Rate Of Sugar Accumulation Research Articles

Phloem anatomy predicts berry sugar accumulation across 13 wine-grape cultivars.

Climate change is impacting the wine industry by accelerating ripening processes due to warming temperatures, especially in areas of significant grape production like California. Increasing temperatures accelerate the rate of sugar accumulation (measured in ⁰Brix) in grapes, however this presents a problem to wine makers as flavor profiles may need more time to develop properly. To alleviate the mismatch between sugar accumulation and flavor compounds, growers may sync vine cultivars with climates that are most amenable to their distinct growing conditions. However, the traits which control such cultivar specific climate adaptation, especially for ⁰Brix accumulation rate, are poorly understood. Recent studies have shown that higher rates of fruit development and sugar accumulation are predicted by larger phloem areas in different organs of the plant. Here we test this phloem area hypothesis using a common garden experiment in the Central Valley of Northern California using 18 cultivars of the common grapevine (Vitis vinifera) and assess the grape berry sugar accumulation rates as a function of phloem area in leaf and grape organs. We find that phloem area in the leaf petiole organ as well as the berry pedicel is a significant predictor of ⁰Brix accumulation rate across 13 cultivars and that grapes from warm climates overall have larger phloem areas than those from hot climates. In contrast, other physiological traits such as photosynthetic assimilation and leaf water potential did not predict berry accumulation rates. As hot climate cultivars have lower phloem areas which would slow down brix accumulation, growers may have inadvertently been selecting this trait to align flavor development with sugar accumulation across the common cultivars tested. This work highlights a new trait that can be easily phenotyped (i.e., petiole phloem area) and be used for growers to match cultivar more accurately with the temperature specific climate conditions of a growing region to obtain satisfactory sugar accumulation and flavor profiles.

Severe shoot topping slows down berry sugar accumulation rate, alters the vine growth and photosynthetic capacity, and influences the flavoromics of Cabernet Sauvignon grapes in a semi-arid region

Severe shoot topping (SST) is a viticultural technique that has been proposed to face global warming in recent years. In the present study, a three-year study (2018–2020) was performed to investigate the comprehensive impact of SST on vine physiology, berry sugar accumulation rate and flavoromics of Cabernet Sauvignon grapes in a semi-arid climate. Results showed that manipulating different SST treatments could cause a reduction of 0.4–1.7 mg/berry/d (0.02–0.11°Brix/d) in grape sugar accumulation without affecting the yield. Photosynthetic compensation was found in consecutively SST-treated vines across vintages. The berry skin anthocyanins and flavanols showed lower concentrations in SST grapes than in the control. However, the individual flavonols, including myricetin-based and kaempferol-based flavonols, had higher concentrations in SST grapes. A minor difference was found in aroma compounds regarding the SST influence, which seemed vintage-dependent. Through principal component analysis, the metabolites that showed high correlations with vintages, SST treatment (SST vs control) and different SST time were evaluated. Our results provided an available viticultural strategy to face climate change in the semi-arid region.

Development of kinetic models for prediction of reducing sugar content in potatoes using literature data on multiple potato varieties

Reducing sugar (RS) content in potatoes beyond a certain limit leads to browning of chips and the formation of acrylamide (carcinogen). The data for RS vs time at different storage temperatures was collected for 51 potato varieties. Out of these, 16 varieties with RS data available for at least three temperatures were used for development of two models (A and B). Model A consisted of two equations (linear, log) fitted to RS data of entire storage duration for each potato variety and most of these equations had R2adj in the range 0.75–0.95. Model B consisted of a common linear equation form fitted to data of 100 days (where most of the change occurs) with R2 value 0.7–0.98. The activation energy for most of the varieties was in the range of −120 to −300 kJ/mol. Considering the wide variation in the rate of sugar accumulation, potato varieties were categorized as Cold-resistant (CR) and Cold-sensitive (CS) and two separate model equations were developed. These models were validated using data collected through in-house experiments and literature data. The models predicted RS of different potato varieties with Root Mean Square Error of 0.02–3 g/kg FW (Fresh Weight) and Accuracy factor below 1.8.

Crop Load and Plant Water Status Influence the Ripening Rate and Aroma Development in Berries of Grapevine (Vitis vinifera L.) cv. Cabernet Sauvignon.

