Grape Maturity Research Articles

НОВЫЙ БЕССЕМЯННЫЙ СОРТ ВИНОГРАДА КИВИН

Interspecific hybridization is a common method in the selection of grape varieties with resistance to diseases and adverse environmental conditions. The main direction of the breeding programs of ARRIV&W - branch of FSBSI “FRARC” is the breeding of varieties with disease resistance and high adaptive potential to the adverse effects of weather conditions. The novelty of the research lies in the creation of a new seedless grape variety, the study of its adaptive potential, economic usefulness and value in the growing conditions of the Rostov region. The research was carried out according to the generally accepted methods of M.A. Laza- revsky, N.N. Prostoserdov, P.N. Nedov, K.V. Smirnov. The origin of the Kivin variety and the results of agrobiological and ampelmetric studies are given. The characteristics of the main indicators of the variety according to research data for 5 years (2018–2022) are presented. The main parameters of the leaf were performed according to the coding program of the grape variety according to the OIV ampelometric descriptors for 33 indicators. The Kivin grape variety is very early ripening, the berries are white with a medium-thick skin, meaty flesh and harmonious taste with light berry tones, weighing 2.3 g. The sugar content in the juice of berries at the time of removal of maturity averages 170 g/dm3 , the content of total acids is 5.9 g/dm3 . The yield is above average (147 c/ha). Its withstands frost down to minus 25 °C, damage by mildew, oidium, Alternaria at the level of 2.0 points. Admitted to the State Test in 2022, it is characterized by high biological plasticity, resistance to temperature stresses and fungal diseases. The crop is used for fresh consumption, the production of dried products and ordinary table wine. The variety is recommended for cultivation in the North Caucasus (the sixth region) in an uncovered culture. According to the sum of the active temperatures required for the ripening of grapes, the variety is suitable for cultivation in the central regions of Russia and the Southern Urals.

Efekti spontane i inokulisane fermentacije na sadržaj ukupnih fenolnih jedinjenja i antioksidativnu aktivnost vina Cabernet Sauvignon i prevrele komine

The total phenolic content and antioxidant activity of wine and fermented pomace (FP) from Cabernet Sauvignon grapes harvested at the stage of full ripeness were evaluated by spectrophotometric analysis. Wine and pomace were obtained after prolonged maceration during spontaneous and inoculated fermentation of fully ripe grapes. Three individual vinifications were inoculated with the following commercial yeasts: BDX (Lallemand, Montréal, QC, Canada), FX10 (Laffort, Bordeaux, France) and Qa23 (Lallemand, Montréal, QC, Canada). For each vinification, maceration lasted 0, 3, 5, 7, 14 and 21 days, respectively. The total phenolic content was determined spectrophotometrically using the Folin-Ciocalteu method. Two different methods were used to evaluate the antioxidant activity of the wine and pomace samples: the Ferric Reducing Activity of Plasma (FRAP) and the Trolox Equivalent Antioxidant Capacity (TEAC). The use of a winemaking process that included different maceration times and inoculation with yeasts, as well as spontaneous fermentation, significantly modulated the total phenolic content of the obtained wines and FP. This study could provide a good basis for the practical application and obtaining wines with a high content of phenolic compounds and antioxidant properties.

Histological and transcriptomic insights into the interaction between grapevine and Colletotrichum viniferum.

