Grape Wine Quality Research Articles

Canopy-Applied Benzothiadiazole (BTH) during the Pre-Harvest Period as a Tool to Increase Polyphenol Accumulation and Color Intensity in Cabernet Gernischt and Cabernet Franc

Despite the wealth of studies on benzothiadiazole (BTH) and its capacity to modulate grape polyphenol metabolism, comprehensive data detailing polyphenol accumulation at various grape growth stages remain scarce. Therefore, the present study utilized pre-harvest (at 21 days after flowering) canopy-applied BTH (50 mg/L) on Cabernet Gernischt and Cabernet Franc grapes to investigate the physicochemical and polyphenolic changes during grape maturation. The results showed that BTH treatment significantly affected the accumulation of total phenols, flavonoids, flavanols, anthocyanins, and tannins. Concurrently, it induced an increase in colorimetric parameters (CIRG, L*, b*, a*, and C*ab), resulting in the treated grapes exhibiting a greater color intensity and enhanced red-bluish colorimetric characteristics. Moreover, the BTH treatment amplified the anthocyanin content in the grapes, with the levels of petunidin-3-O-glucoside and peonidin-3-O-glucoside exhibiting remarkable increases, particularly in the Cabernet Franc grape. Notably, the content of peonidin-3-O-glucoside even surpassed that of malvidin-3-O-glucoside throughout the growth stages, indicating significant advantages in the treated samples. Additionally, the levels of flavanol, flavonols, phenolic acids, and stilbenes experienced a significant boost post-treatment. In conclusion, the application of BTH treatment can effectively enhance the accumulation of polyphenols and intensify the color of Cabernet Gernischt and Cabernet Franc grapes, thereby significantly improving the overall quality of wine grapes and ensuring the production of higher-quality wines. The research findings will serve as a theoretical foundation and provide scientific data for the appropriate utilization of BTH in wine grape cultivation.

Foliar Co-Applications of Nitrogen and Iron on Vines at Different Developmental Stages Impacts Wine Grape (Vitis vinifera L.) Composition.

The co-application of N and Fe can improve wine grape composition and promote the formation of flavor compounds. To understand the effects of foliar co-application of N and Fe on wine grape quality and flavonoid content, urea and EDTA-FE were sprayed at three different developmental stages. Urea and EDTA-Fe were sprayed during the early stage of the expansion period, at the end of the early stage of the expansion period to the late stage of the veraison period, and during the late stage of the veraison period. The results demonstrated that the co-application of urea and EDTA-Fe, particularly N application during the late stage of the veraison period and Fe application during the early stage of the berry expansion period (N3Fe1), significantly improved grape quality. Specifically, the soluble solid content of berries increased by 2.78-19.13%, titratable acidity decreased by 6.67-18.84%, the sugar-acid ratio became more balanced, and yield increased by 13.08-40.71%. Further, there was a significant increase in the relative content of amino acids and flavonoids. In conclusion, the application of Fe and N fertilizers at the pre-expansion and late veraison stages of grapes can significantly improve the quality and yield of berries; ultimately, this establishes a foundation for future improvement in the nutritional value of grapes and wine.

Comparison of machine learning and deep learning models for the assessment of rondo wine grape quality with a hyperspectral camera

Hyperspectral images provide rich spectral/spatial data and have shown remarkable performance in precision viticulture. Standardized data-processing methods are necessary to reduce the dimensionality and to identify powerful wavelengths. Toward this goal, we evaluated and compared the performance and novel-wavelength-identification ability of five renowned machine learning models: the linear models Ridge and LASSO, a 1D + 2D convolutional neural network (1D +2D CNN) non-linear model, a gradient boosting decision tree (GBDT) using XGBoost as an ensemble model, and an explainable boosting machine (EBM) followed by support vector regression (SVR) as a hybrid model. The model evaluations were conducted using leave-one-out cross-validation (LOOCV) as we sought to clarify the best-fitted machine learning model. Our results demonstrated that Ridge, LASSO, showed better performance with relatively high accuracy but were weak as a wavelength identifier. GDBT-XGBoost showed considerable prediction power and wavelength identification. EBM-SVM emerged as the most powerful model, demonstrating exceptional stability and clear wavelength classification even for destructive measurements under varying environmental stresses across Rondo's growth stages. The combined approach of 1D + 2D CNN algorithms was advantageous to handle the dynamic shapes of spectral curve and horizontal shift of the wavelengths obtained from outdoor data acquisition, and notably, it showed the highest accuracy to predict the brix and pH of wine grapes for both indoor and outdoor sensings. But the combined effects of 1D and 2D CNN algorithms were difficult to clarify the importance of spectral features for the brix and pH prediction. The integrated machine learning models with dimensionality reduction, and proper image acquisition can increase the model's accuracy. The common absorption peaks were observed in the near-infrared region of 700 nm and 900 nm. Those wavelengths should be considered for the development of low-cost sensing platforms with fewer bands. Wavelengths over 900 nm are also important to develop outdoor sensing platforms.

