Weight loss from ripening berries of Shiraz grapevines (Vitis vinifera L. cv. Shiraz)

Environmental and phenological correlatives associated with the onset of weight loss during ripening in Vitis vinifera cv. Shiraz berries were examined. An irrigation experiment concerned with transient water deficit effects on berry growth over four consecutive seasons provided source data. Timing of maximum berry weight was more closely correlated with the number of days after flowering than with temperature summation. Prior to maximum berry weight, Brix was more closely correlated with days after flowering than with temperature summation, while the number of days from flowering to 10 and 15Brix was remarkably uniform despite contrasting seasons. Driving variables for weight loss during advanced ripening remain a matter of conjecture, but loss of berry water under highly evaporative conditions of late summer is a likely contributor.     

Accumulation of potassium and calcium by ripening berries on field vines of Vitis vinifera (L) cv. Shiraz

Ripening berries of Vitis vinifera (L) cv. Shiraz can show pre-harvest weight loss at sub-optimal sugar content (shrinkage). This later-age decline in berry weight implies that water loss from mature berries has begun to exceed water inflow from the parent grapevine. Such decrease in net inflow has been attributed to a cessation of xylem flow subsequent to veraison, followed by a cessation of phloem flow into berries during later stages of ripening. We address this issue in this present paper, and show a continuing increase in berry content of both potassium and calcium throughout ripening. We measured changes in berry fresh weight and berry content of potassium (phloem mobile) and calcium (phloem immobile) in fruit on field vines sampled from set to harvest. Berry fresh weight reached a plateau between 81 and 95 days after flowering, then declined to 75% of maximum fresh weight by 115 days. Dry weight maximum occurred 14 days after the onset of the fresh weight plateau. Potassium accumulation was slow pre-veraison, increased 3.5-fold post-veraison, and continued during berry shrinkage. Calcium content per berry also showed a linear increase throughout fruit enlargement and ripening phases. Assuming both potassium and calcium were entering berries via vascular conduits, our results imply a continuing connection between parent grapevine and ripening berries. Moreover, an abrupt change (increase) in the ratio of potassium/calcium content per berry subsequent to veraison implies that phloem inflow has increased relative to xylem inflow during post-veraison enlargement.     

Vascular function in berries of Vitis vinifera (L) cv. Shiraz

Anatomical studies on the movement of a xylem tracer dye were combined with functional studies on changes in grape berry volume during final stages of berry ripening to gauge xylem effectiveness. Movement of a xylem tracer dye into pre-veraison fruit was compared with movement into post-veraison fruit by feeding a solution of acid fuchsin to excised shoots with bunches still attached, and then sectioning fruit for photo-microscopy. Those comparisons confirmed published studies showing an apparent blockage to dye movement along major vessels within the brush tissue of post-veraison fruit. However, our functional approach yielded a different impression of vascular activity. A continuation of xylem transport in ripening fruit was inferred from comparisons of berry volume where pedicels were either girdled (phloem interrupted, but xylem intact) or excised (both phloem and xylem interrupted). Volume changes in manipulated berries were compared with immediately adjacent intact control berries within the same bunch. Control fruit lost volume subsequent to 78 days after flowering (DAF) while manipulated fruit lost volume from the first day of treatment at 67 DAF. By harvest time at 95 DAF, both control fruit and girdled fruit had fallen to 91% and excised fruit to 46% of maximum volumes recorded around 78 DAF. Berry volume loss in girdled fruit was further enhanced by deficit irrigation. We conclude that xylem flow into those Shiraz berries must have continued beyond veraison despite dye evidence of a vessel blockage within the brush region of analogous post-veraison fruit.     

