Wine Grape Cultivars Research Articles

Investigation of hand forces applied to a pruning tool - pilot study.

Winter pruning is a cultivation practice necessary for maintaining the balance between the vegetative and the productive activity of plants and requires many working days using hand scissors. This operation involves the subjects carrying out a series of gestures that are repeated with considerable frequency, which are all musculo-skeletal disorders risk factors (MSDs) for the hand-wrist area. The aim of this study was to investigate the forces applied to pruning tools. Using a sensor matrix, peak and average forces were measured which are exerted while cutting branches of 3 different diameters, from 5 wine-grape cultivars. Samples were tested on 8 participants using sensored scissors to record, in 6 hand areas, the forces necessary to cut. Results showed that while cutting, the factors which can impact the force employed (peak and average forces) by the subjects are branch diameter and percentage of branch humidity. Cut duration was inversely related to the size of the subject's hand. The middle finger area of the hand recorded the highest force average and peak levels, while the hand region least affected during the cuts was the farthest from the thumb. The study enabled the highlighting of which factors influence the forces employed by the operator while cutting grape branches, and to identify the hand regions where muscle activation is at its most. These findings can be relevant in preventing MSDs. Further studies need to be conducted with a larger number of subjects.

Comparison of Sustained Deficit and Pre- and Postveraison Regulated Deficit Irrigation on Malbec and Syrah Grapevines

The objective of this study was to compare the effect of sustained deficit irrigation and regulated deficit irrigation strategies on the yield components and berry composition of two winegrape cultivars (Vitis vinifera L.) that differ in their hydraulic behavior. Malbec and Syrah grapevines were grown in southern Idaho under arid conditions and were drip-irrigated weekly from fruit set until harvest to supply 35 or 70% of estimated vine water demand that was delivered either as a sustained amount (35, 70) or the amount was altered at veraison (3570, 7035). In both cultivars, the 7035 and 35 treatments produced fruit with a greater concentration of anthocyanins and phenolics than the 3570 and 70 treatments. In both cultivars, the yield of the 7035 treatment was ~30% greater than the 35 treatment and ~15% lower than the 70 treatment. The 7035 treatment was provided ~58% more water than the 35 treatment and ~20% less water than the 70 treatment. In both cultivars, the 3570 and 7035 treatments had a similar ratio of yield reduction to water savings, similar carbon isotope composition, and similar seasonal average weekly midday leaf water potential. The 3570 and 35 treatments had greater bud injury (low pruning weight and low cluster number per vine) and slower recovery from injury than the 7035 and 70 treatments after exposure to an extreme cold weather event. Despite inherent differences in carbon isotope composition, the 70 and 7035 treatments offer the best potential in both cultivars for sustained productivity under challenging climatic conditions.

Developing Functional and Antioxidant-Rich Table Grape Cultivars by Crossing Alicante Bouschet x Alphonse Lavallee

Recently, red and black colored grape cultivars are getting more popular due to anthocyanins in the skin and flesh of berries which are called teinturier grapes. Anthocyanins are a group of polyphenolics which can prevent many diseases by inhibiting or delaying the oxidative damage. But there is no a teinturier table grape cultivar in Turkey, but there are some teinturier wine grape cultivars such as Alicante Bouschet. Main goal of this study was to obtain tenturier genotypes by crossing of Alphonse Lavallee and Alicante Bouschet grape cultivars and to compare anthocyanin coloration of cotyledon and true leaves for early selection for tenturier candidates. Anthocyanin coloration was visually observed in cotyledon leaves. Amount of anthocyanin were determined in true leaves by spectrophotometrically disc method. Cotyledon and true leaves of most genotypes had the green color and there were parallelism between both leaves. The amount of anthocyanin of true leaves weredetermined as 50.21 mg/kg in green colored leaves and 131.51 mg kg-1 in dark colored leaves.

Diploid Genome Assembly of the Wine Grape Carménère.

