Berry Basis Research Articles

Development of Tannins and Methoxypyrazines in Grape Skins, Seeds, and Stems of Two Pinot Noir Clones during Ripening.

Two Pinot noir clones (AM10/5 and UCD5) were analyzed for tannin and methoxypyrazines (MPs) in different grape tissues during berry development using liquid chromatography and two-dimensional gas chromatography-mass spectrometry. On a per berry basis, skin tannins reached the maximum level about 2-3 weeks after véraison, seed tannins at around véraison, and stem tannins 4 weeks before véraison. Clone AM10/5 showed significantly higher levels of seed and stem tannins on a per berry basis at harvest. Tannin concentration and composition varied among the different tissues. On a per berry basis, stem tannin levels were comparable to skin tannins but were 3 to 4 times lower than seed tannins, while stem tannins had an intermediate galloylation (5-7%) between seed tannins (12-18%) and skin tannins (2%) and lower prodelphinidin (4-7%) than skin tannins (31-36%). The mean degree of polymerization of stem tannins was similar to seed tannins but lower than skin tannins. MPs, including 3-isopropyl-2-methoxypyrazine (IPMP), 3-s-isobutyl-2-methoxypyrazine (SBMP), and 3-isobutyl-2-methoxypyrazine (IBMP), showed significantly higher concentrations than their sensory thresholds in grape stems but not in skins. The MPs development in stems showed an increasing trend toward véraison and then a decreasing trend toward harvest. Compared to AM 10/5, UCD5 stems showed a higher level of MPs, especially significantly higher concentrations of IPMP and IBMP at harvest. The extraction of MPs from grape stems could contribute negative green and vegetative characters to Pinot noir wines.

Proximal Sensing of Soil Electrical Conductivity Provides a Link to Soil-Plant Water Relationships and Supports the Identification of Plant Water Status Zones in Vineyards.

The majority of the wine grapes are grown in Mediterranean climates, where water is the determining factor for grapevine physiology and berry chemistry. At the vineyard scale, plant water status is variable due to the variability in many environmental factors. In this study, we investigated the ecophysiological variability of an irrigated Cabernet Sauvignon (Vitis vinifera L.) vineyard. We used equidistant grid sampling to assess the spatial variations of the plants and soil, including plant water status by stem water potential (Ψstem), leaf gas exchange, and on-site soil analysis. We also measured soil electrical conductivity (EC) by proximal sensing at two depths [0.75 – 1.5 m (sub soil); 0 – 0.75 m (top soil)]. Ψstem integrals were calculated to represent the season-long plant water status. On the base of realized Ψstem integrals, the vineyard was delineated into two functional homogeneous zones (fHZs) with one severely water stressed zone and one moderately water stressed zone. Sub soil EC was directly related to Ψstem (r2 = 0.56) and gs (r2 = 0.39) when the soil was proximally sensed at harvest in 2018. Although the same trend was evident in 2019 we could not deduce a direct relationship. The fruits from the two fHZs were harvested differentially. Comparing the two fHZs, there was no significant difference in juice total soluble solids or pH. The severely water stressed zone showed significantly higher malvidin and total anthocyanins on a dry skin weight basis, but lower peonidin, malvidin on a per berry basis in 2018. In 2019, there were more quercetin and total flavonols per berry in the severely water stressed zone. Overall, this study provided fundamental knowledge of the viability of managing spatial variability by delineating vineyard into distinct zones based on plant water status, and the potentiality of proximally sensed soil EC in the spatial assessment of plant water status and the supporting of vineyard management.

Grape Berry Flavonoid Responses to High Bunch Temperatures Post Véraison: Effect of Intensity and Duration of Exposure.

