Effects of Table Grape Cultivars on Fruit Quality and Aroma Components.

The basic physical and chemical qualities, nutrition, aroma components, and sensory evaluation of 17 varieties of table grapes were studied. The quality evaluation system of different table grape varieties was preliminarily determined. Our results show that the soluble solid content in Ruby Seedless was 21.17%, which was higher than that of other varieties. The black varieties Aishenmeigui and Sweet Sapphire had the highest total phenol content. Aishenmeigui had high levels of tannin and vitamin C. In addition, the aroma contents in Meixiangbao, Ruby Seedless, and Shine-Muscat were higher than those in other varieties. Manicure Finger and Ruby Seedless had higher levels of C6 compounds. Moreover, the "Kyoho" series of grape Meixiangbao, Sunmmer Black, Jumeigui, Hutai 8 hao, and Black Beet were high in ester content, while Muscat varieties, including Zaoheibao, Aishenmeigui, Jumeigui, and Shine-Muscat were rich in terpene substances. Ruby Seedless, Shine-Muscat, and Heibaladuo had higher comprehensive scores in sensory evaluation. Hence, the comprehensive quality of Shine-Muscat, Ruby Seedless, and Aishenmeigui was better. These results may serve as references for determining the quality differences between table grape varieties.

Physiological and transcriptomic analysis of Cabernet Sauvginon (Vitis vinifera L.) reveals the alleviating effect of exogenous strigolactones on the response of grapevine to drought stress.

Drought stress can significantly affect the growth and yield of grapevine. The application of exogenous strigolactone can relieve the drought symptoms of grapevine; however, little is known about the transcription levels in grapevine under drought stress following exogenous strigolactone application. The mitigative effect of exogenous strigolactone on grapevine leaves under drought stress was studied by transcriptome analysis based on RNA sequencing. On the 10th day of drought stress, the strigolactone treatment group had a higher relative water content and lower electrical conductivity, which significantly alleviated the drought damage. Compared to the drought (D) group, a total of 5955 differentially expressed genes (DEGs) (2966 up-regulated genes and 2989 down-regulated genes) were detected in the exogenous strigolactone (DG) groups. Based on Gene Ontology analysis, the DEGs in the D and DG treatments were enriched in the processes of photosynthesis and organic acid catabolism. Pathway analysis showed that the DEGs in the D and DG treatments were enriched in carbon metabolism, ribosome, starch and sucrose metabolism, flavonoid biosynthesis, and circadian rhythm. Additionally, in the DG group, the antioxidant enzyme genes of CAT1, GSHPX1, GSHPX2, POD42, APX6, and SODCP were up-regulated, two NAC, three WRKY, and four MYB transcription factor genes were down-regulated, and the key gene of strigolactone synthesis D14 was up-regulated, compared with that in the D group. The results provide a new perspective for studying the adaptation of plants to drought stress.

Anthocyanin and Phenolic Acids Contents Influence the Color Stability and Antioxidant Capacity of Wine Treated With Mannoprotein.

Wine is consumed by humans worldwide, but the functional components are lost and the color changes during its production. Here, we studied the effects of mannoprotein (MP) addition (0, 0.1, and 0.3 g/L) upon crushing and storage. We measured anthocyanins, phenolic acids profiles, color characteristics, and antioxidant activities of wine. The results showed that the addition of MP before fermentation significantly increased the total phenolic content (TPC), total anthocyanin content, total tannin content (TTC), total flavonoid content, and total flavanol content in wine, whereas the addition of MP during storage had the opposite effect. The addition of MP before alcohol fermentation significantly increased the amount of individual anthocyanins and individual phenolic acids, maintained the color, and increased the antioxidant capacity of wine. In addition, the addition of 0.3 g/L MP during storage increased the content of individual phenolic acids and TPC of wine. However, the addition of 0.1 g/L MP during storage significantly reduced the TPC, TAC, TTC, and individual anthocyanin content (except for malvidin-3-glucoside and malvidin-3-acetly-glucoside); meanwhile, the treatment attenuated the color stability and antioxidant capacity of wine. The results demonstrated that the addition of MP before alcohol fermentation could increase the functional components and improve the color stability and antioxidant capacity of wine.

The condensed tannin chemistry and astringency properties of fifteen Vitis davidii Foex grapes and wines.

