Optimal Ranges and Thresholds of Grape Berry Solar Radiation for Flavonoid Biosynthesis in Warm Climates

Impacts of Climate Change and Mitigation Strategies for Some Abiotic and Biotic Constraints Influencing Fruit Growth and Quality

Factors such as extreme temperatures, light radiation, and nutritional condition influence the physiological, biochemical, and molecular processes associated with fruit development and its quality. Besides abiotic stresses, biotic constraints can also affect fruit growth and quality. Moreover, there can be interactions between stressful conditions. However, it is challenging to predict and generalize the risks of climate change scenarios on seasonal patterns of growth, development, yield, and quality of fruit species because their responses are often highly complex and involve changes at multiple levels. Advancements in genetic editing technologies hold great potential for the agricultural sector, particularly in enhancing fruit crop traits. These improvements can be tailored to meet consumer preferences, which is crucial for commercial success. Canopy management and innovative training systems are also key factors that contribute to maximizing yield efficiency and improving fruit quality, which are essential for the competitiveness of orchards. Moreover, the creation of habitats that support pollinators is a critical aspect of sustainable agriculture, as they play a significant role in the production of many crops, including fruits. Incorporating these strategies allows fruit growers to adapt to changing climate conditions, which is increasingly important for the stability of food production. By investing in these areas, fruit growers can stay ahead of challenges and opportunities in the industry, ultimately leading to increased success and profitability. In this review, we aim to provide an updated overview of the current knowledge on this important topic. We also provide recommendations for future research.

Geographical identification of Chinese wine based on chemometrics combined with mineral elements, volatile components and untargeted metabonomics

Identifying the geographic origin of a wine is of great importance, as origin fakery is commonplace in the wine industry. This study analyzed the mineral elements, volatile components, and metabolites in wine using inductively coupled plasma-mass spectrometry, headspace solid phase microextraction gas chromatography-mass spectrometry, and ultra-high-performance liquid chromatography-quadrupole-exactive orbitrap mass spectrometry. The most critical variables (5 mineral elements, 13 volatile components, and 51 metabolites) for wine origin classification were selected via principal component analysis and orthogonal partial least squares discriminant analysis. Subsequently, three algorithms-K-nearest neighbors, support vector machine, and random forest -were used to model single and fused datasets for origin identification. These results indicated that fused datasets, based on feature variables (mineral elements, volatile components, and metabolites), achieved the best performance, with predictive rates of 100% for all three algorithms. This study demonstrates the effectiveness of a multi-source data fusion strategy for authenticity identification of Chinese wine.

Postharvest UV-B exposure drives changes in primary metabolism, phenolic concentration, and volatilome profile in berries of different grape (Vitis vinifera L.) varieties

BACKGROUND

The ultraviolet-B (UV-B) radiation can alter grape metabolism during berry development, but little is known on the effect of postharvest UV-B exposure. In this study, we evaluated the effect of postharvest UV-B exposure on berry primary and secondary metabolites in four grapevine varieties (Aleatico, Moscato bianco, Sangiovese, and Vermentino) in order to evaluate the possibility to increase the grape quality and its nutraceutical properties.

RESULTS

The treatment did not significantly affect the berry primary metabolism in terms of organic acids, carbohydrates, and amino acids profile, regardless of the variety. UV-B exposure reduced the total anthocyanin content, particularly the tri-substituted and di-substituted forms in Aleatico and Sangiovese, respectively. An overall negative effect of UV-B irradiation on the flavonols profile of Aleatico, Moscato bianco, and Vermentino berries was found, whereas it enhanced the quercetin, myricetin and kaempferol concentration in Sangiovese. The free fraction of berry volatile organic compounds increased in UV-B-treated Aleatico and Moscato bianco berries, especially C13 -norisoprenoids and volatile phenols, as well as key monoterpenes, such as the linalool derivatives. However, higher concentrations of glycosylated monoterpenes and C13 -norisoprenoids were measured in Sangiovese and Vermentino berries treated with UV-B.

