Whole Plant Temperature Manipulation Affects Flavonoid Metabolism and the Transcriptome of Grapevine Berries

Metabolomics analysis based on UHPLC-QqQ-MS/MS to discriminate grapes and wines from different geographical origins and climatological characteristics

With the proliferation of the consumer's awareness of wine provenance, wines with unique origin characteristics are increasingly in demand. This study aimed to investigate the influence of geographical origins and climatological characteristics on grapes and wines. A total of 94 anthocyanins and 78 non-anthocyanin phenolic compounds in grapes and wines from five Chinese viticultural vineyards (CJ, WH, QTX, WW, and XY) were identified by UHPLC-QqQ-MS/MS. Chemometric methods PCA and OPLS-DA were established to select candidate differential metabolites, including flavonols, stilbenes, hydroxycinnamic acids, peonidin derivatives, and malvidin derivatives. CCA showed that malvidin-3-O-glucoside had a positive correlation with mean temperature, and quercetin-3-O-glucoside had a negative correlation with precipitation. In addition, enrichment analysis elucidated that the metabolic diversity in different origins mainly occurred in flavonoid biosynthesis. This study would provide some new insights to understand the effect of geographical origins and climatological characteristics on phenolic compounds in grapes and wines.

Use of an automatic fruit-zone cooling system to cope with multiple summer stresses in Sangiovese and Montepulciano grapes

Grapevines are frequently subjected to heatwaves and limited water availability during ripening. These conditions can have consequences for the physiological health of the vines. Moreover, the situation is often exacerbated by intense solar radiation, resulting in reduced yield due to sunburn and a decline in quality. In light of these challenges, our study aimed to develop a fruit-zone cooling system designed to mitigate grape sunburn damage and improve the microclimate conditions within the vineyard. The system comprises a network of proximal sensors that collect microclimate data from the vineyard and an actuator that activates nebulizers when the temperature exceeds the threshold of 35°C. The research was conducted over two years (2022 and 2023) in Bologna (Italy) using potted Sangiovese and Montepulciano vines. These two vintages were characterized by high temperatures, with varying amounts of rainfall during the test period, significantly impacting the evaporative demand, which was notably higher in 2023. Starting from the veraison stage we compared three treatments: Irrigated control vines (WW); Control vines subjected to 50% water restriction during the month of August (WS); WS vines treated with nebulized water in the bunch area during the stress period (WS+FOG). The application of nebulized water effectively reduced the temperature of both the air around the clusters and the clusters themselves. As we expected, Montepulciano showed better single leaf assimilation rate and stomatal conductance under non-limiting water conditions than Sangiovese while their behavior was unaffected under water-scarce conditions. Importantly, for the first time, we demonstrated that nebulized water positively affected gas exchange in both grape varieties. In addition to this, the vines treated with the misting system exhibited higher productivity compared to WS vines without affecting technological maturity. In the 2023 vintage, the activation of the system prevented the ripening blockage that occurred in Montepulciano under water stress. Regarding the concentration of total anthocyanins, a significant increase in color was observed in WS+FOG treatment, suggesting a predominant role of microclimate on anthocyanin biosynthesis and reduction of oxidative phenomena. In conclusion, the fruit-zone cooling system proved to be an invaluable tool for mitigating the adverse effects of multiple summer stresses.

The Role of Terroir on the Ripening Traits of V. vinifera cv 'Glera' in the Prosecco Area

The grapevine (Vitis vinifera L.) is widely cultivated worldwide owing to the substantial commercial value of the grapes and other products derived from their processing, wines in particular. The grapevine is characterized by a remarkable phenotypic plasticity within the same variety, which shapes the final berry quality attributes hence reflecting the complex interactions between the plant and the environment leading to the expression of wine typicity. In this study, we explored the metabolomic and transcriptomic basis of the plasticity of Glera, a white berry grapevine variety particularly renowned for the production of wine Prosecco. The two selected vineyards varied for site altitude and pedoclimatic conditions. We highlighted that these environments determined different berry ripening dynamics at the level of both technological parameters and the total abundance and intrafamily distribution of phenolic compounds. Moreover, a clear impact on the grape aroma profile was observed. The genome-wide gene expression analysis of the berries revealed remarkable differences in the ripening transcriptomic program, reflecting the differences in water status, light exposure, and temperature experienced by the plants while growing at the two sites. Overall, this survey portrayed how the quality attributes of the cv 'Glera' grape berries may be affected by different environmental conditions within the typical area of Prosecco wine production.

Variation in Flavonoid Compounds, Volatiles and Yield Related Traits in Different Iranian Rosa damascena Mill. Cultivars Based on SPME Arrow and LC-MS/MS

Damask rose (Rosa damascena Mill.) is an aromatic industrial plant with different applications. Selection of cultivars with high-value metabolites such as flavonoids-with acceptable yields-can lead to elite cultivars for mass propagation in various industries. A field experiment was carried out in a randomized complete block design (RCBD) to evaluate metabolites and some yield-related morphological data. In the present investigation, for the first time 13 flavonoid components of nine Iranian damask rose cultivars were compared using LC-MS/MS. As a result, 13 flavonoids were identified, most of which were reported for the first time in rose petals. Phloridzin (72.59-375.92 mg/100 g dw), diosmetin (82.48-153.16 mg/100 g dw) and biochanin A (0-1066.89 mg/100 g dw) were the most abundant, followed by trans-chalcone (0-106.29 mg/100 g dw) and diosmin (41.55-84.57 mg/100 g dw). Levels of naringenin also ranged from 3.77 in B111 to 54.70 mg/100 g dw in C294, while luteolin varied from 4.37 in B111 to 28.87 mg/100 g dw in C294. The SPME Arrow technique also was applied to determine the real aroma of the studied cultivars. Phenethyl alcohol was the most abundant compound, in the range of 69.28 to 77.58%. The highest citronellol/geraniol (C/G) was observed in D234 (4.52%) and D237 (4.30%), while the lowest amount belonged to A104 (1.28%). Rose oxide, as the most crucial factor for odor, ranged from 0.06% in D237 to 0.15% in D211. Based on cluster and principal component analysis (PCA), D234 cultivar can be suggested as a promising cultivar with high yield, high C/G content and high rose oxide, while D234 and C294 were the most valuable cultivars in terms of flavonoids with high yield. Finally, these cultivars can be introduced for further breeding programs and industrial cultivation.

Impact of Climate Change on Altered Fruit Quality with Organoleptic, Health Benefit, and Nutritional Attributes

As a consequence of global climate change, acute water deficit conditions, soil salinity, and high temperature have been on the rise in their magnitude and frequency, which have been found to impact plant growth and development negatively. However, recent evidence suggests that many fruit plants that face moderate abiotic stresses can result in beneficial effects on the postharvest storage characters of the fruits. Salinity, drought, and high temperature conditions stimulate the synthesis of abscisic acid (ABA), and secondary metabolites, which are vital for fruit quality. The secondary metabolites like phenolic acids and anthocyanins that accumulate under abiotic stress conditions have antioxidant activity, and therefore, such fruits have health benefits too. It has been noticed that fruits accumulate more sugar and anthocyanins owing to upregulation of phenylpropanoid pathway enzymes. The novel information that has been generated thus far indicates that the growth environment during fruit development influences the quality components of the fruits. But the quality depends on the trade-offs between productivity, plant defense, and the frequency, duration, and intensity of stress. In this review, we capture the current knowledge of the irrigation practices for optimizing fruit production in arid and semiarid regions and enhancement in the quality of fruit with the application of exogenous ABA and identify gaps that exist in our understanding of fruit quality under abiotic stress conditions.

Temperature differences between sites lead to altered phenylpropanoid metabolism in a varietal dependent manner

Elevated temperature has already caused a significant loss of wine growing areas and resulted in inferior fruit quality, particularly in arid and semi-arid regions. The existence of broad genetic diversity in V. vinifera is key in adapting viticulture to climate change; however, a lack of understanding on the variability in berry metabolic response to climate change remains a major challenge to build ad-hoc strategies for quality fruit production. In the present study, we examined the impact of a consistent temperature difference between two vineyards on polyphenol metabolism in the berries of 20 red V. vinifera cultivars across three consecutive seasons (2017-2019). The results emphasize a varietal specific response in the content of several phenylpropanoid metabolites; the interaction factor between the variety and the vineyard location was also found significant. Higher seasonal temperatures were coupled with lower flavonol and anthocyanin contents, but such reductions were not related with the level of expression of phenylpropanoid related genes. Hierarchical clustering analyses of the metabolic data revealed varieties with a location specific response, exceptional among them was Tempranillo, suggesting a greater susceptibility to temperature of this cultivar. In conclusion, our results indicate that the extensive genetic capacity of V. vinifera bears a significant potential to withstand temperature increase associated with climate change.

