Berry Skin Research Articles

Electrical Stimulation as a Potential Technique for Enlarging Table Grape Berry Size by Enhancing Cell Division

Enlarging table grape berry size enhances commercial value. The texture and feel of large berries broken down in the mouth are important considerations for consumer purchase in East Asia. We report herein that electrical stimulation enlarges table grape berry size by enhancing cell division. Two field-grown grapevines cultivated in Yamanashi Prefecture, Japan, Shine Muscat and Pione, were exposed to electrical stimulation in two growing seasons using a solar panel from budbreak to harvest. Soluble solids content and total acid content in berries exposed to electrical stimulation were similar to those in untreated grapevines (control), whereas grapevines exposed to electrical stimulation had enlarged berry size irrespective of cultivar. Microscopic analysis of berry skins demonstrated that cell number per unit area of skin epidermis in grapevines exposed to electrical stimulation was higher than that of the control, suggesting that electrical stimulation enlarged berry size by enhancing cell division, but not cell elongation. This suggestion was supported by gene expression profiling of grape cultured cells exposed to electrical stimulation. Electrical stimulation upregulated the transcription of kinesin-like protein <i>KIN-5C</i> and nuclear pore complex protein <i>NUP88</i>, which regulate the cell cycle and cytokinesis, respectively, but not expansins, which play a role in plant cell elongation. One of the merits of exposing grapevine to electrical stimulation is that the electrical stimulation may reduce labor hours and load compared with other techniques, such as irrigation and girdling for berry enlargement. These findings could help in the development of a novel and innovative viticultural technique to enhance the commercial value of table grapes.

Differential Protein Expression in Berry Skin from Red Grapes with Varying Hybrid Character.

Protein expression from the berry skin of four red grape biotypes with varying hybrid character was compared at a proteome-wide level to identify the metabolic pathways underlying divergent patterns of secondary metabolites. A bottom-up shotgun proteomics approach with label-free quantification and MaxQuant-assisted computational analysis was applied. Red grapes were from (i) purebred Vitis vinifera (Aglianico cv.); (ii) V. vinifera (local Sciascinoso cv.) grafted onto an American rootstock; (iii) interspecific hybrid (V. vinifera × V. labrusca, Isabel), and (iv) uncharacterized grape genotype with hybrid lineage, producing relatively abundant anthocyanidin 3,5-O-diglucosides. Proteomics supported the differences between hybrids and purebred V. vinifera grapes, consistently with distinct phenotypic metabolite assets. Methanol O-anthraniloyltransferase, which catalyses the synthesis of methyl anthranilate, primarily responsible for the “foxy” odour, was exclusive of the Isabel hybrid grape. Most of the proteins with different expression profiles converged into coordinated biosynthetic networks of primary metabolism, while many possible enzymes of secondary metabolism pathways, including 5-glucosyltransferases expected for hybrid grapes, remained unassigned due to incomplete protein annotation for the Vitis genus. Minor differences of protein expression distinguished V. vinifera scion grafted onto American rootstocks from purebred V. vinifera skin grapes, supporting a slight influence of the rootstock on the grape metabolism.

Application of abscisic acid (S-ABA) at different stages of ripening on color development of ‘Rubi’ table grape