Hyperspectral Imaging Spectroscopy for Non-Destructive Determination of Grape Berry Total Soluble Solids and Titratable Acidity

Wine grape quality heavily influences the price received for a product. Hyperspectral imaging has the potential to provide a non-destructive technique for predicting various enological parameters. This study aims to explore the feasibility of applying hyperspectral imaging to measure the total soluble solids (TSS) and titratable acidity (TA) in wine grape berries. A normalized difference spectral index (NDSI) spectral preprocessing method was built and compared with the conventional preprocessing method: multiplicative scatter correction and Savitzky–Golay smoothing (MSC+SG). Different machine learning models were built to examine the performance of the preprocessing methods. The results show that the NDSI preprocessing method demonstrated better performance than the MSC+SG preprocessing method in different classification models, with the best model correctly classifying 93.8% of the TSS and 84.4% of the TA. In addition, the TSS can be predicted with moderate performance using support vector regression (SVR) and MSC+SG preprocessing with a root mean squared error (RMSE) of 0.523 °Brix and a coefficient of determination (R2) of 0.622, and the TA can be predicted with moderate performance using SVR and NDSI preprocessing (RMSE = 0.19%, R2 = 0.525). This study demonstrates that hyperspectral imaging data and NDSI preprocessing have the potential to be a method for grading wine grapes for producing quality wines.

Impact of exogenous melatonin foliar application on physiology and fruit quality of wine grapes (Vitis vinifera) under salt stress.

Soil salinisation is an important abiotic stress faced in grape cultivating, leading to weakened plant vigour and reduced fruit quality. Melatonin as a novel hormone has shown positive exogenous application value. Therefore, this study used wine grape (Vitis vinifera ) 'Pinot Noir' as a test material to investigate the changes of foliar spraying with different concentrations of melatonin on the physiology and fruit quality of wine grapes in a field under simulated salt stress (200mmolL-1 NaCl). The results showed that foliar spraying of melatonin significantly increased the intercellular CO2 concentration, maximum photochemical quantum yield of PSII, relative chlorophyll and ascorbic acid content of the leaves, as well as the single spike weight, 100-grain weight, transverse and longitudinal diameters, malic acid, α-amino nitrogen and ammonia content of fruits, and decreased the initial fluorescence value of leaves, ascorbate peroxidase activity, glutathione content, fruit transverse to longitudinal ratio and tartaric acid content of plants under salt stress. Results of the comprehensive evaluation of the affiliation function indicated that 100μmolL-1 melatonin treatment had the best effect on reducing salt stress in grapes. In summary, melatonin application could enhance the salt tolerance of grapes by improving the photosynthetic capacity of grape plants under salt stress and promoting fruit development and quality formation, and these results provide new insights into the involvement of melatonin in the improvement of salt tolerance in crop, as well as some theoretical basis for the development and industrialisation of stress-resistant cultivation techniques for wine grapes.

Rapid Detection of Tannin Content in Wine Grapes Using Hyperspectral Technology.