Grape is of high economic value. Colletotrichum viniferum, a pathogen causing grape ripe rot and leaf spot, threatens grape production and quality. This study investigates the interplay between C. viniferum by Cytological study and transcriptome sequencing. Different grapevine germplasms, V. vinifera cv. Thompson Seedless (TS), V. labrusca accession Beaumont (B) and V. piasezkii Liuba-8 (LB-8) were classified as highly sensitive, moderate resistant and resistant to C. viniferum, respectively. Cytological study analysis reveals distinct differences between susceptible and resistant grapes post-inoculation, including faster pathogen development, longer germination tubes, normal appressoria of C. viniferum and absence of white secretions in the susceptible host grapevine. To understand the pathogenic mechanisms of C. viniferum, transcriptome sequencing was performed on the susceptible grapevine "TS" identifying 236 differentially expressed C. viniferum genes. These included 56 effectors, 36 carbohydrate genes, 5 P450 genes, and 10 genes involved in secondary metabolism. Fungal effectors are known as pivotal pathogenic factors that modulate plant immunity and affect disease development. Agrobacterium-mediated transient transformation in Nicotiana benthamiana screened 10 effectors (CvA13877, CvA01508, CvA05621, CvA00229, CvA07043, CvA05569, CvA12648, CvA02698, CvA14071 and CvA10999) that inhibited INF1 (infestans 1, P. infestans PAMP elicitor) induced cell death and 2 effectors (CvA02641 and CvA11478) that induced cell death. Additionally, transcriptome analysis of "TS" in response to C. viniferum identified differentially expressed grape genes related to plant hormone signaling (TGA, PR1, ETR, and ERF1/2), resveratrol biosynthesis genes (STS), phenylpropanoid biosynthesis genes (PAL and COMT), photosynthetic antenna proteins (Lhca and Lhcb), transcription factors (WRKY, NAC, MYB, ERF, GATA, bHLH and SBP), ROS (reactive oxygen species) clearance genes (CAT, GSH, POD and SOD), and disease-related genes (LRR, RPS2 and GST). This study highlights the potential functional diversity of C. viniferum effectors. Our findings lay a foundation for further research of infection mechanisms in Colletotrichum and identification of disease response targets in grape.

Vitis species and varietal resistance of mature berries against inoculation of an isolate of the Colletotrichum acutatum complex that causes grape ripe rot

<i>Vitis</i> species and varietal resistance of mature berries against inoculation of an isolate of the <i>Colletotrichum acutatum</i> complex that causes grape ripe rot

Bio-Dealcoholization of Wines: Can Yeast Make Lighter Wines?

The relationship between climate change and viticulture has become increasingly apparent in recent years. Rising temperatures have been a critical factor in early grape ripening. This, in turn, has led to wines with imbalanced acidity and, more importantly, higher alcohol content and pH values. Today, consumers demand high-quality and healthy products, and this trend has extended to wine consumption. Consumers prefer wines with reduced alcohol content due to the health risks associated with alcohol consumption. To meet this demand, researchers have developed modified yeast strains that reduce wine alcohol content during fermentation. These strains ferment less sugar or redirect carbon metabolism. However, their use may pose challenges, such as producing undesired secondary metabolites that can affect wine characteristics. Additionally, consumers are still divided on using genetically modified organisms (GMOs) in food and beverages. This review examines the impact of climate change on wine quality and consumer perception, taking into account new technologies used to reduce wine alcohol content or produce low-alcohol-content wines, such as low-cost techniques like bio-dealcoholization performed by non-GMO wine yeast, Saccharomyces, and non-Saccharomyces.

Efeito do Ethephon na desfolha da zona de cacho, podridão cinzenta de cachos e desempenho vitícola da uva ‘Cabernet Sauvignon’ em região serrana do sul do Brasil

ABSTRACT: Phytoregulators have been used as grapevine defoliants in cluster zones to manage and improve grape quality and production. The present study evaluated the effect of the phytoregulator ethephon on the grapevine defoliation of the cluster region, Botrytis bunch rot (BBR) epidemiology, and the viticultural performance of ‘Cabernet Sauvignon’, during the 2018/2019 and 2019/2020 growing seasons, in the highland region of the Santa Catarina State, Southern Brazil. Ethephon was applied in the bunch region of both sides of the grapevine vegetative canopy, at the phenological stage of beginning of ripening (BBCH-81) in five active ingredient doses (0 mg L-1 (control); 720 mg L-1; 1,440 mg L-1; 2,160 mg L-1; and 2,880 mg L-1), following a randomized block design with four replications and five plants per replication. The following parameters were evaluated: BBR epidemiology, vegetative, productive, and technological and phenolic maturation. The increasing ethephon doses significantly reduced the linear leaf drop and affected the technological and phenolic grape maturation parameters, improving the must pH, total polyphenols, color 420, 520, and 620 ղm, color intensity (°hue angle), and anthocyanin, and reducing the total solubre solids in the ‘Cabernet Sauvignon’ grapevine. However, this significant effect on the linear leaf drop and the technological and phenolic maturation parameters did not interfere with other vegetative, productive, and BBR epidemiology parameters evaluated in the edaphoclimatic conditions of the highland region of southern Brazil.