CONCLUSION

This study provides new insights on the effect of postharvest UV-B radiation on berry secondary metabolism, highlighting a different modulation between varieties and suggesting the potential use of this technique to increase some nutraceutical and quality characteristics of grape berry. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Source-Sink manipulations have major implications for grapevine berry and wine flavonoids and aromas that go beyond the changes in berry sugar accumulation

Sugar levels in grape berries are necessary for wine production but also, they are the main driver of most ripening processes. Sugar levels are very responsive to canopy and crop load adjustments. The aim of this study is to test the effect of different levels of defoliation and cluster thinning on grape ripening and wine composition. 'Cabernet sauvignon' grapevines (Vitis vinifera L.) were subjected to defoliation (keeping 100 %, 66 % and 33 % of the leaves) and fruit thinning treatments (keeping 100 %, 66 % and 33 % of the clusters) combined in a factorial design. The experiment was repeated for 2 consecutive seasons (2017 and 2018) and the plants were left untreated for a third season (2019) to observe the carry-over effects of the treatments. The treatments implied precise adjustments of leaf and cluster numbers. However, the proportion of leaf area to fruit mass tended to compensate each other and interact resulting in smaller differences in leaf area or fruit mass by harvest. Berry mass was strongly reduced by defoliation even in the subsequent season where no defoliation was applied. Berry ripening indicators (soluble solids, acidity and anthocyanin levels) were also more affected by defoliation than fruit thinning. Anthocyanin profile was shifted to a higher proportion of Malvidin-derived anthocyanins for defoliated vines and lower proportion of Malvidin-derived anthocyanins in the case of thinned vines. However, when it came down to wine, the physicochemical parameters as well as the aroma profile were more affected by cluster thinning. There was a clear relationship between sugar levels of the unfermented must and many wine-aroma compounds. Green aromas (2-isobutyl-3-methoxypyrazine, hexanol and cis-3-Hexen-1-ol) were among those presenting a negative correlation to must sugar whereas other compounds like Isobutyric acid, Benzyl alcohol, 1-Octen-3-ol and γ-Nonalactone had a positive correlation. This study reveals a higher level of complexity of source sink relations where leaves and clusters do not only act as a source and a sink of carbon, respectively. Therefore, the results of this study should be considered before making comparisons of leaf area to fruit mass ratios across different vine-growing systems.

Evolution of anthocyanin content during grape ripening and characterization of the phenolic profile of the resulting wine by comprehensive two-dimensional liquid chromatography

The typical phenolic profile in grapes is characterized by its complexity both in terms of number of diverse chemical structures and their variation during ripening. Besides, the specific phenolic composition of grapes directly influences the presence of those components in the resulting wine. In this contribution, a new method based on the application of comprehensive two-dimensional liquid chromatography coupled to a diode array detector and tandem mass spectrometry has been developed to obtain the typical phenolic profile of Malbec grapes cultivated in Brazil. Moreover, the method has been demonstrated to be useful to study how the phenolic composition in grapes evolved during a 10-week ripening period. Main detected compounds in grapes and in the wine derived from them were anthocyanins, although a good number of polymeric flavan-3-ols were also tentatively identified, among other compounds. Results show how the amount of anthocyanins present in grapes was increased during ripening up to 5-6 weeks and then decreased towards week 9. The two-dimensional approach applied was demonstrated to be useful for the characterization of the complex phenolic profile of these samples, involving more than 40 different structures and has the potential to be further applied to the study of this important fraction is different grapes and wines systematically.

Untargeted metabolomics analysis based on LC-IM-QTOF-MS for discriminating geographical origin and vintage of Chinese red wine

Identifying wine geographical origin and vintage is vital due to the abundance of fraudulent activity associated with wine mislabeling of region and vintage. In this study, an untargeted metabolomic approach based on liquid chromatography/ion mobility quadrupole time-of-flight mass spectrometry (LC-IM-QTOF-MS) was used to discriminate wine geographical origin and vintage. Wines were well discriminated according to region and vintage with orthogonal partial least squares-discriminant analysis (OPLS-DA). The differential metabolites subsequently were screened by OPLS-DA with pairwise modeling. 42 and 48 compounds in positive and negative ionization modes were screened as differential metabolitesfor the discrimination of different wine regions, and 37 and 35 compounds were screened for wine vintage. Furthermore, new OPLS-DA models were performed using these compounds, and the external verification trial showed excellent practicality with an accuracy over 84.2%. This study indicated that LC-IM-QTOF-MS-based untargeted metabolomics was a feasible tool for wine geographical origin and vintage discrimination.

