Onset Of Veraison Research Articles

Phenolic compounds in juice of “Isabel” grape treated with abscisic acid for color improvement

Isabel grape is the main cultivar used to produce juice in Brazil, which has rusticity and high productivity, but it is deficient in anthocyanins, a pigment responsible for the color. Thus, an alternative is the application of abscisic acid (S -ABA), which is responsible to promote the synthesis of anthocyanins. The aim of this work was to evaluate the phenolic compounds composition in “Isabel” grape juice treated with S -ABA, by HPLC-DAD–ESI-MS/MS technique. The results showed the increasing in total anthocyanin concentration in juices, with S -ABA treatments, as well as the proportion of B-ring tri-substituted anthocyanidins. Regarding total flavonols, differences were only significant in juices obtained in 2012 season. S -ABA treatments did not significantly affect the hydroxycinnamic acid derivatives, flavan-3-ols, resveratrol and antioxidant capacity of juices. Juice from “Isabel” grapes treated with S -ABA provides an enhancement of total anthocyanin concentration, mainly when grapes are treated before or at the onset of veraison .

Winemaking practice affects the extraction of smoke‐borne phenols from grapes into wines

Background and Aims: Exposure to smoke and uptake of taint imparting phenols in grapes and wines is a significant problem in bushfire-prone regions of Australia and other countries. The effects of smoke exposure on taint occurrence in wines, however, can be variable. This study assessed the influence of cultivar on uptake and accumulation of smoke-borne phenols in grapes and of subsequent processing and winemaking methods on extraction of phenols into wines. Methods and Results: Smoke-exposure experiments were conducted in commercial vineyards of Chardonnay, Merlot and Sauvignon Blanc 14 days after the onset of veraison. At maturity, grapes were harvested for winemaking, which included malolactic fermentation (MLF) for Merlot. Volatile and glycoconjugated phenols were determined in grapes and the resultant wines. All cultivars had a similar concentration of smoke-derived total phenols in their grapes. The apparent extraction of total phenols from grapes into wines, however, differed markedly among the three traditional winemaking methods. Red winemaking (Merlot) with skin contact extracted 88% of total grape phenols, whereas white winemaking either by crushing before pressing (Sauvignon Blanc) or by whole-bunch pressing without crushing (Chardonnay), respectively, released 39 and 18% of total phenols. For Merlot wines, MLF did not affect the extraction of total smoke-derived phenols. Conclusions: Under standardised exposure conditions (duration, intensity and phenology), the three cultivars studied accumulated a similar concentration of total phenols in grapes. The grape-processing and winemaking methods, however, can bring about a fourfold difference in the concentration of total phenols of wines. The smoke-derived phenols extracted from grapes into wine and the distribution of these phenols between the volatile and conjugated pools were not affected by MLF. Significance of the Study: The key findings reported here have the potential to improve decision-making by grapegrowers and winemakers on the effect of cultivar and winemaking practice on potential smoke taint in wine.

Elevated root-zone temperature hastens vegetative and reproductive development in Shiraz grapevines

Background and Aims Springtime root-zone warming activates mobilisation of the root carbohydrate reserves, a critical source of carbon for early canopy and reproductive development in grapevines following winter dormancy. Seasonal variability in soil temperature during spring may result in inconsistent vegetative growth and fruitset with consequences for berry growth and ripening. Methods and Results We monitored flowering and berry ripening in Shiraz grapevines (Vitis vinifera L.) grown in large temperature-controlled pots. The vines were exposed to a cool, ambient and warm root-zone temperature from budburst to fruitset. Root starch mobilisation after budburst was linearly correlated to the cumulative heat units received by the soil. A warm root-zone temperature also hastened leaf expansion, net positive carbon assimilation, onset of flowering and fruit set, berry enlargement and the onset of veraison. At harvest, berry pH and nitrogen concentration as well as fresh and dry mass were higher for the vines exposed to a warm root-zone while berry acidity was lower. Conclusions Warm soil temperature in spring stimulated the mobilisation of carbohydrates in the roots and accelerated shoot and reproductive development, resulting in larger berries with lower acidity. Significance of the Study Because root-zone temperature is an environmental driver of berry size and composition, models predicting yield and berry composition can be fine-tuned to incorporate this critical parameter.