CLIMATIC FACTORS CHARACTERIZING THE MOISTURE SUPPLY OF THE TERRITORY AND THEIR EFFECT ON THE QUALITY INDICATORS OF GRAPES

The study of scientific problem, to which this research is devoted, is due to planetary climate change, manifested in an increase in the average annual air temperature, rapid changes in winter and summer temperatures, and a lack of precipitation.&#x0D; For today, there is a serious problem of adapting plants to climate change due to an increase in water deficiency in many regions of the world. Climate change creates significant uncertainty in the potential adaptability of grape plants, as well as in the prospects for viticulture development in general.&#x0D; The study and generalization of territorial distribution of climatic factors that characterize a particular region, as well as their effect on the quality characteristics of raw materials and finished products, are attractive from the point of better understanding and forecasting the potential impact on agricultural systems. The obtained data consumption will allow improving the forecast of climate change consequences in the medium term, and in relation to particular terroirs.&#x0D; The goal is to study the effect of climatic factors that characterize the moisture supply of the territory on the quality indicators of grapes.&#x0D; Materials and methods. The objects of the study were grapes of white and red cultivars, different in agroecological aspect, and growing in micro regions of Crimea. To identify the effect of factors characterizing the moisture supply of the territory on the quality indicators of raw materials for winemaking products, the amount of precipitation from the beginning of growing season to the harvesting, the amount of precipitation for the last month before harvest, and hydrothermal coefficient of Selyaninov were selected. The assessment of grapes was carried out according to the indicators of carbohydrate-acid complex (mass concentration of sugars, titratable acids, pH value, profile of organic acids), as well as the glucoacidimetric indicator revealing the degree of grape ripeness.&#x0D; Results and conclusion. Climatic factors characterizing the moisture supply of viticultural and winemaking regions of Crimea were assessed. The studies carried out made it possible to reveal variations in the concentration of carbohydrate-acid complex components depending on the changing ability of environmental factors. A significant precipitation deficiency was observed on the Peninsula. According to the value of hydrothermal coefficient of Selyaninov (did not exceed 1), most of the territory was classified as an arid or very arid zone. A correlation between the hydrothermal coefficient and mass concentration of grape sugars (r=-0.63) was established for red grapevine cultivars. The data obtained indicate that an increase in the amount of precipitation during growing season contributes to a moderation of sugar accumulation in grapes. Similar pattern was not established for white grapevine cultivars. There was a direct correlation of the mass concentration of malic acid on the amount of precipitation in the last month before harvest (r=0.78).

Bunch transpiration is involved in the hastening of grape berry ripening under elevated temperature and low relative humidity conditions

The present study aimed: i) to evaluate the impact of the changes in temperature and relative humidity (RH), projected by the year 2100, on grape ripening, and ii) to assess if bunch transpiration is a key physiological process involved in the advancement in grape development under future climate conditions. Fruit-bearing cuttings of Vitis vinifera L. cv. ‘Tempranillo’ were grown, from fruit set to maturity, in glasshouses under two conditions: 24°C/14°C and 55%/70% RH (day/night) (T) vs 28°C/18°C and 43%/58% RH (T+4). To elucidate the role of bunch transpiration in grape development in a future climate scenario, the bunches of half of the plants in the T+4 glasshouse were sprayed with an antitranspirant (AT+4). T+4 increased bunch transpiration, hastened the ripening process, increasing the rate of total soluble solid (TSS) accumulation and malic acid degradation, and reduced the concentration of total anthocyanins. The application of antitranspirant partially alleviated the effects of combined high temperature and low RH on maturation times, through lower TSS accumulation rates. Berries in AT+4 had the lowest concentrations of anthocyanins and color, likely related to a reduction in light transmittance by the antitranspirant film and to higher anthocyanin degradation due to the longer exposure to elevated temperatures. The results show a negative impact of elevated temperature and low RH on grape composition. The increased bunch transpiration under these conditions played an important role in the changes observed in phenology and sugar accumulation.