This study sought to determine the effects of variety on the astringency and chemistry of condensed tannins of spine grapes and wines. Fifteen varieties of red spine grape (Vitis davidii Foex) were used. Condensed tannin content, composition, and wine astringency were determined. The condensed tannin profiles were assessed by high-performance liquid chromatography coupled with diode array detector (HPLC-DAD). The condensed tannin content highly depended on the variety ranging from 0.30 mg/g to 7.80 mg/g (in skins), from 3.12 mg/g to 8.82 mg/g (in seeds), and from 62.60 mg/L to 225.90 mg/L (in wines). There were significant differences in proportions of certain constitutive subunits (as mole%) and mean degree of polymerization (mDp) among the varieties. Correlation analysis revealed that condensed tannin concentration and composition had a significant effect on the sensory evaluation and quantitative analysis of astringency. A positive correlation between mDp and astringency was also observed. The present results expand knowledge of the characterization of spine grape and wine condensed tannin chemistry and astringency.

Targeted Metabolomic and Transcript Level Analysis Reveals Quality Characteristic of Chinese Wild Grapes (Vitis davidii Foex).

Native to China, spine grapes (Vitis davidii Foex) are an important wild grape species. Here, the quality characteristics of one white and three red spine grape clones were evaluated via targeted metabolomic and transcription level analysis. Xiangzhenzhu (XZZ) had the highest soluble sugar and organic acid content. Malvidin-3-acetyl-glucoside and cyanidin-3-glucoside were the characteristic anthocyanins in spine grapes, and significant differences in anthocyanin composition between different clones were detected. Anthocyanins were not detected in Baiyu (BY) grapes. The transcript levels of VdGST, VdF3'H, VdOMT, VdLDOX, and VdUFGT were significantly related to the anthocyanin biosynthesis and proportions. A total of 27 kinds of glycosidically bound volatiles (including alcohols, monoterpenes, esters, aldehydes, ketones, and phenolic acid) were identified in spine grapes, with Gaoshan #4 (G4) and BY grapes having the highest concentrations. The VdGT expression levels were closely related to glycosidically bound volatile concentrations. These results increase our understanding of the quality of wild spine grapes and further promote the development and use of wild grape resources.

Overexpression of grapevine VvNAC08 enhances drought tolerance in transgenic Arabidopsis.

NAC [No apical meristem (NAM), Arabidopsis transcription activation factor (ATAF), Cup-shaped cotyledon (CUC)] transcription factors (TFs) play an important role in plant growth and response to various environmental stress. Drought stress is the primary factor limiting the growth and fruit quality of grapevines worldwide. However, the biological function of the NAC family members in grapevine is not clear. In this study, we reported that VvNAC08, a novel NAC transcription factor gene, was expressed after drought, salicylic acid (SA) and abscisic acid (ABA), jasmonic acid (JA) and melatonin (MT) treatments in grapevine. VvNAC08 was expressed in various tissues. The open reading frame (ORF) of VvNAC08 was 792 bp, encoding 263 amino acids. The VvNAC08 protein could bind to NACRS [CGTA/CACG] in yeast. When subjected to drought and dehydration stress, VvNAC08-overexpression (OE) Arabidopsis had a higher survival rate and a lower water loss rate than wild type (WT) plants. Under drought conditions, transgenic Arabidopsis overexpressing VvNAC08 had a lower malondialdehyde (MDA), H2O2 contents, but a higher peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) activities as well as more proline content. Moreover, the expressions of marker genes, including ABI5, AREB1, COR15A, COR47, P5CS, RD22, and RD29A, were up-regulated in VvNAC08-overexpression lines when subjected to drought treatments. The results suggest that the transgenic Arabidopsis overexpressing VvNAC08 enhances resistance to drought while up-regulating the expressions of ABA- and stress-related genes.

VvNAC17, a novel stress-responsive grapevine (Vitis vinifera L.) NAC transcription factor, increases sensitivity to abscisic acid and enhances salinity, freezing, and drought tolerance in transgenic Arabidopsis.