The color of the berries is an important aspect of the quality of table grapes and crucial for marketing. The ‘Rubi’ table grapes grown in the subtropical climate generally lack color intensity due to the inhibition of anthocyanins by high temperatures during ripening. The exogenous application of abscisic acid (S-ABA) can be used to overcome this problem as the accumulation of anthocyanins in the berry skin is regulated by this plant growth regulator. The objective of this study was to assess the effect of the exogenous application of S-ABA at different stages of ripening on color development in ‘Rubi’ table grapes using the soluble solids (SS) content as a marker of ripening. The study was conducted during two seasons in commercial vineyards. The first trial was conducted in Marialva, Parana, Brazil, during the 2019 summer season crop (harvest in December). S-ABA (400 mg L-1) was exogenously applied at different stages of ripening of ‘Rubi’ table grapes (determined by the SS content of the berries): control (without application); SS = 8-9 ºBrix; SS = 10-11 ºBrix; SS = 8-9 ºBrix (two applications; the second one applied 10 days after the first); and SS = 10-11 ºBrix (two applications; the second one applied 10 days after the first). The second trial was conducted in Cambira, Parana, Brazil, during the 2020 off-season crop (harvest in May). S-ABA (400 mg L-1) was exogenously applied at different stages of ripening of ‘Rubi’ grapes: control (without application); SS = 6-7 ºBrix; SS = 7-8 ºBrix; SS = 9-10 ºBrix; SS = 6-7 ºBrix (two applications; the second one applied 14 days after the first); SS = 7-8 ºBrix (two applications; the second one applied 14 days after the first); and SS = 9-10 ºBrix (two applications; the second one applied 14 days after the first). A randomized block design was used as the statistical model with four replications, and each plot consisted of one vine. The variables analyzed were total anthocyanin contents, color index (CIRG), and color attributes (L*, C*, h°, and ΔE) of berry skin. The total anthocyanin accumulation and color attributes of the berries were evaluated every 10 and 7 days after the first application of S-ABA until harvest in the first and second trials, respectively, and the other variables were evaluated at harvest. In the summer-season crop, when the SS content was 8-11 ºBrix, the application of S-ABA increased the concentration of the total anthocyanins 4 times compared to that in the control, improving berry color development. Furthermore, in the off-season crop, when the SS content was 6-10 ºBrix, the application of S-ABA increased the concentration of total anthocyanins 2-3 times compared to that in the control, improving the color attributes of berries. In both crops, a single application of the plant growth regulator was sufficient to intensify the color of the berries.

Grafting with rootstocks promotes phenolic compound accumulation in grape berry skin during development based on integrative multi-omics analysis.

In viticulture, grafting has been practiced widely and influences grape development as well as berry and wine quality. However, there is limited understanding of the effects of rootstocks on grape phenolic compounds, which are located primarily in the berry skin and contribute to certain sensory attributes of wine. In this study, scion–rootstock interactions were investigated at the green-berry stage and the veraison stage when grapevines were hetero-grafted with three commonly used rootstock genotypes (5BB, 101-14MG, and SO4). Physiological investigations showed that hetero-grafts, especially CS/5BB, contained higher concentrations of total proanthocyanidins (PAs) and various PA components in berry skins compared with the auto-grafted grapevines. Further metabolomics analysis identified 105 differentially accumulated flavonoid compounds, the majority of which, including anthocyanins, PAs, and flavonols, were significantly increased in the berry skins of hetero-grafted grapevines compared with auto-grafted controls. In addition, transcriptomic analysis of the same samples identified several thousand differentially expressed genes between hetero-grafted and auto-grafted vines. The three rootstocks not only increased the transcript levels of stilbene, anthocyanin, PA, and flavonol synthesis genes but also affected the expression of numerous transcription factor genes. Taken together, our results suggest that hetero-grafting can promote phenolic compound accumulation in grape berry skin during development. These findings provide new insights for improving the application value of grafting by enhancing the accumulation of nutritious phenolic components in grape.

Systematic analysis reveals O-methyltransferase gene family members involved in flavonoid biosynthesis in grape

O-methyltransferases (OMTs) are an important group of enzymes involved in the methylation of various secondary metabolites, including flavonoids. However, the features and functions of OMTs have not been comprehensively studied in grape (Vitis vinifera), a rich source of methylated flavonoids. Here, 47 OMT members were identified in grape genome. They were unevenly distributed on grape chromosomes and some genes were tandem duplicated, indicating the role of duplication processes in the expansion of this gene family. Based on the phylogenetic relationship, these OMTs were clustered into CCoAOMT and COMT subclades, which were further supported by the results of conserved motif and gene structure analysis. Correlation analysis revealed that three members (VvCCoAOMT1, VvCCoAOMT4, and VvCOMT1) were potentially involved in the synthesis of most methylated flavonoids in the berry skins. Expression profiling based on RNA-seq data and qRT-PCR experiments indicated that VvCCoAOMT1 and VvCCoAOMT4 had specific and high expression in berry skins, and responded to abscisic acid and high temperature treatments; and that VvCOMT1 expression was significantly induced during berry development and UVC treatment. Cis-regulatory element analysis suggested important roles of OMTs in growth, development, and defense against stresses. We further demonstrated the transcriptional regulation of VvCCoAOMT4 by VvMYBA1, a master regulator of grape berry anthocyanin, and verified the protein localization of VvCCoAOMT4 in membrane and nucleus. These findings facilitate a better understanding of the characteristics of OMT gene family, especially of the potential members involved in the formation of O-methylated flavonoids in grape.