Exploration of 5-Azacytidine and Trichostatin A in the modulation of postharvest quality of 'Shine Muscat' grape berries

Grapes have excellent commercial characteristics and high nutritional value, but postharvest storage inevitably reduces their quality. Previously, we studied the regulatory mechanisms of methylation for grape ripening. To further investigate the effects of epigenetic modifications on postharvest quality of grape berries, Transcriptome deep sequencing (RNA-seq) and metabolome sequencing were performed on 5-Azacytidine (5azaC) or Trichostatin A (TSA) treated grape berries. TSA delayed the depletion of soluble sugar and organic acid content in postharvest grapes compared to controls, while 5azaC had the opposite effect. In addition, TSA and 5azaC affected the content and composition of volatile organic compounds (VOCs) in the berries, of which the decrease in linalool content may be directly responsible for the reduction of muscat flavor in the berries. RNA-Seq analysis showed that 626 and 2253 differentially expressed genes (DEGs) were generated by 5azaC and TSA treatments, respectively. GO and KEGG enrichment analyses revealed significant differences in the biological pathways involved in the two collections of DEGs. Metabolomic analyses further clarified the marker metabolites induced by TSA and 5azaC related to fruit quality. In addition, the results of HDAC activity and transcript levels of acetylation-related genes suggest that VvHDA15 may acetylation modification affects the key regulators of postharvest fruit quality. This study not only provides abundant data information, but also offers new insights into the regulation of fruit quality by epimodification.

Grape ripe rot disease caused by Colletotrichum spp.: current status, concerns and future perspectives

Grape ripe rot disease caused by Colletotrichum spp.: current status, concerns and future perspectives

Discrimination of Maturity Stages of Cabernet Sauvignon Wine Grapes Using Visible-Near-Infrared Spectroscopy.

Grape quality and ripeness play a crucial role in producing exceptional wines with high-value characteristics, which requires an effective assessment of grape ripeness. The primary purpose of this research is to explore the possible application of visible-near-infrared spectral (Vis-NIR) technology for classifying the maturity stages of wine grapes based on quality indicators. The reflection spectra of Cabernet Sauvignon grapes were recorded using a spectrometer in the spectral range of 400 nm to 1029 nm. After measuring the soluble solids content (SSC), total acids (TA), total phenols (TP), and tannins (TN), the grape samples were categorized into five maturity stages using a spectral clustering method. A traditional supervised classification method, a support vector machine (SVM), and two deep learning techniques, namely stacked autoencoders (SAE) and one-dimensional convolutional neural networks (1D-CNN), were employed to construct a discriminant model and investigate the association linking grape maturity stages and the spectral responses. The spectral data went through three commonly used preprocessing methods, and feature wavelengths were extracted using a competitive adaptive reweighting algorithm (CARS). The spectral data model preprocessed via multiplicative scattering correction (MSC) outperformed the other two preprocessing methods. After preprocessing, a comparison was made between the discriminant models established with full and effective spectral data. It was observed that the SAE model, utilizing the feature spectrum, demonstrated superior overall performance. The classification accuracies of the calibration and prediction sets were 100% and 94%, respectively. This study showcased the dependability of combining Vis-NIR spectroscopy with deep learning methods for rapidly and accurately distinguishing the ripeness stage of grapes. It has significant implications for future applications in wine production and the development of optoelectronic instruments tailored to the specific needs of the winemaking industry.

