Zhumei Xi

The ameliorative effects of exogenous melatonin on grape cuttings under water-deficient stress: antioxidant metabolites, leaf anatomy, and chloroplast morphology

Grapes are an important economic crop and are widely cultivated around the world. Most grapes are grown in arid or semi‐arid regions, and droughts take a heavy toll in grape and wine production areas. Developing effective drought‐resistant cultivation measures is a priority for viticulture. Melatonin, an indoleamine, mediates many physiological processes in plants. Herein, we examined whether exogenously applied melatonin could improve the resistance of wine grape seedlings grown from cuttings to polyethylene glycol‐induced water‐deficient stress. The application of 10% polyethylene glycol (PEG) markedly inhibited the growth of cuttings, caused oxidative stress and damage from H2O2 and O2∙− , and reduced the potential efficiency of Photosystem II and the amount of chlorophyll. Application of melatonin partially alleviated the oxidative injury to cuttings, slowed the decline in the potential efficiency of Photosystem II, and limited the effects on leaf thickness, spongy tissue, and stoma size after application of PEG. Melatonin treatment also helped preserve the internal lamellar system of chloroplasts and alleviated the ultrastructural damage induced by drought stress. This ameliorating effect may be ascribed to the enhanced activity of antioxidant enzymes, increased levels of nonenzymatic antioxidants, and increased amount of osmoprotectants (free proline). We conclude that the application of melatonin to wine grapes is effective in reducing drought stress.

Regulating the secondary metabolism in grape berry using exogenous 24-epibrassinolide for enhanced phenolics content and antioxidant capacity

The objective of this study is to investigate the influence of application of exogenous 24-epibrassinolide (EBR) on the antioxidant capacity, anthocyanins and phenolics content of Vitis vinifera grape berry (cvs. Yan 73 and Cabernet Sauvignon). The grapevine clusters were sprayed with 0 (control), 0.10, 0.40, or 0.80 mg/l of 24-epibrassinolide during veraison, respectively. The EBR application increased the activities of phenylalanine ammonia-lyase (PAL) and UDP-glucose: flavonoid 3-O-glucosyltransferase (UFGT), the content of total phenolics, tannins, flavonoids and anthocyanins, individual anthocyanins and the antioxidant capacity of matured grape skins in both varieties. The application also increased the content of flavonoids and anthocyanins in Yan73 pulp. Compared to the other treatments, the treatment of EBR at 0.40 mg/l had significantly higher level than the control in all above assays. Our results indicated that the exogenous EBR treatment can significantly promote grape ripening and enhance anthocyanins and other phenolics contents and antioxidant capacity in the grape skin.

Brassinosteroids Regulate Anthocyanin Biosynthesis in the Ripening of Grape Berries

Anthocyanins are important components in the skins of grapes and in the development of wine colour. Various environmental factors cause poor coloration in some areas, even for the same cultivars planted in different production areas. The objective of this study was to evaluate the effect of exogenous brassinosteroids (BR) on the accumulation of anthocyanins and gene expression of anthocyanin biosynthesis in wine grape berry skins. The results show that total anthocyanin content in BR-treated grapes was higher than that in the control (CT) grapes, and that 0.4 mg/L was the most effective treatment concentration. The effect of BR on downstream genes was more effective than that on upstream genes. Full coloration of BR-treated grapes was achieved seven days earlier than in the case of CT. Moreover, BR enhanced the transcript level of the downstream genes of anthocyanin biosynthesis, which caused the total anthocyanin content to increase. The induction of structural and regulatory genes of the flavonoid pathway suggests that the interrelationships between developmental and environmental signalling pathways were magnified by BR treatment, which actively promoted fruit coloration, namely anthocyanin biosynthesis.

Promoting Effect of Foliage Sprayed Zinc Sulfate on Accumulation of Sugar and Phenolics in Berries of Vitis vinifera cv. Merlot Growing on Zinc Deficient Soil