In this genome report, we describe the sequencing and annotation of the genome of the wine grape Carménère (clone 02, VCR-702). Long considered extinct, this old French wine grape variety is now cultivated mostly in Chile where it was imported in the 1850s just before the European phylloxera epidemic. Genomic DNA was sequenced using Single Molecule Real Time technology and assembled with FALCON-Unzip, a diploid-aware assembly pipeline. To optimize the contiguity and completeness of the assembly, we tested about a thousand combinations of assembly parameters, sequencing coverage, error correction and repeat masking methods. The final scaffolds provide a complete and phased representation of the diploid genome of this wine grape. Comparison of the two haplotypes revealed numerous heterozygous variants, including loss-of-function ones, some of which in genes associated with polyphenol biosynthesis. Comparisons with other publicly available grape genomes and transcriptomes showed the impact of structural variation on gene content differences between Carménère and other wine grape cultivars. Among the putative cultivar-specific genes, we identified genes potentially involved in aroma production and stress responses. The genome assembly of Carménère expands the representation of the genomic variability in grapes and will enable studies that aim to understand its distinctive organoleptic and agronomical features and assess its still elusive extant genetic variability. A genome browser for Carménère, its annotation, and an associated blast tool are available at http://cantulab.github.io/data.

The Area-Wide Spatio-Temporal Distribution of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) in a Heterogenous Fruit Production Region of the Western Cape, South Africa

The area-wide spatio-temporal distribution of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) trap catches was investigated in the regions of Elgin/Grabouw, Villiersdorp and Vyeboom, collectively known as EGVV, Western Cape, South Africa. The primary fruit crops planted in EGVV include various varieties and cultivars of pome fruit, stone fruit, citrus, wine grapes and berries. Fruit fly trapping data from four consecutive seasons were sourced from a centralised database managed by a non-profit company, which operates an area-wide integrated pest management (AW-IPM) programme, incorporating the sterile insect technique (SIT) for C. capitata fruits flies, within EGVV. Mean trap catch between regions and seasons was compared. The spatio-temporal variation of mean trap catch was also investigated. A geographic information system (GIS) was used to symbolise and map mean trap catch per trap location. There was no significant difference in the mean trap catch between regions. Significant differences did occur between some seasons in Villiersdorp and Vyeboom but not in Elgin/Grabouw. The spatial distribution of trap catches between seasons varied greatly, indicating no definitive pattern. However, traps with the highest seasonal trap catch occurred mostly in the southeastern parts of each region and traps with lower levels were distributed mostly in the northwestern parts of each region. The results suggest a relationship between the geographic characteristics of EGVV and the abundance and distribution of C. capitata. It is recommended that an in-depth spatio-temporal analysis be carried out to better understand the geographical distribution of trap catches in the study area.

Assessment of Pierce's disease susceptibility in Vitis vinifera cultivars with different pedigrees

Pierce's disease (PD) of grapevine is caused by the bacterium Xylella fastidiosa. In this study, an integrated approach was applied to assess PD susceptibility among different Vitis vinifera cultivars that incorporated disease severity, bacterial pathogen abundance and loss of stem xylem hydraulic conductivity. It was hypothesized that levels of PD susceptibility in V. vinifera can be attributed in part to the host anatomical features that are shaped by its pedigree background. Two popular wine grape cultivars were initially selected from the occidentalis group, Merlot and Cabernet Sauvignon, and one from the orientalis group, Thompson Seedless. The more recently bred table grape cultivar Scarlet Royal, that has mixed pedigree parentage, was also included. PD susceptibility was compared to the known PD resistant b43‐17 V. arizonica/candicans wild grape species from North America. The data indicated that Thompson Seedless was ranked as the most susceptible to PD because it significantly exhibited the most severe disease symptoms at 12 weeks post‐inoculation and hosted the highest X. fastidiosa titre of the cultivars, and lost over 90% of its stem hydraulic conductivity. In contrast, the other three cultivars displayed less susceptibility to PD. The way in which the xylem anatomy could impact PD susceptibility in V. vinifera cultivars is discussed, together with how grape pedigrees and their cognate centre of domestication may have influenced xylem anatomical features. This work provides a reference framework to further test the hypothesis that V. vinifera cultivars with wide xylem vessels may be more prone to PD decline.