Comparing defoliation and canopy sprays to delay ripening of Sauvignon blanc grapes

Higher temperatures caused by climate change are responsible for early maturation process which is often linked to low quality of grapes and wines. In this study, different canopy management techniques were tested and compared over three consecutive years (2017–19) with the aim to evaluate their capacity to delay ripening of Sauvignon blanc/SO4 grapes. These included a defoliation performed at veraison and the applications of antitranspirant (containing pinolene), kaolin and chitosan at bunch closure and veraison. The effects of the treatments on grapevine leaf gas exchanges, chlorophyll content and overall water status were measured during the three vegetative seasons. Moreover, soluble solids content and titratable acidity of berries were monitored from veraison until harvest, when final yield and berry composition were assessed. Pinolene transiently reduced the carbon assimilation rate and, independently from the growing season, significantly reduced sugar concentration in berries at harvest by -1.5°Brix as compared to the control. The defoliation reduced vine yield by 10–15 %, without significantly affecting total sugar and acid concentrations at harvest when compared to control. Kaolin and chitosan increased significantly berry acidity at harvest as compared to other treatments (i.e. defoliation and pinolene), but not to control. Under the temperate and rainy growing conditions of northeastern Italy, the antitranspirant product proved its potential as ripening retardant on a white grapevine cultivar. The high frequency of the rainfall events during the considered seasons partially hindered the full potential efficacy of the considered products sprayed to the canopy, questioning their overall efficacy under such conditions and mode of application.

Rapid Determination of Wine Grape Maturity Level from pH, Titratable Acidity, and Sugar Content Using Non-Destructive In Situ Infrared Spectroscopy and Multi-Head Attention Convolutional Neural Networks.

In the pursuit of enhancing the wine production process through the utilization of new technologies in viticulture, this study presents a novel approach for the rapid assessment of wine grape maturity levels using non-destructive, in situ infrared spectroscopy and artificial intelligence techniques. Building upon our previous work focused on estimating sugar content (∘Brix) from the visible and near-infrared (VNIR) and short-wave infrared (SWIR) regions, this research expands its scope to encompass pH and titratable acidity, critical parameters determining the grape maturity degree, and in turn, wine quality, offering a more representative estimation pathway. Data were collected from four grape varieties-Chardonnay, Malagouzia, Sauvignon Blanc, and Syrah-during the 2023 harvest and pre-harvest phenological stages in the vineyards of Ktima Gerovassiliou, northern Greece. A comprehensive spectral library was developed, covering the VNIR-SWIR spectrum (350-2500 nm), with measurements performed in situ. Ground truth data for pH, titratable acidity, and sugar content were obtained using conventional laboratory methods: total soluble solids (TSS) (∘Brix) by refractometry, titratable acidity by titration (expressed as mg tartaric acid per liter of must) and pH by a pH meter, analyzed at different maturation stages in the must samples. The maturity indicators were predicted from the point hyperspectral data by employing machine learning algorithms, including Partial Least Squares regression (PLS), Random Forest regression (RF), Support Vector Regression (SVR), and Convolutional Neural Networks (CNN), in conjunction with various pre-processing techniques. Multi-output models were also considered to simultaneously predict all three indicators to exploit their intercorrelations. A novel multi-input-multi-output CNN model was also proposed, incorporating a multi-head attention mechanism and enabling the identification of the spectral regions it focuses on, and thus having a higher interpretability degree. Our results indicate high accuracy in the estimation of sugar content, pH, and titratable acidity, with the best models yielding mean R2 values of 0.84, 0.76, and 0.79, respectively, across all properties. The multi-output models did not improve the prediction results compared to the best single-output models, and the proposed CNN model was on par with the next best model. The interpretability analysis highlighted that the CNN model focused on spectral regions associated with the presence of sugars (i.e., glucose and fructose) and of the carboxylic acid group. This study underscores the potential of portable spectrometry for real-time, non-destructive assessments of wine grape maturity, thereby providing valuable tools for informed decision making in the wine production industry. By integrating pH and titratable acidity into the analysis, our approach offers a holistic view of grape quality, facilitating more comprehensive and efficient viticultural practices.