Temporospatial pattern of flavonoid metabolites and potential regulatory pathway of PbMYB211-coordinated kaempferol-3-O-rhamnoside biosynthesis in Phoebe bournei

Phoebe is a well-known timber tree species that contains abundant metabolites characterized by flavonoids that are widely used in the pharmaceutical industry. Nevertheless, temporospatial flavonoid metabolism variations substantially impact the Phoebe industry. Thus, a metabolomics analysis was carried out and identified 465 metabolites (102 flavonoids) in P. bournei, revealing distinct distribution patterns among five studied organs, and most of the flavonoids were dominant in the leaves. Furthermore, three kaempferol glycoside derivatives were significantly accumulated in the leaves and showed higher contents in young leaves than in mature leaves and differences between spring and autumn. For instance, greater accumulation of kaempferol-7-O-rhamnoside was detected in spring, whereas higher contents of kaempferol-3-O-arabinofuranoside and kaempferol-3-O-rhamnoside were found in autumn. Integrated metabolomics and transcriptomics identified 20 transcription factors (TFs) and 12 structural genes that participate in kaempferol derivative synthesis and elucidated a potential regulatory mechanism in P. bournei. Of the identified genes, PbMYB211 might contribute significantly to the kaempferol-3-O-rhamnoside content by regulating the target structural gene PbUGT139, as revealed by transient overexpression analysis. Overall, this study illuminated the temporospatial accumulation of flavonoids among different organs, seasons, and developmental stages in P. bournei and elucidated a potential regulatory pathway of kaempferol-3-O-rhamnoside. The results provide important insights into harvest techniques and a theoretical basis for the comprehensive utilization of P. bournei.

Bunch microclimate influence amino acids and phenolic profiles of Pinot noir grape berries

Introduction

The increase of temperature due to climate change at different phenological stages of grapevine has already been demonstrated to affect accumulation of primary and secondary metabolites in grape berries. This has a significant implication for Pinot noir especially in New Zealand context as these compounds can have direct and indirect effects on wine quality.

Methods

This study investigates how varying bunch microclimate through changes in temperature applied at veraison stage can affect: fresh weight, total soluble solids, the accumulation of anthocyanins, total phenolics and amino acids of the grape berries. This was studied over two growing seasons (2018/19 and 2019/20) with Pinot noir vines being grown at two different temperatures in controlled environment (CE) chambers. The vines were exposed to 800 µmol/m2/s irradiance with diurnal changes in day (22°C or 30°C) and night (15°C) temperatures. This experimental set up enabled us to determine the accumulation of these metabolite at harvest (both seasons) and throughout berry development (second season).

Results and discussion

The results showed that berry weight was not influenced by temperature increase. The total soluble solids (TSS) were significantly increased at 30°C, however, this was not at the expense of berry weight (i.e., water loss). Anthocyanin content was reduced at higher temperature in the first season but there was no change in phenolic content in response to temperature treatments in either season. The concentrations of total amino acids at harvest increased in response to the higher temperature in the second season only. In addition, in the time course analysis of the second season, the accumulation of amino acids was increased at mid-ripening and ripening stage with the increased temperature. Significant qualitative changes in amino acid composition specifically the α-ketoglutarate family (i.e., glutamine, arginine, and proline) were found between the two temperatures.

Significance

This study is the first to provide detailed analysis and quantification of individual amino acids and phenolics in Pinot noir in response to changes in temperature applied at veraison which could aid to develop adaptation strategies for viticulture in the future.

A molecular phenology scale of grape berry development

Fruit growth and development consist of a continuous succession of physical, biochemical, and physiological changes driven by a genetic program that dynamically responds to environmental cues. Establishing recognizable stages over the whole fruit lifetime represents a fundamental requirement for research and fruit crop cultivation. This is especially relevant in perennial crops like grapevine (Vitis vinifera L.) to scale the development of its fruit across genotypes and growing conditions. In this work, molecular-based information from several grape berry transcriptomic datasets was exploited to build a molecular phenology scale (MPhS) and to map the ontogenic development of the fruit. The proposed statistical pipeline consisted of an unsupervised learning procedure yielding an innovative combination of semiparametric, smoothing, and dimensionality reduction tools. The transcriptomic distance between fruit samples was precisely quantified by means of the MPhS that also enabled to highlight the complex dynamics of the transcriptional program over berry development through the calculation of the rate of variation of MPhS stages by time. The MPhS allowed the alignment of time-series fruit samples proving to be a complementary method for mapping the progression of grape berry development with higher detail compared to classic time- or phenotype-based approaches.

Global transcriptome and gene co-expression network analyses reveal regulatory and non-additive effects of drought and heat stress in grapevine

Despite frequent co-occurrence of drought and heat stress, the molecular mechanisms governing plant responses to these stresses in combination have not often been studied. This is particularly evident in non-model, perennial plants. We conducted large scale physiological and transcriptome analyses to identify genes and pathways associated with grapevine response to drought and/or heat stress during stress progression and recovery. We identified gene clusters with expression correlated to leaf temperature and water stress and five hub genes for the combined stress co-expression network. Several differentially expressed genes were common to the individual and combined stresses, but the majority were unique to the individual or combined stress treatments. These included heat-shock proteins, mitogen-activated kinases, sugar metabolizing enzymes, and transcription factors, while phenylpropanoid biosynthesis and histone modifying genes were unique to the combined stress treatment. Following physiological recovery, differentially expressed genes were found only in plants under heat stress, both alone and combined with drought. Taken collectively, our results suggest that the effect of the combined stress on physiology and gene expression is more severe than that of individual stresses, but not simply additive, and that epigenetic chromatin modifications may play an important role in grapevine responses to combined drought and heat stress.

The influences of fungal endophytes inoculation on the biochemical status of grape cells of different varieties in vitro

The metabolic patterns of grape cells can be specifically shaped by different strains of dual-cultured fungal endophytes. In this work, a solid co-culture system was furtherly proposed to illustrate the different impacts of endophytic fungi on the biochemical status of grape cells of different varieties. By measuring the metabolic impacts of contact fungal endophytes on grape cells of the varieties 'Rose honey' (RH) and 'Cabernet sauvignon' (CS), we observed that most of the fungal strains used had promoting effects on grape cellular biochemistry parameters. Compared with the control, inoculation with most of the fungal strains increased the superoxide dismutase (SOD) and phenylalanine ammonia-lyase (PAL) activities as well as the total flavonoid (TF) and total phenolics (TPh) contents in both types of grape cells. Among the tested strains, RH34, RH49 and MDR36 had relatively stronger biochemical impacts on grape cells. More interestingly, in addition to the varietal specificity, a certain degree of fungal genus specificity was also observed during the metabolic interactions between fungal endophytes and grape cells, as fungal endophytes from the same genus tended to be clustered into the same group based on the affected biochemical traits. This work revealed the differential biochemical status effects of fungal endophytes on different varietal grape cells and raised the possibility of reshaping grape qualities by applying endophytes.

Effect of a triacontanol-rich biostimulant on the ripening dynamic and wine must technological parameters in Vitis vinifera cv. 'Ribolla Gialla'

Biostimulants are organic compounds which can influence the biochemical activity of the whole plant. Lately, great attention has been focused on the possibility of using these stimulants in the viticulture sector. Due to this, the aim of this work was to investigate the foliar application of a biostimulant made by Fabaceae tissue, rich in amino acids and peptides along with the high presence of natural triacontanol (C₃₀H₆₂O) (>6 mg kg^-1), previously reported in many crops as chemicals able to stimulate different yield components, the technological composition of musts still having an effect on some of the microbial population of different fruits/crops. Hence, this research was conducted during the growing seasons 2020 and 2021 in a commercial vineyard of the 'Ribolla Gialla' grapevine (Vitis vinifera, L.), in the Friuli Venezia Giulia Region (North-Eastern Italy), in order to understand the effect on this woody perennial crop not yet investigated. After a two-year-study, a physiological response occurred, as ripening and veraision were brought forward in the treated plants as well as the harvest time, having higher enological parameters (sugars, total titrable acidity and citric acid content) than the non-treated at every stage. Thus, grapes in the treated plants reached a full technological maturity earlier than the non-treated, in both study years. There was a positive effect on must microbial ecology important for winemaking, hence, the biostimulant have promoted the growth of the microbial community on berry skin translating into what found in the must.