Microbial community composition on grape surface controlled by geographical factors of different wine regions in Xinjiang, China.

Native microorganisms on wine grape surface contribute to regional wine characteristics and quality. The Xinjiang Uygur Autonomous Region in northwest China is one of the eight main wine-producing areas in China. To investigate the relationship between the microbial community structure of wine grape epidermises and environmental conditions, 16S rDNA and ITS sequences of 48 wine grape samples from four wine grape cultivars and six wine-growing regions in Xinjiang were sequenced, based on Illumina high-throughput sequencing technology. A total of 691 operational taxonomic units (OTUs) in 16 bacterial phyla and 349 OTUs in three fungal phyla were identified. Among them, Proteobacteria and Ascomycota were the predominant bacteria and fungi, respectively. Canonical correspondence analysis indicated that bacterial community diversity was largely related to altitude, latitude and longitude, while that of the fungi was closely related to altitude, dryness, frost-free period, latitude and longitude. Our results suggest that microbial community structure on the surface of wine grape is controlled primarily by geographical conditions.

Visible-near infrared spectroradiometry-based detection of grapevine leafroll-associated virus 3 in a red-fruited wine grape cultivar

Grapevine leafroll disease (GLD) is one of the major threats to wine grapes (Vitis vinifera) causing substantial economic losses to the growers. This study was undertaken to evaluate the applicability of visible and near infrared (VIS-NIR) spectroradiometery as a rapid, robust and non–destructive optical sensing method for the detection of Grapevine leafroll-associated virus 3 (GLRaV-3) at different phenological stages in a red-berried wine grape cultivar. Using VIS-NIR spectroradiometer, data was collected from the healthy and GLRaV-3-infected leaf samples from cv. Cabernet Sauvignon for two seasons at specific intervals during asymptomatic and symptomatic stages of the disease. Fiber optic leaf clip was used to collect spectral responses from grapevine leaves under field conditions. Salient feature extraction using stepwise multilinear regression and partial least square regression methods showed significant differences between healthy and virus–infected leaves in the visible (351, 377, 501, 526, 626 and 676 nm) and near infrared (701, 726, 826, 901, 951, 976, 1001, 1027, 1052 and 1101 nm) regions. Spectral wavelengths from near infrared region (1001, 1027 and 1052 nm) were validated at different phenological stages spanning both asymptomatic and symptomatic stages of the disease. Selected spectral wavelengths demonstrated robustness in virus detection with overall classification accuracies in the range of 75–99% using quadratic discriminant analysis (QDA) classifier. QDA based classification accuracies for healthy, infected and overall classes were significantly higher compared to Naïve Bayes classifier. The accuracy for virus detection during asymptomatic stages was not significantly different from the symptomatic phase, indicating reliability of the selected features for early detection of GLRaV–3–infected grapevines.

Evaluation of amino acid contents and enzyme activities of seeds from Semillon and Carignane wine grape cultivars grown under different irrigation conditions

The effects of deficit irrigations (DI50, DI75) and full irrigation (FI100) level together with control (Rainfed) treatment on amino acid contents and enzyme activities of seeds of Semillon and Carignane wine grape varieties were evaluated. Irrigation was started when the midday leaf water potential reached -10 bars. Accordingly, irrigation was initiated after berry set and continued at weekly intervals until the harvest time in the study area. To calculate of water volumes applied to the irrigated plots were considered 50%, 75% and 100% of the cumulative evaporation from the Class A Pan for a week duration. The results of this study showed that irrigation affected the phytochemical parameters in both cultivars. In terms of glutathione S-transferase enzyme activity and amino acid contents (except aspartate), Semillon gave higher values than those of Carignane. However, values of glutathione and catalase enzyme activities, quaternary amines and aspartate amino acids were higher in Carignane. Phytochemical contents of the seeds changed according to the irrigation levels. Generally, the values of quaternary amines, dehydrins and histidine, cystine, lysine, proline in amino acids considerably increased in the control and DI50 treatments. However, there were no significance differences in terms of amino acids (glutamine, glycine, thionine, arginine, hydroxy proline and sarcosine) among the irrigation levels. As a result of the study, it can be concluded that the amounts of compounds analyzed in the grape seeds increased with rainfed and deficit irrigation together with the rainfall under experimental conditions.