Suppression of Colletotrichum spp. on grape berries, vine leaves, and plants using Bacillus velezensis S26 endospores

Grape ripe rot and anthracnose are fungal diseases caused by Colletotrichum spp., which negatively impact viticulture. Disease management often involves the use of synthetic fungicides, whose toxicity poses risks to the environment and human health. As a result, biopesticides have been developed as an alternative approach for suppressing plant diseases in the field or postharvest. The present study aimed to evaluate the inhibitory potential of a bacterial inoculant containing endospores of Bacillus velezensis strain S26 against seven isolates of Colletotrichum spp. in grapevines (Vitis vinifera and V. labrusca). The bioassays were performed on grape berries, leaf discs, and micropropagated plants using both a fresh inoculant and an inoculant stored for six months at room temperature. The findings revealed that the biocontrol activity was more pronounced in fruit when compared to vine plants and leaves. Besides, the bacterial inoculant demonstrated a strain-dependent capacity to suppress the pathogen, with higher effectiveness observed in controlling the disease in V. vinifera compared to V. labrusca. Regarding the effect of storage on bacterial antagonism, the stored inoculant maintained its inhibitory ability against the pathogen. In summary, B. velezensis S26 demonstrates potential as a biocontrol agent against Colletotrichum spp. in grapevines, making it suitable for use in the development of bioproducts.

Precision maturation assessment of grape tissues: Hyperspectral bi-directional reconstruction using tomography-like based on multi-block hierarchical principal component analysis

This paper introduces a tomography-like method for assessing grape maturation. It analyses inner tissue spectra through point-of-measurement (POM) sensing. A multi-block hierarchical principal component analysis (MHPCA) algorithm was used for the spectral reconstruction of total grapes (skin, pulp, and seed). Two grape cultivars, Loureiro (white; n = 216) and Vinhão (red; n = 205) were measured at 12 dates after veraison (DAV). The reconstructed spectra showed no significant differences (p < 0.001) from the originals for both grapes. Loureiro had better statistical metrics (Person's correlation coefficient (r) values for: total grape: 0.99, skin: 1; pulp: 1, seed: 0.94) than Vinhão (r values for: total grape: 0.92, skin: 0.92; pulp: 0.95, seed: 0.95). Using self-learning artificial intelligence (SL-AI), the following parameters were predicted for both grapes: soluble solids content (%; MAPE <13%), puncture force (N; MAPE <29%), chlorophyll content (a.u.; MAPE <29%), and anthocyanin content (a.u.; MAPE <17%, Vinhão only). When comparing observed values with predicted skin, pulp, and seed spectra, Vinhão showed no statistical differences for most parameters, except pulp chlorophyll on one DAV in the final maturation stage. The same was done with the Loureiro cultivar. Although Loureiro mostly showed no statistical differences in assessed parameters across tissues and dates, variations were found in pulp and skin chlorophyll content and puncture force. This tomography-like approach based on tissue maturation can help viticulturists to access instant data on grape maturation, supporting informed decision-making and promoting more sustainable agricultural practices.

Influence of Benzothiadiazole on the Accumulation and Metabolism of C6 Compounds in Cabernet Gernischt Grapes (Vitis vinifera L.).

Pre-harvest application of elicitors improves grape quality, specifically the phenolic compounds and color characteristics. Limited research has been conducted on the impact of elicitors on the C6 compounds found in grapes. This is due to lack of comprehensive studies examining the combined effects of bound aroma compounds, enzyme activity, and substrate availability. This study aimed to assess the impact of benzothiadiazole (BTH) on the physicochemical properties and C6 compounds of Cabernet Gernischt grapes during ripening. Compared with the control group (CK), BTH treatment significantly increased the 100-berry weight, skin/berry ratio, pH, total phenolic content, and total flavonoid content in ripe grapes. Additionally, BTH treatment led to significant reductions in reducing sugar, total soluble solids, titratable acidity, linoleic acid, linolenic acid, and free C6 aldehydes. Furthermore, BTH treatment significantly decreased the contents of free C6 alcohols and increased the levels of free and bound C6 esters. BTH treatment also increased the activities of lipoxygenase, alcohol dehydrogenase, and alcohol acetyltransferase enzymes, while it decreased the activity of hydroperoxide lyase enzyme. The application of BTH resulted in changes to the physicochemical properties and levels of C6 compounds in Cabernet Gernischt grapes by up-regulating enzyme activity and down-regulating precursors.

