Grapevine Berry Research Articles

Grapevine Pinot gris virus in Germany: From where did the virus come, and when?

AbstractGrapevine Pinot gris virus (GPGV) isolates were obtained from German vineyards to investigate their diversity. Phylogenetic and dating analyses of these and GPGV genes and genomes available in GenBank showed that the virus probably diverged from grapevine berry inner necrosis virus (GINV) in wild and cultivated Vitis species, notably Vitis coignetiae, growing in North‐east Asia around 3500 years ago. GPGV probably infected the Eurasian grape (Vitis vinifera subsp. vinifera) when those cultivars were first taken to China during the Han Dynasty (226 BCE–220 CE). GPGV then spread to Europe around 1800 CE, probably via the dissemination of infected plants, and from there, eventually spread worldwide. German isolates were only found in all parts of the post‐1800 CE phylogeny. The German isolates were genetically more diverse, for both MP and CP genes, than those of other European populations, suggesting that the initial stages of the GPGV invasion of Europe were in Germany, not Italy. We discuss the likely North‐east Asian origin of both GPGV and GINV, and the possible coincidences of phylogenetic date estimates with changes to European and world viticulture practices.

A mobile device to investigate the response of grapevine berries to heat stress

Reproducibly comparing the heat stress response of grapevine berries from different cultivars in the field is often limited by weather conditions during the growing season. This work presents a mobile heating device capable of controlled heat-stress induction on grapevine berries. The heater consisted of six 150 W infrared lamps mounted in a profile frame. The heating power of the lamps could be set individually by a control unit consisting of a single board computer and six temperature sensors positioned as desired. The heat energy applied to individual berries within a cluster decreases by the squared distance to the heat source, enabling the establishment of temperature profiles within individual clusters. Infrared thermography of the fruit surface and measurements conducted with a thermocouple inserted at the epidermis level showed comparable temperatures. Berries treated with high temperatures were sampled according to their visual appearance (i.e., sunburn symptoms). Only symptomatic berries showed a significant increase in electrolyte leakage, indicating cell damage. In a field experiment, the induction of sunburn necrosis symptoms with the presented device was used to predict a Lethal Dose (LD50) for sunburn necrosis symptoms of the Vitis vinifera L. cultivars Bacchus and Silvaner. The LD50 of Bacchus, known as a heat-sensitive cultivar, was about 3.2 °C lower than that of Silvaner. The presented device offers possibilities for a wide range of applications and the induction of precise temperature dynamics in the context of heat stress on fleshy fruit.

Anthocyanin Accumulation and Its Corresponding Gene Expression, Total Phenol, Antioxidant Capacity, and Fruit Quality of ‘Crimson Seedless’ Grapevine (Vitis vinifera L.) in Response to Grafting and Pre-Harvest Applications

The color of grapevine berries is one of the most important quality parameters that define the appearance, attracts the consumer, and determines the price, especially in red grape cultivars. Some grape varieties show less color development due to many factors such as temperature, light intensity, and agricultural management. The present study aimed to evaluate diverse phytohormones coupled with grafting on quality and fruit coloration of ’Crimson Seedless‘ grapes. Pre-harvest foliar treatments of abscisic acid (ABA) at 400 mg L−1, methyl jasmonate (MeJ) at 1 mM L−1, ethephon (Eth) at 480 mg L−1, and melatonin (Mel) at 100 μmol were applied after 7 days and repeated after 21 days of ‘Veraison’ (beginning of the coloring phase). The results exposed that the ABA application provided the best anthocyanin accumulation with grafted grapevines whereas Eth displayed the maximum anthocyanin accumulation with ungrafted grapevines. Moreover, the expression of anthocyanin biosynthesis genes (chalcone synthase (CHS), flavanone 3-hydroxylase (F3H), and flavanol 3-O-glucosyl transferase (UFGT)) was consistent with the anthocyanin concentration in berry peel. Moreover, Eth treatment revealed the highest total phenols and antioxidant capacity for both grafted and ungrafted grapevines. MeJ phytohormone exhibited the largest total yield, whereas the treatment of Eth increased the weight of 50 berries and the bunch. Furthermore, ABA induced the uppermost firmness and removal force. Regarding the chemical attributes, the Mel treatment revealed the minimum value of titratable acidity (TA) and the highest polyphenol oxidase (PPO) activity, while the MeJ treatment recorded the superior soluble solids content (SSC), in addition to phenylalanine ammonia-lyase (PAL) and catalase (CAT) enzymes activities. Eth treatment produced the highest activity of the peroxidase (POD) enzyme. Finally, the grafting treatment improved most of the studied fruit attributes.