Melatonin enhances stress tolerance in pigeon pea by promoting flavonoid enrichment, particularly luteolin in response to salt stress

Melatonin improves plant resistance to multiple stresses by participating in the biosynthesis of metabolites. Flavonoids are an important family of plant secondary metabolites and are widely recognized to be involved in resistance; however, the crosstalk between melatonin and flavonoid is largely unknown. We found that the resistance of pigeon pea (Cajanus cajan) to salt, drought, and heat stresses were significantly enhanced by pre-treatment with melatonin. Combined transcriptome and LC-ESI-MS/MS metabolomics analyses showed that melatonin significantly induced the enrichment of flavonoids and mediated the reprogramming of biosynthetic pathway genes. The highest fold-increase in expression in response to melatonin treatment was observed for the CcF3´H family, which encodes an enzyme that catalyses the biosynthesis of luteolin, and the transcription factor CcPCL1 directly bonded to the CcF3´H-5 promoter to enhance its expression. In addition, salt stress also induced the expression of CcPCL1 and CcF3´H-5, and their overexpression in transgenic plants greatly enhanced salt tolerance by promoting the biosynthesis of luteolin. Overall, our results indicated that pre-treatment of pigeon pea with melatonin promoted luteolin biosynthesis through the CcPCL1 and CcF3´H-5 pathways, resulting in salt tolerance. Our study shows that melatonin enhances plant tolerance to multiple stresses by mediating flavonoid biosynthesis, providing new avenues for studying the crosstalk between melatonin and flavonoids.

Cluster spatial positions varied the phenolics profiles of 'Cabernet Sauvignon' grapes and wines under a fan training system with multiple trunks

The fan training system with multiple trunks (F-MT) is widely used in the northern China winegrape region with high yield and convenience for burying soil to prevent winter cold. However, the wide distribution of clusters under F-MT usually leads to variations in berry compositions. In two consecutive years, clusters from different spatial positions were collected to determine the phenolic composition in grapes and resultant wines by HPLC-QqQ-MS/MS. Results showed that light exposure promotes the accumulation of flavonols and 3'-hydroxylated anthocyanins in berries. Wines made from upper clusters had higher alcohol degree, lightness, monomeric anthocyanins and flavonols, whereas wines made from lower clusters had relatively higher total acidity, red color component, polymeric anthocyanin and total flavanols. Most of the wine parameters were also significantly affected by vintage. In conclusion, the quality of grapes and wines varied from different cluster positions, graded harvesting helps to maximize the characteristics of grape berries.

Juxtaposition of the Source-to-Sink Ratio and Fruit Exposure to Solar Radiation on cv. Merlot (Vitis vinifera L.) Berry Phenolics in a Cool versus Warm Growing Region

The grapevine source-to-sink ratio and berry exposure to solar radiation both influence grape flavonoid biosynthesis and accumulation. Here, we compared these concepts on cv. Merlot in two different growing locations (Michigan (MI) and Friuli-Venezia Giulia (FVG), IT) to understand whether the environment influences flavonoid sensitivity to these parameters. Three levels of leaf removal (LR0, LR5, LR8) were implemented at the pea-size phenological stage to compare conditions of increased cluster light exposure with a decreasing vine source-to-sink ratio on berry flavonoid accumulation. Treatments did not affect total soluble solids (TSSs) or pH, but titratable acidity (TA) was lower in LR8 at harvest in both locations. LR5 increased anthocyanins and flavonols in MI but decreased most phenolics in FVG. The decreased expression of VviLAR1 and VviF3'5'Hh during ripening supported the lower concentrations of flavan-3-ol monomers and anthocyanins in FVG. In summary, flavonoid biosynthesis and accumulation were more sensitive to solar radiation than the source-to-sink ratio, and the vineyard environment dictated whether solar radiation was beneficial or detrimental to flavonoid biosynthesis.

Comparative Transcriptomic and Metabolic Analyses Reveal the Coordinated Mechanisms in Pinus koraiensis under Different Light Stress Conditions

Light is one of the most important environmental cues that affects plant development and regulates its behavior. Light stress directly inhibits physiological responses and plant tissue development and even induces mortality in plants. Korean pine (Pinus koraiensis) is an evergreen conifer species widely planted in northeast China that has important economic and ecological value. However, the effects of light stress on the growth and development of Korean pine are still unclear. In this study, the effects of different shading conditions on physiological indices, molecular mechanisms and metabolites of Korean pine were explored. The results showed that auxin, gibberellin and abscisic acid were significantly increased under all shading conditions compared with the control. The contents of chlorophyll a, chlorophyll b, total chlorophyll and carotenoid also increased as the shading degree increased. Moreover, a total of 8556, 3751 and 6990 differentially expressed genes (DEGs) were found between the control and HS (heavy shade), control and LS (light shade), LS vs. HS, respectively. Notably, most DEGs were assigned to pathways of phytohormone signaling, photosynthesis, carotenoid and flavonoid biosynthesis under light stress. The transcription factors MYB-related, AP2-ERF and bHLH specifically increased expression during light stress. A total of 911 metabolites were identified, and 243 differentially accumulated metabolites (DAMs) were detected, among which flavonoid biosynthesis (naringenin chalcone, dihydrokaempferol and kaempferol) metabolites were significantly different under light stress. These results will provide a theoretical basis for the response of P. koraiensis to different light stresses.

Non-destructive fluorescence sensing for assessing microclimate, site and defoliation effects on flavonol dynamics and sugar prediction in Pinot blanc grapes

In an era of growing international competition in modern viticulture, the study and implementation of innovative technologies to increase the production of high-quality grapes and wines are of critical importance. In this study, the non-destructive portable sensor Multiplex, based on fluorescence sensing technique, was applied to evaluate grape maturity parameters and flavonol content of the understudied Pinot blanc variety. The effects of environmental and agronomical factors on flavonol content of Pinot blanc grapes were investigated in eight vineyards characterised by different microclimatic and agronomic conditions. Furthermore, the direct impact of canopy management treatment on the flavonol dynamics of the grapes oriented in the four cardinal directions was assessed. Results highlight the positive role of moderate temperatures and direct sunlight exposure on Pinot blanc flavonol content; however, no direct vineyard-elevation effect was observed. The ability to modulate and evaluate the flavonol content in field represent crucial factors because of their potential effect on flavonoids-dependent wine characteristics, such as stability and ageing. In the present study, for the first time, two calibration curves were reported for pre- and post-veraison periods between flavonol indices and the berry skin flavonol content and a good correlation was observed between Multiplex measurement and the total polyphenolic content of grape juice. Moreover, the strong correlation between the chlorophyll index with grape juice sugar content and titratable acidity revealed the practical application of non-destructive sensors to predict the optimal harvest time for Pinot blanc grapes. In conclusion, the non-destructive fluorescence sensor Multiplex is a high-potential tool for innovative viticulture, for evaluating grape skin composition variables in white grape varieties.

Cluster Thinning Improves Aroma Complexity of White Maraština (Vitis vinifera L.) Wines Compared to Defoliation under Mediterranean Climate

Defoliation and cluster thinning are useful canopy management techniques to modulate grapevine carbon distribution and microclimate. Both techniques are directed to achieve the proper balance between fruit and foliage, and to maximize production of well-ripened fruits and quality wines. We performed five canopy treatments on Maraština grapevine grown at a commercial vineyard in the Vrgorac Valley region of Croatia: three different times of basal defoliation, cluster thinning at the veraison, and an untreated control. The effects of the canopy changes on the chemical composition of grapes and wines were studied. The treatments had variable impacts on yield components and basic wine composition. Volatile aroma compounds in produced wines were analyzed using gas chromatography–mass spectrometry coupled with a mass-selective detector. The concentrations of 70 of the 96 individual volatile compounds were significantly influenced by the canopy technique used. The concentrations of 58 of these compounds were different according the timing of defoliation. Cluster thinning at an intensity of 35% produced wines with more terpenes, esters, higher alcohols, other alcohols, volatile phenolic compounds, lactones, and other compounds than other treatments. Among terpenes, cluster thinning increased terpinen-4-ol, linalool, trans-β-farnesen, and geraniol. Odor activity value analysis revealed 16 volatile compounds that contributed to the aroma of cluster-thinned wines.