Difference Between Coloration and Endogenous Abscisic Acid Accumulation Patterns in Two Red Grape Cultivars, ‘Aki Queen’ and ‘Ruby Roman’ (&lt;i&gt;Vitis labruscana&lt;/i&gt; Bailey) Berries

Changes in anthocyanin and endogenous abscisic acid (ABA) contents in the berry skins of Vitis labruscana × V. vinifera cultivars, ‘Aki Queen’, and ‘Ruby Roman’ were investigated during the fruit development period. Color development of ‘Aki Queen’ berries mainly occurred within 20 days post véraison, while that of the ‘Ruby Roman’ was prolonged for about 40 days. In both cultivars, the ABA level in the berry skin started to increase a few days before véraison; however, ABA accumulation ceased approximately 10 days after véraison in ‘Aki Queen’, while it continued until the late stage of maturation in ‘Ruby Roman’. In addition, higher indole-3-acetate aspartate (IAA-Asp) and lower isopentenyladenine (iP) contents were observed in ‘Ruby Roman’ than in ‘Aki Queen’ at the late development stage. The expression analysis of genes involved in ABA metabolism revealed that V. vinifera 9-cis-epoxycarotenoid dioxygenase 3 (VviNCED3), which is assumed to play a major role in ABA biosynthesis, remained relatively higher in ‘Ruby Roman’ than in ‘Aki Queen’ after véraison. Considering that ABA plays a regulatory role in grape maturation, these results may indicate that the coloration of ‘Ruby Roman’ at the later stage of maturation is partly attributable to an increased ABA pool in berry skins.

Gret1 retrotransposon and VvmybA1 gene sequences in somatic mutants of new table grape varieties ‘Brasil’ and –Black Star’ (Vitis vinifera L.).

Somatic mutations in grapes are relatively frequent and associated with diversity in grape skin color and berry morphology. Mutations that occur on a side branch of the ‘Benitaka’ cultivar with rosy-red berry skin color generated the ‘Brasil’ cultivar, and mutations that occurred on a side branch of ‘Brasil’ generated the ‘Black Star’ cultivar, both showing a black color in the berry skin. Therefore, genetic characterization of the Gret1 retrotransposon and the VvmybA1 gene in ‘Italia’, ‘Rubi’, ‘Benitaka’, ‘Brasil’, and ‘Black Star’ was started to find whether the altered coloration of berries in ‘Brasil’ and ‘Black Star’ is a product of different mutation patterns in the investigated sequences. Six primer combinations were used for the amplification of different sequences of the Gret1 retrotransposon and VvmybA1 gene of the five cultivars. Polymerase chain reaction (PCR) of the Gret1 retrotransposon and the VvmybA1 gene and sequencing of the amplified products using six primer combinations showed no different alleles or different nucleotide sequences in ‘Brasil’ and ‘Black Star’. The sequencing of the VvmybA1 gene in the present study showed that the mutations that occurred in the cultivar ‘Italia’ for generating the ‘Benitaka’ cultivar persisted in the ‘Brasil’ and ‘Black Star’ cultivars.

Potential of Entomopathogenic Nematodes for the Control of Plangia graminea (Orthoptera: Tettigoniidae) under Laboratory Conditions

Plangia graminea, locally known as a katydids or “krompokkels”, is a minor pest of vineyards in the Western Cape province of South Africa. Is feed on leaves, and sporadically on the skin of grapevine berries. Under natural conditions, katydids are not of much agricultural importance, but pest outbreaks during favourable conditions can result in significant foliar damage. Observations indicate an increase in katydid abundance and damage intensity in recent years. Currently, no agrochemicals are registered for the control of this species, and its present natural enemies are unlikely to provide sufficient control without augmentation. In this study, 12 entomopathogenic nematode (EPN) species were evaluated against the nymphs of Plangia graminea in laboratory bioassays, and mortality by infection was investigated. Seven locally occurring nematode species achieved significant mortality, with H. zealandica, H. indica, S. jeffreyense and S. yirgalemense being found to perform the best (&gt; 90% mortality).