Vegetative growth and cluster development in Shiraz grapevines subjected to partial root-zone cooling.

Heterogeneity in root-zone temperature both vertically and horizontally may contribute to the uneven vegetative and reproductive growth often observed across vineyards. An experiment was designed to assess whether the warmed half of a grapevine root zone could compensate for the cooled half in terms of vegetative growth and reproductive development. We divided the root system of potted Shiraz grapevines bilaterally and applied either a cool or a warm treatment to each half from budburst to fruit set. Shoot growth and inflorescence development were monitored over the season. Simultaneous cooling and warming of parts of the root system decreased shoot elongation, leaf emergence and leaf expansion below that of plants with a fully warmed root zone, but not to the same extent as those with a fully cooled root zone. Inflorescence rachis length, flower number and berry number after fertilization were smaller only in those vines exposed to fully cooled root zones. After terminating the treatments, berry enlargement and the onset of veraison were slowed in those vines that had been exposed to complete or partial root-zone cooling. Grapevines exposed to partial root-zone cooling were thus delayed in vegetative and reproductive development, but the inhibition was greater in those plants whose entire root system had been cooled.

Thermotolerance Responses in Ripening Berries of Vitis vinifera L. cv Muscat Hamburg

Berry organoleptic properties are highly influenced by ripening environmental conditions. In this study, we used grapevine fruiting cuttings to follow berry ripening under different controlled conditions of temperature and irradiation intensity. Berries ripened at higher temperatures showed reduced anthocyanin accumulation and hastened ripening, leading to a characteristic drop in malic acid and total acidity. The GrapeGen GeneChip® combined with a newly developed GrapeGen 12Xv1 MapMan version were utilized for the functional analysis of berry transcriptomic differences after 2 week treatments from veraison onset. These analyses revealed the establishment of a thermotolerance response in berries under high temperatures marked by the induction of heat shock protein (HSP) chaperones and the repression of transmembrane transporter-encoding transcripts. The thermotolerance response was coincident with up-regulation of ERF subfamily transcription factors and increased ABA levels, suggesting their participation in the maintenance of the acclimation response. Lower expression of amino acid transporter-encoding transcripts at high temperature correlated with balanced amino acid content, suggesting a transcriptional compensation of temperature effects on protein and membrane stability to allow for completion of berry ripening. In contrast, the lower accumulation of anthocyanins and higher malate metabolization measured under high temperature might partly result from imbalance in the expression and function of their specific transmembrane transporters and expression changes in genes involved in their metabolic pathways. These results open up new views to improve our understanding of berry ripening under high temperatures.

Involvement of abscisic acid and polyamines in berry ripening ofVitis vinifera(L.) subjected to water deficit irrigation

Background and Aims: Partial rootzone drying (PRD) is an irrigation system that permits better control of vegetative growth without reducing fruit yield. However, little is known about how grapevine reproductive development is regulated when irrigated under PRD. Therefore, the aim of this work was to investigate the relationship between abscisic acid (ABA) and polyamines (PAs) in leaves and berries during ripening, and how hormonal balance is affected under different irrigation regimes. Methods and Results: The study was carried out using container-grown Superior Seedless grapevines with a split-root system and grown under controlled conditions in a greenhouse. Three irrigation treatments were imposed: control (well watered), and two forms of deficit irrigation – PRD and sustained deficit irrigation (SDI). PRD plants have higher yield and berry size than SDI vines. At the onset of veraison, PRD berries have higher ABA, free PAs and free to bound PA ratio than other treatments. Conclusions: Although the restriction of vegetative growth in PRD might be partly a response to the volume of water applied and therefore similar to a SDI response, our results suggest that specific hormonal factors may explain the effects on reproductive growth and yield. Significance of the Study: The study demonstrates that changes induced in berry ABA during PRD conditions could be counterbalanced by changes in PA metabolism so that berry size and yield are maintained.