Different Temperature and UV Patterns Modulate Berry Maturation and Volatile Compounds Accumulation in Vitis sp

Volatile compounds (VCs) in grapevine berries play an important role in wine quality; however, such compounds and vine development can be sensitive to environmental conditions. Due to this sensitivity, changes in temperature patterns due to global warming are likely to further impact grape production and berry composition. The aim of this study was to determine the possible effects of different growing-degree day accumulation patterns on berry ripening and composition at harvest. An experimental field was conducted using Vitis sp. L'Acadie blanc, in Nova Scotia, Canada. Using on-the-row mini-greenhouses, moderate temperature increase and reduced ultraviolet (UV) exposure were triggered in grapevines during pre-veraison (inflorescence to the beginning of berry softening), post-veraison (berry softening to full maturity), and whole season (inflorescence to full maturity), while controls were left without treatment. Free and bound VCs were extracted from berries sampled at three different phenological stages between veraison and maturity before analysis by gas chromatography-mass spectrometry (GC-MS). Berries from grapevines exposed to higher temperatures during early berry development (pre-veraison and whole) accumulated significantly higher concentrations of benzene derivatives 2-phenylethanol and benzyl alcohol at harvest, but lower concentrations of hydroxy-methoxy-substituted volatile phenols, terpenes, and C13-norisoprenoids than the control berries. These results illustrate the importance of different environmental interactions in berry composition and suggest that temperature could potentially modulate phenylpropanoid and mevalonate metabolism in developing berries. This study provides insights into the relationships between abiotic conditions and secondary metabolism in grapevine and highlights the significance of early developmental stages on berry quality at harvest.

Climate Change Effects on Grapevine Physiology and Biochemistry: Benefits and Challenges of High Altitude as an Adaptation Strategy

Grapevine berry quality for winemaking depends on complex and dynamic relationships between the plant and the environment. Winemakers around the world are demanding a better understanding of the factors that influence berry growth and development. In the last decades, an increment in air temperature, CO₂ concentration and dryness occurred in wine-producing regions, affecting the physiology and the biochemistry of grapevines, and by consequence the berry quality. The scientific community mostly agrees in a further raise as a result of climate change during the rest of the century. As a consequence, areas most suitable for viticulture are likely to shift into higher altitudes where mean temperatures are suitable for grape cultivation. High altitude can be defined as the minimum altitude at which the grapevine growth and development are differentially affected. At these high altitudes, the environments are characterized by high thermal amplitudes and great solar radiations, especially ultraviolet-B (UV-B). This review summarizes the environmental contribution of global high altitude-related climatic variables to the grapevine physiology and wine composition, for a better evaluation of the possible establishment of vineyards at high altitude in climate change scenarios.

A Review on the Observed Climate Change in Europe and Its Impacts on Viticulture

The European climate is changing displaying profound on agriculture, thus strongly reaching the scientific community’s attention. In this review, the compilation of selected scientific research on the agroclimatic conditions’ changes and their impact on the productivity parameters (phenology timing, product quality and quantity) of grapevines and on the spatiotemporal characteristics of the viticultural areas are attempted for the first time. For this purpose, a thorough investigation through multiple search queries was conducted for the period (2005–2021). Overall, increasing (decreasing) trends in critical temperature (precipitation) parameters are the reality of the recent past with visible impacts on viticulture. The observed climate warming already enforces emerging phenomena related to the modification of the developmental rate (earlier phenological events, shortening of phenological intervals, lengthening of the growing season, earlier harvest), the alteration of product quality, the heterogeneous effects on grapevine yield and the emergence of new cool-climate viticulture areas highlighting the cultivation’s rebirth in the northern and central parts of the continent. The vulnerability of the wine-growing ecosystem urges the integration of innovative and sustainable solutions for confronting the impacts of climate change and safeguarding the production (quantity and quality) capacity of viticultural systems in Europe under a continuously changing environment.

Regulation of Plant Tannin Synthesis in Crop Species

Plant tannins belong to the antioxidant compound family, which includes chemicals responsible for protecting biological structures from the harmful effects of oxidative stress. A wide range of plants and crops are rich in antioxidant compounds, offering resistance to biotic, mainly against pathogens and herbivores, and abiotic stresses, such as light and wound stresses. These compounds are also related to human health benefits, offering protective effects against cardiovascular and neurodegenerative diseases in addition to providing anti-tumor, anti-inflammatory, and anti-bacterial characteristics. Most of these compounds are structurally and biosynthetically related, being synthesized through the shikimate-phenylpropanoid pathways, offering several classes of plant antioxidants: flavonoids, anthocyanins, and tannins. Tannins are divided into two major classes: condensed tannins or proanthocyanidins and hydrolysable tannins. Hydrolysable tannin synthesis branches directly from the shikimate pathway, while condensed tannins are derived from the flavonoid pathway, one of the branches of the phenylpropanoid pathway. Both types of tannins have been proposed as important molecules for taste perception of many fruits and beverages, especially wine, besides their well-known roles in plant defense and human health. Regulation at the gene level, biosynthesis and degradation have been extensively studied in condensed tannins in crops like grapevine (Vitis vinifera), persimmon (Diospyros kaki) and several berry species due to their high tannin content and their importance in the food and beverage industry. On the other hand, much less information is available regarding hydrolysable tannins, although some key aspects of their biosynthesis and regulation have been recently discovered. Here, we review recent findings about tannin metabolism, information that could be of high importance for crop breeding programs to obtain varieties with enhanced nutritional characteristics.

High Temperature Alters Anthocyanin Concentration and Composition in Grape Berries of Malbec, Merlot, and Pinot Noir in a Cultivar-Dependent Manner

Climate is determinant for grapevine geographical distribution, berry attributes, and wine quality. Due to climate change, a 2−4 °C increase in mean diurnal temperature is predicted by the end of the century for the most important Argentine viticulture region. We hypothesize that such temperature increase will affect color intensity and other quality attributes of red grapes and wines. The present study investigated the effect of high temperature (HT) on anthocyanin concentration and composition, pH, and resveratrol and solids content in berries of three major wine-producing varieties during fruit ripening in two seasons. To this end, a structure that increased mean diurnal temperature by 1.5−2.0 °C at berry sites, compared to Control (C) plants grown without such structure, was implemented in field grown vineyards of Malbec, Merlot, and Pinot Noir. Results revealed a cultivar-dependent response to HT conditions, with Malbec and Pinot Noir berries exhibiting significant decreases in total anthocyanin concentration (TAC) at veraison and harvest, respectively, while Merlot maintained an unaffected pigment content under HT. The decrease in TAC was associated with reduced levels of delphinidin, cyanidin, petunidin, peonidin, and malvidin glycosides, and increased ratios of acylated (AA)/non-acylated anthocyanins (NAA), suggesting pigment acylation as a possible stress-response mechanism for attenuating HT negative effects. Under HT, Pinot Noir, which does not produce AA, was the only cultivar with lower TAC at harvest (p < 0.05). pH, resveratrol, and solids content were not affected by HT. Our results predict high, medium, and low plasticity with regard to color quality attributes for Malbec, Merlot, and Pinot Noir, respectively, in the context of climate change.

The Effect of Topo-Climate Variation on the Secondary Metabolism of Berries in White Grapevine Varieties (Vitis vinifera)

Exploiting consistent differences in radiation and average air temperature between two experimental vineyards (Ramat Negev, RN and Mitzpe Ramon, MR), we examined the impact of climate variations on total carotenoids, redox status, and phenylpropanoid metabolism in the berries of 10 white wine grapevine (Vitis vinifera) cultivars across three consecutive seasons (2017-2019). The differences in carotenoid and phenylpropanoid contents between sites were seasonal and varietal dependent. However, the warmer RN site was generally associated with higher H₂O₂ levels and carotenoid degradation, and lower flavonol contents than the cooler MR site. Enhanced carotenoid degradation was positively correlated with radiation and daily degree days, leading to a greater drop in content from véraison to harvest in Colombard, Sauvignon Blanc, and Semillon berries. Analyses of berry H₂O₂ and phenylpropanoids suggested differences between cultivars in the links between H₂O₂ and flavonol contents. Generally, however, grapes with higher H₂O₂ content seem to have lower flavonol contents. Correlative network analyses revealed that phenylpropanoids at the warmer RN site are tightly linked to the radiation and temperature regimes during fruit ripening, indicating potentially harmful effect of warmer climates on berry quality. Specifically, flavan-3-ols were negatively correlated with radiation at RN. Principal component analysis showed that Muscat Blanc, Riesling, Semillon, and Sauvignon Blanc were the most site sensitive cultivars. Our results suggest that grapevine biodiversity is likely the key to withstand global warming hazards.