Climate models predict an increase in the frequency and duration of heatwaves with an increase in intensity already strongly evident worldwide. The aim of this work was to evaluate the effect of two heatwave-related parameters (intensity and duration) during berry ripening and identify a threshold for berry survival and flavonoid accumulation. A Doehlert experimental design was used to test three temperature intensities (maxima of 35, 46, and 54 °C) and five durations (3 to 39 h), with treatments applied at the bunch level shortly after véraison. Berry skin and seeds were analysed by liquid chromatography-triple quadrupole-mass spectrometry (LC-QqQ-MS) for flavonoids (flavonols, anthocyanins, free flavan-3-ols, and tannins). Berries exposed to 46 °C showed little difference compared to 35 °C. However, berries reaching temperatures around 54 °C were completely desiccated, and all flavonoids were significantly decreased except for skin flavonols on a per berry basis and seed tannins in most cases. Some compounds, such as dihydroxylated flavonoids and galloylated flavan-3-ols (free and polymerised), were in higher proportion in damaged berries suggesting they were less degraded or more synthesised upon heating. Overall, irreversible berry damages and substantial compositional changes were observed and the berry survival threshold was estimated at around 50–53 °C for mid-ripe Shiraz berries, regardless of the duration of exposure.

Changes in pathogenesis-related proteins and phenolics in Vitis vinifera L. cv. ‘Sauvignon Blanc’ grape skin and pulp during ripening

Grape proteins, particularly pathogenesis-related (PR) proteins, are responsible for white wine haze formation which is of great concern to winemakers. Phenolic substances in grapes have also been reported with involvement in protein haze formation by interaction with proteins. The protein and phenolic substances in grapes are important in determining their concentrations in juice and resultant wine, and thus consequent wine protein stability. This study investigated the changes in these haze formation related components in ‘Sauvignon Blanc’ grape skin and pulp during ripening. The phenolic content on per berry basis generally increased in grape skin and pulp, but the phenolic concentration on per gram of berry basis showed a decreasing trend in grape skin, suggesting the accumulation effect of phenolics in skin is less than the dilution effect caused by berry growth. Tannin was only detected in grape skin but not in the pulp and the changes in tannin were similar to total phenolics. PR proteins were synthesized and accumulated along with the increase of total soluble solids (TSS) in both skin and pulp from véraison until harvest during ripening. The increase of PR proteins in grapes during ripening was also reflected in corresponding juice. The results suggested most of PR proteins in juice is likely extracted from grape pulp, and the riper the grapes the more PR proteins may be extracted into juice. The higher level of phenolics in riper grapes could increase the extraction of phenolics into juice and thus decrease the final concentration of PR proteins.

Changes in Tannin Composition of Syrah Grape Skins and Seeds during Fruit Ripening under Contrasting Water Conditions.

Tannin accumulation and composition were determined in skins and seeds isolated from Vitis vinifera cv. Syrah grapes submitted to contrasting water regimes under semiarid climatic conditions. Three irrigation treatments were conducted, starting at berry set through harvest of two growing seasons, 2011 and 2012: irrigation at 100% of crop evapotranspiration ETc (FI), irrigation at 50% of ETc (DI) and non-irrigated (NI). Seed total tannins did not vary with maturity but those of skins underwent a progressive decline (especially in 2011), expressed both on a fresh weight and on a per berry basis. Skin total tannin concentration and content per berry were increased under NI and DI conditions, mainly in 2012. In contrast, seed total tannins (in 2012) and flavan-3-ol monomers and tannin oligomers (both years) were higher in the fully irrigated vines (FI). Skin polymer size increased during ripening, NI and DI skins showing higher mean degree of polymerization (mDP) compared to FI at harvest. NI was also associated with a lower percentage of galloylation (%G) in skin oligomeric fraction (in 2012) and a lower percentage of prodelphinidins in the skin polymeric fraction (both years) at harvest. The mDP and %G of seed extracts did not vary during ripening and were higher in NI but only in 2012. According to the results, management of vine water status was shown to influence tannin amount and composition of Syrah grapes grown under semiarid conditions.

