Vineyard variability in Marlborough,New Zealand: characterising spatial and temporal changes in fruit composition and juice quality in the vineyard

Background and Aims: Previous work has demonstrated that vineyards are spatially variable and that this variability can be understood in terms of the underlying characteristics of the land (soils, topography) supporting the vineyard. Selectively harvesting blocks in response to such variability may be highly profitable. While it has also been shown that crop maturation is spatially variable, there may also be temporal variations in the rate of maturation. Integrating knowledge of how spatial variation in fruit composition may be moderated in time has not previously been attempted and is the key objective in this work. Methods and Results: We used a proximal sensor to map vine vigour at high spatial resolution in a 5.9‐ha Marlborough vineyard planted with Sauvignon Blanc. Vigour measurements were also related to fruit‐soluble solids (SS), titratable acidity (TA) and pH – key indices of crop maturity. Knowledge of crop phenology and maturation was used to predict how these indices changed with time. The pooled opinions of over 50 Marlborough winemakers on the optimum juice SS, pH and TA at harvest to produce a ‘typical Marlborough Sauvignon Blanc’ were used to develop a juice index (JI), which in turn was mapped in space and time at the study site. The JI showed marked spatial and temporal variation. Conclusions: In addition to being spatially variable, grape quality in vineyards also changed with time. Thus, the optimisation of decisions about harvest timing requires knowledge of spatial variability. Conversely, strategies such as selective harvesting cannot be properly optimized without knowledge of crop phenology, the maturation of fruit and their implications for fruit quality – which are all also spatially variable. In this study, we have shown that, by integrating knowledge of crop phenology with an understanding of vineyard variability and winemaker objectives through the construction of a JI, it is possible for the optimum harvest decision to be made such that fruit destined for a particular end use are harvested at the right time and from the right place. Significance of the Study: This is the first study in which knowledge of both spatial and temporal vineyard variation has been integrated. It demonstrates that in order to be optimal, strategies such as selective harvesting need to incorporate knowledge of crop phenology rather than rely on knowledge of spatial variation alone.     

Vine vigour effects on leaf gas exchange and resource utilisation

Background and Aims: Variability in vine vigour is a commonly observed feature in vineyard blocks. Although this aspect is well recognised among viticulturalists, impacts of vigour variability on vine function and resource use efficiency are seldom considered in management decision-making. This study examined influences of vine vigour variability on vine physiological performance and resource use in a commercially managed vineyard block. Methods and Results: The vineyard block was divided into different vigour zones using plant cell density data derived from aerial multi-spectral imaging of the study block. Gas exchange and under-vine soil moisture status were measured in some of the vigour zones. Low vigour vines had consistently lower photosynthesis and stomatal conductance rates than high vigour vines. The differences were evident both during soil-drying and rewetting. Similarly, irrigation water utilisation was markedly lower in low than in high vigour vines. Vine fruit yield was linearly and positively related to vines' capacity to utilise applied water. Conclusions: Vigour has considerable influence on vine physiological performance and on resource utilisation capacity. Uniform irrigation application to a block with variable vigour (which is the norm currently) leads to spatially inefficient resource use, and consequently to a marked within-block variation in irrigation water productivity. Significance of the Study: The demonstration that variation in vigour has a corresponding effect on resource utilisation has direct relevance for managing vineyard inputs such as irrigation or fertilisers.     

Environmental effects on cv Cabernet Sauvignon (Vitis vinifera L.) grown in Hawke's Bay, New Zealand.: 1. Phenology and characterisation of viticultural environments

Six Cabernet Sauvignon vineyard sites in Hawke's Bay (New Zealand), selected out of 28 sites observed in 1996/97, were studied over three consecutive seasons in order to characterise viticultural environments of this region for this cultivar. Indices of precocity of vine phenology were used to analyse the relationship between phenology at the selected sites and vegetative growth, productivity, fruit ripening and wine sensory characteristics. Marked differences in indices of precocity existed between sites. These differences were mostly correlated with vine vegetative growth and canopy indices. There was no relationship between yield and vine phenology. Indices of precocity were correlated with certain juice constituents measured on a common date, as well as the sensory scores of wines produced by microvinification from grapes harvested on different dates and maturity levels. Vineyard sites that differed in indices of precocity also differed in their environmental characteristics, particularly in soil physical properties and water balance.     