Influence of abscisic acid,Ascophyllum nodosumandAloe veraon the phenolic composition and color of grape berry and wine of 'Cabernet Sauvignon' variety

In viticulture, various techniques can be used to improve productivity, tolerance to biotic or abiotic stress, the quality of grapes and wines such as the use of plant regulators and biostimulants. Thus, the objective of this work was to evaluate the effect of application of abscisic acid (S-ABA),Ascophyllum nodosum (A. nodosum)seaweed extract andAloe vera (A. vera)gel on phenolic composition and chromatic characteristics of grapes from the 'Cabernet Sauvignon' variety. The experiment was conducted in a commercial vineyard in Campo Largo - Paraná, in two consecutive seasons, 2017/18 and 2018/19, involving the following treatments: 1) control; 2) (S-ABA) 400 mg/L; 3) S- ABA 600 mg/L; 4)A. veragel 200 mL/L; 5)A. veragel 400 mL/L; 6) seaweed extract 0.2 mL/L; 7) seaweed extract 0.4 mL/L. Two applications were performed with the seaweed extract andA.gel when the bunches were atveraisonstage (50 and 75% of grape berries with coloration). Total anthocyanins content, total polyphenols content and activity of phenylalanine ammonia-lyase (PAL), polyphenoloxidase and peroxidase enzymes were assessed in the berries skin. Total anthocyanins, individual anthocyanins and total polyphenol contents as well as lightness, chroma and hue angle were analyzed in the corresponding wines. S-ABA increased the content of anthocyanins and total polyphenols, as well as the activity of PAL in the first season.A. nodosum(AN) seaweed extract increased the total polyphenol content, total anthocyanins content and PAL in the berry skin of 'Cabernet Sauvignon' variety. S-ABA increased the total polyphenol content and anthocyanins in wine, as well as theA. nodosum, in at least one of the evaluated seasons.

Characteristics of newly created grapevine varieties Vozd and Vladun

This paper presents the most important morphological and production-technological characteristics of newly created grapevine varieties Vozd and Vladun, intended for the production of red wines. The newly created varieties were compared with the standard variety Cabernet Sauvignon during the three-year period of testing (2015-2017) in the relation studied properties. The variety Vozd obtained from the crossing combination Zacinak x Prokupac, and the variety Vladun from the crossing combination Merlot x Zupski Bojadiser. The investigated varieties differed considerably in terms of some morphological traits and represents unique genotypes. The newly recognized varieties have a hermaphrodite type of flower, dense bunch, globose berry shape and blue black color of berry skin. The yield, bunch weight, bunch length and bunch width were higher at both varieties than for the standard variety. The Vozd variety had a yield of 1.29 kg/m2 and a bunch weight of 174.3 g, and the Vladun variety had a yield of 0.87 kg/m2 and a bunch weight of 153.7 g. For the standard variety the grape yield was 0.78 kg/m2 and the bunch weight was 134.0 g. The content of sugar and total acids in the must of the Vozd variety was 20.5% and 6.5 g/l, while for the Vladun variety it was 21.8% and 6.0 g/l respectively. Wine of both varieties was drinkable, harmonious, with a specific varietal of smell and taste and contained 12.1 vol. % of alcohol (Vozd variety), or 12.6 vol. % of alcohol (Vladun variety). Due to the many positive features of the grapes and wines from the Vozd and Vladun varieties, their spread to the production vineyards of Serbia is expected.

Comparative Analysis of Cuticular Wax in Various Grape Cultivars During Berry Development and After Storage

Cuticular wax covering the surface of fleshy fruit is closely related to fruit glossiness, development, and post-harvest storage quality. However, the information about formation characteristics and molecular mechanisms of cuticular wax in grape berry is limited. In this study, crystal morphology, chemical composition, and gene expression of cuticular wax in grape berry were comprehensively investigated. Morphological analysis revealed high density of irregular lamellar crystal structures, which were correlated with the glaucous appearances of grape berry. Compositional analysis showed that the dominant wax compounds were triterpenoids, while the most diverse were alkanes. The amounts of triterpenoids declined sharply after véraison, while those of other compounds maintained nearly constant throughout the berry development. The amounts of each wax compounds varied among different cultivars and showed no correlation with berry skin colors. Moreover, the expression profiles of related genes were in accordance with the accumulation of wax compounds. Further investigation revealed the contribution of cuticular wax to the water preservation capacity during storage. These findings not only facilitate a better understanding of the characteristics of cuticular wax, but also shed light on the molecular basis of wax biosynthesis in grape.