The Effect of Partial Defoliation on Quality Characteristics of Vitis vinifera L. cv. Cabernet Sauvignon Grapes 1. Sugars, Acids and pH

The effect was studied of partial defoliation (33% and 66%) on the sugar and acid accumulation and pH in grapes of Vitis vinifera L. cv. Cabernet Sauvignon. Although the total soluble sugar (TSS) in grapes of partially defoliated vines was significantly higher than that of non-defoliated vines in some cases, no significant differences were generally found. No significant differences in total titratable acidity (TT A) were found between treatments. The timing of defoliation had no effect on TSS in grapes, whereas TT A tended to be higher the earlier partial defoliation was commenced. In general, 33 % and 66% defoliated vines respectively produced approximately 33 % and 200% more TSS and TT A in the fruit per cm2 leaf area than non-defoliated vines. No significant differences between defoliation treatments were found on a per gram dry berry mass or per berry basis for glucose and fructose or tartaric and malic acid. However, 66% defoliated vines had significantly less soluble solids in berries per shoot, which was probably caused by a lower total berry mass per shoot. Although no significant differences in sugar composition could be found between defoliation treatments, tartaric acid levels tended to be higher and malic acid levels lower as a result of partial defoliation. Partial defoliation had no effect on the accumulation patterns of sugars and acids. Glucose dominated in berries at veraison, with fructose dominating at ripeness. The highest total tartaric and malic acid concentrations occurred at pea size. Malic acid content decreased rapidly from veraison, whereas the decrease in tartaric acid was not pronounced. Must pH was not affected by partial defoliation. The results seem to suggest that the general metabolism of vines was favourably changed by partial defoliation, mainly in terms of a more favourable source: sink ratio, more efficient photosynthesis, and an improved canopy microclimate.

Methoxypyrazine Accumulation and O-Methyltransferase Gene Expression in Sauvignon blanc Grapes: The Role of Leaf Removal, Light Exposure, and Berry Development.

Methoxypyrazines are present in the grapes of certain Vitis vinifera varieties including Sauvignon blanc and contribute herbaceous/green aromas to wine. Environmental factors such as light exposure and temperature can influence methoxypyrazine levels, and viticultural interventions such as canopy manipulation have the ability to reduce methoxypyrazine accumulation in grapes. We assessed methoxypyrazine levels and showed that leaf removal significantly reduces accumulation in Sauvignon blanc grapes. The main effect of reducing methoxypyrazines was preveraison, as postveraison treatments had no effect on concentrations at harvest. Methoxypyrazine concentrations in controls peaked preveraison and decreased through harvest. Dilution due to an increase in berry weight was found to be the major driver of decreasing concentrations, as methoxypyrazine levels on a per berry basis were found to increase through development in two of three seasons. In the one year of our study that showed contrasting results, analyses of weather data indicate that warmer than average temperatures appear to be the principal factor affecting the berries' ability to accumulate and retain methoxypyrazines. We also explored the expression of potential biosynthetic O-methyltransferase genes VvOMT1, VvOMT2, and VvOMT3; no significant differences were observed with respect to effect of leaf removal and light exposure.

Physical and Physiological Heterogeneity within the Grape Bunch: Impact on Mechanical Properties during Maturation

Mechanical properties are emerging as complementary criteria to evaluate grape berry quality for winemaking. As texture is evaluated on a berry per berry basis, it is important to assess the impact of the within grape heterogeneity on mechanical properties. Evolution of textural maturity of Cabernet franc was assayed throughout ripening using double compression 20% tests. Berries were sampled from whole grape bunches rather than randomly picked in the vineyard. Results showed coherent and significant evolution of double compression parameters: F1, Grad0, Grad1, W1, and gumminess significantly decreased whereas cohesiveness significantly increased during maturation. Variations in mechanical parameters were related with major physiological and physical traits. Mechanical parameters differed significantly according to berry position. Among these parameters, Grad1 was highly correlated with berry density and Brix (r = −0.91 for both), and W1 was highly correlated with water content (r = 0.87). Within-bunch heterogeneity was illustrated by different distributions of physical, physiological, and mechanical parameters. A negative gradient was shown from the top to the bottom of bunches for dry weight, density, Brix, cohesiveness, and gumminess. Berries at the distal part of the bunch were more advanced in maturity and were softer than berries at the top. Results are discussed with regard to the sampling strategy in the assessment of grape berry quality based on mechanical properties.