Metabolomics Insight into the Variety-Mediated Responses to Aspergillus carbonarius Infection in Grapevine Berries.

Limited knowledge regarding the susceptibility of grape varieties to ochratoxin A (OTA)-producing fungi is available to date. This study aimed to investigate the susceptibility of different grape varieties to Aspergillus carbonarius concerning OTA contamination and modulation at the metabolome level. Six grape varieties were selected, sampled at early veraison and ripening, artificially inoculated with A. carbonarius, and incubated at two temperature regimes. Significant differences were observed across cultivars, with Barbera showing the highest incidence of moldy berries (around 30%), while Malvasia and Ortrugo showed the lowest incidence (about 2%). OTA contamination was the lowest in Ortrugo and Malvasia, and the highest in Croatina, although it was not significantly different from Barbera, Merlot, and Sauvignon Blanc. Fungal development and mycotoxin production changed with grape variety; the sugar content in berries could also have played a role. Unsupervised multivariate statistical analysis from metabolomic fingerprints highlighted cultivar-specific responses, although a more generalized response was observed by supervised OPLS-DA modeling. An accumulation of nitrogen-containing compounds (alkaloids and glucosinolates), phenylpropanoids, and terpenoids, in addition to phytoalexins, was observed in all samples. A broader modulation of the metabolome was observed in white grapes, which were less contaminated by OTA. Jasmonates and oxylipins were identified as critical upstream modulators in metabolomic profiles. A direct correlation between the plant defense machinery and OTA was not observed, but the information was acquired and can contribute to optimizing preventive actions.

Effects of Global Warming on Grapevine Berries Phenolic Compounds—A Review

The steadfast propensity to global warming has had a severe impact on overall viticulture. Given the observed increase in growing season temperatures in Europe (+1.7 °C from 1950 to 2004), between 2000 and 2049, it is assumed that temperatures for major wine regions will increase on average by about +0.42 °C per decade and will generally increase by +2.04 °C. Phenolic compound development is affected by environmental parameters such as ultraviolet (UV) radiation, sunlight, maximum and minimum temperatures, and grapevine water status. Proanthocyanidins, flavan-3-ol monomers, and other pigmented polymers are impacted by soil management and canopy handling strategies, as well as obtaining a microclimate around the developing bunch. This review, after a necessary summary of the synthesis of phenolic compounds in the berry (flavonoids and non-flavonoids) to let the lector delve into the topic, describes the impact of climate change and therefore of environmental factors on their accumulation and storage throughout ripening and harvesting. For example, high berry temperatures can reduce the total concentrations of skin anthocyanin; a 35 °C temperature entirely obstructed anthocyanin synthesis, and instead quercetin 3-glucoside could be enhanced with exposure to solar radiation. In addition, increments via water deficit in the relative abundance of methoxylated anthocyanins were also found. The vineyard management strategies to mitigate the degradation of phenolic compounds and preserve their concentration are also further discussed. Finally, it is believed that it is necessary today to establish an elastic and variable approach towards the single wine year, moving away from the concept of product standardization.