A Deep Learning Approach for Precision Viticulture, Assessing Grape Maturity via YOLOv7.

In the viticulture sector, robots are being employed more frequently to increase productivity and accuracy in operations such as vineyard mapping, pruning, and harvesting, especially in locations where human labor is in short supply or expensive. This paper presents the development of an algorithm for grape maturity estimation in the framework of vineyard management. An object detection algorithm is proposed based on You Only Look Once (YOLO) v7 and its extensions in order to detect grape maturity in a white variety of grape (Assyrtiko grape variety). The proposed algorithm was trained using images received over a period of six weeks from grapevines in Drama, Greece. Tests on high-quality images have demonstrated that the detection of five grape maturity stages is possible. Furthermore, the proposed approach has been compared against alternative object detection algorithms. The results showed that YOLO v7 outperforms other architectures both in precision and accuracy. This work paves the way for the development of an autonomous robot for grapevine management.

Total Soluble Solids in Grape Must Estimation Using VIS-NIR-SWIR Reflectance Measured in Fresh Berries

Total soluble solids (TSS) is a key variable taken into account in determining optimal grape maturity for harvest. In this work, partial least square (PLS) regression models were developed to estimate TSS content for Godello, Verdejo (white), Mencía, and Tempranillo (red) grape varieties based on diffuse spectroscopy measurements. To identify the most suitable spectral range for TSS prediction, the regression models were calibrated for four datasets that included the following spectral ranges: 400–700 nm (visible), 701–1000 nm (near infrared), 1001–2500 nm (short wave infrared) and 400–2500 nm (the entire spectral range). We also tested the standard normal variate transformation technique. Leave-one-out cross-validation was implemented to evaluate the regression models, using the root mean square error (RMSE), coefficient of determination (R2), ratio of performance to deviation (RPD), and the number of factors (F) as evaluation metrics. The regression models for the red varieties were generally more accurate than the models of those for the white varieties. The best regression model was obtained for Mencía (red): R2 = 0.72, RMSE = 0.55 °Brix, RPD = 1.87, and factors n = 7. For white grapes, the best result was achieved for Godello: R2 = 0.75, RMSE = 0.98 °Brix, RPD = 1.97, and factors n = 7. The methodology used and the results obtained show that it is possible to estimate TSS content in grapes using diffuse spectroscopy and regression models that use reflectance values as predictor variables. Spectroscopy is a non-invasive and efficient technique for determining optimal grape maturity for harvest.

Reintroducing Autochthonous Minor Grapevine Varieties to Improve Wine Quality and Viticulture Sustainability in a Climate Change Scenario