Behavior of 3-Isobutyl-2-hydroxypyrazine (IBHP), a Key Intermediate in 3-Isobutyl-2-methoxypyrazine (IBMP) Metabolism, in Ripening Wine Grapes

3-Isobutyl-2-hydroxypyrazine (IBHP) is thought to be a key intermediate in both the biosynthesis and degradation of the herbaceous smelling 3-isobutyl-2-methoxypyrazine (IBMP), but its behavior during the growing season is not well understood. First, an improved method for IBHP quantification was developed. A deuterated IBHP standard was added to samples prior to isolation by mixed-mode cation exchange solid phase extraction. Extracts were silylated prior to quantification by GC-MS. A limit of detection of ca. 20 ng/L could be achieved for a 100 mL juice sample. This method was used to quantify IBHP during the 2010 growing season in berries of two clones of Cabernet franc in the Finger Lakes region of New York and of Merlot grown in the California Central Valley. For all three sources, IBHP was detectable at the earliest sampling point, and its concentration per berry increased to a maximum around veraison, 208-477 pg/berry. On a per berry basis, IBHP peaked and began to decline 1-2 weeks after IBMP, indicating that previous studies that sampled preveraison fruit have missed the true maximum value of IBHP. The highest per berry concentration of IBHP observed was in the California Merlot. However, after veraison, IBHP declined more rapidly in the California Merlot than in the New York Cabernet franc, such that the Merlot had the lowest IBHP concentration at harvest. Thus, IBHP at harvest cannot be used as a proxy for IBMP at veraison as was previously suggested.

Anthocyanins, flavonols and hydroxycinnamates: an attempt to use them to discriminate Vitis vinifera L. cv ‘Barbera’ clones

Anthocyanin and flavonol profiles of Vitis vinifera berry skin have been diffusely studied in past years to identify the effects exerted by climate, environment and cultural practices on their biosynthesis. They have also been used for chemotaxonomic purposes with the aim of classifying grape varieties. Hydroxycinnamates and phenolic acids are the most important group of non-flavonoid phenols in grapes and wines. In the present work six ‘Barbera’ clones were grown in the same site to evaluate the influence of two seasons on the accumulation of flavonoids and hydroxycinnamates at maturity. Berry skins were extracted in an ethanolic buffer and flavonoids and hydroxycinnamates were separated by HPLC. Two principal component analysis (PCA) models were built to identify phenolic parameters exploitable to classify clones. The PCA scores were taken further to perform discriminant analysis to evaluate the degree of classification possible. A significant seasonal variability was observed for most phenolic features, whereas some parameters such as total anthocyanin expressed on a per berry basis, the sum of tri-hydroxylated anthocyanin percentages, the percentages of kaempferol glucuronide and the total hydroxycinnamate content were stable over the seasons. The percentage of individual anthocyanin alone, not associated with maturity data, was not effective in classifying clones; in association with maturity data it allowed to discriminate clones, similarly to what it was previously assessed for classifying varieties. The results indicated that LDA models developed on the PCA scores including maturity data correctly classified 75% of clones.

Inception, Progression, and Compositional Consequences of a Berry Shrivel Disorder

Berry shrivel (BS) is a ripening disorder of grapes; symptoms include shriveling of berries and low soluble solids before and at harvest. BS is distinct from bunchstem necrosis (BSN) in that BS rachis tissue remains green and does not undergo necrosis. BS berries were somewhat firmer than normally developing berries until just after veraison, but then softened faster than normally developing fruit. Soluble solids increased in all berries after veraison, but sugar accumulation on a per berry basis essentially stopped in BS berries several weeks before visible symptoms. Compared to normally developing berries, BS berries lost weight through water loss and mesocarp cell viability began to decline at about the same time as shriveling became apparent. BS berries had reduced anthocyanins in the skin, but had more skin tannin at harvest. Juice pH of BS berries was lower than that of normally developing berries, although amounts of tartrate and malate per berry were similar at harvest. Nonshriveled berries on vines that had BS symptomatic clusters had composition intermediate between BS and normally developing berries for sugar per berry, soluble solids, pH, anthocyanins, and skin tannins, indicating that BS disorder affects the entire vine rather than individual clusters or berries. BS vines at one site had consistently less negative water potentials than normally developing vines, but that was not the case at a second site. BS and normally developing vines were tested for common viruses as well as <i>Xylella fastidiosa</i> bacteria, but no differences were found.