Biocontrol of Botrytis cinerea on Grape Berries in Chile: Use of Registered Biofungicides and a New Chitosan-Based Fungicide

In organic phytosanitary management of vineyards, it is crucial to understand the available pathogen control alternatives in order to progress towards a more sustainable form of viticulture. The objective of this study was to evaluate the efficacy of seven biofungicides registered in Chile for the prevention and treatment of Botrytis Bunch Rot (BBR), and to test a novel fungicide composed of chitosan and riboflavin (CH-RF). Biofungicides including Trichoderma spp., Aureobasidium pullulans, and Melaleuca alternifolia were evaluated using biotests with grapevine berries. Registered products (specifically biological control agents) significantly reduced the in vitro growth of B. cinerea. However, the degree of pathogen control varied significantly among products in grapevine berries of the Chardonnay cultivar, and disease incidence and severity changed depending on the inoculation time. High control effectiveness was achieved with two biofungicides, A. pullulans (average efficacy 34%) and M. alternifolia oil (average efficacy 29%). In vitro tests showed CH-RF significantly reduced mycelial growth of B. cinerea. Noticeable differences between the new CH-RF fungicide (incidence under 50% and infection score under 1) and A. pullulans- and M. alternifolia-based products were detected in grapevine berries. Therefore, the new experimental formulation CH-RF constitutes a promising alternative for the control of B. cinerea and provides a basis for further research.

Secondary metabolites in grapevine: crosstalk of transcriptional, metabolic and hormonal signals controlling stress defence responses in berries and vegetative organs.

Abiotic stresses, such as temperature, heat waves, water limitation, solar radiation and the increase in atmospheric CO2 concentration, significantly influence the accumulation of secondary metabolites in grapevine berries at different developmental stages, and in vegetative organs. Transcriptional reprogramming, miRNAs, epigenetic marks and hormonal crosstalk regulate the secondary metabolism of berries, mainly the accumulation of phenylpropanoids and of volatile organic compounds (VOCs). Currently, the biological mechanisms that control the plastic response of grapevine cultivars to environmental stress or that occur during berry ripening have been extensively studied in many worlds viticultural areas, in different cultivars and in vines grown under various agronomic managements. A novel frontier in the study of these mechanisms is the involvement of miRNAs whose target transcripts encode enzymes of the flavonoid biosynthetic pathway. Some miRNA-mediated regulatory cascades, post-transcriptionally control key MYB transcription factors, showing, for example, a role in influencing the anthocyanin accumulation in response to UV-B light during berry ripening. DNA methylation profiles partially affect the berry transcriptome plasticity of different grapevine cultivars, contributing to the modulation of berry qualitative traits. Numerous hormones (such as abscisic and jasmomic acids, strigolactones, gibberellins, auxins, cytokynins and ethylene) are involved in triggering the vine response to abiotic and biotic stress factors. Through specific signaling cascades, hormones mediate the accumulation of antioxidants that contribute to the quality of the berry and that intervene in the grapevine defense processes, highlighting that the grapevine response to stressors can be similar in different grapevine organs. The expression of genes responsible for hormone biosynthesis is largely modulated by stress conditions, thus resulting in the numeourous interactions between grapevine and the surrounding environment.

Identification of UGT85A glycosyltransferases associated with volatile conjugation in grapevine (Vitis vinifera × Vitislabrusca)

Glycosylated volatiles are considered as hidden aroma precursors that affect fruit flavor and are involved in plant defense response. Several uridine-diphosphate (UDP)-glycosyltransferase (UGT) members related to the glycosylation of volatiles have been identified from grapevine berries. Although grapevine leaves produced much higher levels of glycosylated volatiles than berries, UGTs responsible for the production of glycosylated volatiles in leaves have not yet been identified. Here, eight novel UGT genes were cloned, among these four members that belong to UGT85A family (named UGT85A24, UGT85A25, UGT85A26, and UGT85A27) were localized in the cytoplasm and their recombinant proteins showed activity toward volatiles detected in grapevine, with geraniol as the preferred substrate in vitro. Two UGT genes with 98.1% homology differ in R/S-linalool selection. The UGT85A26-catalyzed substrate showed enrichment in S-linalool, whereas UGT85A27 showed a strong preference for R-linalool. UGT85A24 and UGT85A25 were expressed mainly in berries, and UGT85A26 and UGT85A27 were expressed predominantly in grapevine mature leaves and correlated with the highest content of glycosylated volatiles in the mature leaves. Methyl jasmonate (MeJA) induced the expression of UGT85A26 and UGT85A27 as well as the production of linalyl-β-glucoside, citronellyl-β-glucoside and phenethyl-β-glucoside. Transient overexpression of UGT85A26 and UGT85A27 in tobacco leaves led to the accumulation of linalyl-β-glucoside and an increase in citronellyl-β-glucoside in vivo. These results indicate that the expression of UGT85A26 and UGT85A27 is a major regulator affecting the content of glycosylated volatiles in grapevine.