Wine made from grapes subjected to accelerated ripening, an increasingly frequent phenomenon occurring in many wine regions due to peaks of heat and water stress, displays higher alcohol levels and lacks balance with color and flavor compounds. Herein, the rate of sugar accumulation of grapes was manipulated by varying the crop load and irrigation regime and the development of secondary metabolites was monitored by gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC). A 3-week delay in ripening correlated to an increase in the concentration of some monoterpenes and norisoprenoids and a greater decrease of green aroma compounds. Delayed ripening had a positive impact on the phenolic composition of grapes, displaying higher contents of total anthocyanins, total phenolics, quercetin glycosides, and polymeric pigments. A map of the chemical composition of grapes close to harvest allowed discrimination of compounds mainly responsive to delayed ripening from those driven by crop load or irrigation.

Vegetative, Yield, and Berry Quality Response of Aglianico to Shoot-Trimming Applied at Three Stages of Berry Ripening

The rise in air temperature due to climate change is causing an increase in the sugar accumulation rate in grape berries, resulting in increased wine alcohol concentrations. Postveraison leaf area removal (defoliation, shoot-trimming) is a suitable canopy management strategy to slow carbohydrate accumulation in the berries. However, in late-ripening cultivars, the phenological stage between veraison onset and harvest can be very long. Therefore, it can be hypothesized that the specific timing when leaf area removal is applied during the phenological stage can affect carbohydrate accumulation in the berries and berry composition. A two-year experiment was designed to compare the responses of Aglianico grapevines, a late-maturing cultivar, to shoot-trimming applied at three different stages of berry ripening. The experimental design included: (a) three trimming treatments applied at total soluble solids of 6, 12, and 18 Brix, respectively; and (b) a control treatment (untrimmed vines). Independent of the application timing, shoot-trimming decreased berry total soluble solids at harvest below that of control vines, but the later the shoot-trimming was applied, the lower berry total soluble solids was at harvest. Shoot-trimming did not affect other berry parameters. These results confirm that, at least for late-maturing cultivars, the timing of application of late shoot-trimming plays a key role in modulating the intensity of the effects of this management practice on berry composition.

The effect of light intensity and temperature on berry growth and sugar accumulation in Vitis Vinifera "Shiraz" under vineyard conditions

Temperature and light are key climatic factors which affect grapevine physiology in the growing season. Our aim was to investigate the interactive effects of temperature and light intensity on reproductive growth responses of 'Shiraz' vines in vineyard conditions. Well-watered vines were covered with no shade, light, medium and heavy shade covers in a vineyard over three consecutive seasons. Several heat events, i.e., air temperatures exceeding 40 °C for several days, occurred in two of the seasons. Heavy shade reduced canopy temperatures by 3.2-6 °C in the cooler season and by 4-6 °C in the warmer seasons, relative to air temperature and compared with the open canopy. The onset of berry growth was delayed by the heavy shade but the rate of sugar accumulation was not affected. During the season with the most severe heat events, berry dry matter accumulation was significantly higher in the shaded treatments compared to the unshaded vines. The hypothesis was confirmed that medium and heavy shade conferred high levels of protection on the berry ripening process from high summer temperatures and the concurrent exposure to light intensities.

Enhanced phytostabilization of cadmium by a halophyte—Acanthus ilicifolius L.

ABSTRACTHeavy metal pollution in mangrove wetlands has become a growing matter of concern as it serves as sink and source for toxic heavy metals including cadmium (Cd). The present study evaluates the phytostabilization potential of a halophyte, Acanthus ilicifolius L., toward Cd under hydroponic culture conditions. Accumulation, translocation, and effects of Cd on the antioxidant system of A. ilicifolius were studied. Results indicated that A. ilicifolius accumulated Cd mainly in roots (96.4%) as compared to stem (1.4%) and leaves (0.6%) and the accumulated Cd is retained in root rather than being translocated to shoots as indicated by TF < 0.26. Moreover, malondialdehyde (MDA) content increased upon Cd treatment, which is further detoxified by the enzymatic and nonenzymatic antioxidant mechanism. Antioxidants like proline, ascorbate, and amino acid recorded an increased accumulation in the Cd-treated plants followed by the upregulation of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX), and ascorbate peroxidase (APX). Therefore, the rate of sugar accumulation was found to be decreased in plants treated with Cd as compared to the control plants. Thus, having relatively high BCFroot (69.3) and low TFshoot (0.26) values, A. ilicifolius can be suggested as a potential candidate for phytostabilization of Cd in mangrove wetlands.