Whole‐of‐block experimentation for evaluating a change to canopy management intended to enhance wine quality

Background and Aims: Earlier papers have shown the utility of the whole‐of‐block approach to viticultural experimentation for assessing the relative merits of different mid‐row management strategies to improve vine vigour, and ‘reduced input’ spray programs for the control of fungal disease. Here, a similar approach was used to evaluate alternative canopy management strategies as a means of improving grape and wine quality in a Shiraz vineyard in the Coonawarra region of South Australia. Methods and Results: Two different canopy management strategies were compared: the existing practice of spur pruning to 45–50 buds per vine and shoot trimming (control) in comparison to spur pruning to 35 buds per vine, shoot thinning and shoot trimming (SPST). Contrasting treatment effects, both in terms of treatment response and its spatial extent, were observed during the trial. In 2005, the SPST treatment led to a significant improvement in some fruit quality parameters and a decline in yield. In 2006, significant treatment effects were only observed for bunch weight and the number of berries per bunch. Whilst reasons for these contrasting effects could not be deduced from the available data, it was demonstrated that the inherent variability of vine vigour within the block had a greater effect than the applied treatments. Conclusions: Consistent with the other whole‐of‐block experiments described in this series, we conclude that this experimental approach offers advantages in comparison to plot‐based approaches to viticultural experimentation. The spatial information obtained in this study created a better understanding of inherent vineyard heterogeneity and the effects this has on control options for vine vigour and grape composition than would have derived from a plot‐based experiment. Significance of the Study: This study is the first application of the whole‐of‐block experimental approach to assessment of alternative canopy management options. The work provides further demonstration of the value which accrues through using spatial variability as an experimental tool.     

An assessment of rootstocks for Sunmuscat (Vitis vinifera L.): a new drying variety

Sunmuscat scions, either grafted onto one of seven rootstock, or as own-rooted vines, were grown under irrigation according to the practices of warm-climate viticulture in north-western Victoria. The trial was located within a commercial vineyard on a sandy loam soil, and represented a typical replant situation. Grapevine performance was assessed over five seasons, viz. 1999–2004 inclusive, in terms of yield per vine, berry weight, juice composition and vigour (based on trunk girth). The highest yielding rootstock over the trial period was 1103 Paulsen (28.9 kg /vine) followed by 140 Ruggeri and Ramsey (26.1 and 25.8 kg /vine respectively), S04 (22.5 kg /vine), Schwarzmann, 101-14 and Teleki 5A (19.9, 18.7 and 18.4 kg /vine respectively). Scions on their own roots returned lowest yield (15.5 kg /vine). Berry weights were largest for the three high yielding rootstocks (2.3 g) and smallest with own roots (2.0 g). Total soluble sugars in harvested fruit were largely unaffected by rootstock in most seasons, although taken over all seasons, fruit from scions grafted onto Ramsey rootstock had the lowest levels, while Teleki 5A had the highest levels (viz. 23.4^oBrix and 24.7^oBrix respectively). Comparative vigour for all seven graft combinations was inferred from trunk circumference. There was a 2-fold difference in rootstock girth below the graft union (viz. 265 mm for 1103 Paulsen, compared to 135 mm for S04), whereas differences in the scion girth above the graft union were minor (only 16%). Relative compatibility of scion and stock was inferred from 'girth ratio' of trunk circumference above compared with below the graft union. Girth ratio was highest for Sunmuscat scions grafted onto SO4 rootstock, and lowest for scions on 1103 Paulsen. Scion girth and vine yield were broadly correlated.     