EBR and JA regulate aroma substance biosynthesis in 'Ruidu Hongyu' grapevine berries by transcriptome and metabolite combined analysis.

Volatile compounds including terpenes, aldehyde, phenol, and alcohol are significantly contributed floral and fruity aromas to the Muscat variety. 'Ruidu Hongyu' grapevine is one of the newly developed grape varieties, and cultivation of this variety has been extended across China due to unique quality traits and taste. In this study, HS-SPME/GC-MS and transcriptome sequencing analysis were performed to evaluate the impact of exogenous 2,4-epibrassinolide (EBR), jasmonic acid (JA), and their signaling inhibitors brassinazole (Brz)/sodium diethyldithiocarbamate (DIECA) on the biosynthesis of aroma substances in 'Ruidu Hongyu' grapevine. According to the results, exogenous BR and JA promoted the accumulation of various aroma substances, including hexenal, 2-hexenal, nerol oxide, vanillin, hotrienol, terpineol, neral, nerol, geraniol, and geranic acid. After EBR and JA treatments, most of the genes responsible for terpene, aldehyde, and alcohol biosynthesis expressed at a higher level than the CK group. Relatively, EBR treatment could not only promote endogenous BR biosynthesis and metabolism but also elevate BR signaling transduction. JA treatment contributed to endogenous JA and MeJA accumulation, as well. Through transcriptome sequencing, a total of 3043, 903, 1470, and 607 DEGs were identified in JA vs. JD, JA vs. CK, BR vs. CK, and BR vs. Brz, respectively. There were more DEGs under both EBR and JA treatments at late fruit ripening stages. The findings of this study increase our understanding regarding aroma substances biosynthesis and endogenous BR/JA metabolism in response to exogenous EBR and JA signals.

Identification of Vitis vinifera MYB transcription factors and their response against grapevine berry inner necrosis virus

BackgroundThe myeloblastosis (MYB) superfamily is the largest transcription factor family in plants that play diverse roles during stress responses. However, the biotic stress-responsive MYB transcription factors of the grapevine have not been systematically studied. In China, grapevine berries are often infected with the grapevine berry inner necrosis virus (GINV), which eventually reduces the nutritional quality and commodity value.ResultsThe present study identified and characterized 265 VvMYB or VvMYB-related genes of the “Crimson seedless” grapevine. Based on DNA-binding domain analysis, these VvMYB proteins were classified into four subfamilies, including MYB-related, 2R-MYB, 3R-MYB, and 4R-MYB. Phylogenetic analysis divided the MYB transcription factors into 26 subgroups. Overexpression of VvMYB58 suppressed GINV abundance in the grapevine. Further qPCR indicated that among 41 randomly selected VvMYB genes, 12 were induced during GINV infection, while 28 were downregulated. These findings suggest that VvMYB genes actively regulate defense response in the grapevine.ConclusionA deeper understanding of the MYB TFs engaged in GINV defense response will help devise better management strategies. The present study also provides a foundation for further research on the functions of the MYB transcription factors.

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.

Cover Crops and No-Tillage Show Negligible Effects on Grapevine Physiology in Mediterranean Vineyard Agroecosystems