Anthocyanin content and composition in four red winegrape cultivars (Vitis vinifera L.) under variable irrigation

Aim: The aim of this study was to determine and compare anthocyanin content and profile under variable irrigation regimes in four red grape cultivars (Vitis vinifera L.), the Greek indigenous cvs. Agiorgitiko and Xinomavro, alongside Syrah and Grenache noir.Methods and results: Three irrigation treatments were applied in a 6-year-old vineyard comprising all four varieties in a block design, starting at bunch closure (E-L 32) through harvest of 2012 and 2013: full irrigation (FI) at 100% of crop evapotranspiration (ETc), deficit irrigation (DI) at 50% of ETc and non-irrigated (NI). The identification of the compounds was performed by HPLC. Results showed that, under the hot summer conditions of the Greek climate, the four cultivars had a similar response regarding vigor and yield parameters, with values increasing with water supply. Anthocyanin concentration was maximized under non-irrigated conditions in all cultivars, but anthocyanin profile and relative distribution of individual anthocyanins among irrigation treatments showed a strong cultivar effect.Conclusion: Xinomavro seemed to favor the synthesis of more stable forms of anthocyanins under limited water supply (acylated over non-acylated and tri-oxygenated & methoxylated on the B-ring over di-oxygenated & hydroxylated) while Agiorgitiko had an opposite behavior, which might imply a need for a different irrigation strategy.Significance and impact of the study: To the best of our knowledge, this is the first comparative report of anthocyanin composition and profile in berry skin, under contrasting water status, for the two most important red winegrapes of Greece.

A plant regeneration platform to apply new breeding techniques for improving disease resistance in grapevine rootstocks and cultivars

Worldwide grapevine cultivation is based on the use of elite cultivars, in many cases strictly linked to local important wine brands. Most ofVitis viniferacultivars have high susceptibility to fungal and viral diseases therefore, new breeding techniques (e.g. Cisgenesis, RNAi and gene editing) offer the possibility to introduce new clones of the main cultivars with increased diseases resistance, in order to reduce environmental impact and improve quality in the intensive wine grape industry. This study is finalized to develop efficientin vitroregeneration and transformation protocols to extend the application of these technologies in wine grape cultivars and rootstocks. With this aim,in vitroregeneration protocols based on the production of meristematic bulks (Mezzetti et al., 2002) were optimized for different grapevine cultivars (Glera, Vermentino, Sangiovese, Thompson Seedless) and rootstocks (1103 Paulsen, and 110 Richter). The meristematic bulks were then used as explants forAgrobacteriummediated genetic transformation protocols, by comparing the use of NPTII and e-GFP as marker genes. Results confirmed the efficiency of meristematic bulks as the regenerating tissue to produce new modified plants in almost all the above genotypes. The highest regeneration efficiency in some genotypes allowed the selection of stable modified lines/calli with only the use of e-GFP marker gene. This protocol can be applied in the use of MYB marker gene for the production of cisgenic lines. Genotypes having the highest regeneration and transformation efficiency were also used for transformation experiments using a hairpin gene construct designed to silence the RNA-dependent RNA polymerase (RpRd) of the GFLV and GLRaV3, which would induce multiple virus resistances, and the Dicer-like protein 1 (Bc-DCL1) and Bc-DCL2 to controlB. cinereainfection.