Effects of Mechanical Thinning on Yield and Fruit Composition of Tempranillo and Grenache Grapes Trained to a Vertical Shoot-Positioned Canopy

The impact of mechanical thinning using a machine harvester on yield components and fruit composition of Tempranillo and Grenache (<i>Vitis vinifera</i> L.) vines was investigated. Experiments were conducted in two Spanish vineyards, both trained to a vertical shoot-positioned canopy over two consecutive seasons. The height of the harvester and the position of the bow rods were adjusted so that fruit was removed by the vibration of the canopy caused by the bow rods striking the vine trunks. The Tempranillo was thinned ~10 days before veraison and the Grenache was thinned when 10 to 15% of berries were colored. Mechanical thinning significantly reduced berry number per cluster, cluster weight, and cluster compactness; a similar amount of fruit (~65%) was removed from both varieties. <i>Botrytis</i> incidence was reduced by mechanical thinning of the Grenache in 2007 and was otherwise not affected by thinning treatments. Soluble solid concentration was higher under mechanical thinning treatments over the two seasons in Tempranillo and in 2006 in Grenache, suggesting that damage to the canopy was minimal. Phenolic concentration (both berry and berry fresh weight basis) was higher in fruit from the mechanically thinned vines compared with the control (unthinned) in Tempranillo in 2007 and only on a per berry basis in Grenache in 2006. Mechanical thinning conducted with a machine harvester has the potential to be a cost-effective technique to regulate yield in vineyards with vertical shoot-positioned canopies.

Grape Berry cv. Shiraz Epicuticular Wax and Transpiration during Ripening and Preharvest Weight Loss

Preharvest weight loss of <i>Vitis vinifera</i> L. cv. Shiraz berries may be the result of cuticle disruption leading to high transpiration rates relative to earlier stages of ripening. Scanning electron microscopy showed very few but functional stomata on young berries and wax-filled stomata on older berries and, aside from slight cracks along the stomatal protuberance, did not reveal any fissures in the surface of berries that may lead to increased transpiration rates. Preveraison berry epicuticular wax platelets were defined and intricate, while postveraison and shriveled berry surfaces had large areas of amorphous waxes. Postveraison, the area of amorphous wax relative to intricate wax was not correlated with berry age or degree of shrivel. Extraction of surface waxes revealed that total wax on a surface-area basis decreased during veraison then remained stable as the berries ripened and entered the weight-loss phase. Berry transpiration, estimated from loss of fresh weight of detached berries over time, during this final shriveled phase was 16% of the preveraison rate on a per berry basis. Nevertheless, berry transpiration could account for an average 15 mg loss in fresh weight per berry per day. We conclude that weight loss during late ripening of Shiraz berries was not the result of cuticle disruption or high transpiration rates alone. It is hypothesized that decreased vascular flow of water into the berry combined with continued transpiration leads to the weight loss.

Growth and Developmental Responses of Seeded and Seedless Grape Berries to Shoot Girdling

The relationship of assimilate supply to grape (Vitis vinifera L.) berry growth and development was studied with a seeded (`Kyoho') and a seedless (`Seedless Wuhehong') cultivar. A single shoot girdling between the second and third nodes below the basal cluster at the end of Stage I of berry growth shortened Stage II (the lag phase) of `Kyoho' grape berries by 10 days, and eliminated Stage II in `Seedless Wuhehong' grape berries. Double shoot girdling between the second and third nodes below the basal cluster and above the upper cluster, respectively, at the same time at the end of Stage I, advanced Stage II by 3 days in both cultivars. Normal accumulation of dry weight in the `Kyoho' grape berry is in a double sigmoidal pattern, but it became a single sigmoidal pattern in response to a single basal girdling. The highest percent moisture in berries was at 20 days after full bloom. Rapid changes in berry pectin substances lagged behind those of soluble solids and titratable acidity, and behind the onset of berry softening at veraison in `Kyoho', but not in `Seedless Wuhehong', for which the three processes were concurrent. It is suggested that the slow growth of the berries during Stage II is a result of a decrease in the rate of water accumulation on a whole berry basis and a decrease in accumulation of dry matter in the skin and flesh (pericarp) due to assimilate competition within grapevines and within berries. The relationships between levels of endogenous hormones (IAA, GA3, zeatin, zeatin riboside, and ABA) and berry growth were also studied with `Kyoho' grapes. The results showed that the slow growth of grape berries during Stage II was associated with assimilate competition between the skin-flesh (pericarp) and seeds, and with peak shifts of concentrations of IAA, GA3, zeatin and zeatin riboside. Changes in ABA levels were closely associated with ripening and senescence during late Stage III.

