Fruit composition and ripening of Pinot Noir (Vitis vinifera L.) in relation to leaf area

Fruit development from pea size to maturity was investigated in grape berries on fruit-bearing cuttings subjected to a range of leaf removal treatments. Pot-grown vines were trained as a single shoot, with four basal leaves retained. From this point four treatments were applied: 100% leaves retained (control); 66% leaves retained; 33% leaves retained; 0% leaves retained. Leaves were removed as they appeared. The fruit of all treatments passed through veraison, accumulated water, coloured and displayed the typical double sigmoid change in volume, but the onset of growth and colour development associated with ripening was delayed by up to 25 days when leaves were removed. Berry dry weight, sugar content and soluble solids were more affected by leaf removal than berry volume or fresh weight. Bunches from the 0% leaf retained treatment formed seed, but increased very little in dry weight or soluble solids during the course of sampling. This indicates that seed growth and development are independent of sugar accumulation in pericarp tissues.     

Crop thinning (hand versus mechanical), grape maturity and anthocyanin concentration: outcomes from irrigated Cabernet Sauvignon (Vitis vinifera L.) in a warm climate

Crop thinning subsequent to fruit set can help regulate yield and improve fruit composition at harvest. Accordingly, an experiment was established in two vineyards (Site 1 Riverland District of South Australia; Site 2 Sunraysia District of Victoria) to investigate effects of crop removal after fruit set (when berries were pea size) using a machine harvester. Specific zones of the canopy were targeted for thinning to remove a predetermined percentage of the fruit and avoid over‐thinning. Cropping responses to mechanical thinning were compared with control (un‐thinned) vines, and with hand thinned vines (where fruit was removed from a similar portion of the canopy as for mechanical thinning). In a fourth treatment, bunches damaged by mechanical thinning were removed by hand. Inclusion of hand thinning treatments enabled us to distinguish between the potential benefits of reduced yield and the potential damage caused by the mechanical harvester to foliage and/or remaining fruit. Both the mechanical and the hand thinning treatments reduced bunch number as well as yield by a similar amount (approximately 24% on Site 1 and approximately 45% on Site 2) and advanced fruit maturity (soluble solids accumulation at harvest), relative to un‐thinned controls, by approximately 1.6 % and 1.7% respectively. Soluble solids accumulated at a similar rate for all treatments at sites, despite differences in yield, implying that the impact of thinning treatments originated prior to veraison. Berry weight was increased by hand thinning at Site1, and by all thinning treatments at Site 2. Anthocyanin concentration (berry fresh weight basis) was higher in fruit from the mechanically thinned vines compared to controls (un‐thinned). Mechanical thinning successfully reduced crop level to the target yield, and improved fruit quality. Mechanical thinning, via modified use of a machine harvester, thus offers some potential to regulate yield over large and minimally pruned vineyards, in a timely and cost‐effective fashion.     

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.     

Effects of defoliation on quality attributes of Nero di Troia (Vitis vinifera L.) grape and wine

Field studies were conducted in Puglia (Italy) to evaluate the influence of defoliation around cluster zones on grape and wine quality. Nero di Troia grapes were subjected to four different treatments: N: no leaf removal; E: leaf removal in the area of the clusters along the east side (at complete veraison); E/W: leaf removal in the area of the clusters along the east and west side (at complete veraison); and F: almost complete leaf removal along the west side (at complete veraison) and at pre-harvest also along the east side. Grapes of defoliated vines generally showed higher sugar content, lower titratable acidity, total flavonoids, flavonoids different from anthocyanins, and total phenolic content than grapes from non-defoliated vines while their total anthocyanin concentration was not affected by defoliation at a significant level. Concerning wines, alcohol content, residual soluble solids, different forms of anthocyanins but also volatile acidity were generally higher in samples from defoliated vines. Differences were also highlighted among the defoliation treatments: the best results in terms of dry matter, sugar and alcohol content were observed in the samples submitted to the more severe defoliation as a consequence of the higher light availability and berry temperature. Concerning the concentration of the individual phenolics, significant differences were highlighted for: caffeic and caftaric acids, peonidin- and malvidin-3-p-coumaroylglucoside, which were higher in the E wines; quercetin-3-glucoside, galactoside, and rhamnoside, and procyanidins, which were higher in F wines.     

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.     

Effect of foliar nitrogen and sulfur on petit manseng (Vitis vinifera L.) grape composition

Vineyard applications of foliar nitrogen (N) and sulfur were evaluated in the Yadkin Valley of North Carolina in 2011 and 2012 as a means to modify grape composition of Vitis vinifera cv. petit manseng. Four treatments were applied each year in a randomized complete block design with six replicates of six vines each: untreated control, soil N at 30?kg/ha, foliar N at 15?kg/ha and foliar N at 15?kg/ha plus sulfur at 5?kg/ha. Fruit ammonia and yeast assimilable nitrogen (YAN) concentrations increased in foliar-treated vines both seasons compared to control vines. Total glycosides (TGGs) increased ～80% in foliar N/sulfur-treated vines compared to control vines in 2011, and TGGs increased ～157% in foliar N/sulfur-treated vines relative to glycoside level in foliar N alone in 2012. Foliar N and foliar N/sulfur applications increased the majority of amino acid concentrations analyzed in 2011. Measured concentrations of various amino acids, partly responsible for aroma and flavor of petit manseng wines, were differentially dependent on the method of N application. Foliar applied nitrogen may be an effective technique to contribute to berry composition optimization of petit manseng grown in a warm, humid climate.     