Wine grape quality is influenced by the variety and growing environment, and the quality of the grapes has a significant impact on the quality of the wine. Tannins are a crucial indicator of wine grape quality, and, therefore, rapid and non-destructive methods for detecting tannin content are necessary. This study collected spectral data of Pinot Noir and Chardonnay using a geophysical spectrometer, with a focus on the 500-1800 nm spectrum. The spectra were preprocessed using Savitzky-Golay (SG), first-order differential (1D), standard normal transform (SNV), and their respective combinations. Characteristic bands were extracted through correlation analysis (PCC). Models such as partial least squares (PLS), support vector machine (SVM), random forest (RF), and one-dimensional neural network (1DCNN) were used to model tannin content. The study found that preprocessing the raw spectra improved the models' predictive capacity. The SVM-RF model was the most effective in predicting grape tannin content, with a test set R2 of 0.78, an RMSE of 0.31, and an RE of 10.71%. These results provide a theoretical basis for non-destructive testing of wine grape tannin content.

Effect of nitrogen and iron synergistic application on physiological growth, berry quality, and flavonoid content of wine grapes

Effect of nitrogen and iron synergistic application on physiological growth, berry quality, and flavonoid content of wine grapes

Potassium fertigation and organic fertilisation in ‘Syrah’ grape in Northeastern Brazil: yield, must characteristics and phenolic compounds

The effect of both potassium and organic fertilisation on grape yield and must composition originating from wine grapevines cultivated in the São Francisco river basin, in the semi-arid region of Northeastern Brazil, is not well known. Since soils from that region usually have low organic matter content, we hypothesise that soil application of organic fertiliser and potassium application through drip irrigation enhances the availability of this nutrient in the soil, and it influences grape yield and quality. Hence, five doses of potassium (0, 20, 40, 80 and 160 kg ha-1) applied through a drip irrigation system and two doses of goat manure as organic fertiliser applied into the soil (0 and 7.5 m3 ha-1) after pruning were evaluated concerning yield and berry quality of grapevine ‘Syrah’ over four growing seasons (April 2013 to July 2015) in Petrolina, state of Pernambuco, Brazil. The experimental design was randomised blocks with 5 replications. We evaluated yield (t ha-1), weight of 100 berries (g), must volume (mL), total soluble solids (°Brix), pH and total titratable acidity (‰), K, Mg and Ca contents and phenolic compounds (total polyphenols, anthocyanins and flavonoids). The increasing application of potassium at the different doses of organic fertiliser did not alter the crop yield, except in the second season. Nonetheless, K concentration in grape must was influenced in the four growing seasons, with higher values at fitted K2O doses by polynomial regression of 83.62 kg ha-1 (first season), 101.25 kg ha-1 (second season), 120.00 kg ha-1 (third season) and 77.99 kg ha-1 (0 m3 ha-1 organic fertiliser) and 96.07 kg ha-1 (7.5 m3 ha-1 organic fertiliser) in the fourth season. The addition of increasing doses of potassium interfered with the wine grape quality, which is an important factor to be considered in relation to its acidity. Organic fertilisation did not affect the most quality characteristics of the grapes.

Hyperspectral imaging to assess wine grape quality

AbstractBackgroundGrape composition is of high interest for producing quality wines. For that, grape analyses are necessary, and require sample preparation, whether with classical analyses or with NIR analyses. The aim of the study was to test the ability of hyperspectral imaging (HSI), a nondestructive analysis to assess their composition. For that, seven grape varieties were analyzed for two vintages. Partial least squares (PLS) and discriminate (PLS‐DA) and PLS‐R were realized respectively in order to classify the berries, to validate the data sets, and to provide models to assess grape composition after a 1st derivative data pretreatment.ResultsHSI allowed a 100% good classification of the grape varieties. It showed good results to assess technological ripening parameters (sugar and acid contents) as well as phenolic content (TPI, Total Phenolics, Total Anthocyanins, Total Flavonoids, and their extractable equivalents) (globally R2 > 0.81). However, it was not possible to reach the color intensity of grapes.ConclusionHSI led to generate good models to assess wine grape composition. The quality of the generated models was dependent on the color of grapes and the parameter considered.

Air speed and plastic crate vent-holes for wine grape quality during postharvest dehydration: commercial and laboratory studies.