Transcriptome and metabolome reveal the effects of three canopy types on the flavonoids and phenolic acids in 'Merlot' (Vitis vinifera L.) berry pericarp

The flavonoids and phenolic acids in grape berries greatly influence the quality of wine. Various methods are used to shape and prune grapevines, but their effects on the flavonoids and phenolic acids remain unclear. The flavonoids and phenolic acids in the berry pericarps from grapevines pruned using three types of leaf canopy, namely, V-shaped, T-shaped, and vertical shoot-positioned (VSP) canopies, were compared in this study. Results showed that the V-shaped canopy was more favorable for the accumulation of flavonoids and phenolic acids. Transcriptome and metabolome analyses revealed that the differentially expressed genes (DEGs) and differentially regulated metabolites (DRMs) were significantly enriched in the flavonoid and phenylpropanoid biosynthesis pathways. A total of 96 flavonoids and 32 phenolic acids were detected among the DRMs. Their contents were higher in the V-shaped canopy than in the T-shaped and VSP canopies. Conjoint analysis of transcriptome and metabolome showed that nine DEGs (e.g., cytochrome P450 98A9 and 98A2) were significantly correlated to nine phenolic acids (e.g., gentisic acid and neochlorogenic acid) and three genes (i.e., chalcone isomerase, UDP-glycosyltransferase 88A1, and caffeoyl-CoA O-methyltransferase) significantly correlated to 15 flavonoids (e.g., baimaside and tricin-7-O-rutinoside). These genes may be involved in the regulation of various flavonoids and phenolic acids in grape berries, but their functions need validation. This study provides novel insights into the effects of leaf canopy on flavonoids and phenolic acids in the skin of grape berries and reveals the potential regulatory networks involved in this phenomenon.

Severe Shoot Trimming and Crop Size as Tools to Modulate Cv. Merlot Berry Composition

Viticulture production is challenged by climate change and the consequent higher accumulation of carbohydrates in grapevine berries, resulting in high-alcoholic wines. This study investigates the application of severe shoot trimming performed at three different stages and crop size management as tools for the modulation of cv. Merlot berry composition, aimed at reducing the sugar content in the berry. In the first study, the effects of severe shoot trimming carried out at three different phenological stages were studied. In the second study, late severe shoot trimming was combined with two crop sizes and regulated by shoot thinning. The obtained results demonstrated that severe shoot trimming in earlier stages of berry development limited the accumulation of both sugars and anthocyanins as compared to the control treatment. However, when severe shoot trimming was performed at late veraison (at approximately 14 Brix), it decreased only the accumulation of sugars, without affecting the accumulation of anthocyanins. The results of the second study showed that the modification of crop size by shoot thinning significantly affected the measured yield parameters, whereas the effect on Brix and anthocyanins was seasonally dependent. It was concluded that among the studied techniques, severe shoot trimming at late veraison is the most effective way to reduce sugar content in the berry without affecting the accumulation of anthocyanins.

Early Basal Leaf Removal at Different Sides of the Canopy Improves the Quality of Aglianico Wine

It is well known that the early removal of basal leaves is a viticultural practice adopted to improve the exposure of clusters to direct sunlight and UV radiation and increase the phenolic compounds and anthocyanin concentration in the berries. The aim of this work was to study the influence of early basal leaf removal on Aglianico wines produced in the Apulia region (southern Italy) during three consecutive seasons. Three vine treatments were carried out, where 100% of the cluster-zone leaves on the north, south and both sides of the canopy were removed. Undefoliated plants were used as a control. The effect of the treatments on the basic chemical parameters, phenol content and volatile composition of wines was investigated using WineScan FT-MIR, spectrophotometry, HPLC-DAD and SPME-GC/MS. Early defoliation increased the amounts of flavonoids (+35–40%), anthocyanins (+15–18%), total polyphenols (+10%), antioxidant activity (+8–14%) and colour intensity (+10%), especially when leaf removal was applied on the south side. Moreover, leaf removal led to a 40% increase in free anthocyanins when applied on the south side of the canopy, while a 24% increase was observed when applied to the north side and 21% when applied to the north and south sides. A negative effect was observed on volatile compounds, which decreased by about 18, 14 and 13% when the treatment was applied on the north, north-south and south sides of the canopy, respectively. In conclusion, early leaf removal treatments allow for the modulation of the phenolic and volatile concentrations of Aglianico wines.