Effects of pre-bloom leaf removal on growth of berry tissues and must composition in two red Vitis vinifera L. cultivars

Background and Aims:  Little work has been conducted on the effects that summer pruning operations have on the relative growth of grapevine berry parts. Our paper studies whether pre-bloom leaf removal is able to modify the proportions of seed, skin and flesh in ripe grapevines berries and the related effects on must composition.
Methods and Results:  Pre-bloom defoliation (D) of the first six basal leaves on main shoots was applied to the field-grown cvs Barbera and Lambrusco salamino ( Vitis vinifera L.) in Italy's Po Valley and compared with non-defoliated controls. D showed reduced fruitset, hence yield per shoot, and concurrently improved must soluble solids and total anthocyanins in both cultivars as a likely result of increased leaf-to-fruit ratio (+3.4 cm²/g and +5.2 cm²/g for Barbera and Lambrusco, respectively) and improved relative skin mass (from 6.0 to 9.0% in Barbera and from 8.1 to 10.4% in Lambrusco). In both cultivars, skin and seed mass were highly correlated with total berry mass and changes in relative skin mass were generally not related to berry size.
Conclusions:  These results indicate that berry size per se is not the primary factor in determining final grape composition, which instead seems to depend upon factors differentially affecting the growth of the various berry components.
Significance of the Study:  Pre-bloom D induced a consistent, site and cultivar-independent increase in relative skin mass suggesting this effect being strongly physiologically regulated.     

Growth and dry matter partitioning of Pinot Noir (Vitis vinifera L.) in relation to leaf area and crop load

Treatments varying source:sink ratio (leaf number per vine in relation to crop load) on container-grown Pinot Noir grapevines produced differences in vine growth and dry matter accumulation and partitioning. Vines with (+) and those without (-) fruit were subject to a range of leaf removal treatments. All treatments retained leaves at nodes 1–4 from the shoot base and then had: 100% (control); 66%; 33%; or 0% leaves retained from node 5 to the apex of the shoot. Leaf removal was done as leaves appeared. Leaf removal reduced vine weight. The presence of crop and the number of leaves influenced nodes per shoot and dry weight of the shoots. Removal of leaves did not influence shoot length although un cropped vines were larger in all of the above categories. Removal of either leaves or crop had an impact on leaf number, area per vine, area per leaf and leaf dry weight.'crop' vines carried fewer, and smaller leaves then the 'crop' vines. Carbon partitioning between above ground vegetative organs and roots followed the same relationship, regardless of harvest date, crop status or defoliation treatment. The 'crop 33% leaf retained' vines compensated for leaf removal by increasing their leaf size and dry weight over the '66% leaf retained' and the control.     

Physicochemical characteristics and functional properties of grape (Vitis vinifera L.) seeds protein

The amino acid composition, physicochemical and functional properties of grape (Vitis vinifera L.) seeds protein (GSP) were evaluated and compared with those of soybean protein isolate (SPI). Amino acid analyses of GSP revealed high levels of glutamic/glutamine, glycine and aspartic/asparagines. SDS‐PAGE analysis demonstrated that globulin was the major protein component in GSP, whose subunit molecular weights were mainly varied from 25.5 to 40.0 kDa. The isoelectric pH of GSP was found to be at the acidic pH of around 3.8. At all the pHs tested except pH 2.0, no significant changes of GSP secondary structure were observed. GSP exhibited beneficial functional properties such as preferable solubility and emulsifying activity, while the foaming properties and water holding capacity were relatively poor compared to SPI. It could then be employed to soup, sauce, beverage or meat product for improving nutritional and sensory quality of these foods at appropriate pHs.     

Vine performance and grape composition as affected by early-season source limitation induced with anti-transpirants in two red Vitis vinifera L. cultivars

Background and Aims: Previous work has shown that an early (i.e. pre-flowering) source limitation achieved with either hand or mechanical basal shoot zone defoliation is effective in controlling yield while improving grape composition in several environments and Vitis vinifera genotypes. Our study was designed to determine whether similar results can be reproduced by using a film-forming anti-transpirant. Methods and Results: The entire canopies of field grown cvs. Sangiovese and Ciliegiolo vines were treated twice pre-flowering with the anti-transpirant Vapor Gard® (Intrachem Bio Italia, Grassobbio, BG, Italy) (T) and compared with an unsprayed control (C). Leaf assimilation and transpiration in both cultivars showed similar reductions (30–70%) for several weeks after spraying as compared with control vines, while intrinsic water use efficiency increased in treated vines soon after first application and after veraison. In Sangiovese, treated vines showed reduced yield, berry weight, bunch compactness and, on a 2-year basis, lower vigour and unchanged vine capacity every year. At harvest, treated vines showed higher °Brix in all seasons and higher anthocyanin concentration in 2 out of 3 years. Results of a 2-year run in Ciliegiolo mimicked those of Sangiovese in terms of yield regulation. Conclusions: Early season applications of a film-forming anti-transpirant caused a leaf function limitation strong enough to reduce yield and bunch compactness through smaller final berry size. Significance of the Study: Anti-transpirant applications can be proposed as a much easier way than manual or mechanical leaf removal to induce crop regulation through early source limitation.     

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.     

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.     

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.