Airflow is an important issue to favor postharvest dehydration keeping wine grape quality. The aim of this experimental work was to analyze the grape quality during postharvest dehydration: (i) in a commercial facility ('fruttaia') by monitoring the efficiency of the ventilation system and (ii) at laboratory level, studying the influence of crate type and airflow direction. In the fruttaia, the airflow was provided by an air duct hanging from the ceiling, and by floor fans. A great gap in air speed from 0 up to 3.7 m s-1 was measured in different sectors of the fruttaia, leading to a different weight loss and grape quality in crates, depending on crate stack height and sector. At the laboratory level, two tunnels, with exhaust or supply fans, were used and four crate types with different percentages of vent-holes were adopted. A decrease of about 5% delayed the weight loss rate depending on the type of crate, and the exhaust fan guaranteed a faster dehydration. The results clarified the inefficiency of the commercial ventilation system in ensuring homogeneous grape weight loss in all crates. In addition, the exhaust fan guaranteed a more uniform air distribution around crates, and a slightly higher air speed. © 2023 Society of Chemical Industry.

Comprehensive evaluation of nine grape varieties based on fundamental physical and chemical indicators, color and volatile compounds

BACKGROUND: In todays’ society, the rapid development of the wine industry and the improvement of peoples’ living standards make people pay more and more attention to wine grape quality. OBJECTIVE: To evaluate the wine grape varieties in Northeast Chinas’ grape growing regions for better wine grape quality, we evaluated the quality of different varieties of wine grapes. METHODS: The grape varieties ‘Hassan’ ‘Zuoshaner’ ‘Beibinghong’ ‘Zuoyouhong’ ‘Beta’ ‘Shuanghong’ ‘Zijingganlu’ ‘Cabernet Sauvignon’ and ‘Syrah’ were planted in the grape growing area of Jilin, Northeast China, were used as the subjects of this study. The grape berries were analyzed and tested for morphological indicators, basic physicochemical indicators, color, and phenolic and aromatic composition. RESULTS: According to lab results, ‘Hassan’ contained the highest amount of total phenolics; ‘Zuoyouhong’ had the highest solids and total sugar content; ‘Shuanghong’ had the most elevated total acid and anthocyanin content; ‘Zijngganlu’ had the highest tannin content and acid fixation ratio; Seventy-one volatile compounds were detected in nine grape varieties. CONCLUSIONS: Each of the nine grape varieties has a distinctive flavor, and because of this, grape processing products with regional flavors can be created. The same offer valuable data for future scientific grape resource collection, conservation, and exploitation.

Foliar Application of CaCO3-Rich Industrial Residues on 'Shiraz' Vines Improves the Composition of Phenolic Compounds in Grapes and Aged Wine.

The quality of wine grapes and wine depends on their content of phenolic compounds. Under commercial conditions, the phenolic maturity of grapes is mostly achieved by applying abscisic acid analogues. Some Ca forms represent a cost-effective alternative for these compounds. In this study, 'Shiraz' vines (veraison of 90%) were sprayed with CaCO3-rich residues from the cement industry (4.26 g of Ca per L). Fruit from treated and untreated vines was harvested 45 days after CaCO3 spraying and evaluated for quality. The fruit was vinified, and the obtained wines were bottled and stored in darkness for 15 months at 20 °C. Wines were evaluated for quality after storage. The evaluation of grape and wine quality included the content of phenolic compounds and antioxidant capacity. The treatment with CaCO3 did not affect the ripening rate of grapes. However, the treatment improved the fruit yield as well as the color development, the content of phenolic compounds, and antioxidant capacity of grapes and wine. The treatment favored especially the accumulation of malvidin-3-O-glucoside, pelargonidin-3-O-glucoside, caftaric acid, caffeic acid, trans-cinnamic acid, quercetin, catechin, epicatechin, resveratrol, and the procyanidins B1 and B2. Wine made with treated fruit was of higher quality than that of control fruit.

