondary metabolites. In this study, four-year-old Cabernet Gernischt grapevines were used as experimental material and exposed to four training systems, including the Ningxia traditional vertical trunk (control, CK); the gobelet (T1); single guyot (T2); slant trunk with vertical shoot positioning (STVSP) (T3). The results showed that total soluble solid total phenol content was 12.69%, 57% higher under T3 training systems than in the control, and T3 alleviated the canopy density, leading to improving the leaf photosynthetic efficiency gas chromatography-mass spectrometry (GC-MS) assay used to detect the aroma compounds. The results indicated that the T3 training system enhanced the accumulation of alcohols, carbonyl compounds, C6/C9 and esters, which account for the largest proportion of volatile compounds, and the qRT-PCR reveals that VvEcar, Vvter, VvCCD1, and VvLis were raised under T3 at the transcriptional level. Moreover, T3 contributes to most free amino acid synthesis. Additionally, the PCA reveals the correlation of free amino acids under four training systems, which reflected the mostly amino acid related to T3, and thus, we could speculate that T3 enhances the overall aroma. These results may lead to new strategies to select a new, short trunk training system to achieve mechanized buried soil, to prevent cold and produce high-quality wine in this area.