Pectin methylesterase and polygalacturonase in the developing grape skin

Ripening of grape (Vitis vinifera L.) berry immediately precedes harvesting and the evolution of the skin tissue is important as it contains the key compounds for wine quality. Grape softening is thought to result from extensive cell wall modifications that occur during ripening. These modifications result from the activity of different cell wall-modifying enzymes. Two of the most significant pectin-degrading enzymes are pectin methylesterase (EC 3.1.1.11) and polygalacturonase (EC 3.2.1.15). In this work, the activities of both enzymes were monitored in skin tissue throughout berry development. Pectin methylesterase activity was present before the onset of veraison and increased during skin maturation. No polygalacturonase activity could be detected. The accumulation of mRNA encoding a pectin methylesterase and two polygalacturonase isoforms was examined using RT-PCR. Transcripts for pectin methylesterase were present in all stages analyzed with a maximal accumulation at the end of color change. Accumulation of VvPG1 transcript was closely correlated with berry softening, and expression of this gene was markedly increased during the color change. VvPG2 mRNA accumulation began before veraison and was low during skin ripening. A phylogenic analysis showed that this gene is classified in a different group than VvPG1. These findings suggest that both genes are associated with different mechanisms during skin development. VvPG1, in particular, is most likely to play a role in skin softening and VvPG2 in triggering the ripening process.

Possible roles of both abscisic acid and indol-acetic acid in controlling grape berry ripening process

<p style="text-align: justify;"><strong>Aims</strong>: The objective was to better understand the mechanisms involved in grape ripening that brings about important changes in the physiology and chemistry of the fruit. So we focused on the involvement of two growth regulators: abscisic acid (ABA) and indol-acetic acid (IAA) in controlling grape berry ripening process.</p><p style="text-align: justify;"><strong>Methods and results</strong>: We described the evolution of the two plant growth regulators during the development of cv. Merlot grapes (Vitis vinifera L.). In order to better understand the role of ABA and IAA in the ripening control, these two growth regulators were applied on the grapes at the onset of veraison. The hormonal profile was established on treated berries and different physiological parameters were assayed to evaluate the effects of both applications. The partitioning of both plant growth regulators in nontreated berries showed that ABA and IAA accumulated at the onset of ripening. Moreover, it appeared that endogenous ABA decreased progressively in the flesh while accumulated in the skin from the beginning of the colour change to maturity. The hormonal treatments modified the hormonal profile and several physiological parameters: sugar, acidity, colour, and Botrytis sensibility.</p><p style="text-align: justify;"><strong>Conclusion</strong>: These findings suggest that both treatments have modified the ripening process. Exogenous ABA has induced advancement in grape ripening, while IAA application has delayed this process. These observations support the view that the grape ripening process may be influenced by the hormonal status.</p><p style="text-align: justify;"><strong>Significance and impact of study</strong>: This study gives new information about the ripening control of the non-climacteric fruits. In grape berries, it provides evidence of a possible co-involvement of ABA and IAA in controlling ripening process.</p>

Impacts of using polyethylene sleeves and wavelength selective mulch in vineyards. II. Effects on growth, leaf gas exchange, yield components and fruit quality of Vitis vinifera cv. Merlot

Response of Merlot vines to wavelength-selective polyethylene mulch in the planted row and clear polyethylene enclosures (sleeves) around canes or cordons for 7 wk in the spring was studied in three Okanagan Valley vineyards. The mulch had no detectable effects on vine development, yield components and fruit quality. The sleeves advanced budbreak by 3 to 6 d, depending on the vineyard site, and increased the early growth rate of shoots. Time of budbreak and shoot growth rate were better predicted by cumulative daily mean temperature than by cumulative degree days (base 10°C). On the day sleeves were removed or opened at top, photosynthesis rates were higher in open-top sleeves than under ambient conditions due to higher mesophyll and stomatal conductances. Sleeves advanced the date of 50% bloom in all vineyards by approximately 10 d. Time of bloom, onset of veraison and the rate of fruit maturation were predictable from degree day accumulation. Sleeves advanced fruit maturation by 7 to 26 d, depending on the site, and reduced juice titratable acidity relative to °Brix at the coolest site. Sleeve effects on yield and yield components were inconsistent among sites. Sleeves reduced yield at one site due to lower cluster weights and apparently fewer berries per cluster. At another site, higher berry weights compensated for the apparent reduction in the number of berries per cluster in response to sleeves, and there was no effect on yield. At the third site, berry weights were lower in response to sleeves, likely in compensation for a higher number of berries per cluster. At one site where vines were shoot-thinned to retain primary shoots in the following year, the number of clusters per vine was unaffected by the treatments indicating that the treatments had no effect on bud fruitfulness. Key words: Wine grapes, photosynthesis, stomatal conductance, mesophyll conductance, plasticulture