Drought stress is the primary factor limiting the growth and fruit quality of grapevines worldwide. However, the biological function of the NAC [No apical meristem (NAM), Arabidopsis transcription activation factor (ATAF), Cup-shaped cotyledon (CUC)] transcription factor (TF) in grapevine is not clear. In this study, we reported that VvNAC17, a novel NAC transcription factor, was expressed in various tissues following drought, high temperature (45 °C), freezing (4 °C), salicylic acid (SA), and abscisic acid (ABA) treatments in grapevine. The VvNAC17 protein was localized in the nucleus of Arabidopsis thaliana protoplasts and demonstrated transcriptional activation activities at its C-terminus in yeast. The VvNAC17 gene was overexpressed in Arabidopsis thaliana. Under mannitol and salt stress, the germination rates of the VvNAC17-overexpression lines were higher than those of the wild-type plants, as were the root lengths. The VvNAC17-overexpression lines showed greater tolerance to freezing stress along with a higher survival rate. Following ABA treatment, the seed germination rate and the root length of the VvNAC17-overexpression lines were inhibited, and the stomatal opening and stomatal density were reduced. When subjected to drought and dehydration stress, the VvNAC17-overexpression lines showed improved survival and reduced water loss rates in comparison to the wild-type plants. Under drought conditions, the VvNAC17-overexpression lines had lower malondialdehyde and H2O2 contents, but higher peroxidase, superoxide dismutase, and catalase activities as well as higher proline content. Moreover, the expression of marker genes, including ABI5, AREB1, COR15A, COR47, P5CS, RD22, and RD29A, was up-regulated in the VvNAC17-overexpression lines when subjected to ABA and drought treatments. The results suggest that in transgenic Arabidopsis over-expression of VvNAC17 enhances resistance to drought while up-regulating the expression of ABA- and stress-related genes.

Anthocyanin accumulation and biosynthesis are modulated by regulated deficit irrigation in Cabernet Sauvignon (Vitis Vinifera L.) grapes and wines.

Anthocyanins contents and compositions play an important role in grape berries and wines. Grapevines are widely cultivated in arid and semi-arid areas, and water shortage restricts the development of wine industry. The aim of this work was to gain insight on the effect of regulated deficit irrigation (RDI) on the accumulation and biosynthesis of anthocyanins in Cabernet Sauvignon (Vitis Vinifera L.) grapes and wines. High-performance liquid chromatography (HPLC) was used for anthocyanins profiles analyses and real-time quantitative PCR (qRT-PCR) was used for the genes expressions measurement. The grapevines were treated with 60% (RDI-1), 70% (RDI-2), 80% (RDI-3), 100% (CK, traditional drip irrigation) of their estimated evapotranspiration (ETc) respectively. RDI treatments significantly reduced titration acid and increased pH with higher total soluble solids. RDI-1 treatment increased total anthocyanins contents in berries and wines in both two vintages. RDI-1 and RDI-2 treatments significantly increased the contents of acylated anthocyanins in berries and wines, especially Malvidin-3-acetly-glucoside. RDI treatments significantly increased non-acylated anthocyanins contents in wines, such as Delphinidin-3-gliucoside and Malvidin-3-glucoside. RDI treatments upregulated the expressions of VvPAL, VvC4H, VvCHS, VvF3'H, VvF3'5'H, VvLDOX, and VvOMT in both two vintages. Correlation analysis showed the accumulation of anthocyanins was closely related to the key genes expressions, including VvPAL, VvF3'H, VvF3'5'H etc. The present results provided direct evidence and detailed data to explain that RDI treatments regulated the accumulation of anthocyanins by regulating genes expressions in the anthocyanin synthesis pathway.

Physiological, micro-morphological and metabolomic analysis of grapevine (Vitis vinifera L.) leaf of plants under water stress.

Grapes are one of the most important fruits because of their economic and nutritional benefits, and grapevines are widely cultivated in arid and semi-arid areas. Therefore, it is critical to study the mechanism by which grapevines respond to water stress. In this research, micro-morphological and metabolomic analyses were conducted to evaluate the effects of water stress on stomatal morphology and volatile compounds extracted from the leaves of grapevine plants. There were two treatments: well-watered plants (watered daily) and drought-stressed plants (no irrigation). Plant weights were recorded, and the well-watered plants were irrigated daily to replace the water lost to evapotranspiration. The water status of the grapevines was determined according to their relative water content. The changes in proline content, hydrogen peroxide content, lipid peroxidation and antioxidant activities, as well as those of photosynthetic parameters and chlorophyll fluorescence, were monitored as markers of water stress. The microscopic changes in stomatal behavior were observed using a scanning electron microscope. A total of 12 secondary volatile compounds, including aldehydes, ketones and alcohols, were detected in the grapevine leaves. Among them, (E)-2-hexenal and 3-hexenal showed a significant increase after water stress. Multivariate statistical analysis revealed that the levels of 3-hexenal and (E)-2-hexenal were closely related to the changes in proline, hydrogen peroxide (H2O2), malondialdehyde (MDA), catalase (CAT) and superoxide dismutase (SOD). These results suggested that water stress could regulate the accumulation of green leaf volatiles, especially (E)-2-hexenal and 3-hexenal, in coordination with the reactive oxygen species (ROS) scavenging system. These compounds may act as signaling compounds in response to water stress in grapevines.