Direct measurement of hydraulic properties in developing berries of Vitis vinifera L. cv Shiraz and Chardonnay

Berries of Vitis vinifera L. cv Shiraz can undergo weight loss during later stages of ripening. Existing published views on how weight loss occurs are based on changes in capacity of the vascular system to import water during development (McCarthy and Coombe, Australian Journal of Grape and Wine Research, 5, 17–21, 1999). One important element of these views is the proposed cessation of water flow through the xylem after veraison. We have now measured the water flow into berries of Shiraz and Chardonnay as they develop using the pressure probe and the high pressure flow meter (HPFM). The pressure probe connected to the pedicel of individual berries provided measurements of single berry hydraulic conductance. By systematic excision of tissue segments of the berry and pedicel we determined where in the pathway hydraulic conductance changed during development. The HPFM was used on whole bunches showing that berries (including pedicels) represent parallel high hydraulic resistances and that the hydraulic resistance of the bunch axis was rather small. The hydraulic conductance per berry could be determined from excision experiments. There was close agreement between the pressure probe and HPFM measurements. Both showed a ten‐fold reduction in hydraulic conductance of whole berries from veraison to full ripeness. Shiraz had hydraulic conductances that were 2‐ to 5‐fold higher than those for Chardonnay. Shiraz maintained a higher hydraulic conductance past 90 days after flowering than Chardonnay. The decrease in hydraulic conductance occurred in both the distal and proximal parts of the berry for both varieties. The pressure probe also provided measurements of the xylem pressure that non‐transpiring berries could develop. These pressures were –0.2 to –0.1 MPa until veraison and increased to zero when the juice osmotic potential reached about –3 MPa in Chardonnay and –4 MPa in Shiraz. The results suggest values of the reflection coefficient of the osmotic barrier around the xylem vessels of about 0.1–0.2 at veraison decreasing to 0 at harvest. It is suggested that in addition to changes in xylem anatomy, aquaporins in berry membranes may play a role in regulating hydraulic conductance. Water movement from the berry back to the parent vine via the xylem (backflow) may be an important component of berry weight loss in Shiraz, particularly if the phloem ceases functioning at high osmotic potentials near maximum weight. Backflow could account for a weight loss of 43 mg per day in Shiraz berries for a relatively small gradient of 0.1 MPa.     

Involvement of abscisic acid and polyamines in berry ripening of Vitis 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.     

Occurrence of anthocyanin pigments in berries of the white cultivar Muscat Gordo Blanco (Vitis vinifera L.)

Rose coloration of skin was observed to sometimes develop late during ripening on the normally white grape berries of cv. Muscat Gordo Blanco. The nature of the pigment was investigated by HPLC analysis of skin extracts of single berries. The predominant anthocyanin was identified as cyanidin-3-glucoside with minor amounts of delphinidin- and peonidin-3-glucosides. This composition resembles the skin composition of coloured, small-seeded muscat cultivars which it also resembles by the monoterpene composition of the juice. The pigments occurred only in berries with levels of total soluble solids in excess of 24°Brix in the juice and such berries tended to have smaller fresh weight. Berry pigmentation occurred on vines with various root systems. The specific conditions under which pigment developed in Muscat Gordo berries may offer a useful tool in the study of anthocyanin biosynthesis.     

Development of seed polyphenols in berries from Vitis vinifera L. cv. Shiraz

Polyphenols extracted from the seeds of Vitis vinifera L. cv. Shiraz berries were monitored during berry development. Initially seeds were green, plump and had pliable seed coats, but beginning at veraison the seeds browned in colour, became desiccated and the seed coats hardened. Isolated polyphenols consisted of flavan-3-of monomers ((+)-catechin, (-)-epicatechin and (-)-epicatechin-3-O-gallate) and procyanidins. The procyanidins were maximal in the 3 weeks prior to veraison, increasing little during this period. The amounts of flavan-3-ol monomers increased 5-fold during this same period of time, indicating that the procyanidins and the flavan-3-ol monomers accumulate at different stages. Beginning at veraison, amounts of all polyphenols declined and changed in composition. The decrease in amount followed second-order kinetics. Polyphenol changes after veraison could be explained by oxidation and therefore, electron paramagnetic resonance (EPR) spectroscopy was used to follow the potential development of radical species in the developing seeds. Spectra consistent with a phenoxyl radical were observed in the developing seeds. The concentration of radicals remained low until veraison but then increased, reaching a maximum three weeks later, declining slowly thereafter. Changes in radical intensity together with other documented changes in the seed are consistent with an oxidative event occurring during fruit ripening.     