Determination of Some Phytochemical Contents of Local and Standard Grape Varieties Grown in Diyarbakır Province

Grape (Vitis vinifera L.) has been the subject of many research studies because of its phenolic compounds and antioxidant properties which are known to have positive effects on health. In this research study, some phytochemical contents of local and standard grape varieties widely grown in Diyarbakır province were determined. Amount of total phenolic, total anthocyanin and total flavonoid were examined in the berry seed, berry pulp and berry skin of each variety. The statistical differences among Boğazkere, Öküzgözü and Kızıl Banki were obtained and with the addition of Şire variety all varieties were compared in terms of statistical differences. Content of total phenolic was between 389.15 mg GAE / kg and 4050.17 mg GAE / kg, while content of total anthocyanin was recorded between 25.60 mg / kg and 634.00 mg / kg.Total flavonoid content was recorded from 2.34 mg CE /kg to 2402.00 mg CE/kg.With this study, it was determined that some phytochemical contents of different tissues of the grapes vary and this difference also occurs between the grape varieties.

Applied GA5, GA4, and GA4/7 increase berry number per bunch, yield, and grape quality for winemaking in Vitis vinifera L. cv. Malbec

The gibberellins (GAs) GA5 (inhibitor of GA3 -oxidase), GA4 (biologically active), GA4/7 (commercially available mixture of Ga4 and GA7 ) prohexadione-calcium (ProCa, inhibitor of dioxygenases that render GAs bioactive, negative control), and GA3 (positive control) were applied to bunches of Vitis vinifera cv. Malbec. Different techniques, doses, and timings were used in a 3-year field experiment. In year1, GA5 , ProCa, and GA3 were applied at 35, 20, and 0 days before veraison (DBV) by dipping bunches three times. In year2, single applications of GA5 and GA3 , also by immersion, were tested at 60, 45, and 30 DBV. In year3, applications at 60 and 30 DBV of GA5 , GA4 , and a mixture of GA4/7 were evaluated by dipping or spraying the bunches. Vegetative growth, berry weight, and sugar content were unaffected by treatments. ProCa did not affect the yield with respect to water control, although it reduced the levels of phenolics in berry skins, an undesirable effect for winemaking. GA5 , in the dose range 5-50 mg L-1 , raised berry numbers, thereby augmenting bunch weight and skin phenolics at harvest, so increasing berry quality for winemaking. GA4 and GA4/7 produced similar benefits to GA5 , with similar doses. The applications of GA5 , GA4 , and GA4/7 to developing grape berry bunches, in a range of concentrations and by dipping or spraying, increased berry numbers per bunch at harvest. The method can be used as a viticultural practice to improve the production and quality of wine grapes. © 2021 Society of Chemical Industry.

Changes in Major Phenolic Compounds of Seeds, Skins, and Pulps from Various Vitis spp. and the Effect of Powdery and Downy Mildew Diseases on Their Levels in Grape Leaves.

The main purpose of this study is to determine the contents of 3 major phenolic compounds (gallic acid, catechin, and epicatechin) in 22 different grape cultivars/hybrids obtained from 2 different breeding programs. Additionally, changes in these phenolic components in the grape leaves of some resistant/tolerant species were determined in relation to powdery and downy mildew diseases in viticulture. The skin, pulp, and seeds of grape berries were analysed over two years, while changes in the phenolic contents of grape leaves were determined before and after these diseases for two years. The major phenolic contents of new hybrids/cultivars were compared with those of popular cultivars in different parts of the grapes, and significant differences in phenolic contents were found among hybrids/cultivars and different grape parts. Variations in the contents of phenolics in grape seeds, skins, and pulp were high, but seeds contained higher levels of these phenolics than pulp and skin. Analyses of the relationship between two viticultural diseases and phenolic changes in resistant/tolerant cultivars in relation with the susceptible “Italia” cultivar revealed that an increase in the content of the phenolic compounds was found after powdery mildew disease. Hybrids/cultivars with high phenolic contents are recommended to develop new superior cultivars, which are resistant to grape fungal diseases, in breeding programs.

Effects of exogenous methyl jasmonate and light condition on grape berry coloration and endogenous abscisic acid content.