Adapting wine grape production to climate change through canopy architecture manipulation and irrigation in warm climates

Grape growing regions are facing constant warming of the growing season temperature as well as limitations on ground water pumping used for irrigating to overcome water deficits. Trellis systems are utilized to optimize grapevine production, physiology, and berry chemistry. This study aimed to compare 6 trellis systems with 3 levels of applied water amounts based on different replacements of crop evapotranspiration (ET_c) in two consecutive seasons. The treatments included a vertical shoot position (VSP), two modified VSPs (VSP60 and VSP80), a single high wire (SH), a high quadrilateral (HQ), and a Guyot pruned VSP (GY) combined with 25%, 50%, and 100% ET_c water replacement. The SH had greater yields, whereas HQ was slower to reach full production potential. At harvest in both years, the accumulation of anthocyanin derivatives was enhanced in SH, whereas VSPs decreased them. As crown porosity increased (mostly VSPs), berry flavonol concentration and likewise molar % of quercetin in berries increased. Conversely, as leaf area increased, total flavonol concentration and molar % of quercetin decreased, indicating a preferential arrangement of leaf area along the canopy for overexposure of grape berry with VSP types. The irrigation treatments revealed linear trends for components of yield, where greater applied water resulted in larger berry size and likewise greater yield. 25% ET_c was able to increase berry anthocyanin and flavonol concentrations. Overall, this study evidenced the efficiency of trellis systems for optimizing production and berry composition in Californian climate, also, the feasibility of using flavonols as the indicator of canopy architecture.

Transcriptional regulation mechanism of flavonoids biosynthesis gene during fruit development in astragalus membranaceus

Astragalus membranaceus, as an important medicinal plant, are an excellent source of flavonoids. Flavonoid compounds in A. membranaceus have been widely used in medicine and supplement, but known of the molecular mechanism of flavonoid biosynthesis is still very few. Here, we analyzed the association between flavonoid content and gene expression pattern during six different fruit developmental stages. Sixteen gene expression trends were significantly identified, involving 8,218 genes. The gene expression trend in profile 0 was positively correlated with flavonoid content, while the gene expression trend in profile 79 was negatively correlated with flavonoid content at six developmental stages. The expression level of genes involved in the general phenylpropane pathway was higher than that of genes involved in the flavonoid biosynthesis pathway. A total of 37 genes involved in flavonoid synthesis were identified in A. membranaceus. The expression pattern of flavonoid-related genes was highly correlated with flavonoid content. Our study deepened the understanding of the flavonoid synthesis mechanism and provided useful resources for future studies on the high flavonoid molecular breeding of A. membranaceus.

Plant flavonoids: Classification, distribution, biosynthesis, and antioxidant activity

Flavonoids are a group of natural polyphenol substances abundant in vegetables, fruits, grains, and tea. As plant secondary metabolites, flavonoids play essential roles in many biological processes and responses to environmental factors in plants. Flavonoids are common in human diets and have antioxidant effects as well as other bioactivities (e.g., antimicrobial and anti-inflammatory properties), which reduce the risk of disease. Flavonoid bioactivity depends on structural substitution patterns in their C6-C3-C6 rings. However, reviews of plant flavonoid distribution and biosynthesis, as well as the health benefits of its bioactivity, remain scarce. Therefore, in the present review, we systematically summarize recent progress in the research of plant flavonoids, focusing on their biosynthesis (pathway and transcription factors) and bioactive mechanisms based on epidemic evidence, in vitro and in vivo research, and bioavailability in the human body. We also discuss future opportunities in flavonoid research, including biotechnology, therapeutic phytoproducts, and dietary flavonoids.