Foliar application of kaolin and zeolites to adapt the adverse effects of climate change in Vitis vinifera L. cv. Sangiovese

One of the first effects of climate change in wine-growing areas is the advancement of phenological stages, especially concerning early berry ripening. In this condition, the decoupling between technological and phenolic maturity often occurs. Anthocyanins in red grapes are among the compounds that mostly contribute to phenolic maturity. However, their accumulation in the grape berries is known to be impaired by high temperatures. Therefore, this study aims to evaluate the efficacy of mineral-based compounds treatments with kaolin and zeolite, based on chabasite, on the enhancement of anthocyanins accumulation, also at the molecular level, analysing the gene expressions along the flavonoid biosynthesis pathway during ripening of Sangiovese berries. In addition, the temperature of berries and grape leaves, vine water status, leaf photosynthetic efficiency, total soluble solids, titratable acidity and pH were measured throughout the growing season. Hence, in the current study, it has been demonstrated the efficacy of kaolin and zeolite treatments not only in lowering the daily maximum grape berries temperature but also in the improvement of grapes anthocyanins accumulation correlated with the enhancement of expression of those genes involved in their biosynthesis pathway. Moreover, treatments had no significant effect on productive parameters.

Plant Flavonoids in Mediterranean Species: A Focus on Flavonols as Protective Metabolites under Climate Stress

Flavonoids are specialized metabolites largely widespread in plants where they play numerous roles including defense and signaling under stress conditions. These compounds encompass several chemical subgroups such as flavonols which are one the most represented classes. The most studied flavonols are kaempferol, quercetin and myricetin to which research attributes antioxidative properties and a potential role in UV-defense through UV-screening mechanisms making them critical for plant adaptation to climate change. Despite the great interest in flavonol functions in the last decades, some functional aspects remain under debate. This review summarizes the importance of flavonoids in plant defense against climate stressors and as signal molecules with a focus on flavonols in Mediterranean plant species. The review emphasizes the relationship between flavonol location (at the organ, tissue and cellular scales) and their function as defense metabolites against climate-related stresses. It also provides evidence that biosynthesis of flavonols, or flavonoids as a whole, could be a crucial process allowing plants to adapt to climate change, especially in the Mediterranean area which is considered as one of the most sensitive regions to climate change over the globe.

Plant Secondary Metabolites Produced in Response to Abiotic Stresses Has Potential Application in Pharmaceutical Product Development

Plant secondary metabolites (PSMs) are vital for human health and constitute the skeletal framework of many pharmaceutical drugs. Indeed, more than 25% of the existing drugs belong to PSMs. One of the continuing challenges for drug discovery and pharmaceutical industries is gaining access to natural products, including medicinal plants. This bottleneck is heightened for endangered species prohibited for large sample collection, even if they show biological hits. While cultivating the pharmaceutically interesting plant species may be a solution, it is not always possible to grow the organism outside its natural habitat. Plants affected by abiotic stress present a potential alternative source for drug discovery. In order to overcome abiotic environmental stressors, plants may mount a defense response by producing a diversity of PSMs to avoid cells and tissue damage. Plants either synthesize new chemicals or increase the concentration (in most instances) of existing chemicals, including the prominent bioactive lead compounds morphine, camptothecin, catharanthine, epicatechin-3-gallate (EGCG), quercetin, resveratrol, and kaempferol. Most PSMs produced under various abiotic stress conditions are plant defense chemicals and are functionally anti-inflammatory and antioxidative. The major PSM groups are terpenoids, followed by alkaloids and phenolic compounds. We have searched the literature on plants affected by abiotic stress (primarily studied in the simulated growth conditions) and their PSMs (including pharmacological activities) from PubMed, Scopus, MEDLINE Ovid, Google Scholar, Databases, and journal websites. We used search keywords: "stress-affected plants," "plant secondary metabolites, "abiotic stress," "climatic influence," "pharmacological activities," "bioactive compounds," "drug discovery," and "medicinal plants" and retrieved published literature between 1973 to 2021. This review provides an overview of variation in bioactive phytochemical production in plants under various abiotic stress and their potential in the biodiscovery of therapeutic drugs. We excluded studies on the effects of biotic stress on PSMs.

Crimean autochthonous grape varieties as a factor of high-quality winemaking in a changing climate

An increase in ambient temperature affects the quality of wines, which is largely due to a change in the metabolism of phenolic substances in grapes. A possible solution to the problem is the use of autochthonous varieties adapted to unfavorable conditions. The influence of agroecological conditions of 4 vineyards on the phenolic complex of the Crimean grape variety ‘Kokur Belyi’ has been studied. Methods of geoinformation and mathematical modeling, HPLC were used. It is established: vineyards differ in heat resources in the row: Vilino < Privetnoe < Solnechnaya Dolina < Morskoe. An increase in the heat supply of territories caused the accumulation of phenolic acids, flavonols, (+)-D-catechine and procyanidins B4 in grape seeds and a decrease in the content of phenolic acids, (-)-epicatechine, procyanidins B3 in skin and pulp. The highest content of procyanidins in seeds and the lowest content of monomeric phenolic components in skin and pulp was determined in grapes from the village of Morskoye. Grapes from Vilino contain 3.7 times less procyanidins in the seeds, 6.5 and 3.6 times more monomeric components in the skin and pulp. Conclusion: the heat supply of vineyards contributes to both the biosynthesis of monomeric phenolic components and their polymerization during the ripening of grapes, leads to a significant differentiation of the phenolic complex of grapes ‘Kokur Belyi’.

Effect of the Seasonal Climatic Variations on the Flavonoid Accumulation in Vitis vinifera cvs. ‘Muscat Hamburg’ and ‘Victoria’ Grapes under the Double Cropping System

Under the double cropping system, berries usually showed significant quality variations in the summer and winter seasons. In the two-year/four-consecutive-season study, two table grapes of ‘Muscat Hamburg’ and ‘Victoria’ were investigated to determine the phenolic compounds in their berries. Different from those of the summer season, the berries in the winter season suffered no high-temperature stress since veraison to harvest in 2014 and 2015. The variations in the season temperatures led to a higher anthocyanin concentration in the winter season berries of ‘Muscat Hamburg’ grapes than that in the summer berries, while the summer season berries had higher proportions of acylated and methylated anthocyanins than those in the winter season berries. Similar to the anthocyanins, the winter season berries also had a higher flavonol concentration in both varieties. Transcriptome analysis showed that the upregulated genes involved in the flavonoid pathway in the winter season berries were agreed with the changes found in the metabolites. However, the influence of the growing seasons on the flavanols was not consistent in the two varieties, and the variations in VviLARs between the grapes of ‘Muscat Hamburg’ and ‘Victoria’ might be the cause. This research helped us better understand the double cropping system and how the climate factors affected the phenolic compounds in the double cropping system.

Responses to larval herbivory in the phenylpropanoid pathway of Ulmus minor are boosted by prior insect egg deposition

Elms, which have received insect eggs as a 'warning' of larval herbivory, enhance their anti-herbivore defences by accumulating salicylic acid and amplifying phenylpropanoid-related transcriptional and metabolic responses to hatching larvae. Plant responses to insect eggs can result in intensified defences against hatching larvae. In annual plants, this egg-mediated effect is known to be associated with changes in leaf phenylpropanoid levels. However, little is known about how trees-long-living, perennial plants-improve their egg-mediated, anti-herbivore defences. The role of phytohormones and the phenylpropanoid pathway in egg-primed anti-herbivore defences of a tree species has until now been left unexplored. Using targeted and untargeted metabolome analyses we studied how the phenylpropanoid pathway of Ulmus minor responds to egg-laying by the elm leaf beetle and subsequent larval feeding. We found that when compared to untreated leaves, kaempferol and quercetin concentrations increased in feeding-damaged leaves with prior egg deposition, but not in feeding-damaged leaves without eggs. PCR analyses revealed that prior insect egg deposition intensified feeding-induced expression of phenylalanine ammonia lyase (PAL), encoding the gateway enzyme of the phenylpropanoid pathway. Salicylic acid (SA) concentrations were higher in egg-treated, feeding-damaged leaves than in egg-free, feeding-damaged leaves, but SA levels did not increase in response to egg deposition alone-in contrast to observations made of Arabidopsis thaliana. Our results indicate that prior egg deposition induces a SA-mediated response in elms to feeding damage. Furthermore, egg deposition boosts phenylpropanoid biosynthesis in subsequently feeding-damaged leaves by enhanced PAL expression, which results in the accumulation of phenylpropanoid derivatives. As such, the elm tree shows similar, yet distinct, responses to insect eggs and larval feeding as the annual model plant A. thaliana.