Establishing the temperature dependency of vegetative and reproductive growth processes and their threshold temperatures of vineyard-grown Vitis vinifera cv. Semillon vines across the growing season.

A hydrocooling system provided canopy temperature control of Vitis vinifera L. cv. Semillon vines at set points of 30, 35 and 40°C. The impacts on vegetative and reproductive growth over the growing season were assessed. Dynamics and rates of leaf expansion, bunch biomass and sugar accumulation were strongly affected by canopy temperatures - being highest at 30°C and lowest at 40°C. Leaf and stem biomass accumulation at 40°C was detrimentally affected but was otherwise little affected by temperature. Leaf expansion was earliest, leaf sizes greatest and rates of expansion all optimal at 30°C and all were strongly temperature dependent. Bunch biomass accumulation was earliest at 35°C but amount of biomass in bunches and rates were both highly temperature dependent and optimal at 30°C. Rates of sugar accumulation and total amounts accumulated at harvest were both highly temperature-dependent processes: fastest and greatest at 30°C. Many of the temperature-dependent processes decreased in rates and amounts linearly between 30 and 40°C. Despite the effects of temperature on bunch and berry growth, there were no treatment effects on the yield per vine. The study confirms that the threshold temperature for most processes was 35°C, where some depreciation in dry matter and sugar accumulation occurred, whereas 40°C was detrimental to all growth processes.

Interactions of summer pruning techniques and vine performance in the whiteVitis viniferacv. Ortrugo

Background and Aims The increasing interest by the wine market in sparkling white wines challenges how the desired grape composition can be achieved under the pressure of global warming. The aim of the present study was to assess the viability of summer pruning as a tool to pilot ripening towards desired compositional patterns. Methods and Results Ortrugo was subjected to basal leaf removal applied either at pre-flowering (ELR) or in lag-phase (LLR) and to bunch thinning (BT; removal of 50% of crop at lag-phase) in comparison with untreated control (C). Treatments induced large variation in bunch mass (30% less in ELR vs BT), yield per vine (37 and 21% less in BT and ELR vs C) and total soluble solids at harvest (BT scored 2.9°Brix higher than that of C). Conversely, given the same harvest date, all practices failed to maintain titratable acidity (TA) at the threshold of 6.5 g/L. Conclusions The data suggest that crop regulation achieved in the high yielding Ortrugo, through either BT or ELR, increases sugar accumulation rate so that concurrent optimal TA level (≅6.5 g/L) can be easily achieved by slightly anticipating harvest date. Under conditions of thermal or light stress, or weather conducive to bunch rot, preference should be given to ELR. Significance of the Study Suitable summer pruning techniques might be used as flexible and powerful tools to direct ripening towards the desired crop composition.

Unexpected relationships between δ&lt;sup&gt;13&lt;/sup&gt;C and wine grape performance in organic farming

&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Aim&lt;/strong&gt;: To evaluate the relationship between carbon isotope ratio (δ&lt;sup&gt;13&lt;/sup&gt;C) and wine grape viticultural and oenological performance in organic farming.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Methods and results&lt;/strong&gt;: The study was carried out for four years in the Chianti Classico wine production district (Central Italy), on five non irrigated vineyards conducted in organic farming. The reference variety was Sangiovese. Eleven sites were chosen for vine monitoring and grape sampling. The performance parameters were alcohol and must sugar content, sugar accumulation rate, mean berry weight, and extractable polyphenols. δ&lt;sup&gt;13&lt;/sup&gt;C, stem water potential, and soil water availability were also monitored. Finally, soil nitrogen as well as yeast available nitrogen in the must were measured. δ&lt;sup&gt;13&lt;/sup&gt;C was directly related to stem water potential and soil water deficit, and indicated a range of water stress conditions from none and moderate to strong. However, its relationship with viticultural and oenological results was contrary to expectation, that is, performance linearly increased along with soil moisture. On the other hand, the worst performance was obtained where both water and nitrogen were more limiting.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Conclusions&lt;/strong&gt;: The unexpected relationship between δ&lt;sup&gt;13&lt;/sup&gt;C and Sangiovese performance was caused by low nitrogen availability. The studied sites all had low-fertility soils with poor or very poor nitrogen content. Therefore, in the plots where soil humidity was relatively higher, nitrogen plant uptake was favoured, and Sangiovese performance improved. Macronutrient being the main limiting factor, the performance was not lower in the plots where soil water availability was relatively larger. Therefore, the best viticultural result was obtained with no water stress conditions, at low rather than at intermediate δ&lt;sup&gt;13&lt;/sup&gt;C values.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Significance and impact of the study&lt;/strong&gt;: Water nutrition is crucial for wine grape performance. δ&lt;sup&gt;13&lt;/sup&gt;C is a method used to assess vine water status during the growing season and to estimate vine performance. A good performance is expected at moderate stress and intermediate δ&lt;sup&gt;13&lt;/sup&gt;C values. A better knowledge of the interaction between water and nutrient scarcity is needed, as it can affect the use of δ&lt;sup&gt;13&lt;/sup&gt;C to predict vine performance.&lt;/p&gt;