Response of Wine Grape Quality to Rainfall, Temperature, and Soil Properties in Hexi Corridor

This study aimed to clarify the relationship between grape (Vitis vinifera L.) quality and environmental factors (climate and soil), and to elucidate the theoretical basis and provide technical guidance for the rational planning of the cultivation area and the precise regulation of the cultivation mode in the future. The fruits of three different grape cultivars, Pinot Noir, Merlot, and Vidal, as well as soil samples and meteorological data were collected from three wine grape growing areas (Wuwei, Zhangye, and Jiayuguan) in the Hexi Corridor, Northwest China. Principal-component analysis (PCA) and correlation analysis were conducted to understand the relationship of grape quality with weather conditions and soil properties. The results showed that the titratable acid content of grape berries was significantly negatively correlated with average temperature from August to September, average minimum temperatures from August to September, and from April to October, mean annual minimum temperature, growing degree days from August to September, and soil total nitrogen content, and significantly positively correlated with average rainfall from April to October, annual mean rainfall, and soil available potassium content. In addition, the pH of grape juice was significantly negatively correlated with annual mean rainfall and soil available potassium content. However, it was significantly positively correlated with average temperature and average minimum temperature from August to September, average minimum temperature from April to October, growing degree days from August to September, as well as soil total nitrogen content. In addition, the results of PCA showed that the fruit quality scores of ‘Vidal’ in Jiayuguan, ‘Merlot’ in Zhangye, and ‘Pinot Noir’ in Wuwei were the highest, respectively. In conclusion, the contents of titratable acid, pH, and Brix° are greatly affected by climate and soil factors. ‘Vidal’, ‘Merlot’, and ‘Pinot Noir’ were suitable for planting in Jiayuguan, Zhangye, and Wuwei, respectively. Nowadays, few reports focus on the relationship between grape quality and soil and climate conditions. Based on the investigation and analysis of the differences of climate, soil, and grape berries quality in the three production areas of Hexi Corridor, the relationship among climate, soil, and grape quality by using statistical methods was studied, which could provide references for clarifying the reasons why environmental factors affect grape quality and select the suitable area for wine grape cultivation.

Lateral shoots removal has little effect on berry growth of grapevine (Vitis vinifera L.) ‘Riesling’ in cool climate

Bunch compactness is an important trait that affects the sanitary status and quality of wine grapes. Many studies have demonstrated that canopy managements, such as leaf removal, shoot trimming, and postponed first shoot topping, can effectively reduce compactness. However, few studies have determined the effects of canopy management measures on bunch compactness. Shoot wrapping has been previously shown to elongate the rachis length and reduce bunch compactness. Here, we tested whether the presence of laterals affects cluster growth in Vitis vinifera L. ‘Riesling’ through a field experiment with four treatments over two consecutive seasons: shoot wrapping with laterals, shoot wrapping without laterals, hedging with laterals, and hedging without laterals. Laterals were removed weekly. Lateral removal had little effect on cluster compactness; the effect was shown temporarily and not consistent the growing seasons. The effect of laterals on cluster compactness and rachis length slightly varied with years. The short-term and variable effect of laterals may be explained by the fact that they experienced little competition with clusters.

Widely Targeted Metabolomics Profiling Reveals the Effect of Powdery Mildew on Wine Grape Varieties with Different Levels of Tolerance to the Disease.

Powdery mildew is an economic threat for viticulture because it not only affects grape yield, but also causes a series of impacts on the qualities of fruit and wine, especially the flavors and various metabolites. Different grape varieties may have different levels of powdery mildew resistance/tolerance and their components of their metabolome are also various. In this study, two wine grape varieties, Guipu No.6 (GP6) and Marselan (Mar) with different levels of powdery mildew tolerance, were used to compare the quality differences in metabolism level by using the widely targeted metabolomics method. The results show that GP6 has a better powdery mildew leaf tolerance than Mar. A total of 774 metabolites were detected by using a UPLC-QQQ-MS-based metabolomics approach, and 57 differential metabolites were identified as key metabolites that were accumulated after infection with powdery mildew in GP6 and Mar, including phenolic acids, flavonoids, terpenoids, stilbenes, lipids, nucleotides and derivatives, lignans and coumarins, and quinones. This finding indicates that the defense mechanisms of grape fruit are mainly associated with phenylpropane-flavonoid metabolism. Specifically, stilbenes had greater variations after powdery mildew infection in GP6; while in Mar, the variations of flavonoids, especially kaempferol-3-O-glucuronide and luteolin-7-O-glucuronide, were more remarkable. The above results demonstrate that stilbenes may play a more important role than flavonoids in resisting powdery mildew infection in GP6’s fruits, and the drastic variations of these phenolic compounds in different wine grapes after powdery mildew infection might also lead to quality difference in the flavors. This study can provide new insights into the understanding of the cause of powdery mildew tolerance in different grape varieties and the effects on the quality of wine grapes infected with the disease exerted by metabolism level.