From bud to berry, with special reference to inflorescence and bunch morphology in Vitis vinifera L.

A brief review of the reproductive system of the grapevine is presented. Phases discussed include floral induction and initiation during early spring, inflorescence primordium growth during summer to dormancy, flower formation at budburst in the subsequent growing season, and finally flowering and berry development. Difficulties in clearly defining and describing some of these developmental stages will be outlined, especially the complex bud system, the morphology of buds at budburst, and the course of flowering. The course of floral development during dormancy and at the time of budburst requires further attention, especially the reported effect that low temperature at budburst leads to increased numbers of flowers. Also, the recent finding that 'intercarpellar' floral organs can be induced by applying auxin is of particular interest and will be described. Case studies from Burgundy vineyards with Chardonnay, Pinot Noir and Gamay ovaries and berries will be included.
A detailed analysis of what constitutes a grape bunch will be presented from observations of Chardonnay inflorescences and bunches collected at random after set and at harvest in two seasons from spur-pruned, cane-pruned and hedged vines growing on two sites varying in climate and productivity (Adelaide Hills and Southern Vales of South Australia). This analysis covered variability in numbers of branches and flowers and in per cent berry set, as well as relationships between branch numbers and flower numbers. Relationships between flower numbers and per cent set, per cent set and berry size along the inflorescence, and berry size and seed complement are outlined. Likely implications of inter-bunch and intra-bunch variability for bunch compactness, berry composition and yield components are discussed.     

The effect of transient water deficit on berry development of cv. Shiraz (Vitis vinifera L.)

A new method for quantitative evaluation of the microbial load of cork and cork stoppers, coded CORA (Cork Activity Assay) is described. It is based on measurement by gas chromatography of dimethylsulfide (DMS) evolving from the reduction of dimethylsulfoxide (DMSO) by microbial activity. The method is accurate, gives results within 48 h and can be automated. Test results for various types of cork, sampled before, during and after the manufacturing process of bottle closures, are provided. The use of CORA as a tool for the development of better production processes to limit cork infection by micro-organisms and for advanced microbiological quality control is discussed.     

Scion photosynthesis and leaf gas exchange in Vitis vinifera L. cv. Shiraz: Mediation of rootstock effects via xylem sap ABA

Limited water resources are placing pressure on the wine grape industry to improve vineyard water use efficiency by continuing improvements in vineyard management. One way to improve vineyard water use efficiency is to improve transpiration efficiency, and judicious use of scion-rootstock combination can play a role. Accordingly, this paper examines the influence of rootstocks on the water use physiology of a common scion variety (Shiraz) and assesses the importance of variation in xylem sap abscisic acid (ABA) as an indicator of relative water use efficiency of different scion-rootstock combinations. Shiraz scions (clone BVRC12) grafted to seven rootstock varieties (along with an ungrafted control), were observed over two consecutive seasons in a field trial located in Adelaide, South Australia. Those two seasons (2001/02 and 2002/03) offered sharp contrasts with respect to soil and atmospheric water stress. Rootstock genotype had a significant impact on scion gas exchange, water status, canopy growth and yield in both seasons. Those impacts were associated with an inverse relationship between xylem sap ABA and stomatal conductance. We suggest that strategic analysis of xylem sap ABA may provide a marker for comparative water-use physiology of different stock-scion combinations, while recognising that irrigation pre-history, and associated degree of vine water stress, will be a further source of variation in grapevine water use.     

Synthesis of flavonols and expression of flavonol synthase genes in the developing grape berries of Shiraz and Chardonnay (Vitis vinifera L.)