Identification of Wine Grape Varieties Based on Near-infrared Hyperspectral Imaging

Abstract. Wine grape variety is one of the main determinants of wine quality. The objective of this study is to explore the feasibility of using hyperspectral imaging (HSI) to identify six red and six white wine grape cultivars during the ripening period. Abnormal spectral data were removed by the Mahalanobis distance, and six different methods were employed to preprocess the spectral data. Next, the effective wavelengths for the classification of grape varieties were selected using principal component analysis (PCA) loadings to improve the HSI processing speed. Finally, three methods were applied to classify grape samples: a support vector machine (SVM), a random forest (RF), and an AdaBoost model. The results indicated that the model established by Savitzky-Golay (S-G) Filter + PCA + SVM achieves the best classification result. The average calibration and validation accuracy for red grapes reached 93.06% and 90.01%, respectively, and for white grapes, they reached 83.77% and 81.09%, respectively, which are slightly lower than those achieved by the full-spectrum model. This study revealed that hyperspectral imaging has great potential for rapid variety discrimination of different wine grapes. Keywords: Hyperspectral imaging, Random forest, Support vector machine, Variety identification, Wine grape.

Drought Tolerance of Some Wine Grape Cultivars Under in Vitro Conditions

Drought Tolerance of Some Wine Grape Cultivars Under in Vitro Conditions

Dynamics of partitioning of major sugars, total phenols and flavonoids in the juice of seven wine grape (Vitis spp.) cultivars during different stages of berry development

The juices of seven grapevine (wine) cultivars grown in the Fruit Research Farm, Department of Fruit Science, PAU Ludhiana, were analyzed for sugar, phenol and flavonoids at four different stages of berry development, in 2015 and 2016. When the unripe berries were almost in full size, the glucose, fructose and sucrose contents ranged from 1.650–4.433 g/100 ml, 1.030–2.940 g/100 ml and 0.063–1.043 g/100 ml in the year 2015 and 1.500–3.760 g/100 ml (2016), 0.703–2.757 g/100 ml and 0.023–1.030 g/100 ml in the year 2016, while the level of phenols and flavonoids was very low. At verasion sugar content increased slightly. However dramatic changes in all genotypes were recorded after verasion. In the final analysis the total sugar content varied from 20.293 g/100 ml (CBR)–26.087 g/100 ml (Merlot) in the year 2015 and 17.750 g/100 ml (Carolina Black Rose)–24.337 g/100 ml (Merlot) n the year 2016, and the phenol and total flavonoid content of mature berries range from 3.070 g/100 ml (Merlot)–4.967 g/100 ml (H-144) in the year 2015 and 2.296 g/100 ml–4.453 g/100 ml (H-144) in the year 2016. This study gives valuable information for further understanding the sugar, phenol and total flavonoid changes that occur in some grape cultivars during berry maturation. Therefore, the results are useful for research on biochemistry of grapes during berry development.

Effects of a biodegradable liquid film on winter chill protection of winegrape cultivars

In China, according to the climatic zoning, more than 90% Vitis vinifera are distributed in areas where the vines must be buried under a layer of soil during winter (vine burial) to protect them from severe winter chill (Li et al., 2006; Wang et al., 2018). Vine burial in winter followed by vine excavation and straightening in spring are difficult and expensive tasks, posing risks to the plants and the environment. Therefore, the goal of this work was to identify a biodegradable liquid film (BLF) suitable for grapevine application to replace vine burial as an alternate strategy to protect against winter chill. We evaluated the influence of BLF spraying on vines after being trained in winter (BLF spraying treatment) and compared it with vine burial (VB). The study evaluated the grapevine death rate of BLF treatment following freezing events in January 2016, and compared germination date, yields, berry quality, and a cost analysis of the two treatments during the winter of 2015 to the spring of 2017 at Heyang Station of Viticulture, NWAFU, in China. The results showed that BLF application can protect some cultivars from winter chill in Heyang and delays bud germination date in cold years. BLF treatment has the opposite trend of reducing sugar and titratable acid content for Cabernet Sauvignon and Italian Riesling, causes higher polyphenols content of berries under most conditions, and requires lower winter vineyard operations costs than VB treatment.

Construction of a high-density linkage map and QTL detection of downy mildew resistance in Vitis aestivalis-derived 'Norton'.