This study aimed to evaluate the effects of annual or perennial cover crops and tillage regimes on whole grapevine physiology and berry composition. We studied the interactive effects of tillage and cover crops on grapevine water status, leaf gas exchange, components of yield, berry composition and resulting water footprint in two contrasting production regions (Fresno County-hot climate and Napa County-warm climate) of California. The treatments included a perennial grass (PG), resident vegetation (RV), and an annual grass (AG) grown under conventional tillage (CT) and no-till (NT) settings. Neither cover crop nor tillage affected grapevine leaf gas exchange. However, at the Napa County vineyard, NT detrimentally affected grapevine water status compared to CT. Grapevine mineral nutrition, when assessed during anthesis revealed no effects of cover cropping in either year or at either location. Cover crop type did not affect yield components or berry composition, however CT increased titratable acidity (TA) at both sites. The water footprint of vineyards at either location was not affected by cover crops or tillage. Our results provided evidence that both in hot and warm climate vineyards cover cropping had negligible beneficial effects on grapevine physiology, mineral nutrition or productivity with no detrimental effects on vineyard water footprint; tillage was beneficial in younger vineyards to improve plant water status in semi-arid regions.

Wind speed, sun exposure and water status alter sunburn susceptibility of grape berries.

In the context of climate change, yield and quality losses from sunburn necrosis are challenging grape growers around the world. In a previous review, we identified the role of wind speed, duration of heat exposure, drought stress and adaptation as major knowledge gaps that prevent a better predictability of sunburn events. In this paper we present results of targeted experiments aiming to close these knowledge gaps. The effects of drought stress and adaptation on sunburn susceptibility were investigated in a combined drought stress/ defoliation experiment. Riesling grapevines growing in an arid climate were fully irrigated or drought stressed, and clusters were exposed to sunlight by fruit-zone leaf removal (defoliation) at two developmental stages. Sunburn symptoms were induced using infrared heaters while fruit surface temperature was measured using thermal imaging enabling the establishment of threshold temperatures. The influence of the duration of heat exposure of berries was examined by heating grape clusters to a stable temperature and monitoring the evolution of sunburn symptoms over time. To examine the effects of wind speed on the appearance of sunburn necrosis symptoms, fruit surface temperatures and sunburn severity were measured along an artificially induced wind speed gradient in two cultivars using thermal imaging and visual inspection. Longer durations of heat exposure required lower fruit surface temperatures to induce damage, while the differences in temperature after 60 min and 90 min of exposure were marginal (47.82 ± 0.25 °C and 47.06 ± 0.26 °C). Clusters of vines grown under water deficit were less susceptible to sunburn compared to those of well-irrigated plants following defoliation. The lethal temperature of clusters exposed to sunlight for seven days did not differ from those exposed to sunlight for 28 days, indicating that a full adaptation ocurred within this period. Higher wind speeds led to lower cluster temperatures and reduced sunburn severity. First evidence of a drought priming induced heat tolerance of grapevine berries was found, while adaptation had a more pronounced effect on the susceptibility to sunburn compared to water stress.

Grapevine genome analysis demonstrates the role of gene copy number variation in the formation of monoterpenes.

Volatile organic compounds such as terpenes influence the quality parameters of grapevine through their contribution to the flavour and aroma profile of berries. Biosynthesis of volatile organic compounds in grapevine is relatively complex and controlled by multiple genes, the majority of which are unknown or uncharacterised. To identify the genomic regions that associate with modulation of these compounds in grapevine berries, volatile metabolic data generated via GC-MS from a grapevine mapping population was used to identify quantitative trait loci (QTLs). Several significant QTLs were associated with terpenes, and candidate genes were proposed for sesquiterpene and monoterpene biosynthesis. For monoterpenes, loci on chromosomes 12 and 13 were shown to be associated with geraniol and cyclic monoterpene accumulation, respectively. The locus on chromosome 12 was shown to contain a geraniol synthase gene (VvGer), while the locus on chromosome 13 contained an α-terpineol synthase gene (VvTer). Molecular and genomic investigation of VvGer and VvTer revealed that these genes were found in tandemly duplicated clusters, displaying high levels of hemizygosity. Gene copy number analysis further showed that not only did VvTer and VvGer copy numbers vary within the mapping population, but also across recently sequenced Vitis cultivars. Significantly, VvTer copy number correlated with both VvTer gene expression and cyclic monoterpene accumulation in the mapping population. A hypothesis for a hyper-functional VvTer allele linked to increased gene copy number in the mapping population is presented and can potentially lead to selection of cultivars with modulated terpene profiles. The study highlights the impact of VvTPS gene duplication and copy number variation on terpene accumulation in grapevine.