Delaying Riesling grape berry ripening with a synthetic auxin affects malic acid metabolism and sugar accumulation, and alters wine sensory characters.

An improved understanding of the hormonal control of grape (Vitis vinifera L.) berry ripening and the ability to manipulate it are of interest scientifically and commercially. Grapes are nonclimacteric fruit with ethylene unlikely to have a principal role in berry ripening but there are several other hormones thought to be involved. In this work, a significant delay in Riesling berry ripening was achieved through preripening treatments with the synthetic auxin 1-naphthaleneacetic acid (NAA). The initiation of sugar accumulation was delayed and the rate of sugar accumulation was lower in NAA-treated fruit, resulting in a 15-day delay in harvest. NAA treatments also reduced the rate of decline in malic acid levels that occurs during ripening, and increased the synchronicity of malic acid and berry sugar accumulation. Sensory panel assessment revealed a significant difference between wine made from control and NAA-treated fruit. Analysis of the volatile composition of the wines' headspace showed that the concentration of several compounds was altered significantly by the NAA treatment. These data provide further support for the involvement of auxins in inhibiting ripening and suggest that auxin treatments may be useful in controlling both winery intake, and fruit and wine composition.

Quaternary landscape history determines the soil functional characters of terroir

The soil functional properties that characterise the terroirs of a denomination of origin area are products and witnesses of the Quaternary events, natural and human induced, which occurred in that landscape. Knowing the Quaternary history can enhance the awareness of stakeholders about the possible environmental and economic losses that can derive from irrational soil management, which can lead to the worsening or loss of irreproducible soils of the best terroirs.In the ”Vino Nobile di Montepulciano” wine territory, a four-year research project was conducted on the relationships between the soil and the viticultural and oenological behaviour of the Sangiovese vine. The study soils of the Montepulciano vineyard ranged notably in fertility conditions and functional characters, even when formed on the same kind of sediments. The grape production and vintage, as well as the organoleptic characteristics of the wine, depended on the kind of soil. The wines obtained from a first group of soils had a good structure and typicity, but the stability of the wine’s sensorial profile from different vintages was low. A second group exhibited good structure, typicity, and a good stability of wine sensorial profile. A third group had the highest values of yield per vine, mean cluster weight, 100 berries weight and total acidity. Also, sugar content level and sugar accumulation rate were the lowest of all vineyards. Wines showed low structure, low typicity, and high astringency in all the years of the research.The oldest soils of the Montepulciano vineyard started their formation during the Pleistocene. During the middle Holocene, humans deeply influenced pedogenesis, but it is during the last 50 years that the intensity of anthropic action has reached its maximum. Pre-plantation activities of the new specialized vineyards upset the land. Where soils before vine plantation were deep and rather homogeneous, functional characters remained the same, whereas they changed significantly where soils were shallower. Shallow soils on marine clays, in particular, have been very vulnerable to change. The best soils for Nobile di Montepulciano wine production, that is, those belonging to the second group, were Pleistocene and Holocene paleosols, formed as a consequence of unique natural and human induced geomorphological events. Therefore, they should be considered as cultural heritages.