Physiological and Transcriptional Responses to Saline Irrigation of Young 'Tempranillo' Vines Grafted Onto Different Rootstocks

The use of more salt stress-tolerant vine rootstocks can be a sustainable strategy for adapting traditional grapevine cultivars to future conditions. However, how the new M1 and M4 rootstocks perform against salinity compared to conventional ones, such as the 1103-Paulsen, had not been previously assessed under real field conditions. Therefore, a field trial was carried out in a young 'Tempranillo' (Vitis vinifera L.) vineyard grafted onto all three rootstocks under a semi-arid and hot-summer Mediterranean climate. The vines were irrigated with two kinds of water: a non-saline Control with EC of 0.8 dS m-1 and a Saline treatment with 3.5 dS m-1. Then, various physiological parameters were assessed in the scion, and, additionally, gene expression was studied by high throughput sequencing in leaf and berry tissues. Plant water relations evidenced the osmotic effect of water quality, but not that of the rootstock. Accordingly, leaf-level gas exchange rates were also reduced in all three rootstocks, with M1 inducing significantly lower net photosynthesis rates than 1103-Paulsen. Nevertheless, the expression of groups of genes involved in photosynthesis and amino acid metabolism pathways were not significantly and differentially expressed. The irrigation with saline water significantly increased leaf chloride contents in the scion onto the M-rootstocks, but not onto the 1103P. The limitation for leaf Cl- and Na+ accumulation on the scion was conferred by rootstock. Few processes were differentially regulated in the scion in response to the saline treatment, mainly, in the groups of genes involved in the flavonoids and phenylpropanoids metabolic pathways. However, these transcriptomic effects were not fully reflected in grape phenolic ripeness, with M4 being the only one that did not cause reductions in these compounds in response to salinity, and 1103-Paulsen having the highest overall concentrations. These results suggest that all three rootstocks confer short-term salinity tolerance to the scion. The lower transcriptomic changes and the lower accumulation of potentially phytotoxic ions in the scion grafted onto 1103-Paulsen compared to M-rootstocks point to the former being able to maintain this physiological response in the longer term. Further agronomic trials should be conducted to confirm these effects on vine physiology and transcriptomics in mature vineyards.

The effect of harvest time and vintage year on the phenolic composition of Nero and Bianca wines

Fungal disease resistant (PIWI) interspecific grape varieties are playing an important role as an alternative for organic wine production. Organic (bio) wines are demanded by numerous conscious consumers around the globe. They choose this kind of wines predominantly because of the absence of synthetic pesticides, fertilisers and sustainable agriculture. Resistant grape growing moreover results in additional environmental and health benefits. Nero and Bianca are among Hungary's most promising interspecific grape cultivars gaining international interest recently, there are, however, limited vitivinicultural knowledge on them. Our aim was to examine the flavonoid and anthocyanin composition for both interspecific varieties during different harvest times in two consecutive vintages. The date of harvest and vintage played a significant effect on grape and wine quality.

Land Suitability Analysis for Vineyard Cultivation in the Izmir Metropolitan Area

The grapevine, so-called Vitis vinifera L., is one of the most diffuse perennial crop plantations in the world due to a flourishing market that shaped the landscape and the societal values. Turkey has been a historical vine producer, counting on an overall vineyard extension of 550,000 hectares. Besides, Turkey has some favorable pre-requisites to be one of the most fertile lands for vineyard production: variegated topography, rich soil diversity, heterogeneous morphology, and several micro-climatic conditions. However, establishing a flourishing and fully productive vineyard requires many years, and therefore, the selection and management of sites should be considered with great attention. Within this work, a first land suitability analysis for vineyard production has been established for the entire metropolitan area of Izmir according to the most scientifically-agreed criteria: elevation, slope, aspect, land capability, and solar radiation. These criteria were superimposed through spatial overlay analysis using Esri ArcGIS (ver.10.8) and evaluated using the Principal Component Analysis technique. The first three bands were then extracted to define the most suitable areas for vineyard production in Izmir. The final layer has been used to define which areas can be considered for future strategic expansion and management. The discussion focuses on the Kozak plateau, where a new policy of vineyard plantation will be promoted with techniques that aim to maintain and revalorize the traditional vineyard landscapes and conserve traditional methods and practices that have evolved with the cultural values of the villagers and producers.