Iodine application in Vitis vinifera L. cv. ‘Cabernet Sauvignon’ improve bioactive compounds and enzymatic activity in berries

Iodine (I) deficiency disorders represent a worldwide public health problem, with at least 1.9 million people estimated to have an unsatisfactory intake of this trace element. I content in plant foods is particularly low; however, it can be improved by biofortification. In this study, the effect of foliar fertilization with I (0, 0.25, 0.5, 0.75, 1.0, and 1.25 mg L-1) on yield, bioactive compound content, and bioaccumulation in grapevine berries was evaluated. Biofortification with I has positively modified yield, bioactive compound content and bioaccumulation. Intermediate doses (0.75 mg L-1) increased yield (57%), while high doses (1.25 mg L-1) decreased yield (28%) and incremented the phenols, flavonoids, antioxidant capacity, vitamin C, anthocyanin (50,34,31,71,26% respectively), catalase (73%) and peroxidase activity (57%), and their bioaccumulation in berries (59%). Agronomic biofortification with I is an alternative to increase yield, enzymatic and non-enzymatic antioxidants, as well as the concentration of this trace element in grape berries.

Viticulture adaptation to global warming: Modelling gas exchange, water status and leaf temperature to probe for practices manipulating water supply, canopy reflectance and radiation load

Associated with climate change, the frequency, duration, and intensity of heatwaves are increasing in most of the key wine regions worldwide. Depending on timing, intensity, and duration, heatwaves can impact grapevine yield and berry composition, with implications for wine quality. To overcome these negative effects, two types of mitigation practices have been proposed (i) to enhance transpiration and (ii) to reduce the radiation load on the canopy. Here we use a biophysical model to quantify the impact of these practices on canopy gas exchange, vine water status, and leaf temperature (Tl). Model validation was performed in a commercial vineyard. Modelled Tl from 14 to 43 °C, and transpiration, from 0.1 to 5.4 mm d−1, aligned around the identity line with measurements in field-grown vines; the RMSD was 2.6 ºC for temperature and 0.96 mm day−1 for transpiration. Trellis system and row orientation modulate Tl. A sprawling single wire trellis with an EW orientation maintained the canopy around 1ºC cooler than a Vertical Shoot Positioned canopy with NS for the same range of total fraction of soil available water (TFAW). Although irrigation before a heatwave is a recommended practice, maximum transpiration can be sustained even when TFAW is reduced, limiting the heat dampening effect of irrigation. Alternatively, canopy cooling can be achieved through Kaolin application, the installation of shade cloth placement, or canopy trimming. Shade cloth produced a greater cooling than Kaolin in all the simulated scenarios; however, Tl differences between them varied. Trimming reduced Tl from 2 ºC to almost 8 ºC compared to its non-trimmed counterpart. Our analysis presents new insights to design heat wave mitigation strategies and supports agronomically meaningful definitions of heat waves that include not only temperature, but also wind, VPD, and radiation load as these factors influence crop physiology under heat stress.

Integrative genomic and transcriptomic analyses of a bud sport mutant 'Jinzao Wuhe' with the phenotype of large berries in grapevines.

Bud sport mutation occurs frequently in fruit plants and acts as an important approach for grapevine improvement and breeding. 'Jinzao Wuhe' is a bud sport of the elite cultivar 'Himord Seedless' with obviously enlarged organs and berries. To date, the molecular mechanisms underlying berry enlargement caused by bud sport in grapevines remain unclear. Whole genome resequencing (WGRS) was performed for two pairs of bud sports and their maternal plants with similar phenotype to identify SNPs, InDels and structural variations (SVs) as well as related genes. Furthermore, transcriptomic sequencing at different developmental stages and weighted gene co-expression network analysis (WGCNA) for 'Jinzao Wuhe' and its maternal plant 'Himord Seedless' were carried out to identify the differentially expressed genes (DEGs), which were subsequently analyzed for Gene Ontology (GO) and function annotation. In two pairs of enlarged berry bud sports, a total of 1,334 SNPs, 272 InDels and 74 SVs, corresponding to 1,022 target genes related to symbiotic microorganisms, cell death and other processes were identified. Meanwhile, 1,149 DEGs associated with cell wall modification, stress-response and cell killing might be responsible for the phenotypic variation were also determined. As a result, 42 DEGs between 'Himord Seedless' and 'Jinzao Wuhe' harboring genetic variations were further investigated, including pectin esterase, cellulase A, cytochromes P450 (CYP), UDP-glycosyltransferase (UGT), zinc finger protein, auxin response factor (ARF), NAC transcription factor (TF), protein kinase, etc. These candidate genes offer important clues for a better understanding of developmental regulations of berry enlargement in grapevine. Our results provide candidate genes and valuable information for dissecting the underlying mechanisms of berry development and contribute to future improvement of grapevine cultivars.