Quantifying the onset, rate and duration of sugar accumulation in berries from commercial vineyards in contrasting climates of Australia

Background and Aim: To predict the trajectory of sugar accumulation in berries for planning of harvest and post-harvest operations, we derived a simple model that is consistent with the known biological and viticultural drivers of berry ripening and requires inputs that are readily available to industry. Methods and Results: We used data from three vintages in climatically contrasting regions of Australia to derive a relationship between total soluble solids (TSS) and thermal time. A linear-plateau function was fitted to the 90th percentile data, hence providing a boundary function representing the potential for each variety-environment combination. Biologically relevant parameters were derived including the rate of change in TSS, maximum TSS (TSSmax), the threshold thermal time when berries reached TSSmax, the onset and the duration of the period of linear increase in TSS. Gaps, calculated as the difference between actual TSS and the boundary function, correlated positively with vapour pressure. A model with the observed onset of ripening as an input and a variety and site specific rate as parameter accounted for 81–92% of the variation in TSS for independent data sets. Conclusion: The trajectory of TSS in berries can be modelled ‘as if’ the main environmental and management sources of variation affect the onset rather than the rate of sugar accumulation. Significance of the Study: Our onset-rate model can be coupled with: (i) short-term temperature forecasts to predict the trajectory of TSS for management purposes; and (ii) long-term records of temperature to produce probabilistic profiles of maturity date.

Climate shifts in south-eastern Australia: early maturity of Chardonnay, Shiraz and Cabernet Sauvignon is associated with early onset rather than faster ripening

Background and Aim: Early maturity of grape crops associated with recent warming is well documented but poorly understood. Here, we ask the question: is early maturity associated with early onset of ripening or with increased rate of sugar accumulation? Methods and Results: We used records of grape juice total soluble solids (TSS) for Chardonnay, Shiraz and Cabernet Sauvignon collected in commercial vineyards between 1995 and 2009. The combination of 15 vintages and three climatic regions yielded a range of average seasonal temperature between 15.5 and 20.5°C. Using boundary functions of TTS versus time, we derived the onset and rate of increase in TSS, and the time of maturity set at 12 °Be for comparative purposes. Pooled across varieties, the rate of change in maturity was −9.8 ± 0.94°C/d. Shifts in onset accounted for 86% of the variation in time of maturity and the rate of ripening for the remaining variation. Conclusion: Early maturity associated with higher temperature (and related factors including higher radiation and higher vapour pressure deficit) is primarily driven by early onset of ripening under a wide range of production systems in south-eastern Australia. Significance of the Study: Viticultural practices aiming at delaying maturity to counteract the effect of high temperature, high radiation and high vapour pressure deficit are more likely to be successful if they target the onset of ripening.

It is possible to predict Sangiovese wine quality through a limited number of variables measured on the vines

&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Aims&lt;/strong&gt;: The research work aimed at creating and testing a method to evaluate vine performance of Sangiovese (VPS), in particular, a method able to predict the potential oenological result through a limited number of variables measured on the vines.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Methods and results&lt;/strong&gt;: A matching table was created on the basis of literature and the experience acquired over twenty years of research activity on Sangiovese vine and wine quality in Tuscany, which allowed the selection of eight viticultural parameters and three VPS classes. In order to validate the matching table, a specific experiment was conducted during the years 2002 and 2003 in 10 vineyards (selected from 7 farms) representative of the main soils and climates of the vine cultivation areas of the Province of Siena (Italy). The experimental results validated the proposed matching table through a non parametric statistical analysis. A multivariate regression analysis between wine sensory evaluation (score) and viticultural parameters significantly predicted wine quality even with only 4 grape parameters (&lt;em&gt;P&lt;/em&gt; &amp;lt; 0.05).&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Conclusion&lt;/strong&gt;: It was possible to predict VPS by means of a matching table based upon eight simple viticultural parameters. The reliability of the wine quality prediction increased proportionally according to the number of viticultural parameters, but remained rather high (R&lt;sup&gt;2&lt;/sup&gt; = 0.606) when taking into account only sugar content, sugar accumulation rate, mean berry weight, and extractable polyphenol index (EPI).&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Significance and impact of the study&lt;/strong&gt;: It is now possible to predict the quality of Sangiovese wines with a few selected grape parameters. Because of the wide variability in soil and climatic condition of the viticultural areas of the Province of Siena, where the method was developed, and the strong climatic contrast between the years when the method was validated, the use of both matching table and multiple regression is recommended for VPS prediction in Mediterranean environments.&lt;/p&gt;

Quantifying the dynamics of sugar concentration in berries of Vitis vinifera cv. Shiraz: a novel approach based on allometric analysis