Flavonols were determined in Shiraz and Chardonnay grapes throughout berry development. The predominant flavonols were quercetin-3-glycosides with trace amounts of kaempferol-3-glycosides detected in Shiraz flowers but not in developing berries. Flavonols were present in the skin of ripening grapes but were not detected in seeds or flesh. Flavonols were also present in buds, tendrils, inflorescences, anthers and leaves. The concentration of flavonols in flowers (mg/g fresh weight) was high and decreased between flowering and berry set then remained relatively constant through berry development. The total amount of flavonols in berries (mg/berry) was low until pre-veraison then increased during berry development, particularly before veraison, the onset of ripening, in Chardonnay and during ripening in Shiraz. Two cDNA fragments with homology to genes encoding the enzyme flavonol synthase (FLS) were isolated from Shiraz flowers. In the overlapping region of the two cDNAs, they had 80% sequence identity at the nucleotide level and both had high homology to FLS genes from other plants. VvFLS1 was expressed in leaves, tendrils, pedicels, buds and inflorescences as well as in developing grapes. Expression was highest between flowering and fruit set then declined, increasing again during ripening coincident with the increase in flavonols per berry. Expression of VvFLS2 was much lower than for VvFLS1 and did not change during berry development. The results indicate that two distinct periods of flavonol synthesis occur in grapes, the first around flowering and the second during ripening of the developing berries.     

Canopy microclimate and berry composition: The effect of bunch exposure on the phenolic composition of Vitis vinifera L cv. Shiraz grape berries

Studies on the effect of light exposure on specific phenolic compounds of berries from Shiraz vines grown in a hot climate are reported. Berries that had developed on bunches receiving high levels of ambient light generally had the highest relative levels of quercetin-3-glucoside and a lower proportion of their malvidin anthocyanins as the coumarate derivative, compared to berries that had developed on bunches in shaded canopy conditions. The response of total anthocyanin levels to treatment conditions was variable and depended on the degree of bunch shading and the resultant berry temperature. It appears that a high degree of bunch exposure in hot climates is not conducive to optimal anthocyanin accumulation in berries. The interactive effects of light and temperature on berry phenolic content and concentration are discussed.     

Phenological sensitivity of berry growth and composition of Tempranillo grapevines (Vitis vinifera L.) to water stress

Background and Aims:  The effect of water stress on berry quality is not fully understood. This study was designed to analyse the differential phenological sensitivity of Tempranillo berry quality to water stress during three phenological stages.
Methods and Results:  Two-year-old potted Tempranillo vines were exposed to four levels of irrigation (100, 50, 25, and 0% of evapotranspiration) during three phenological stages (Stage I, from anthesis to fruitset; Stage II, pre-veraison; Stage III, post-veraison). Vine water status was monitored by means of leaf water potential measurements. Berry quality was measured at harvest and defined by the following parameters: berry dry weight, soluble solids content, titratable acidity, polyphenol and anthocyanin concentrations in the must. Berry dry-matter accumulation was more sensitive to water stress applied during Stage I and Stage II than in Stage III. Berry quality tended to decrease linearly with increasing water stress during Stage II. During Stage III, berry quality increased linearly for light-to-mild levels of water stress, whereas quality decreased above a certain water-stress threshold (Ψ_leaf = −1.12 MPa).
Conclusions:  Tempranillo berry quality demonstrated great phenological sensitivity to water stress. Pre-veraison water stress negatively affected berry quality in Tempranillo vines, whereas post-veraison water stress increased quality up to a certain threshold of Ψ_leaf.
Significance of the Study:  For the first time, this research reports a plant-based water status threshold in Tempranillo vines above which post-veraison water stress can negatively affect berry quality.     

The effect of post-veraison water deficit on yield components and maturation of irrigated Shiraz (Vitis vinifera L.) in the current and following season

Given their perennial nature, grapevines can respond to deficit irrigation during both the current season as well as during the following season, even though full irrigation may have been restored during that second season. To define the cropping responses involved, three post-veraison irrigation treatments were imposed on spur, mechanically and minimally pruned Shiraz vines that were already receiving restricted water application using Partial Rootzone Drying (PRD). The treatments resulted in the vines receiving 1.25 ML per hectare pre veraison and the three irrigation treatments receiving 1.25, 0.65 and 0 ML of water per hectare in the post-veraison period. Water deficit during the current season reduced berry and bunch weight, and yield. Sugar concentration was reduced, and phenolic concentration increased when less water was applied, but anthocyanin concentration was unaffected. Although irrigation was returned to standard practice (PRD) in the following season, yield was reduced in accordance with deficit irrigation treatments the previous season. This reduction in yield was primarily caused by fewer bunches per vine, which in turn was a direct consequence of fewer shoots per vine (lower budburst). The lower crop load on the vines that had received restricted irrigation post-veraison in the previous season resulted in higher sugar and antho-cyanin concentrations in fruit the following season. Lighter pruning resulted in a greater number of smaller bunches comprising smaller berries. In both seasons the minimal pruning treatment delayed fruit maturity as measured by sugar accumulation. Post-veraison water deficit thus has the potential to impact on both yield and fruit composition during the current season as well as during the subsequent season.     