A major QTL for downy mildew resistance was detected on chromosome 18 (Rpv27) in Vitis aestivalis-derived 'Norton' based on a high-resolution linkage map with SNP and SSR markers as well as 2years of field and laboratory phenotyping data. Grapevine downy mildew caused by the oomycete Plasmopara viticola is one of the most widespread and destructive diseases, particularly in humid viticultural areas where it damages green tissues and defoliates vines. Traditional Vitis vinifera wine grape cultivars are susceptible to downy mildew whereas several North American and a few Asian cultivars possess various levels of resistance to this disease. To identify genetic determinants of downy mildew resistance in V. aestivalis-derived 'Norton,' a mapping population with 182 genotypes was developed from a cross between 'Norton' and V. vinifera 'Cabernet Sauvignon' from which a consensus map was constructed via 411 simple sequence repeat (SSR) markers. Using genotyping-by-sequencing, 3825 single nucleotide polymorphism (SNP) markers were also generated. Of these, 1665 SNP and 407 SSR markers were clustered into 19 linkage groups in 159 genotypes, spanning a genetic distance of 2203.5cM. Disease progression in response to P. viticola was studied in this population for 2years under both laboratory and field conditions, and strong correlations were observed among data sets (Spearman correlation coefficient = 0.57-0.79). A quantitative trait loci (QTL) analysis indicated a resistance locus on chromosome 18, here named Rpv27, explaining 33.8% of the total phenotypic variation. Flanking markers closely linked with the trait can be further used for marker-assisted selection in the development of new cultivars with resistance to downy mildew.

Amelioration of cold-induced oxidative stress by exogenous 24-epibrassinolide treatment in grapevine seedlings: Toward regulating the ascorbate–glutathione cycle

Ascorbate-glutathione (AsA-GSH) cycle plays a key role in tolerance of plant under biotic or abiotic stress. However, little is known regarding the role of brassinolide in AsA-GSH cycle in grape under chilling stress. In this study, a wine grape cultivar, Cabernet Sauvignon (Vitis vinifera), was subjected to chilling stress for different time points after treated by 24-Epibrassinolide (EBR). The result showed EBR plays a positive role in amelioration of leaf morphology and root growth under chilling stress. In terms of physiological aspect, EBR treatment reduce the O2− and H2O2 contents than that in the control. This is primarily related to the improved antioxidant system and the regulation of EBR to AsA-GSH cycle. There was an obvious increase in superoxide dismutase (SOD) activities in EBR treatment compared with in the control, and similar result also was observed in level of AsA, and AsA/DHA. Alleviation of EBR to chilling-stressed injury was also reflected in glutathione (GSH) and GSH/GSSG, as high levels of these parameters were observed in EBR treatment. Furthermore, ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbic acid reductase (DHAR) and monodehydroascorbate reductase (MDHAR) also showed elevated activities in the EBR treatment. Interestingly, the regulation of EBR to these components in AsA-GSH cycle showed a difference in time course, suggesting that the cycle might be affected by EBR at earlier and middle term of chilling stress. Our work will provide the information for understanding the role of EBR in AsA-GSH cycle.

The Relative Occurrence of Grapevine leafroll-associated virus 3 and Grapevine red blotch virus in Washington State Vineyards.

Vineyard surveys were conducted for three consecutive seasons in eastern Washington State, the major grapevine-growing region in the state, to document the occurrence of Grapevine leafroll-associated virus 3 (GLRaV-3) and Grapevine red blotch virus (GRBV). The majority of samples were collected from red-berried wine grape (Vitis vinifera) cultivars exhibiting symptoms of or suspected for grapevine leafroll (GLD) and red blotch (GRBD) diseases. A limited number of samples from white-berried cultivars were collected randomly due to the lack of visual symptoms. Samples were collected from a total of 2,063 grapevines from 18 red-berried cultivars and seven white-berried cultivars planted in eight American Viticultural Areas and tested for GLRaV-3 and GRBV using RT-PCR and PCR, respectively. The results showed 67.77% and 6.01% of total samples positive for GLRaV-3 and GRBV, respectively, and 9.06% of samples positive for both viruses. About 17% of samples tested negative for the two viruses, but some of these samples were positive for GLRaV-2 and GLRaV-4. Overall results indicated that GLRaV-3 was more common than GRBV, independent of cultivars and the geographic origin of samples. Due to variability in symptoms in red-berried cultivars, virus-specific diagnostic assays were deemed necessary for reliable identification of GLRaV-3 and GRBV and to differentiate GLD and GRBD symptoms from those induced by biotic and abiotic stresses in vineyards. A multiplex PCR protocol was developed for simultaneous detection of GLRaV-3 and GRBV in grapevine samples. A global phylogenetic analysis of GRBV genome sequences revealed segregation of virus isolates from Washington State vineyards into two distinct clades, with the majority of isolates belonging to clade II.