Concentrations of key compounds (e.g. sugar) in berries are the net result of relative changes in the amount of compound per berry and berry size. The complex nature of concentrations is widely recognised, but the widespread use of chronological scales for comparisons implies that ontogenetic drift or size-dependent effects are often overlooked. This paper presents an allometric analysis of sugar concentration in berries of cv. Shiraz as a way to formally account for ontogenetic drift. Our starting point is the double-sigmoid growth pattern of a grape berry where we distinguish Phase 1, from flowering to veraison; Phase 2, from veraison to peak berry fresh mass, and Phase 3, after peak fresh mass. Phase 3 explicitly accounts for the late season shrinkage typical of Shiraz berries. We advance an allometric model of sugar per berry with berry fresh mass, rather than time, as descriptor. The condition for an increase in sugar concentration in Phase 2 is that the relative rate of sugar accumulation per berry (RSB) exceeds the relative rate of berry net accumulation of fresh mass (RFM). This is equivalent to an allometric coefficient, calculated as the slope of the regression between amount of sugar per berry and berry mass in a log-log scale, being greater than 1. For Phase 3, the condition for increase of sugar concentration is that a large reduction in berry mass offsets any putative change of sugar per berry, yielding an allometric coefficient < 1. Such an allometric model was tested against measured data from sixteen contrasting crops resulting from the combination of eight water regimes and two seasons. Berry mass peaked between 96 and 105 days after anthesis, and these dates were used to separate Phases 2 and 3. In Phase 2, the relative rate of increase in sugar per berry varied from 0.01 to 0.02 d-1 in comparison to the relative rate of increase in berry fresh mass that varied from 0.0038 to 0.0066 d-1. Sugar per berry thus increased 2.4–3.3 times faster than berry mass, with allometric coefficients between 1.98 and 2.91 accounting for 78% of the variation in the relative rate of change of sugar concentration. In Phase 3, the relative rate of change in sugar per berry was not different from zero (P 0.05) in most cases, whereas the rate of change in berry size ranged from –0.0013 to –0.0035 d-1 and was significant (P < 0.05) in 14 out 16 cases. The small changes in sugar per berry and the net loss of berry material yielded allometric coefficients between 0.17 and 1.11, which accounted for 72% of the variation in the relative rate of change in sugar concentration. We conclude that a model, which pivots around peak berry mass, with allometric coefficients above 1 in Phase 2 and below 1 in Phase 3, is suitable to quantitatively account for ontogenetic drift in the dynamics of sugar concentration in berries of Shiraz. This allometric approach demonstrated that sugar per berry during the stage of berry shrinkage is a plastic trait under significant environmental influence. For the same genotype, environmental conditions could determine either, a putative backflow of water accounting for net loss of berry fresh mass (RFM < 0) that could also carry some sugar from berries back to the parent vine (RSB < 0) or a small gain of sugar (RSB 0) closely coupled with a net loss of berry fresh mass (P= 0.003).

Response of Shiraz grapevines to five different training systems in the Barossa Valley, Australia

Own-rooted Shiraz, spaced 1.5 m apart in 2.75 m wide rows, were compared under five different training systems in the Barossa Valley, South Australia over five seasons starting 1995-96. Our objective was to determine how training affected fruit composition and crop yield in a context of efficient vineyard management. Training systems were: (i) low single wire (LSW), in which vines were trained to bi-lateral cordons, 1.0 m above the ground, non-shoot-positioned; (ii) high single wire (HSW), a higher cordon (1.8 m) version of LSW; (iii) vertically shoot positioned (VSP); (iv) Scott Henry, where canopies of alternate vines were cordon-trained and shoot-positioned upwards (SHU) or downwards (SHD); and (v) minimally pruned (MIN), the same as LSW, except vines were not annually spur-pruned. Crop yields (kg/m of row), over four seasons, averaged 4.9 (MIN), 2.9 (combined Scott Henry), 3.2 (VSP), 2.6 (HSW) and 2.9 (LSW). The greatest year-to-year variation in yield occurred with MIN and Scott Henry training. Crop weight of SHD vines was inferior to that of SHU vines in two seasons due to fewer shoots and bunches per vine, and to fewer bunches per shoot. Individual berry weights (g) were consistently least with MIN (0.89), and greatest with VSP (1.17). Fruit from all training systems exhibited similar rates of sugar accumulation during two seasons in which repeated measures of fruitmaturation were made. Excepting the relatively light yields observed in 1999-2000, sugar accumulation was delayed in MIN vines, relative to other training systems, even when MIN harvest was delayed up to two weeks. The delay is most readily explained by the greater crops of MIN vines. Berry total anthocyanins and total phenolics concentrations (mg/g berry fresh wt.) at harvest were not greatly affected by training system. Berry anthocyanins and total phenolics exhibited a negative relationship with crop/m of canopy and a slight positive relationship with bunch exposure when evaluated across all training systems. Experimental plot soil depth and water availability affected cane pruning weights, yield per vine, berry weight, and canopy characteristics. LSW, HSW and MIN training systems all provided good yields of high quality fruit, although MIN did have a tendency to produce excessive crops in some years. VSP and Scott Henry training were less attractive due to their inherently greater canopy management requirements.