Viticultural experimentation using whole blocks: evaluation of three floor management options

Background and Aims: Vineyard floor cover crops can affect vine vigour because of their requirement for soil, water and nutrients, as well as their interactions with pests and diseases. An on‐farm trial was established to identify the best floor cover management for an organically certified vineyard in the Clare Valley, South Australia, which was characterised by low vine vigour and yield. In establishing this trial, we also sought to evaluate a new approach to field experimentation in which the entire management unit is used for the experiment rather than small plots. Methods and Results: Three different floor covers were compared: the existing ryegrass cover crop with compost under the vine (control), ryegrass with mulch under the vine, and a replacement of the ryegrass with alternating mid‐rows planted to either cereal (Triticum triticosecale) or legume (Vicia faba), in both cases reverting to bare soil during summer. Spatially variable treatment differences were evident in the second and third year of the trial. The greatest benefits, in terms of enhanced yield and vine vigour, were induced by the cereal/legume treatment, although it was shown that only about half of the experimental area (i.e. only half of the entire vineyard) would have increased yields with the adoption of such a floor management strategy. Conclusions: The whole‐of‐block approach offers both researchers and vineyard managers a means of acquiring considerably more useful information than would be obtained from a conventional plot‐based experiment. In this particular vineyard, differential management with ryegrass retained in the southern part, but with the cereal/legume cover crop used in the northern part, is the ideal management practice. Significance of the Study: This study provides a novel demonstration of an approach that makes use of spatial variability as an experimental tool, and which enables experimental results to be acted upon in a way that recognises and exploits the underlying spatial variability of the vineyard.     

Influence of retained cane number and pruning time on grapevine yield components,fruit composition and vine phenology of Sauvignon Blanc vines

Background and Aims: Traditionally, the start of cane pruning is delayed until after leaf fall, when carbohydrate accumulation and cane maturity are complete. However, by starting immediately after harvest, the period for pruning may be increased by at least 4 weeks, reducing peak labour demands. Trials were conducted to investigate the consequences of various pruning times on vine phenology and yield. Methods and Results: Vines were pruned using 2‐ or 4‐canes at one of four times during the winter from shortly after harvest to just before bud break in the spring. Pruning shortly after harvest caused no significant adverse effects on vine phenology or productivity. Pruning just before bud break delayed vine development. Stored total carbohydrate concentrations in the trunk were unaffected by pruning time or cane number retained after pruning. Conclusions: Carbohydrates accumulated in the trunks of grapevines to adequate levels by harvest and any post‐harvest photosynthesis and/or cane maturation that may be occurring at this time had little effect on subsequent vine growth and development. Pruning shortly before bud break delayed bud break and may be an advantage where vines are at risk to spring frosts. Significance of Study: In cool climates where leaves senesce shortly after harvest, pruning immediately after harvest will have no adverse effects on subsequent vine phenology or yield, but will extend the period available to prune the vines, reducing the peak labour demand in the vineyard. Pruning late, slightly delays bud break potentially providing greater tolerance to late spring frosts.     

Mapping grapevine vigour,topographic changes and lateral variation in soils

Direct mapping of variability in soils can be a complex, time-consuming and costly process. Consequently, maps of geophysical data such as ground penetrating radar (GPR) and electromagnetic induction (EMI) are commonly used as proxies for soil maps, and these geophysical maps are most useful if they relate to variations in plant attributes such as grapevine trunk circumference. This article demonstrates that vine trunk circumference in five pinot noir vineyards is primarily influenced by changes in slope, elevation and aspect. Variability in GPR maps shows mixed correlations with vine trunk circumference data. In contrast, multi-frequency EMI surveys yield soil apparent electrical conductivity data that commonly show significant correlations with variations in vine trunk circumference data, especially when coupled with global positioning system surveys, suggesting that this is the preferred geophysical tool for mapping variability in soils.     