COS-OGA Applications in Organic Vineyard Manage Major Airborne Diseases and Maintain Postharvest Quality of Wine Grapes.

In most wine-growing countries of the world the interest for organic viticulture and eco-friendly grape production processes increased significantly in the last decade. Organic viticulture is currently dependent on the availability of Cu and S compounds, but their massive use over time has led to negative effects on environment health. Consequently, the purpose of this study was to evaluate the effectiveness of alternative and sustainable treatments against powdery mildew, gray mold and sour rot under the field conditions on Nero d’Avola and Inzolia Sicilian cultivars. In detail, the efficacy of COS-OGA, composed by a complex of oligochitosans and oligopectates, and its effects in combination with arbuscular mycorrhizal fungi (AMF) were evaluated to reduce airborne disease infections of grape. COS-OGA combined with AMF induced a significant reduction in powdery mildew severity both on Nero d’Avola and Inzolia with a mean percentage decrease of about 15% and 33%, respectively. Moreover, COS-OGA alone and combined with AMF gave a good protection against gray mold and sour rot with results similar to the Cu–S complex (performance in disease reduction ranging from 65 to 100%) on tested cultivars. Similarly, the COS-OGA and AMF integration provided good performances in enhancing average yield and did not negatively impact quality and microbial communities of wine grape. Overall, COS-OGA alone and in combination could be proposed as a valid and safer option for the sustainable management of the main grapevine pathogens in organic agroecosystems.

The impact of sustainable management regimes on amino acid profiles in grape juice, grape skin flavonoids and hydroxycinnamic acids

Organic and biodynamic management practices in viticulture have been sharply increasing worldwide for almost two decades and are seen as one possibility for environmentally friendly production. Consumers often presume that the quality of organically grown crops is different or higher compared to conventionally grown crops.In the current study, wine grape quality under integrated, organic and biodynamic viticulture was assessed in a long-term field trial in Geisenheim, Germany, starting seven years after conversion. Treatments substantially differed in their amino acid concentration in juice, flavonol content and their composition of hydroxycinnamic acids. Organic and biodynamic treatments showed significantly higher concentrations of all amino acids in juice and a significantly higher concentration of flavonols in berry skins. Major drivers of these changes are reductions of yield and pruning weight under organic and biodynamic management on the one hand and increased light exposure of bunches in the respective treatments on the other hand.Linking amino acid composition in juice, grape skin flavonoid and hydroxycinnamate concentration to canopy structure, vigour and yield enables growers to actively control and manipulate wine grape quality in the different management systems.

Grapevine stem water potential estimation based on sensor fusion

Estimating vine water status is essential for achieving the desired balance between wine grape quality and yield in viticulture management and irrigation planning. The growing demands of smart farming for extracting meaningful information from field data to support irrigation decisions may be facilitated using field monitoring technology along with advanced modeling algorithms. This research took place in a Vitis Vinifera cv. “Sauvignon Blanc” experimental plot within a commercial vineyard. The main objective was to generate a water stress estimation model for wine grapevines based on data fusion from multiple sensors. Data were collected using sensors from five monitored grapevines, each treated with a different water stress regime. The sensors provided measurements of trunk and fruit growth, leaf temperature, and soil water content (SWC) at depths of 20 and 40 cm. Additionally, meteorological station in the vineyard recorded the temperature, relative humidity, wind speed, and solar radiation. A daily-scale multivariate time series was composed using the data derived from the sensors. Stem water potential (SWP) values were measured for the monitored vines and analyzed against the multivariate time series of factors to define their interrelations and interactions. Finally, a prediction model for SWP estimation was defined using boosted regression trees (BRT) algorithm, with an optimized set of factors. Validation was conducted using comparative statistics between a randomly selected test set and a predicted set of SWP values achieved using the trained BRT model. After processing the data and eliminating most of the factors due to multicollinearity, the model was composed of daily maximum leaf temperature (LT), SWC at noon at 40 cm, tree water deficit (TWD), SWC daily amplitude at 20 cm, water input, vapor pressure deficit, and phenological stages. The highest contributor to the BRT model was maximum LT (44.5%), followed by SWC at noon at 40 cm (16.9%) and TWD (16%). The model performance was estimated using various measures and resulted in a correlation of 0.9 between the estimated SWP values and the test set. No significant differences were found between their means (t = -0.31, p-value = 0.76) and distributions (D = 0.13, p-value = 0.77). The RMSE was 0.16 MPa which corresponds to a 12% error when normalized to the range of the test set. The suggested sensor fusion approach for estimating SWP is a promising technique that integrates representative factors of the soil–water-plant-atmosphere continuum; it should be further examined in different climate regimes and vine varieties.