Relative proportions of seed, skin and flesh, in ripe berries from Cabernet Sauvignon grapevines grown in a vineyard either well irrigated or under water deficit

Relationships between the fresh mass of seed, skin (exocarp), and flesh (mesocarp) in six different berry size categories, were assessed on ripe fruit from Cabernet Sauvignon grapevines exposed to either High (H), Control (C) or Low (L) water status during post‐veraison berry growth in a vineyard. Berries harvested from each treatment were segregated into six mass categories in order to distinguish between changes in fresh mass components associated with general variation in berry size (on well‐watered grapevines), and those associated with berry size differences due to water stress. Berry fresh mass across all treatments ranged from about 0.4 to 2.0 g. Fresh mass components for both H and C berries comprised approximately 5% seed, 15% skin, and 80% flesh, regardless of variation in berry size, although there was some increase in seed mass relative to whole‐berry fresh mass in larger berries. Berry growth (as inferred from fresh mass at harvest) was much less sensitive to water deficit than published reports for grapevine shoot growth. Midday leaf water potentials around –1.20 MPa (Control) were not sufficient to inhibit berry growth. However, midday water potentials around –1.50 MPa (Low water status) inhibited berry growth by 13–18% of that attained by grapevines grown at high water status (i.e. treatment H where midday leaf water potentials remained around –1.00 MPa). Inhibition of berry growth by water deficit was attributed almost exclusively to reduced growth of mesocarp tissues (for most berry size categories). Water deficit thus increased the proportion of whole‐berry fresh mass represented by seeds and skin (for most berry size categories). Changes in those proportions due to irrigation treatments exceeded differences associated with general (non‐stress) variation in whole‐berry fresh mass. Excluding adverse environmental impacts on whole‐berry fresh mass, our results point to a limited role for variation in berry size per se as a factor determining the solute concentration of juice or wine derived from different sized fruit. By implication, and for all categories of whole‐berry fresh mass represented here, late season water deficit can result in ripe fruit with more skin and seed tissues (relative to whole‐berry fresh mass) compared with well‐watered control fruit.     

Influence of partial rootzone drying on the composition and accumulation of anthocyanins in grape berries (Vitis vinifera cv. Cabernet Sauvignon)

Background and Aims: The aim of the study was to investigate anthocyanin composition and accumulation in grape berries in response to the partial rootzone drying (PRD) irrigation technique.
Method and Results: The experiment was on Vitis vinifera cv. Cabernet Sauvignon, wherein PRD had a 40% water deficit relative to the control treatment. PRD decreased berry weight compared with the control, but did not influence total anthocyanin concentration. A significant increase in glucosides of delphinidin, cyanidin, petunidin and peonidin was found in response to PRD from the onset of anthocyanin accumulation (veraison), while malvidin-glucosides were unaffected by the irrigation treatment. The PRD treatment did not cause changes in the proportions of acetyl-, 3- p -coumaroyl- and monoglucoside anthocyanins. Wines produced from the treatments showed no difference in total monomeric anthocyanin, but relative increases (15%) in wine colour density, total tannin and polymeric pigment occurred in response to the PRD treatment. The anthocyanin composition of the wines reflected the response shown in the grapes, where the relative contribution of non-malvidin anthocyanins to total anthocyanins was significantly increased in wines from the PRD treatment.
Conclusions: The differences in anthocyanin composition observed in response to PRD could not be accounted for by changes in bunch microclimate, and most likely reflect differences in the methylation step of anthocyanin synthesis.
Significance of the Study: The observed changes in anthocyanin composition under the PRD irrigation system have not been previously reported in response to water deficit, and may reflect a unique response to within-vine signalling induced by PRD.