Variation in vine vigour,grape yield and vineyard soils and topography as indicators of variation in the chemical composition of grapes,wine and wine sensory attributes

Background and Aims: Vineyard variability makes satisfaction of winemaker demands for uniform parcels of fruit that are suitable for particular product streams difficult. Indeed, it may not be possible to satisfy these demands without being able to adequately characterise differences between wines derived from different fruit parcels or different areas of the same vineyard, understanding how final wines are affected by management decisions implemented in the vineyard, and/or understanding the effects of variation in the vineyard's biophysical characteristics (e.g. soil, topography) on grape and wine composition. This work sought to identify and examine relationships between the chemical and sensory attributes of wines derived from different parts of the same block and the biophysical characteristics of these different vineyard areas. Methods and Results: Remote sensing of vine vigour, yield mapping and EM38 soil survey were used to identify zones of contrasting vineyard performance in a Cabernet Sauvignon vineyard in the Murray Valley region. Small‐lot wines were made from fruit sourced from these zones. Both sensory and chemical analysis (solid phase microextraction‐gas chromatography‐mass spectrometry) of these wines demonstrated them to be different. Likewise, soil properties and indices of vine nutrition differed between the zones. Conclusions: This work suggests that it is possible for robust relationships to be established between specific (manageable) biophysical attributes of the place where grapes are grown and the sensory and chemical characteristics of the wines derived from them. It also supports the view that terroir is spatially variable at the within‐vineyard scale. Significance of the Study: The work provides a foundation for further research aimed at establishing how specific sensory and/or chemical properties in wines might be modified through targeted management interventions in the vineyard.     

Considerations on spatial crop load mapping

Crop load, the ratio of vine size to mass of fruit harvested, is fundamental to viticulture. Measuring vine size and crop yield, the components of crop load, has historically been a labour intensive exercise that has limited the use of crop load information to improve management in vineyards. Recent advances in assessing vine vigour, size and yield using geo‐referenced sensors are starting to make high resolution crop load mapping possible. In this paper, the concept of crop load is revisited with an emphasis on how vine size and yield can be mapped in vineyards. Existing literature is reviewed on how vine size and yield vary spatially and temporally within vineyard blocks and the inference this has on the spatio‐temporal variability of crop load. An example of crop load mapping using sensor technology is presented to illustrate recent advances in sensor technology in viticulture. Finally, some emerging technology and knowledge gaps for implementing spatial crop load information into vineyard management are discussed.     

Effects of novel hybrid and traditional rootstocks on vigour and yield components of Shiraz grapevines

Background and Aims:  The influence of grapevine rootstocks on vine vigour and crop yield is recognized as an integral part of viticultural management. However, the genetic potential of Vitis species rootstock hybrids for vigour and yield control is not fully exploited in Australian viticulture. The effect of 55 novel inter- and intra-species hybrids and five traditional hybrid rootstock cultivars on winter pruning weight, berry size and fruit yield of grafted Shiraz vines is presented. The genetic predictions that resulted from this analysis were used to illustrate how rootstocks that best perform for a combination of traits may be selected.
Methods and Results:  The use of linear mixed models and residual maximum likelihood procedures took into account repeated measures and spatial variation within a large field trial (720 vines). Over 6 years of assessment, variation of up to 93.9% in winter pruning weight, 81.9% in fruit yield and 21.0% in berry weight between rootstocks was estimated.
Conclusions:  The effect of rootstock genotype accounted for marked differences in conferred pruning weight, berry weight and fruit yield from trial averages. Comparison of statistical analysis techniques illustrated that the choice of such techniques may influence the outcome of genetic selection from field trial data.
Significance of the Study:  Such quantification of the variation between vines in vigour, fruit yield and berry size due to rootstock genotype provides a framework for selection of well-performing genotypes for inclusion in advanced generations of the CSIRO vine rootstock breeding program.     

Delayed winter spur-pruning in New Zealand can alter yield components of Merlot grapevines

The effects of delayed winter spur-pruning on yield, yield components and fruit composition of Merlot vines was evaluated within a commercial vineyard in Marlborough, New Zealand. Vines were spur-pruned, trained using vertical shoot positioning, trickle irrigated and grafted to Kober 5BB rootstock. Delaying pruning from July (usual winter pruning time in New Zealand) until up to October (when apical shoots on canes were 5 cm long) resulted in yield increases of up to 93%, 63%, and 82% over the three seasons of experimentation. These yield increases reflected higher average berry weight and in turn bunch weights. The increase in average berry weight was associated with a change in the relative abundance of different berry types. Later pruning increased the proportion of large seeded berries while the proportion of smaller seedless berries and live green ovaries (shot berries) decreased. The delayed pruning may have enhanced fertilisation of flowers and development of seeds by postponing flowering to a time when climatic conditions are more favourable; measurements of shoot lengths support this proposal. By delaying winter pruning until after budburst the development of basal nodes was inhibited, so that budburst on the resulting spurs was also delayed.     