Use of image analysis for the study of phenolic compounds of the grape berry skin (<em>Vitis vinifera</em> L., cv Cabernet franc)

<p style="text-align: justify;">The localization and quantitative determination of phenolics in grape berry skins, from the onset of veraison, constitute the first step to understand the évolution of these compounds throughout the maturation process. Histological techniques are appropriate to study the evolution of phenolics but manual countings are long and drudgery and do not allow for reliable quantitative results. The image analysis software "Scion Image" proved to be a good tool to improve the quantitative results. This method permitted also to measure the cells area and the area occupied by phenolic compounds inside the vacuoles. Image analysis could be helpful to the understanding of the évolution of phenolics during maturation and possibly contribute to explain their extraction during macération.</p>

Rootstock and salinity effects on rates of berry maturation, ion accumulation and colour development in Shiraz grapes

Shiraz grapevines on either their own roots, or on the rootstocks Ramsey, 1103 Paulsen, 140 Ruggeri or 101-14, were grown at two separate sites within the Murray-Darling viticultural region with similar irrigation regimes but with an irrigation water salinity of either 0.43 dS/m (low salinity site) or 2.3 dS/m (high salinity site). Rootstock effects on grape berry development, ion concentrations, soluble solids and acidity were followed during one season. Wines were also made and compared using spectral analysis and sensory evaluation. Rootstock effects that were common across both sites were (1) a close relationship between K+ and soluble solids accumulation in developing grape berries which commenced at the onset of veraison and was indicative of a link between K+ and sucrose transport in the phloem, and (2), higher wine K+, pH and colour hue for all rootstocks with one exception, namely 101-14 at high salinity where 101-14 responded similarly to own roots. Juice K+, pH and loss of K+ from juice during winemaking were highest for grapes from the high salinity site. Mean berry weight was smaller and the range in berry size across rootstocks was narrower at the saline site. The narrower range in berry sizes may have contributed to fewer rootstock effects on wine spectral characteristics at high salinity. There was no effect of rootstock on CO2 assimilation rate or stomatal conductance at either site, although intrinsic leaf-based water-use efficiency measured as A/g was 50% higher at the saline site. All treatments exhibited berry shrivel at maturity, but the extent was smaller at high salinity. Slower development of berry colour during veraison was observed on some rootstocks, for example 101-14, and while unrelated to canopy size per se, a higher leaf-to-fruit ratio for 101-14 may have been a factor. Slower berry colour development during veraison had no bearing on the colour density of wine made from the harvested grapes.

Fruit Ripening inVitis viniferaL.: Responses to Seasonal Water Deficits

The response of fruit ripening to vine water status was investigated in a hillside Cabernet franc vineyard in the North Coast region of California. Treatments were imposed by drip irrigation at 2 x the standard practice rate (continual) to maintain high water status, by withholding water before (early deficit) or after (late deficit) veraison, or by withholding water throughout most of the season (full deficit). Midday leaf water potential of continual vines decreased from approximately-0.3 MPa before bloom to -1.13 MPa at veraison and to -1.32 MPa at harvest. Leaf water potentials of early deficit and late deficit vines were approximately 0.3 MPa more negative than continual vines at veraison and harvest, respectively. After veraison, water status of early deficit vines recovered to the level of continual vines. These moderate differences in water status at different phenological stages altered fruit composition at harvest. The concentrations of phenolics in juice and dermal extracts and of anthocyanins in dermal extracts were increased by all treatments which withheld water. Malate concentrations were significantly lower in treatments which imposed low vine water status before veraison. Low vine water status after veraison increased proline concentration significantly. There were no treatment effects on the onset of veraison, the duration of ripening, juice pH, or potassium levels, and little difference in °Brix or titratable acidity. Thus, irrigation to obtain seasonal water deficits may offer a cultural control of winegrape composition without significant effects on the time required to reach maturity.