Effect of Early Basal Leaf Removal on Phenolic and Volatile Composition and Sensory Properties of Aglianico Red Wines

The aim of this work was to study the influence of early basal leaf removal on Aglianico wines produced in the Apulia region (Italy). Three treatments were carried out, where 100% of fruit-zone leaves on the north (DN), south (DS) and on both sides of the canopy (DNS) were removed. A control (CT), where all basal leaves were retained, was also performed. Instrumental (HPLC-DAD-MS and GC-MS) and sensory analysis (QDA) were used to evaluate the treatment effect on the phenolic and volatile compositions and on the sensory descriptors of wines. DNS reached the highest amounts of phenolic compounds, showing a change in the phenolic pattern from flavonols and anthocyanins. Moreover, leaf removal influenced the levels of 37.8% of volatile compounds, quantified by increasing the concentration when early leaf removal was applied on the north side of the canopy (DN), with respect to the south (DS) and both sides (DNS). In the sensory analysis, Aglianico wines were defined by 16 sensory attributes with GM > 30%, where the highest values were reached for defoliation treatments vs. control. In conclusion, early leaf removal treatments allowed us to modulate the phenolic and volatile concentrations of Aglianico wines.

Greek Wine Quality Assessment and Relationships with Climate: Trends, Future Projections and Uncertainties

Grapevine phenology is particularly sensitive to temperature variations, with changes in climate shifting events earlier and advancing berry maturation into a hotter part of the growing cycle. Consequently, serious concerns regarding the negative influences of climate change on global wine quality have been raised, with the scientific community focusing on documenting these changes to better understand and address the impacts. This study adds to this knowledge by investigating air temperature and precipitation trends over the last 40 years (i.e., 1980–2019). Over the most recent period of records (i.e., 2000–2019), minimum air temperatures significantly increased at a higher rate than maximum temperatures. On the other hand, precipitation showed the least significant trends over time. In addition, wine quality assessment and identification of the most significant weather variables and climatic indices that correlate with wine quality rating scores have also been performed. To serve this purpose, data of wine quality ratings for nine white (W) and two red (R) indigenous winegrape varieties (Vitis vinifera L., cvs) grown in Greece were obtained from the database of Thessaloniki International Wine and Spirits Competition. The results showed a statistically significant upward trend over the recent past in the majority of the varieties studied. To examine future periods, mixed-effect model outputs for Greek wine-producing regions combining an ensemble dataset using RCP4.5 and RCP8.5 emission pathways during two future periods (i.e., 2041–2065 and 2071–2095) predicts wines of higher quality, especially during the latter time period. These results reveal that Greek wine quality rating variations are mainly driven by higher maximum temperatures and drier conditions during the growing season of the grapevines. However, two important issues need to be more fully explored in Greece and elsewhere; (1) non-linear responses to warming where wine quality could suffer above varietally specific optimum temperature thresholds and (2) a better understanding of how other non-climate-related factors (e.g., canopy management, winemaking innovations) affect wine quality in the face of a changing climate.

Precipitation before Flowering Determined Effectiveness of Leaf Removal Timing and Irrigation on Wine Composition of Merlot Grapevine

Grapevine productivity, and berry and wine flavonoid concentration, depend on the interactions of cultivar, environment, and applied cultural practices. We characterized the effects that mechanical leaf removal and irrigation treatments had on the flavonoid concentration of ‘Merlot’ (Vitis vinifera, L.) grape berries and wines in a hot climate over two growing seasons with contrasting precipitation patterns. Leaves were removed by machine, either at prebloom (PBLR), or at post-fruit-set (PFLR), or not removed (control) and irrigation was either applied as sustained deficit irrigation (SDI) at 0.8 of crop evapotranspiration (ET_c) from budbreak to fruit set, or regulated deficit irrigation (RDI) at 0.8 ET_c from bud break to fruit set, 0.5 ET_c from fruit set to veraison, and 0.8 ET_c from veraison to harvest, of ET_c In 2014, PFLR reduced the leaf area index (LAI) compared to control. The RDI decreased season-long leaf water potential (Ψ_Int) compared to SDI. However, in 2015, none of the treatments affected LAI or Ψ_Int. In 2014, berry flavonoid concentrations were reduced by PBLR as well as SDI. SDI increased the flavonoid concentrations in wine, and PFLR increased some wine flavonols in one season. No factor affected the concentrations of wine proanthocyanidins or mean degree of polymerization. Thus, mechanical PFLR and RDI may increase berry flavonoid accumulation without yield reduction, in red wine grapes cultivars grown in hot climates when precipitation after bud break is lacking. However, spring precipitation may influence the effectiveness of these practices as evidenced by this work in a changing climate.