Effects of gibberellin applications before flowering on the phenotype, ripening, and flavonoid compounds of Syrah grape berries.

Vitis vinifera L. cv. Syrah grapevines in most Chinese viticulture regions generally have compact clusters that increase the susceptibility to diseases and inhibit coloration of the inner berries. Gibberellic acid (GA3 ) is a plant growth regulator that is widely used during grape cultivation to elongate the rachis, control fruit set, and decrease cluster compactness. In this study, Syrah grapevines were treated with GA3 before flowering in 2019 and 2020 to determine the optimal GA3 treatment concentrations and times for decreasing bunch compactness, while minimizing the negative effects on the wine grape cluster weight. Pre-flowering GA3 applications at 3, 5, and 7mg L-1 , especially treatment at 20 days before flowering, decreased Syrah grape bunch compactness by decreasing the fruit set rate and promoting bunch elongation, with minimal adverse effects on the healthy grape cluster weight in both years. The 7mg L-1 GA3 treatment at 20 days before flowering significantly increased reducing sugar, total phenolic, tannin, and total anthocyanin contents of Syrah grape berries in 2019 and 2020. Moreover, high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry, hierarchical cluster, and principal component analysis results indicated GA3 applications before flowering (3, 5, and 7mg L-1 ) significantly affected the accumulation of different anthocyanins in Syrah grape berries. Notably, the application of 7mg L-1 GA3 at 20 days before flowering resulted in the highest anthocyanin content. Pre-flowering gibberellin application can decrease bunch compactness and improve the quality of Syrah grape berries. These findings reflect the potential utility of gibberellin treatments for decreasing cluster compactness and increasing the quality of wine grapes. © 2022 Society of Chemical Industry.

Impact of Adult Popillia japonica (Coleoptera: Scarabaeidae) Foliar Feeding Injury on Fruit Yield and Quality of a Temperate, Cold-Hardy Wine Grape, 'Frontenac'.

Popillia japonica (Newman), is a highly polyphagous, invasive species, first recorded in the U.S. in 1916, and detected in Minnesota in the late 1960s. Historically, research on this pest in the Midwest U.S. has focused primarily on ornamental and turf crops, with little attention placed on adult feeding damage to fruit crops. Recently, wine grape producers in the region noted substantial increases in defoliation from P. japonica feeding, confirming concerns for this perennial high value crop. To address these concerns, studies were conducted during the summers of 2020-2021 to understand the impact of P. japonica foliar feeding on the quality and yield of wine grapes. Trials utilized vines of the wine grape variety, 'Frontenac.' In addition to open plots, whole vines were caged within fine mesh netting and infested with P. japonica at 0, 25, 50, and 100 beetles per meter-row of vine. Beetles used for infestations were collected from natural field populations of P. japonica and left to feed until grapes were ready for harvest. During harvest, data collection included leaf samples for obtaining average percent defoliation, cluster weights, and berry subsamples for soluble solid content, pH, titratable acidity, and phenolic compound measurements. Results from these studies demonstrated that as beetle population density and defoliation per m-row increases, at-harvest measurements of quality parameters are significantly and negatively affected (P < 0.05) when compared with uninfested vines. The negative impacts to fruit quality exhibited in these studies will be important in the development of future management strategies for P. japonica in 'Frontenac.'