Crop Level and Harvest Date Impact on Four Ontario Wine Grape Cultivars. II. Wine Aroma Compounds and Sensory Analysis

Pinot gris, Riesling, Cabernet franc and Cabernet Sauvignon from a vineyard in Virgil, Ontario, Canada were subjected by cluster thinning to two crop-level treatments (full crop, half crop), combined with threeharvest dates (commercial harvest (T0), three weeks after T0 (T1), six weeks after T0 (T2)) in a randomised experiment in 2011 and 2012, with wines produced from all treatment replicates. We hypothesised that afull crop with substantially delayed harvest date might have a greater impact on wine aroma than reducing crop level. Wine aroma volatile analysis was carried out by GC-MS, with quantification by calibration withanalytical standards prepared in model wine. Delayed harvest overcame the effects of crop reduction for almost all volatiles. Pinot gris and Riesling displayed increases in varietal aromas in the T1 and T2 wines, e.g. monoterpenes and norisoprenoids, and in esters, aldehydes and alcohols. Reduced concentrations of volatile acids and green odour compounds (e.g. 1-hexanol) with delayed harvest were also evident. Increases in ethanol were related to increased berry sugars, but higher alcohols did not necessarily increase with harvest date. Crop level had little impact on the sensory properties of these cultivars in both seasons. However, delayed harvest resulted in substantial sensorial changes. Due to these chemical and sensorial effects, delayed harvest is recommended, rather than crop-level reduction, to enhance wine quality in these cultivars. Extended harvest, e.g. T2 treatments, was associated with the production of benzaldehyde, diethyl acetal, and higher concentrations of higher alcohols, e.g. isoamyl alcohol and nonanol, which could be linked to pre-harvest desiccation.

Relationship between post veraison temperature and the dynamics of anthocyanin development and berry quality in red wine grape (Vitis vinifera) cultivars Shiraz and Cabernet Sauvignon

The present investigation was carried out to understand the temperature induced dynamics of berry anthocyanin development and berry quality in wine grape (Vitis vinifera L.) cultivars Shiraz and Cabernet Sauvignon. Temperature variations during fruit maturation period were achieved by altering the pruning dates. Vines were pruned at weekly intervals starting from third or fourth week of October to the end of November. The changes in berry quality parameters such as total soluble solids (TSS), titratable acidity, total anthocyanins, total phenols and total flavonoids were recorded at weekly intervals starting from veraison to harvest. All the quality parameters were significantly higher in early pruned vines of both the cultivars indicating that the best time for pruning to get good quality wine grapes is during the third or fourth week of October. The major quality parameter affected by the temperature during the berry maturation stage was total anthocyanin content. Maximum and minimum temperature (weekly average) during different week from veraison to harvest were recorded. Early pruned vines exposed to a mean day/night temperatures of 30.7°C/14.9°C and 29.6°C/14.1°C in cv. Shiraz and late pruned vines exposed to a mean day/night temperatures of 32.0°C/16.2°C and 32.1°C/16.0°C in cv. Cabernet Sauvignon during 2010 and 2011 respectively. The pattern of anthocyanin development during the berry maturation period (veraison to harvest) indicated that the maximum anthocyanin accumulation was in the second and third week of March; the concentration decreased thereafter irrespective of dates of pruning in both the cultivars during the two years of the study. Correlation coefficients between the skin anthocyanin content and mean maximum and minimum temperatures showed a negative relationship in both the cultivars indicating that the increase in both maximum and minimum temperatures caused a reduction in anthocyanin content at harvest in late pruned vines.