Fungi and mycotoxins in vineyards and grape products

Many fungi may occur on grapes during growth in the vineyard, but the main concern from the viewpoint of mycotoxin contamination is the black Aspergilli, Aspergillus carbonarius and A. niger. These fungi are capable of producing ochratoxin A (OA) which may contaminate grapes and grape products such as wine, grape juice and dried vine fruit. Understanding the ecology and physiology of the black Aspergilli can provide tools for management of OA at all stages of grape production and processing. In the vineyard, careful management of cultivation, irrigation and pruning can assist in minimising the levels of black Aspergilli in the soil, which in turn, can minimise contamination of grapes by these fungi. Minimising damage to grapes on the vine by the use of open vine canopies, grape varieties with resistance to rain damage and by the management of insect pests and fungal diseases (e.g., mildew, Botrytis bunch rot) can reduce the incidence of Aspergillus rot in mature berries. The risk of OA in table grapes can be minimised by careful visual inspection to avoid damaged and discoloured berries. In wine, harvesting grapes with minimal damage, rapid processing and good sanitation practices in the winery assist in minimising OA. During vinification, pressing of grapes, and clarification steps which remove grape solids, grape proteins and spent yeast can also remove a significant proportion of OA. For dried vine fruit production, avoiding berry damage, rapid drying, and final cleaning and sorting to remove dark berries can reduce overall OA levels in finished products.     

Factors influencing grapevine vigour and the potential for control with partial rootzone drying

Maintaining the most cost-effective balance between vegetative and reproductive growth is one of the most testing problems in modern viticulture. Grapevines which exhibit excessive vegetative vigour are likely to produce less fruit of reduced quality, and vines with inadequate vigour may be compromised in terms of their yield potential. The requirement for techniques to better manage excess vigour has become more acute in recent years with the increased use of irrigation, adoption of vigour-imparting rootstocks and the expansion of vineyards into cooler geographic regions. A number of strategies may be used to control vine vigour. Chemical growth regulators, although capable of reducing shoot vigour, have never received acceptance due to undesirable side effects and concerns over chemical residues. Devigorating rootstocks, likewise, may have the potential to control vigour but none are in wide commercial use. Restriction of the effective root volume, achieved through manipulation of planting densities, competition by cover crops, regulation of the soil volume wetted by drip irrigation or regulation of water availability can all achieve a degree of devigoration but often at the expense of fruit yield. Manipulation of vines through pruning and trellis design are probably the most commonly used methods for the control of shoot vigour. A high number of nodes retained at pruning combined with trellises which allow open canopies have proved successful. Advances in the understanding of the physiological factors influencing shoot growth and transpiration have allowed the development of novel irrigation methods for the control of vine vigour. These techniques exploit the fact that chemical signals originating in the roots are primarily responsible for the control of shoot growth and transpiration. Stimulation of the production of these signals through partial drying of the root system results in a significant reduction in shoot growth and water-use while maintaining crop yield and improving fruit quality. These new techniques, in combination with appropriate pruning and trellising methods, are providing new viticultural tools for controlling vine vigour and water-use efficiency.     

Effect of vine age on vine performance of Shiraz in the Barossa Valley,Australia

Background and Aims

Old vineyards are often suggested to be superior to younger ones, a claim that has scarcely been investigated scientifically. The aim of this study was to investigate if vineyard age influences vine performance.

Methods and Results

Five commercial Shiraz vineyards in the Barossa Valley, SA, were selected; each site contained younger vines, which had been vegetatively propagated from older vines on the same site. Measurements of vegetative growth and reproductive development were obtained over three seasons. Results show that the effect of vine age is difficult to measure and separate from seasonal and site interactions. Vine age was strongly correlated with trunk circumference. Vines aged 49 years showed more similarities with older vines (93–168 years old) than with younger vines (6–28 years old).