Effects of Regulated Deficit Irrigation on Amino Acid Profiles and Their Derived Volatile Compounds in Cabernet Sauvignon (Vitis vinifera L.) Grapes and Wines.

Amino acid contents and their derived volatile compositions in Cabernet Sauvignon grapes and wines after regulated deficit irrigation (RDI) were investigated during the 2015 and 2016 growing seasons in Yinchuan (NingXia, China). High-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) were used for amino acid and volatile compound analyses. Three RDI strategies were tested: 60% (RDI-1), 70% (RDI-2), and 80% (RDI-3) of grapevine estimated evapotranspiration (ETc), and 100% ETc was used as the control group (CK). RDI-treated vines had lower yields and berry weights with higher total soluble solids than the control treatment. RDI-1 increased proline levels in berries and wines. RDI-2 enhanced tyrosine and asparagine levels in wines. RDI-3 enhanced arginine, alanine, valine, leucine, and isoleucine levels in berries and wines. RDI-2 and RDI-3 increased the concentrations of 2-methyl-1-butyl acetate, benzaldehyde, 3-methyl-1-pentanol, and 3-methyl-1-butanol in wines. The accumulation of volatile compounds was closely related to the amino acid concentrations-especially isoleucine, valine, and leucine-in grapes. Our results showed that RDI treatments altered amino acid concentrations and their derived volatile compositions in wines.

Effect of regulated deficit irrigation on fatty acids and their derived volatiles in 'Cabernet Sauvignon' grapes and wines of Ningxia, China.

The effect of regulated deficit irrigation (RDI) on fatty acids and their derived volatiles in 'Cabernet Sauvignon' grapes and wines was investigated during two growing seasons in the east foot of Mt. Helan, the semi-arid area. The vines received water with 60% (RDI-1), 70% (RDI-2), 80% (RDI-3), 100% (CK, traditional drip irrigation) of their estimated evapotranspiration (ETc) respectively. RDI treatments resulted in lower yield, berry weight and titratable acidity with higher total soluble solids. RDI-1 increased the content of unsaturated fatty acids in berries and decreased the level of alcohols and esters volatiles in wines. RDI-2 and RDI-3 enhanced 1-hexanol and esters in wines in comparison with CK. The concentrations of C6 aroma compounds were closely correlated with unsaturated fatty acids (p < .05), especially linolenic acid and linoleic acid. The present results provided direct evidence and detailed data to explain the effect of RDI on grapes and wines composition regarding fatty acids and their derived volatiles.

Effect of Exogenous Abscisic Acid and Methyl Jasmonate on Anthocyanin Composition, Fatty Acids, and Volatile Compounds of Cabernet Sauvignon (Vitis vinifera L.) Grape Berries.

The anthocyanin composition, fatty acids, and volatile aromas are important for Cabernet Sauvignon grape quality. This study evaluated the effect of exogenous abscisic acid (ABA) and methyl jasmonate (MeJA) on the anthocyanin composition, fatty acids, lipoxygenase activity, and the volatile compounds of Cabernet Sauvignon grape berries. Exogenous ABA and MeJA improved the content of total anthocyanins (TAC) and individual anthocyanins. Lipoxygenase (LOX) activity also increased after treatment. Furthermore, 16 fatty acids were detected. The linoleic acid concentration gradually increased with ABA concentration. The fatty acid content decreased with increasing MeJA concentration and then increased again, with the exception of linoleic acid. After exogenous ABA and MeJA treatment, the C6 aroma content increased significantly. Interestingly, the exogenous ABA and MeJA treatments improved mainly the content of 1-hexanol, hexanal, and 2-heptanol. These results provide insight into the effect of plant hormones on wine grapes, which is useful for grape quality improvement.