Tannin in Skins and Seeds of Cabernet Sauvignon, Syrah, and Pinot noir Berries during Ripening

A protein precipitation assay was used to separately monitor tannin concentrations in skins and seeds of three red Vitis vinifera winegrape varieties: Cabernet Sauvignon, Syrah and Pinot noir. In 1998, seeds of Cabernet Sauvignon berries showed highest values before veraison, after which the seed tannin per berry declined and remained fairly constant during the four weeks before harvest. In 1999, the decline in seed tannin was slower but reached nearly the same value by harvest as in 1998. In 1998 and 1999, the skin tannin per berry changed little in Cabernet Sauvignon, and in both years the amount of tannin in skins and in seeds was nearly equal on a per berry basis by harvest. Syrah exhibited a pattern similar to Cabernet Sauvignon except that there was nearly three times as much seed tannin per berry as skin tannin. Results with seeds of Pinot noir in 1998 were problematic because of variation observed among replicate samples. Nevertheless, as with Cabernet Sauvignon, the amounts of tannin in seeds and skins of Pinot noir were practically the same at harvest. In 1999, tannin concentrations were measured in commercial wines made from vineyards that were monitored for tannin concentrations in the fruit. There was no relationship between the total tannin per berry and the amount of tannin in the resulting wine among the three varieties studied. Seed tannin per seed varied only 40% among the three varieties, but seed tannin per berry was different by 235%. Thus, the major factor contributing to the difference in total seed tannin per berry among the three varieties was the number of seeds per berry, rather than the amount of tannin per seed. Acknowledgments: This research was supported by grants from the American Vineyard Foundation and the Viticulture Consortium. Cooperation provided by Robert Mondavi Winery, Acacia Winery, Saintsbury, and The R. H. Phillips Vineyard is gratefully acknowledged. This research was conducted in the Department of Viticulture & Enology, University of California, Davis.

Amounts of glycosides in grapevine organs during berry development

Whole berries, leaf blades and petioles from Muscat Gordo Blanco (syn. Muscat of Alexandria), Sultana and Flame Seedless vines were sampled at intervals from three weeks after flowering to fruit ripeness. The glycosidically‐bound constituents present in the samples were quantified through a determination of the glycosyl glucose. At the stage of berry ripeness, the concentration of glycosides per gram fresh weight in the leaf blades was 10–30 times higher than in the fruit. During berry development glycoside concentrations increased in leaf blades and petioles but decreased in fruit. However, when expressed on a per berry basis, the levels of glycosides in the fruit increased as ripening progressed; the levels in ripe fruit were high in Muscat Gordo Blanco and low in Sultana. Further experimentation will be needed to establish whether the glycosides are synthesised in the leaves and transported to the berries or synthesised independently in both organs.

Sugar Accumulation in Grape Berries (Cloning of Two Putative Vacuolar Invertase cDNAs and Their Expression in Grapevine Tissues)

During grape berry (Vitis vinifera L.) ripening, sucrose transported from the leaves is accumulated in the berry vacuoles as glucose and fructose. To study the involvement of invertase in grape berry ripening, we have cloned two cDNAs (GIN1 and GIN2) from berries. The cDNAs encode translation products that are 62% identical to each other and both appear to be vacuolar forms of invertase. Both genes are expressed in a variety of tissues, including berries, leaves, roots, seeds, and flowers, but the two genes have distinct patterns of expression. In grape berries, hexose accumulation began 8 weeks postflowering and continued until the fruit was ripe at 16 weeks. Invertase activity increased from flowering, was maximal 8 weeks postflowering, and remained constant on a per berry basis throughout ripening. Expression of GIN1 and GIN2 in berries, which was high early in berry development, declined greatly at the commencement of hexose accumulation. The results suggest that although vacuolar invertases are involved in hexose accumulation in grape berries, the expression of the genes and the synthesis of the enzymes precedes the onset of hexose accumulation by some weeks, so other mechanisms must be involved in regulating this process.