One of the major challenges that global warming poses to viticulture is the maintenance of adequate acidity at maturity in white grapes for sparkling winemaking. This issue arises from three main occurrences: (i) with higher temperatures, degradation of malic acid is significantly enhanced; (ii) with a general advancement in grapevine phenology, grape maturity may occur under suboptimal climatic conditions; and (iii) harvesting grapes at “traditional” dates results in overripe fruits for sparkling destinations. In this biennial work, we compared the fruit and must composition of a local, widely grown white grape variety in the Colli Piacentini area (cv. Ortrugo, ORT) with those of a minor autochthonous variety, namely, Barbesino (BRB). Furthermore, we compared the composition, aromatic, and sensory profiles of wines obtained from ORT and BRB grapes picked on the same date and, in addition, of a second Barbesino wine from late harvest (BRB-LH). ORT and BRB had a similar sugar accumulation dynamic, whereas BRB exhibited a delayed loss of titratable acidity. In more details, BRB had lower malic acid degradation rates when malate concentration was &lt;9 g/L. As a result, with comparable yield and total soluble solid content (TSS) (∼20°Brix), BRB had a higher berry titratable acidity and malic acid concentration at harvest than ORT. BRB wines showed the highest titratable acidity (TA), while ORT had the lowest TA and a higher pH, and as expected, BRB-LH had the highest pH and a lower TA than BRB although still higher than those of ORT wine. The aroma profiles of wines were mainly characterized by fermentative aromas, including esters, fatty acids, higher alcohols, and C6 compounds, and BRB-LH wines showed the highest concentration of higher alcohols, while the fermentative esters were higher in ORT wines. Panelists considered BRB significantly fresher and with bigger aroma intensity than ORT, confirming that the higher acidity detected in BRB musts is well preserved in final wines. Our work demonstrates that local minor varieties can be reconsidered in light of the new climate change-related issues impairing viticulture sustainability today. In particular, currently neglected cultivars could help preserve must acidity as compared to traditional varieties having early ripening, maintaining the links with terroir and local traditions at the same time.

First report of Colletotrichum siamense causing grape ripe rot in Brazil.

Vitis vinifera cv. BRS Vitória is a seedless black table grape cultivar with an extremely pleasant flavor and is adapted to cultivation in all Brazilian regions. Between November and December 2021, grape berries presenting typical ripe rot symptoms were found in three vineyards located in Petrolina, Pernambuco Brazil. The first symptoms are small and depressed lesions on ripe berries, presenting tiny black acervuli. As the disease progress, lesions enlarge and affect the whole fruit, and abundant orange masses of conidia can be observed. Finally, berries become completely mummified. Symptoms were observed in the three vineyards visited, and disease incidence was above 90%. Some producers are considering eradicating the plantations due to the losses caused by the disease. Control measures used so far are costly and ineffective. Fungal isolation was performed by transferring conidial masses from 10 diseased fruit to plates containing potato dextrose agar medium. Cultures were incubated at 25 °C under continuous light. Seven days after inoculation, three fungal isolates (LM1543-1545) were obtained and subcultivated in pure culture for species identification and pathogenicity test. Isolates presented white to grey cottony mycelia, and hyaline conidia with cylindrical with rounded ends, which resemble the genus Colletotrichum (Sutton 1980). Partial sequences of APN2-MAT/IGS, CAL, and GAPDH loci were amplified, sequenced, and deposited on GenBank (OP643865-OP643872). Isolates from V. vinifera were placed within the clade including the ex-type and representative isolates of C. siamense. The clade was strongly supported (99.8% bootstrap support) in the maximum likelihood multilocus tree of the three loci combined, which confidently assign the isolates to this species. Inoculation on grape bunches was performed to confirm pathogenicity. Grape bunches were surface sterilized for 30 s in 70% ethanol, 1 min in 1.5% NaOCl, rinsed two times with sterile distilled water, and air-dried. Fungal conidial suspensions (106 conidia mL-1) were sprayed to the point of run-off. The negative control was represented by grape bunches sprayed with sterile distilled water. Grape bunches were kept in a humid chamber for 48 h at 25 °C and a light period of 12 h. The experiment was conducted with four replicates (four inoculated bunches per isolate) and repeated once. Typical ripe rot symptoms were observed on grape berries 7 days after inoculation. No symptoms were observed on the negative control. The fungal isolates recovered from inoculated berries were morphologically identical to the C. siamense isolates originally recovered from symptomatic berries collected in the field, fulfilling Koch's postulates. Colletotrichum siamense was reported in association with grape leaves in USA (Weir et al. 2012) and causing grape ripe rot in North America (Cosseboom & Hu 2022). Only C. fructicola, C. kahawae, C. karsti, C. limetticola, C. nymphaeae and C. viniferum were reported causing grape ripe rot in Brazil (Echeverrigaray et al. 2020). To our knowledge, this is the first report of C. siamense causing grape ripe rot in Brazil. This finding is important for disease management because C. siamense has a high phytopathogenic potential due to its wide distribution and host range.