Chiral Flavonoids as Antitumor Agents

Flavonoids are a group of natural products with a great structural diversity, widely distributed in plant kingdom. They play an important role in plant growth, development and defense against aggressors. Flavonoids show a huge variety of biological activities such as antioxidant, anti-inflammatory, anti-mutagenic, antimicrobial and antitumor, being able to modulate a large diversity of cellular enzymatic activities. Among natural flavonoids, some classes comprise chiral molecules including flavanones, flavan-3-ols, isoflavanones, and rotenoids, which have one or more stereogenic centers. Interestingly, in some cases, individual compounds of enantiomeric pairs have shown different antitumor activity. In nature, these compounds are mainly biosynthesized as pure enantiomers. Nevertheless, they are often isolated as racemates, being necessary to carry out their chiral separation to perform enantioselectivity studies. Synthetic chiral flavonoids with promising antitumor activity have also been obtained using diverse synthetic approaches. In fact, several new chiral bioactive flavonoids have been synthesized by enantioselective synthesis. Particularly, flavopiridol was the first cyclin-dependent kinase (CDK) inhibitor which entered clinical trials. The chiral pool approaches using amino acid as chiral building blocks have also been reported to achieve small libraries of chrysin derivatives with more potent in vitro growth inhibitory effect than chrysin, reinforcing the importance of the introduction of chiral moieties to improve antitumor activity. In this work, a literature review of natural and synthetic chiral flavonoids with antitumor activity is reported for the first time.

Metabolite Profiling of Dioscorea (Yam) Leaves to Identify Bioactive Compounds Reveals Their Potential as Renewable Resources

Yams (Dioscorea spp.) are cultivated and consumed as edible tubers, while their leaves are discarded as waste or burned with negative environmental impact. Herein, the metabolites of two yam species (Danma, DAN; Dunggeunma, DUN), harvested in June, July, and August, were profiled using GC-TOF-MS and UHPLC-LTQ-Orbitrap-MS/MS and the antioxidant activity of the extracts was evaluated to stimulate the utilization of yam leaves as a by-product. We observed that the relative levels of amino acids, organic acids, sugars, and saponins decreased linearly with prolonged harvest time, while fatty acid, phenanthrene, and flavonoid levels gradually increased. Furthermore, the leaf extracts obtained in August exhibited the highest antioxidant activity. To determine the antioxidant-contributing metabolites, OPLS-DA was performed for the leaf metabolites of DAN and DUN leaves harvested in August. Hydroxytyrosol-glucoside, apigenin-rhamnoside, and rutin were more abundant in DUN, while luteolin, phenanthrene derivatives, epicatechin, and kaempferide were relatively higher in DAN and their respective metabolites were positively correlated with the antioxidant activity. Moreover, secondary metabolites were more abundant in the leaves than in the roots, and consequently, the antioxidant activity of the former was also higher. Overall, the potential value of yam leaves as a renewable source of bioactive compounds is proposed.

McMYB4 improves temperature adaptation by regulating phenylpropanoid metabolism and hormone signaling in apple

Temperature changes affect apple development and production. Phenylpropanoid metabolism and hormone signaling play a crucial role in regulating apple growth and development in response to temperature changes. Here, we found that McMYB4 is induced by treatment at 28 °C and 18 °C, and McMYB4 overexpression results in flavonol and lignin accumulation in apple leaves. Yeast one-hybrid (Y1H) assays and electrophoretic mobility shift assays (EMSAs) further revealed that McMYB4 targets the promoters of the flavonol biosynthesis genes CHS and FLS and the lignin biosynthesis genes CAD and F5H. McMYB4 expression resulted in higher levels of flavonol and lignin biosynthesis in apple during growth at 28 °C and 18 °C than during growth at 23 °C. At 28 °C and 18 °C, McMYB4 also binds to the AUX/ARF and BRI/BIN promoters to activate gene expression, resulting in acceleration of the auxin and brassinolide signaling pathways. Taken together, our results demonstrate that McMYB4 promotes flavonol biosynthesis and brassinolide signaling, which decreases ROS contents to improve plant resistance and promotes lignin biosynthesis and auxin signaling to regulate plant growth. This study suggests that McMYB4 participates in the abiotic resistance and growth of apple in response to temperature changes by regulating phenylpropanoid metabolism and hormone signaling.

In through the out door: Biochemical mechanisms affecting flavonoid glycoside catabolism in plants

Plants are the sole source of flavonoids, a chemical category that includes flavonols. For the most part, flavonols occur as glycosides with numerous postulated biological roles in plants, including photoprotection, modulation of hormone translocation, and sequestration of reactive oxygen species. Flavonol glycosides are often considered as dead-end metabolites because related flavonoids (i.e., anthocyanins) occur in terminal tissues such as flowers and fruit, but recent evidence points to their turnover in planta, including developing photosynthetic tissues. Although microbial degradation pathways for flavonol glycosides of plant origin are well described, plant catabolic pathways are little studied by comparison. This review will address our current understanding of biochemical processes leading to the loss of flavonol glycosides in plants, with a specific emphasis on the evidence for flavonol-specific β-glucosidases. Complete elucidation of these catabolic pathways is dependent on the identification of regiospecific modifying steps, including enzymes associated with the hydrolysis of rhamnosylated flavonols, as well as flavonol peroxidation and their encoding genes. Herein, we highlight challenges for the identification of hypothetical plant α-rhamnosidases and peroxidases involved in flavonol glycoside degradation, and the potential biological role of this catabolism in mitigating oxidative stress in developing and postharvest plant tissues.

Impact of 2100-Projected Air Temperature, Carbon Dioxide, and Water Scarcity on Grape Primary and Secondary Metabolites of Different Vitis vinifera cv. Tempranillo Clones

The exploration of the grapevine (Vitis vinifera L.) intra-varietal diversity can be an interesting approach for the adaptation of viticulture to climate change. We evaluated the response of four Tempranillo clones to simulated year-2100-expected air temperature, CO₂, and relative humidity (RH) conditions: climate change (CC; 28 °C/18 °C, 700 μmol mol^-1 CO₂, and 35%/53% RH) vs current situation conditions (CS; 24 °C/14 °C, 400 μmol mol^-1 CO₂, and 45%/63% RH), under two irrigation regimes, "well-watered" (WW) vs "water deficit" (WD). The treatments were applied to fruit-bearing cuttings grown under research-oriented greenhouse controlled conditions. CC increased sugar accumulation and hastened grape phenology, an effect that was mitigated by water deficit. Both CC and water deficit modified amino acid concentrations and accumulation profiles with different intensities, depending on the clone. Combined CC and water deficit decreased anthocyanins and the anthocyanin to total soluble solids (TSS) ratio. The results suggest differences in the response of the clones to the 2100-projected conditions, which are not always solely explained by differences observed in the ripening dynamics. Among the clones studied, RJ43 and CL306 were the most affected by CC/WD conditions; meanwhile, 1084 was globally less affected than the other clones.

Molecular Tools for Adapting Viticulture to Climate Change

Adaptation of viticulture to climate change includes exploration of new geographical areas, new training systems, new management practices, or new varieties, both for rootstocks and scions. Molecular tools can be defined as molecular approaches used to study DNAs, RNAs, and proteins in all living organisms. We present here the current knowledge about molecular tools and their potential usefulness in three aspects of grapevine adaptation to the ongoing climate change. (i) Molecular tools for understanding grapevine response to environmental stresses. A fine description of the regulation of gene expression is a powerful tool to understand the physiological mechanisms set up by the grapevine to respond to abiotic stress such as high temperatures or drought. The current knowledge on gene expression is continuously evolving with increasing evidence of the role of alternative splicing, small RNAs, long non-coding RNAs, DNA methylation, or chromatin activity. (ii) Genetics and genomics of grapevine stress tolerance. The description of the grapevine genome is more and more precise. The genetic variations among genotypes are now revealed with new technologies with the sequencing of very long DNA molecules. High throughput technologies for DNA sequencing also allow now the genetic characterization at the same time of hundreds of genotypes for thousands of points in the genome, which provides unprecedented datasets for genotype-phenotype associations studies. We review the current knowledge on the genetic determinism of traits for the adaptation to climate change. We focus on quantitative trait loci and molecular markers available for developmental stages, tolerance to water stress/water use efficiency, sugar content, acidity, and secondary metabolism of the berries. (iii) Controlling the genome and its expression to allow breeding of better-adapted genotypes. High-density DNA genotyping can be used to select genotypes with specific interesting alleles but genomic selection is also a powerful method able to take into account the genetic information along the whole genome to predict a phenotype. Modern technologies are also able to generate mutations that are possibly interesting for generating new phenotypes but the most promising one is the direct editing of the genome at a precise location.