Same Season and Carry-Over Effects of Source-Sink Adjustments on Grapevine Yields and Non-structural Carbohydrates

The grapevine (Vitis vinifera L.) is managed to balance the ratio of leaf area (source) to fruit mass (sink). Over cropping in the grapevine may reveal itself as spontaneous fruit abortion, delayed ripening, or as alternate bearing. The aim of this work was to study the same season and carry-over effects of manipulating source to sink ratios on grapevine phenology, leaf gas exchange, yield components, berry soluble solids accumulation, and reserve carbohydrate and soluble sugar concentration in roots. Cabernet Sauvignon grapevines were subjected to defoliation (33, 66, and 100% of the leaves retained) and fruit removal treatments (33, 66, and 100% of clusters retained) arranged in a factorial design. Results from two seasons of source-sink manipulations were substantially different. In both seasons defoliation treatments affected season-long net carbon assimilation (A _N ) and stomatal conductance (g _s ) where the less leaves were retained, the greater the A _N and g _s , and fruit removal had no impact on leaf gas exchange. In the first season, leaf area to fruit mass was hardly related to berry soluble solids and in the second season they were strongly correlated, suggesting a degree of acclimation. Defoliation treatments had great impacts on berry size, berries per cluster, and total soluble solids in both years. Fruit removal treatments only had effects on berry mass and berries per cluster in the first season, and only on berry soluble solids in the second. The predominant effect of defoliation (carbon starvation) cascaded onto reducing root starch content, root mass and delaying of veraison and leaf senescence, as well as harvest which was delayed up to 9 weeks with 33% of the leaves retained. In a third season, where grapevines grew without treatments, defoliation treatments had resultant carryover effects, including reduced leaf area, number of berries per cluster, clusters per vine, and yield, but not on leaf gas exchange dependent on previous seasons' severity of defoliation. Balancing source-to-sink ratio is crucial to obtain an adequate speed of ripening. However, this was the culmination of a more complex whole-plant regulation where the number of leaves (source strength) outweighed the effects of fruits (sink strength).

Effects of leaf removal on the accumulation of anthocyanins and the expression of anthocyanin biosynthetic genes in Cabernet Sauvignon (Vitis vinifera L.) grapes

BACKGROUND

Anthocyanins, a major flavonoid class, determine the color and quality of wine. Recent research revealed that basal leaf removal can increase the content of these compounds. This study determined the effects of basal leaf removal on the anthocyanin profiles of Cabernet Sauvignon grapes.

RESULTS

The effects of basal leaf removal on anthocyanin composition in Cabernet Sauvignon grapes were investigated over two growing seasons. Leaf removal at 5% veraison (VB6) and at 100% veraison (VC6) was compared with a control. Reducing sugar and total anthocyanin contents in the leaf removal group were significantly higher than in the control group at harvest for both vintages. Leaf removal increased the content of individual anthocyanins and significantly improved the malvidin-3-O-glucoside (Mv-3-glc), peonidin-3-O-glucoside (Pn-3-glc), and malvidin-3-O-(6-acetyl)-glucoside (Mv-3-acglc) content of the VB6 group. At harvest, VB6 treatment increased the transcript abundance of structural and regulator genes in the anthocyanin pathway, especially VvF3'5'H, VvLDOX, and VvDFR.

CONCLUSIONS

Our results suggest that leaf removal at 5% veraison may be useful for improving the anthocyanin content in grapes. © 2020 Society of Chemical Industry.