Berry Ripening and Evapotranspiration inVitis viniferaL

Based on the observation that the allometric situation, <i>i.e</i>., the ratio between berry volume and skin area (smaller vs. larger fruit), and the physical intactness of the skin are paramount in determining final sugar content of mature grapes, water efflux (<i>Jw</i>) by evapotranspiration is hypothesized to be the driving force of berry sugar import and accumulation. This reduction of the physiological process of hexose accumulation to non-metabolic variables allows an assessment and prediction of berry assimilate uptake by relatively simple mathematical equations. Measurements of hexose concentrations and berry diameter in three consecutive years were used to test the model. The post-veraison period was found to separate into two distinct phases with different water flux characteristics. From this emerges that the water status of vine and particularly the conditions in the grape zone must be of practical importance in determining the rate of sugar accumulation during grape ripening.

Sugar Metabolism during Growth and Development in Sugarcane Internodes

Development of sugarcane (Saccharum spp. hybrids) genotypes with higher sucrose concentrations is desirable. Activities of sucrosemetabolizing enzymes during development of internodal storage tissue may determine the rate of total sugar accumulation and final sucrose concentration. Internodes of seven commercial cultivars were tagged prior to elongation and sampled at intervals from July until December during two growing seasons. Internode elongation was completed by about 380°C d (base temperature 18°C). Dry matter accumulated until about 800°C d. Water content decreased from about 920 to about 720 g kg−1 fresh weight (FW). Soluble acid invertase and sucrose synthase (sucrose cleavage direction) had peaks of activity during elongation, then declined to lower levels. Neutral invertase and sucrose‐phosphate synthase activities increased during development. Sugar accumulated, and the sucrose to total sugar ratio approached 1.0 as internodes developed, although the combined sucrose cleavage activity of the invertases and sucrose synthase in most internodes was greater than the synthetic activity of sucrose‐phosphate synthase. Sugar accumulation rate was not consistently correlated with activity of any enzyme assayed. Sucrose content during internode development was correlated with sucrose‐phosphate synthase activity and the difference between sucrose‐phosphate synthase and acid invertase activities. Sucrose content of mature internodes was not correlated with any enzyme activity. The data do not support the hypothesis that sucrose synthase activity is related to the rate of sugar accumulation, but do support the hypothesis that sucrose‐phosphate synthase and acid invertase play key roles in determining sucrose concentration during maturation in sugarcane internodes.

Sucrose metabolism in cold‐stored potato tubers with decreased expression of sucrose phosphate synthase

Transfer of potato tubers to low temperature leads after 2–4 d to a stimulation of sucrose synthesis, a decline of hexose‐phosphates and a change in the kinetic properties, and the appearance of a new form of sucrose phosphate synthase (SPS). Antisense and co‐suppression transformants with a 70–80% reduction in SPS expression have been used to analyse the contribution of SPS to the control of cold sweetening. The rate of sucrose synthesis in cold‐stored tubers was investigated by measuring the accumulation of sugars, by injecting labelled glucose of high specific activity into intact tubers, and by providing 50 mol m–3 labelled glucose to fresh tuber slices from cold‐stored tubers. A 70–80% decrease of SPS expression resulted in a reproducible but non‐proportional (10–40%) decrease of soluble sugars in cold‐stored tubers, and a non‐proportional (about 25%) inhibition of label incorporation into sucrose, increased labelling of respiratory intermediates and carbon dioxide, and increased labelling of glucans. The maximum activity of SPS is 50‐fold higher than the net rate of sugar accumulation in wild‐type tubers, and decreased expression of SPS in the transformants was partly compensated for increased levels of hexose‐phosphates. It is concluded that SPS expression per se does not control sugar synthesis. Rather, a comparison of the in vitro properties of SPS with the estimated in vivo concentrations of effectors shows that SPS is strongly substrate limited in vivo. Alterations in the kinetic properties of SPS, such as occur in response to low temperature, will provide a more effective way to stimulate sucrose synthesis than changes of SPS expression.