Sunburn in Grapes: A Review

Sunburn is a physiological disorder that affects the visual and organoleptic properties of grapes. The appearance of brown and necrotic spots severely affects the commercial value of the fruit, and in extreme cases, significantly decreases yield. Depending on the severity of the damage and the driving factors, sunburn on grapes can be classified as sunburn browning (SB) or as sunburn necrosis (SN). Sunburn results from a combination of excessive photosynthetically active radiation (PAR) and UV radiation and temperature that can be exacerbated by other stress factors such as water deficit. Fruit respond to these by activating antioxidant defense mechanisms, de novo synthesis of optical screening compounds and heat-shock proteins as well as through morphological adaptation. This review summarizes the current knowledge on sunburn in grapes and compares it with relevant literature on other fruits. It also discusses the different factors affecting the appearance and degree of sunburn, as well as the biochemical response of grapes to this phenomenon and different potential mitigation strategies. This review proposes further directions for research into sunburn in grapes.

Impact of Environmental Factors on Stilbene Biosynthesis

Stilbenes are a small family of polyphenolic secondary metabolites that can be found in several distantly related plant species. These compounds act as phytoalexins, playing a crucial role in plant defense against phytopathogens, as well as being involved in the adaptation of plants to abiotic environmental factors. Among stilbenes, trans-resveratrol is certainly the most popular and extensively studied for its health properties. In recent years, an increasing number of stilbene compounds were subjected to investigations concerning their bioactivity. This review presents the most updated knowledge of the stilbene biosynthetic pathway, also focusing on the role of several environmental factors in eliciting stilbenes biosynthesis. The effects of ultraviolet radiation, visible light, ultrasonication, mechanical stress, salt stress, drought, temperature, ozone, and biotic stress are reviewed in the context of enhancing stilbene biosynthesis, both in planta and in plant cell and organ cultures. This knowledge may shed some light on stilbene biological roles and represents a useful tool to increase the accumulation of these valuable compounds.

Spatial distribution of Crimean agroecological resources as a factor of variability of the main and secondary metabolites of grapes

The work is aimed at identifying the relationship between agroecological conditions and the formation of carbohydrate-acid and phenolic grape complexes. The agro-climatic parameters of 14 cv. ‘Cabernet Sauvignon’ industrial vineyards located in five wine-growing regions of Crimea have been determined using the methods of geoinformation and mathematical modeling. According to the similarity of 9 agro-climatic characteristics, the vineyards are united into 6 clusters, significantly different from each other. The dispersion of the main and secondary metabolites of grapes, as well as technological indicators based on them in the harvest from the selected clusters, has been established. According to the combined mass concentration of anthocyanins in berries, potential amount of extractable anthocyanins, anthocyanin extractability, monophenolmonooxygenase activity, glucoacidimetric index and grape ripeness index the selected vineyard clusters are discriminated with Wilks L. = 0.09 at α<0.00001. Sugar content, active acidity index, glucoacidimetric index, and grape ripeness index were found to correlate inversely with the amount of precipitation during the growing season; anthocyanin extractability correlates directly with the Huglin and Winkler indices; monophenolmonooxygenase activity with the sum of active temperatures above 10 °C, Huglin index, total precipitation per year and growing season.

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.

The Exploitation of Local Vitis vinifera L. Biodiversity as a Valuable Tool to Cope with Climate Change Maintaining Berry Quality

(1) Background: The associated increase in global mean surface temperature together with raised atmospheric carbon dioxide (CO₂) concentration is exerting a profound influence on grapevine development (phenology) and grape quality. The exploitation of the local genetic diversity based on the recovery of ancient varieties has been proposed as an interesting option to cope with climate change and maintaining grape quality. Therefore, this research aimed to characterize the potential fruit quality of genotypes from seven local old grapevine varieties grown under climate change conditions. (2) Methods: The study was carried out on fruit-bearing cuttings (one cluster per plant) that were grown in pots in temperature gradient greenhouses (TGG). Two treatments were applied from fruit set to maturity: (1) ambient CO₂ (400 ppm) and temperature (T) (ACAT) and (2) elevated CO₂ (700 ppm) and temperature (T + 4 °C) (ECET). (3) Results: Results showed that some of the old genotypes tested remained quite stable during the climate change conditions in terms of fruit quality (mainly, total soluble solids and phenolic content) and of must antioxidant properties. (4) Conclusion: This research underlines the usefulness of exploiting local grapevine diversity to cope with climate change successfully, although further studies under field conditions and with whole plants are needed before extrapolating the results to the vineyard.

Temperature Shift Between Vineyards Modulates Berry Phenology and Primary Metabolism in a Varietal Collection of Wine Grapevine

Global climate change and the expected increase in temperature are altering the relationship between geography and grapevine (V. vinifera) varietal performance, and the implications of which are yet to be fully understood. We investigated berry phenology and biochemistry of 30 cultivars, 20 red and 10 white, across three seasons (2017-2019) in response to a consistent average temperature difference of 1.5°C during the growing season between two experimental sites. The experiments were conducted at Ramat Negev (RN) and Ramon (MR) vineyards, located in the Negev desert, Israel. A significant interaction between vineyard location, season, and variety affected phenology and berry indices. The warmer RN site was generally associated with an advanced phenological course for the white cultivars, which reached harvest up to 2 weeks earlier than at the MR site. The white cultivars also showed stronger correlation between non-consecutive phenological stages than did the red ones. In contrast, harvest time of red cultivars considerably varied according to seasons and sites. Warmer conditions extended fruit developmental phases, causing berry shriveling and cluster collapse in a few cultivars such as Pinot Noir, Ruby Cabernet, and Tempranillo. Analyses of organic acid content suggested differences between red and white cultivars in the content of malate, tartrate, and citrate in response to the temperature difference between sites. However, generally, cultivars at lower temperatures exhibited lower concentrations of pulp organic acids at véraison, but acid degradation until harvest was reduced, compared to the significant pace of acid decline at the warmer site. Sugars showed the greatest differences between sites in both white and red berries at véraison, but differences were seasonal dependent. At harvest, cultivars of both groups exhibited significant variation in hexose/sucrose ratio, and the averages of which varied from 1.6 to 2.9. Hexose/sucrose ratio was significantly higher among the red cultivars at the warmer RN, while this tendency was very slight among white cultivars. White cultivars seem to harbor a considerable degree of resilience due to a combination of earlier and shorter ripening phase, which avoids most of the summer heat. Taken together, our study demonstrates that the extensive genetic capacity of V. vinifera bears significant potential and plasticity to withstand the temperature increase associated with climate change.

High temperature at veraison inhibits anthocyanin biosynthesis in berry skins during ripening in 'Kyoho' grapevines

We examined the effects of high temperature (HT) at veraison (the onset of ripening) on coloration and anthocyanin biosynthesis in berry skins of 'Kyoho' grapevines (Vitis labruscana L.). The vines were subjected to control, HT (6 °C higher than the control for 10 days), and intermittent HT (IHT; 6 °C higher than the control for 4 days followed by control temperature for 3 days and then 6 °C higher than the control for another 3 days) conditions from 50 to 60 days after full bloom (DAFB) in temperature-controlled rooms. Under control conditions, berry skins were tinted purple from 55 DAFB and turned to reddish-purple thereafter until 80 DAFB, concurrently with the anthocyanin accumulation. The HT and IHT treatments greatly inhibited the coloration and anthocyanin accumulation, with greater inhibition by the HT treatment. The HT and IHT treatments significantly inhibited the expressions of early (EBGs) and late anthocyanin biosynthetic genes (LBGs), and the transcription factor gene VlMYBA2. Abscisic acid (ABA) contents in the control berry skins increased from 50 DAFB, peaked at 55 DAFB, and decreased thereafter. The HT and IHT treatments reduced the increase in ABA contents, with no significant difference between HT- and IHT-treated vines. Gibberellin (GA) contents decreased during veraison in the berry skins of control and IHT-treated vines, but remained unchanged in those of HT-treated vines. These results suggest that the coloration and anthocyanin biosynthesis in berry skins are associated with changes in the ABA/GA ratio.