Grape Berry Secondary Metabolites and Their Modulation by Abiotic Factors in a Climate Change Scenario-A Review

Temperature, water, solar radiation, and atmospheric CO₂ concentration are the main abiotic factors that are changing in the course of global warming. These abiotic factors govern the synthesis and degradation of primary (sugars, amino acids, organic acids, etc.) and secondary (phenolic and volatile flavor compounds and their precursors) metabolites directly, via the regulation of their biosynthetic pathways, or indirectly, via their effects on vine physiology and phenology. Several hundred secondary metabolites have been identified in the grape berry. Their biosynthesis and degradation have been characterized and have been shown to occur during different developmental stages of the berry. The understanding of how the different abiotic factors modulate secondary metabolism and thus berry quality is of crucial importance for breeders and growers to develop plant material and viticultural practices to maintain high-quality fruit and wine production in the context of global warming. Here, we review the main secondary metabolites of the grape berry, their biosynthesis, and how their accumulation and degradation is influenced by abiotic factors. The first part of the review provides an update on structure, biosynthesis, and degradation of phenolic compounds (flavonoids and non-flavonoids) and major aroma compounds (terpenes, thiols, methoxypyrazines, and C13 norisoprenoids). The second part gives an update on the influence of abiotic factors, such as water availability, temperature, radiation, and CO₂ concentration, on berry secondary metabolism. At the end of the paper, we raise some critical questions regarding intracluster berry heterogeneity and dilution effects and how the sampling strategy can impact the outcome of studies on the grapevine berry response to abiotic factors.

Mitigating Heat Wave and Exposure Damage to "Cabernet Sauvignon" Wine Grape With Partial Shading Under Two Irrigation Amounts

Rising temperatures in most agricultural regions of the world are associated with a higher incidence of extreme weather events such as heat waves. We performed an experiment to mitigate the impact of heat waves and exposure of berries in grapevine (Vitis vinifera cv. "Cabernet Sauvignon") with untreated vines (Exposed) or with fruit-zone partial shading (Shaded) under 40 and 80% replacement of crop evapotranspiration (ET _c ) with sustained deficit irrigation in a factorially arranged experiment. The trial was performed in a vineyard with vertically shoot positioned trellis with a row orientation that concentrated solar radiation exposure on the southwest aspect of the fruit zone. Leaf stomatal conductance (g _s ) and net carbon assimilation (A _N ) were significantly lower in shaded leaves under partial fruit-zone shading that resulted in lower pruning mass for Shaded treatments. Stem water potential (Ψ _stem ) responded to a large extent to increased irrigation. However, grapevines with partial fruit-zone shading had transiently better water status under 40% ET _c . Cluster maximum temperatures were 3.9°C greater in Exposed grapevines. Exposed clusters had transiently lower acidity and higher pH. However, Exposed clusters on 40% ET _c had higher total soluble solids (TSS). The experimental vineyard suffered a 4-day heat wave 21 days before harvest, resulting in 25% of the clusters being damaged in Exposed treatment, regardless of irrigation amount. Furthermore, berries in Exposed treatments suffered a great loss of anthocyanins and flavonols even if they were not damaged by direct solar exposure. The pre-planting decision of using a vertically shoot positioned trellis that concentrated solar radiation on the Southwest aspect offered mild protection in a hot climate region with a sunny growing season with extreme heat events during the execution of study. The extreme conditions under which this study was conducted are not unusual, and have become more expected. Our work provided evidence of the vulnerability of grape berry to heat waves and exposure during heat wave events and possible protection methods to mitigate these effects in situ in context of climate change.

Impacts of leaf removal and shoot thinning on cumulative daily light intensity and thermal time and their cascading effects of grapevine (Vitis vinifera L.) berry and wine chemistry in warm climates

Leaf removal (LR), shoot thinning (ST) and their combination (LRST) are known to increase berry solar exposure affecting berry composition and consequently improving wine quality and antioxidant properties. We hypothesized that LR, ST or their combination (LRST) would affect flavonoid content during berry ripening by means of changes of the berry microclimate (light and temperature) as well as wine composition, quality, and antioxidant properties. Thermal time and sum of light intensity thresholds were different to achieve the maximum berry anthocyanin and flavonol contents. ST mostly affected wine characteristics by increasing alcoholic content, acidity, hue and phenolic substances. Wine antioxidant capacity decreased in ST wines likely by decreases in catechin and quercetin contents. ST and LRST increased proanthocyanidin polymerization and decreased monomeric flavan-3-ols, which may reduce wine bitterness and enhance astringency. Therefore, the management of canopy should take into account the warming trends in viticulture regions, rather than being applied preemptively.