Transient Heat Therapy Has Few Effects on Grapevine Performance in the Okanagan Valley, British Columbia, Canada

<h3>Background and goals</h3> The goal of this study was to evaluate a commercially available machine (Agrotherm XT, Agrothermal Systems) for transient heat application to enhance vineyard canopy temperature during the growing season and to study the effects of transient heat application on grapevine performance, phenology, and berry quality. <h3>Methods and key findings</h3> Heat was applied up to six times during the growing seasons in 2019 and 2020 in three vineyards located in East and West Kelowna in the Okanagan Valley in British Columbia, Canada. Shoot and cluster counts, bud fruitfulness, grapevine phenology, leaf greenness, harvest, pruning weight, and crop load data were collected each year. Results showed that transient heat application is not an effective management practice. Results were not consistent among vineyard locations or growing seasons. In 2019, treated Merlot vines had fewer berries per cluster but higher juice pH, and treated Chardonnay 2 vines had reduced leaf greenness but higher pruning weight. In 2020, treated Merlot vines had reduced leaf greenness but higher pruning weights, and treated Chardonnay 2 vines had reduced leaf greenness but higher berry weights and soluble solids. In 2021 only, treated Chardonnay 2 vines had greater fruitfulness (clusters/shoot). <h3>Conclusions and significance</h3> Heat treatment had inconsistent effects on grapevine performance and berry quality and no changes in grapevine phenology were observed. Given the high purchase costs, transient heat therapy is not an effective management strategy to improve grapevine performance and berry quality in the north central part of the Okanagan Valley in British Columbia.

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.

Dissection of the Pearl of Csaba pedigree identifies key genomic segments related to early ripening in grape.

Pearl of Csaba (PC) is a valuable backbone parent for early-ripening grapevine (Vitis vinifera) breeding, from which many excellent early ripening varieties have been bred. However, the genetic basis of the stable inheritance of its early ripening trait remains largely unknown. Here, the pedigree, consisting of 40 varieties derived from PC, was re-sequenced for an average depth of ∼30×. Combined with the resequencing data of 24 other late-ripening varieties, 5,795,881 high-quality single nucleotide polymorphisms (SNPs) were identified following a strict filtering pipeline. The population genetic analysis showed that these varieties could be distinguished clearly, and the pedigree was characterized by lower nucleotide diversity and stronger linkage disequilibrium than the non-pedigree varieties. The conserved haplotypes (CHs) transmitted in the pedigree were obtained via identity-by-descent analysis. Subsequently, the key genomic segments were identified based on the combination analysis of haplotypes, selective signatures, known ripening-related quantitative trait loci (QTLs), and transcriptomic data. The results demonstrated that varieties with a superior haplotype, H1, significantly (one-way ANOVA, P < 0.001) exhibited early grapevine berry development. Further analyses indicated that H1 encompassed VIT_16s0039g00720 encoding a folate/biopterin transporter protein (VvFBT) with a missense mutation. VvFBT was specifically and highly expressed during grapevine berry development, particularly at veraison. Exogenous folate treatment advanced the veraison of "Kyoho". This work uncovered core haplotypes and genomic segments related to the early ripening trait of PC and provided an important reference for the molecular breeding of early-ripening grapevine varieties.