Suitable postharvest treatment methods were investigated to improve the color of grape berries. Culture solutions containing jasmonic acid (JA), methyl jasmonate (MeJA), and prohydrojasmon (PDJ) enhanced the skin coloration of grape berries (‘Pione’) harvested at the initial stage of coloration. MeJA vapor treatment under sealed conditions increased anthocyanin accumulation in grape berries (‘AkiQueen’ and ‘Pione’) harvested at the early stage of skin coloration. Furthermore, promoting skin coloration by MeJA vapor treatment was as effective in mature clusters as it was in detached berries. These effects were confirmed in light conditions but not in constant darkness. Our results showed that postharvest MeJA vapor treatment improved skin coloration in grapes. In addition, postharvest treatment with MeJA was found to have no effect on the endogenous abscisic acid content of grape berry skins. Therefore, we suggest that MeJA vapor treatment can be a useful and labor-saving method for the horticultural industry.

Implication of Row Orientation Changes on Fruit Parameters of Vitis vinifera L. cv. Riesling in Steep Slope Vineyards.

Row orientation, among others, is a crucial factor in determining grapevine performance and health status, thus affecting berry components that form the basis of the later wine profile. However, the literature about the impact of changes in row orientation at steep slope sites on grapevine fruit composition as well as the differentiation between canopy sides hardly exists. Thus, the aim of this work was to gain knowledge about the impact of row orientation in steep slope vineyards on selected primary and secondary metabolites in berries of Vitis vinifera L. cv. Riesling. Samples were taken from both canopy sides of different row orientations of terraced and downslope vineyards in steep slopes. Free amino acids in the juice and flavonols in the berry skin had a positive correlation to sunlight exposure. Furthermore, grapevines showed adaptations to constantly higher light conditions, e.g., physiologically in reduction in chlorophyll content or protective mechanisms resulting in a lower susceptibility to sunburn damage. Thus, grapevine fruit parameters are affected by row orientation change in steep slopes.

Ethylene Induced by Sound Stimulation Enhances Anthocyanin Accumulation in Grape Berry Skin through Direct Upregulation of UDP-Glucose: Flavonoid 3-O-Glucosyltransferase.

Global warming has resulted in the loss of anthocyanin accumulation in berry skin. Sound stimulation can be used as a potential method for enhancing fruit color development since many plants recognize sound vibration as an external stimulus and alter their physiological status in response to it. Sound stimulation (sine wave sound at 1000 Hz) enhanced anthocyanin accumulation in grape cultured cells and berry skins in field-grown grapevines at the early stage of ripening. The transcription of UFGT and ACO2, which encode the key enzymes in anthocyanin and ethylene biosynthesis, respectively, was upregulated in grape cultured cells exposed to sound stimulation. In contrast, the transcription of MybA1 and NCED1, which encode a transcription factor for UFGT and a key enzyme in abscisic acid biosynthesis, respectively, was not affected by the sound stimulation. A treatment with an ethylene biosynthesis inhibitor, aminoethoxyvinyl glycine hydrochloride, revered the enhancement of anthocyanin accumulation by sound stimulation. As the promoter assay using a GUS reporter gene demonstrated that UFGT promoter was directly activated by the ethylene-releasing compound ethephon, which enhanced anthocyanin accumulation in grape cultured cells, we conclude that sound stimulation enhanced anthocyanin accumulation through the direct upregulation of UFGT by ethylene biosynthesis. Our findings suggest that sound stimulation contributes to alleviating poor coloration in berry skin as a novel and innovative practical technique in viticulture.

Melatonin confers enhanced polyamine metabolism and cell tolerance in Vitis vinifera against oxidative damage: Quantitative proteomic evidence