Glutathione Increases in Grape Berries at the Onset of Ripening

Glutathione (GSH) was measured in grape (<i>Vitis vinifera</i> L.) berries during ripening. The Thompson Seedless variety was studied during two consecutive seasons from just before the onset of sugar accumulation until the berries attained commercial maturity. The GSH content increased along with soluble solids in both years. From Julian day 173 to day 197 in 1990 (21 June to 15 July), the GSH increased from 28.8 nmoles/gFW to 319 nmoles/ gFW. The average fresh weight of the berries increased from 0.79 g/berry to 1.95 g/berry during this period, so the GSH increase on a per berry basis was 22.4 nmoles/berry to 639 nmoles/berry. An increase in GSH was also observed in berries of Perlette, another seedless table grape variety. Beauty Seedless, a red variety, showed a gain in GSH accompanying the increase in soluble solids which began with the onset of pigmentation. Pigmented berries on a turning cluster showed higher GSH than green berries on the same cluster. Likewise, a seeded wine variety (Cabernet Sauvignon) had more GSH in berries with higher soluble solids, and more in pigmented berries on a turning cluster than in green berries from the same cluster. The results show that there is an increase in glutathione at the onset of ripening in grape berries. The increase was observed in red, green, seeded and seedless varieties, so GSH accumulation may be a general feature of grape berry ripening. The source of the GSH and a possible explanation for the timing of this phenomenon is discussed.

The Effects of Sun Exposure on the Compositional Development of Cabernet Sauvignon Berries

The effects of sunlight on Cabernet Sauvignon fruit clusters were studied in a Napa Valley, California, commercial vineyard. Clusters were chosen from sun-exposed locations and from locations shaded by the grapevine canopy. Selected exposed and shaded clusters on one vine were monitored for air temperature and light flux. Berry samples were collected weekly from anthesis and were analyzed for tartrate, malate, glucose, and fructose by HPLC and for potassium by emission spectroscopy. Berry juice was also analyzed for pH, titratable acidity, and soluble solids content. Data were presented both on a concentration basis (mg/g fresh weight) and on a per berry basis (mg/berry). Sun berries were significantly higher in concentrations of tartrate, malate, glucose, and fructose as shown by analysis of variance. No significant differences were found when expressed on a per berry basis, however. Potassium expressed either as concentration or per berry, pH, titratable acidity, and soluble solids showed no significant differences between sun and shade berries. Berries from the canopy shade were significantly heavier than berries exposed to the sun. The observed differences in concentration were attributed to a higher water content in the berries from shaded clusters.

ブドウ果粒の発育, 特に成熟に伴う光合成および呼吸の変化

The relationship between berry growth and changes in respiratory rate and photosynthetic CO2-assimilation rate during the development of grape berries and seeds was studied in relation to their ripening.(1) The respiratory rate of berries in terms of dry weight basis became high at an early part of Stage I and thereafter decreased rapidly. When expressed on a single berry basis, the respiratory re ate increased rapidly during Stage I through Stage III, but there was a sudden drop at veraison.(2) The rate of gross-photosynthesis expressed on a dry weight basis showed its peak during the early part of Stage I and decreased rapidly thereafter. When expressed on a single berry basis, the rate of gross-photosynthesis showed two peaks, i.e., later part of Stage I and early part of Stage III.(3) The respiratory rate per seed showed its peak at the onset of Stage II. While, the rate of respiration on a dry weight basis was highest at Stage I and rapidly decreased thereafter.These results led to an assumption that the photosynthetic activity of berries may affect their development markedly at early stages of growth, and the second peak of respiration and gross-photosynthesis may play an important physiological role in controlling the onset of their ripening.