The effect of foliage sprayed zinc sulfate on berry development of Vitis vinifera cv. Merlot growing on arid zone Zn-deficient soils was investigated over two consecutive seasons, 2013 and 2014. Initial zinc concentration in soil and vines, photosynthesis at three berry developmental stages, berry weight, content of total soluble solids, titratable acidity, phenolics and expression of phenolics biosynthetic pathway genes throughout the stages were measured. Foliage sprayed zinc sulfate showed promoting effects on photosynthesis and berry development of vines and the promotion mainly occurred from veraison to maturation. Zn treatments enhanced the accumulation of total soluble solids, total phenols, flavonoids, flavanols, tannins and anthocyanins in berry skin, decreasing the concentration of titratable acidity. Furthermore, foliage sprayed zinc sulfate could significantly influence the expression of phenolics biosynthetic pathway genes throughout berry development, and the results of expression analysis supported the promotion of Zn treatments on phenolics accumulation. This research is the first comprehensive and detailed study about the effect of foliage sprayed Zn fertilizer on grape berry development, phenolics accumulation and gene expression in berry skin, providing a basis for improving the quality of grape and wine in Zn-deficient areas.

Melatonin treatment of pre-veraison grape berries to increase size and synchronicity of berries and modify wine aroma components.

A comprehensive investigation was carried out to determine the effect of exogenous melatonin treatment of pre-veraison grapes on grape berries and its wines. Two melatonin treatments of pre-veraison grape berries increased the weight of the berries by approximately 6.6%. Meanwhile, this melatonin treatment could be beneficial in the reduction of underripe and overripe fruits and in enhancing the synchronicity of the berries. In addition, there were significant differences in the volatile compound composition between the wine produced from the melatonin-treated berries and the wines made from untreated berries. The wine from melatonin-treated pre-veraison grape berries had stronger fruity, spicy, and sweet sensory properties, compared to the wines made from untreated berries. Prolonging the treatment through repeated applications can enhance these effects and under different seasonal conditions, more pronounced effects on the grape quality and wine properties can be observed.

Influence of Fermentation Method on Phenolics, Antioxidant Capacity, and Volatiles in Blackberry Wines

The influence of the type of fermentation method on phenolics, antioxidant capacity, and volatiles in blackberry wine was studied. Dry blackberry wines made by traditional fermentation (TF) and carbonic maceration fermentation (CMF) were analyzed for total polyphenols, flavanols, flavonoids, anthocyanins, proanthocyanidin, and antioxidant capacity. High-performance liquid chromatography was used for analysis of nonflavonoid phenolics (gallic, benzoic, salicylic, syringic, caffeic, coumaric, and ferulic) and flavonoids (catechin, quercetin, and rutin). Volatiles were detected by gas chromatography-mass spectrometry. The results showed that CMF fermentation afforded higher antioxidant activity and phenolic content, especially individual polyphenolics. The total level of phenolics in the CMF wine was substantially higher than in traditional wines: 2953 mg of gallic acid equivalents (GAE)/L for CMF wine vs. 1647 mg of GAE/L for traditional wine. A total of 53 kinds of volatile compounds were detected. Of these, 35 were detected in traditionally brewed wine and 46 in CMF fermented wine. Thus, CMF wine had a more complement volatile profile. The dominance of fruity and floral odor components derived from ethyl esters of fatty acids resulted in the indistinguishable aroma of TF and CMF wines. But, CMF wine had a more complicated aroma. The present results could complement existing theory on the processing of blackberry wines.

Exogenously applied abscisic acid to Yan73 (V. vinifera) grapes enhances phenolic content and antioxidant capacity of its wine

Yan73 is a ‘teinturier’ red wine variety cultivated in China and widely used in winemaking to strengthen red wine colour. The objective of this study was to evaluate the effect of exogenous abscisic acid (ABA) applied to the grapevine cluster on the antioxidant capacity and phenolic content of the wine made from Yan73. Two hundred mg/l ABA was applied on Yan73 grapevine cluster during veraison. As they mature, these ABA-treated and untreated grape berries were transformed into wines, respectively, and the phenolic content and antioxidant capacity of these wines were compared. The results showed that phenolic content (total phenolics, tannins, flavonoids and anthocyanins) and antioxidant capacity were higher in the wine produced with ABA-treated Yan73 grapes than those in the wine from untreated grapes. Compared to Cabernet Sauvignon wine, Yan73 wine had higher phenolic content and stronger antioxidant capacity. These strongly suggest that exogenously applied ABA to Yan73 grapes can enhance phenolic content and antioxidant capacity of its wine, and Yan73 wine has the higher utilization value and potential for development.