Melatonin (MLT) exhibited pleiotropic effects in multiple plant physiological processes; however, its role in the polyamine metabolism and quality performance of postharvest Vitis vinifera berry remain unknown. In the present study, MLT was applied to postharvest Vitis vinifera cv. Kyoho berry, which delayed berry abscission, berry rotten, and promoted cell tolerance to oxidative stress. Notably, the malondialdehyde content of berries was reduced to 40.8 % on the application of 200 μmol L−1 MLT. Furthermore, tandem mass tags (TMT)-based quantitative proteomic analysis identified 5,156 proteins from berry skin, among which 158 proteins showed quantitatively differences in response to MLT application. These differentially expressed proteins were mainly upregulated in the arginine and proline metabolism pathways, lysine degradation, and ascorbate and aldarate metabolism pathways. The abundance of proteins involved in polyamine metabolisms, including N-carbamoylputrescine amidase, spermidine synthase, and aldehyde dehydrogenases were also upregulated. Moreover, MLT application enhanced contents of arginine, proline, 4-aminobutanoic acid, and polyamines, which played an essential role in oxidative stress response. Further, the transcript level of key enzymes involved in polyamine metabolism, including VvADC, VvODC, VvNAC, VvSPDS and VvCuAO were up-regulated on MLT application. Overall, the role of MLT in regulating the polyamine metabolism and subsequently in cell tolerance against oxidative damage was scientifically established for the first time for Vitis vinifera. The empirical findings of this study may propose new insights on MLT application in postharvest berry physiology and provide theoretical regulation for the preservation of berries, perhaps other fruits.

VvERF17 mediates chlorophyll degradation by transcriptional activation of chlorophyll catabolic genes in grape berry skin

Chlorophylls in the skin contribute to grape (Vitis vinifera) berry color and quality. Degradation of chlorophyll occurs during berry development in grape, but less is known about the molecular mechanisms of this process. Here, we characterized an ethylene response factor, VvERF17, as a putative regulator of chlorophyll degradation in grape berry. VvERF17 expression was strongly correlates with development-induced and ETH-triggered chlorophyll degradation. Transient overexpression of VvERF17 in tobacco leaves, tomato fruits, and grape leaves led to color break and chlorophyll degradation, which were resulted from the upregulated expression of chlorophyll catabolic genes (CCGs), including Chlorophyll-b-reductase (NOL), pheophytinase (PPH), pheophorbide a oxygenase (PAO), and red Chlorophyll catabolite reductase (RCCR). Inversely, silencing of VvERF17 in grape leaves partially suppressed the expression of CCGs’ expression. Major CCGs’ expression was closely related to chlorophyll degradation and VvERF17 expression. It was further demonstrated that VvERF17 could activate the expression of major CCGs by directly binding to the ERF binding sites in their promoters. We conclude that VvERF17 mediates chlorophyll degradation by transcriptional activation of NOL, PPH, PAO, and RCCR. These findings elucidate the regulation mechanisms of chlorophyll degradation in grape and enrich our understanding of grape berry color formation.

Grapevine row orientation mediated temporal and cumulative microclimatic effects on grape berry temperature and composition

Ambient radiation and temperature are global drivers of grapevine growth, grape yield and composition, and wine quality. Knowledge of the implications of vineyard row orientation/microclimate is required for decision-making in current and future macro- and mesoclimates. Temporal and cumulative microclimatic changes, induced by vine row orientation (NS; EW; NE-SW; NW-SE) of vertically trellised Shiraz grapevines, on berry pulp temperature and composition at different ripeness levels were investigated. Berries dynamically gained heat energy relative to: ambient climate/weather; direct canopy wall/bunch irradiance; and berry skin colour development. Berries exposed to direct solar radiation during the morning, leading to higher pulp temperatures than ambient, but having a cooling profile after that, resulted in slightly advanced sugar ripening and generally higher skin total anthocyanins and phenols, without significant effects on pH and titratable acidity, at the respective ripeness levels. In contrast, excessive exposure of bunches and those that built up heat, reaching highest temperatures during late afternoon, seemed not conducive to grape composition associated with higher quality. The S, SE, E and NE canopy sides showed consistently higher skin total anthocyanin and phenol contents than their counter sides. Except for acylated forms of peonidin-glucoside, anthocyanin (mono-, acetyl- and coumaroyl-glucosides) accumulation was mostly favoured in berries exposed to exterior canopy sides, but differences in acylated anthocyanins between exterior-facing and interior-facing berries were less than for mono-glucoside anthocyanins. Over-exposure and heat peaking during late afternoon seemed detrimental. Novel information on berry pulp temperature variation in a developing composite grape bunch, exposed to weather and microclimate fluctuation, is provided. An ostensibly homogeneous bunch in reality represents a dynamic berry pulp thermal range at any point in time. Cumulative thermal and radiation impact was evident. This is the first comprehensive attestation on the role of grapevine row orientation (or any viticulture practice) in the management of seasonal nocturnal- and diurnal berry temperature and concomitant composition.