Advances in Biosynthesis and Biological Functions of Proanthocyanidins in Horticultural Plants

Proanthocyanidins are colorless flavonoid polymers condensed from flavan-3-ol units. They are essential secondary plant metabolites that contribute to the nutritional value and sensory quality of many fruits and the related processed products. Mounting evidence has shown that the accumulation of proanthocyanidins is associated with the resistance of plants against a broad spectrum of abiotic and biotic stress conditions. The biosynthesis of proanthocyanidins has been examined extensively, allowing for identifying and characterizing the key regulators controlling the biosynthetic pathway in many plants. New findings revealed that these specific regulators were involved in the proanthocyanidins biosynthetic network in response to various environmental conditions. This paper reviews the current knowledge regarding the control of key regulators in the underlying proanthocyanidins biosynthetic and molecular mechanisms in response to environmental stress. Furthermore, it discusses the directions for future research on the metabolic engineering of proanthocyanidins production to improve food and fruit crop quality.

Rapid dehydration of grape berries dampens the post-ripening transcriptomic program and the metabolite profile evolution

The postharvest dehydration of grape berries allows the concentration of sugars and other solutes and promotes the synthesis of metabolites and aroma compounds unique to high-quality raisin wines such as the passito wines made in Italy. These dynamic changes are dependent on environmental parameters such as temperature and relative humidity, as well as endogenous factors such as berry morphology and genotype, but the contribution of each variable is not well understood. Here, we compared berries subjected to natural or accelerated dehydration, the latter driven by forced air flow. We followed the evolution of transcript and metabolite profiles and found that accelerated dehydration clearly dampened the natural transcriptomic and metabolomic programs of postharvest berries. We found that slow dehydration over a prolonged duration is necessary to induce gene expression and metabolite accumulation associated with the final quality traits of dehydrated berries. The accumulation of key metabolites (particularly stilbenoids) during postharvest dehydration is inhibited by rapid dehydration conditions that shorten the berry life time.

Foliar application of specific yeast derivative enhances anthocyanins accumulation and gene expression in Sangiovese cv (Vitis vinifera L.)

The effect of elicitors on secondary metabolism in vines is receiving much interest, since it has been shown that they are able to increase the accumulation of phenolics, especially anthocyanins. This research aims to investigate the biochemical and molecular effects of the application of a commercial yeast derivative (Saccharomyces cerevisiae) on the accumulation of anthocyanins in potted Sangiovese vines. Experiments were performed on three consecutive years and the yeast derivative was applied at the beginning and at the end of veraison. Technological ripening, accumulation of anthocyanins and expression of the main genes involved in their biosynthesis were assessed. Technological ripening proceeded in a similar way in both treated and untreated berries in the three years. A significant increase in the concentration of anthocyanins was instead detected, following the induction by the yeast derivative of the expression of the genes involved in their biosynthesis. The research highlights the possibility of applying a specific inactivated yeast to increase the anthocyanin concentration even under the current climate change conditions, in Sangiovese, a cultivar extremely sensitive to high temperatures.

Chalcone synthase (CHS) family members analysis from eggplant (Solanum melongena L.) in the flavonoid biosynthetic pathway and expression patterns in response to heat stress

Enzymes of the chalcone synthase (CHS) family participate in the synthesis of multiple secondary metabolites in plants, fungi and bacteria. CHS showed a significant correlation with the accumulation patterns of anthocyanin. The peel color, which is primarily determined by the content of anthocyanin, is an economically important trait for eggplants that is affected by heat stress. A total of 7 CHS (SmCHS1-7) putative genes were identified in a genome-wide analysis of eggplants (S. melongena L.). The SmCHS genes were distributed on 7 scaffolds and were classified into 3 clusters. Phylogenetic relationship analysis showed that 73 CHS genes from 7 Solanaceae species were classified into 10 groups. SmCHS5, SmCHS6 and SmCHS7 were continuously down-regulated under 38°C and 45°C treatment, while SmCHS4 was up-regulated under 38°C but showed little change at 45°C in peel. Expression profiles of key anthocyanin biosynthesis gene families showed that the PAL, 4CL and AN11 genes were primarily expressed in all five tissues. The CHI, F3H, F3’5’H, DFR, 3GT and bHLH1 genes were expressed in flower and peel. Under heat stress, the expression level of 52 key genes were reduced. In contrast, the expression patterns of eight key genes similar to SmCHS4 were up-regulated at a treatment of 38°C for 3 hour. Comparative analysis of putative CHS protein evolutionary relationships, cis-regulatory elements, and regulatory networks indicated that SmCHS gene family has a conserved gene structure and functional diversification. SmCHS showed two or more expression patterns, these results of this study may facilitate further research to understand the regulatory mechanism governing peel color in eggplants.

Regulation of flavonoid metabolism in ginkgo leaves in response to different day-night temperature combinations

Flavonoids are the most important secondary metabolites in ginkgo (Ginkgo biloba L.) leaves that determine its medicinal quality. Studies have suggested that secondary metabolism is strongly affected by temperature in other plant species, but little is known about ginkgo. In this study, we investigated the effects of different day-night temperature combinations (15/10, 25/20, and 35/30 °C (day/night)) on key enzyme activity, growth regulator concentrations, and flavonoid accumulation in ginkgo leaves. We found that phenylalanine ammonia-lyase (PAL) activity was enhanced and inhibited at 15/10 and 35/30 °C, respectively. Cinnamate-4-hydroxylase (C4H) activity was relatively stable under the three temperature conditions, and the p-coumarate CoA ligase (4CL) activity showed different trends under the three temperature conditions. The concentrations of flavonoid constituents (quercetin, kaempferol, and isorhamnetin) were decreased and increased under the 35/30 and 15/10 °C conditions, respectively. Low temperature promoted soluble sugar accumulation, while temperature had a limited impact on the accumulation of soluble protein. The pattern of change in the total flavonoid concentration was not always in agreement with PAL activity due to its complex pathway. Indoleacetic acid (IAA) and gibberellin (GA) changes shared similar patterns and had limited effects on flavonoid accumulation, while abscisic acid (ABA) acted as a promotor of flavonoid accumulation under high-temperature conditions. The total flavonoids achieved the highest content under the 15/10 °C treatment on the 40th day. Therefore, the lower temperature (15/10 °C) is more favorable for flavonoid accumulation and will provide a theoretical basis for further study.

Comprehensive co-expression analysis provides novel insights into temporal variation of flavonoids in fresh leaves of the tea plant (Camellia sinensis)

Flavonoids are the major class of characteristic secondary compounds in Camellia sinensis that affect quality of tea. However, the temporal variation and the underlying regulatory mechanism of flavonoid biosynthesis during different growth months require a further investigation. Here, we combined analyses of the metabolomics and transcriptomics to tea leaves freshly collected during five different months for a comprehensive understanding of flavonoid metabolism regulation in tea plants. Through loading plot analysis, significant changes in the contents of metabolites during growing months were discovered, and further co-expression and association analysis indicated that one flavone glycoside (naringenin-7-O-glucoside) and two flavonol glycosides (quercetin-3-O-galactoside and kaemferol-3-O-(6″-O-p-courmaroyl)-glucoside) were evaluated as growth markers, which may explain the high bitterness and astringency of August teas; additionally, the high levels of two flavan-3-ols (gallocatechin and catechin gallate) may contribute to the flavor formation of April tea. Meanwhile, multiple flavonoid-related structural genes, MYB and bHLH transcription factors exhibit specific expression patterns to modulate the biosynthesis of these key flavonoids. A co-expression regulatory sub-network was constructed based on profiles of differentially expressed genes; one CsbHLH and six transcription factors (three CsbHLHs and three CsMYBs) exhibited negative and positive roles in the regulation of flavonoid biosynthetic genes, respectively. Taken together, our results provide new insights into the regulation of principle flavonoids for unique flavor of tea regulated by many flavonoid-related structural genes and transcription factors during different growth months.