Tissue- Specific Expression Analysis of Anthocyanin Biosynthetic Genes in White- and Red-Fleshed Grape Cultivars

Yan73, a teinturier (dyer) grape variety in China, is one of the few Vitis vinifera cultivars with red-coloured berry flesh. To examine the tissue-specific expression of genes associated with berry colour in Yan73, we analysed the differential accumulation of anthocyanins in the skin and flesh tissues of two red-skinned grape varieties with either red (Yan73) or white flesh (Muscat Hamburg) based on HPLC-MS analysis, as well as the differential expression of 18 anthocyanin biosynthesis genes in both varieties by quantitative RT-PCR. The results revealed that the transcripts of GST, OMT, AM3, CHS3, UFGT, MYBA1, F3′5′H, F3H1 and LDOX were barely detectable in the white flesh of Muscat Hamburg. In particular, GST, OMT, AM3, CHS3 and F3H1 showed approximately 50-fold downregulation in the white flesh of Muscat Hamburg compared to the red flesh of Yan73. A correlation analysis between the accumulation of different types of anthocyanins and gene expression indicated that the cumulative expression of GST, F3′5′H, LDOX and MYBA1 was more closely associated with the acylated anthocyanins and the 3′5′-OH anthocyanins, while OMT and AM3 were more closely associated with the total anthocyanins and methoxylated anthocyanins. Therefore, the transcripts of OMT, AM3, GST, F3′5′H, LDOX and MYBA1 explained most of the variation in the amount and composition of anthocyanins in skin and flesh of Yan73. The data suggest that the specific localization of anthocyanins in the flesh tissue of Yan73 is most likely due to the tissue-specific expression of OMT, AM3, GST, F3′5′H, LDOX and MYBA1 in the flesh.

Comparing the effects of exogenous abscisic acid on the phenolic composition of Yan 73 and Cabernet Sauvignon (Vitis vinifera L.) wines

Phenolic compounds from red wines exert a strong influence on wine quality. Abscisic acid (ABA) is essential for the physiological and biochemical function of plants, but few investigators have thoroughly researched its effects on phenolic compounds in dyer grape varieties. The effects of exogenous ABA treatment on the phenolic composition and individual anthocyanin and non-anthocyanin phenolic contents of Yan 73 and Cabernet Sauvignon wines from the ABA-treated grapes, including anthocyanins, flavan-3-ols, flavonols, phenolic acids, and stilbenes were compared. The phenolic compounds in the Yan 73 wine were different from those in the Cabernet Sauvignon wine. The phenolic content (anthocyanins and non-anthocyanins) of the Yan 73 wine was significantly higher than that of the Cabernet Sauvignon wine. The concentrations of the individual phenolic compounds were enhanced by the ABA treatment for the two different wine varieties. The effects on the compositions varied, a similar trend was observed for the ratios of Cy-derivative and Dp-derivative pigments from the two wine varieties, and all non-acylated pigments were enhanced. The stilbene content was enhanced, the ratios of flavan-3-ol dimers and dimer-glucosides were reduced, and the effects on the composition of other compounds varied between the two grape varieties.

Iron Supply Affects Anthocyanin Content and Related Gene Expression in Berries of Vitis vinifera cv. Cabernet Sauvignon

Anthocyanins are important compounds for red grape and red wine quality, and can be influenced by supply of nutrients such as nitrogen, phosphorus, potassium, zinc, and iron. The present work aims to gain a better understanding of the effect of iron supply on anthocyanins concentration in grape berries. To this end, own-rooted four-year-old Cabernet Sauvignon grapevines (Vitis vinifera) were fertigated every three days with 0, 23, 46, 92, and 184 μM iron (Fe) from ferric ethylenediamine di (o-hydroxyphenylacetic) acid (Fe-EDDHA) in a complete nutrient solution. Fe deficiency or excess generally led to higher concentrations of titratable acidity and skin/berry ratio, and to lower reducing sugar content, sugar/acid ratio, pH, berry weight, and concentration of anthocyanins. Most of the individual anthocyanins detected in this study, except cyanidin-3-O-glucoside, delphinidin-3-O-glucoside, and cyanidin-3-O-(6-O-coumaryl)-glucoside, in moderate Fe treatment (46 μM) grapes were significantly higher than those of other treatments. Genes encoding chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), leucoanthocyanidin dioxygenase (LDOX), and anthocyanin O-methyltransferase (AOMT) exhibited higher transcript levels in berries from plants cultivated with 46 μM Fe compared to the ones cultivated with other Fe concentrations. We suggest that grape sugar content, anthocyanins content, and transcriptions of genes involved in anthocyanin biosynthesis were correlated with Fe supply concentrations.