Conclusions

Vine age had an impact on grapevine reproductive performance. Older vines produced a yield greater than that of younger vines. Greater vine size, measured by increase in trunk circumference over time, may be a key determining factor in increased reproductive capacity.

Significance of the Study

Vine age is commonly attributed to superior vine performance, as a precursor to fruit and wine quality. Our findings suggest that increasing vine age had a positive effect on reproductive performance in terms of yield, contrary to popular belief. This establishes a starting point for future studies that are underway to quantify if these findings have an effect on fruit and wine composition and sensory attributes.     

Airborne high‐resolution images for grape classification: changes in correlation between technological and late maturity in a Sangiovese vineyard in Central Italy

Background and Aims: The goal of this study was to investigate the relationships between NDVI values at different phenological stages and measurements of grape parameters at two different harvest dates. Methods and Results: The research was done on a Sangiovese vineyard in Central Italy. Over four seasons, airborne NDVI measurements acquired between June and August were related to grape parameters (yield per vine, pH, °Brix, anthocyanins and polyphenols) at technological harvest (H1) and two weeks later (H2). Correlations were higher at H1 and decreased at H2 with a different rate depending on the parameter. °Brix and pH correlations showed a moderate rate of variation between H1 and H2; bigger differences and a different inter‐annual dynamic were observed in anthocyanins and polyphenols between H1 and H2. Conclusions: The ability of NDVI to discriminate different grape classes was confirmed, but its efficacy substantially varies depending on the harvest date. These results suggest the existence, within the same vineyard, of different grape populations having specific timing and shape of ripening curve; as a consequence, distinct vigour zones of the vineyard show a different evolution of the content of grape parameters between the two harvests thus influencing the degree of correlation between grape quality and NDVI measurements. Significance of the Study: This is the first study in which harvest date has been considered for its influence on the predictive skill of RS. It therefore highlights not only the importance of spatial variation within the single vineyard, but also the importance of ripening dynamics.     

Influence of fruit ripeness and juice chaptalisation on the sensory properties and degree of typicality expressed by Sauvignon Blanc wines from Marlborough,New Zealand

Background and Aims: Interest in the typical sensory properties exhibited by Sauvignon Blanc wines from Marlborough, New Zealand, is increasing. Although critical from a winemaking standpoint, there is a significant lack of data concerning the extent to which these typical sensory characteristics are affected by fruit ripeness at harvest and juice chaptalisation. Methods and Results: Experimental Marlborough Sauvignon Blanc wines fermented from fruits at three different ripeness stages, with or without juice chaptalisation, were assessed by a panel of wine professionals from Marlborough. Results suggest that the balance between green and fruity ripe flavours that makes a Marlborough Sauvignon Blanc typical of its style would originate from the fruit ripeness at harvest. We also report that juice chaptalisation can modulate the wines' taste and mouthfeel properties and significantly affect their typicality as Marlborough Sauvignon Blanc. Conclusions: The production of Marlborough Sauvignon Blanc wines that well represent their specific style relies primarily on the ripeness of the fruit at harvest, the impact of which can be modulated by juice chaptalisation. Significance of the Study: This is the only study that has considered fruit ripeness and juice chaptalisation as two factors that condition the sensory properties and degree of typicality expressed by Marlborough Sauvignon Blanc wines.     

Rootstock effects on salt tolerance of irrigated field-grown grapevines (Vitis vinifera L. cv. Sultana) 2. Ion concentrations in leaves and juice

Field vines of cv. Sultana, grown either on their own roots, or grafted to a range of rootstocks, were drip‐irrigated at three salinity levels (0.40, 1.75 and 3.50 dS/m) over a five‐year period. Rootstocks comprised Ramsey, 1103 Paulsen, J17‐69 and 4 hybrids (designated R1, R2, R3 and R4) derived from parentage involving Vitis champini, V. berlandieri and V. vinifera. Concentrations of Cl^‐, Na+, K+, Ca²⁺ and Mg²⁺ were measured in petioles at flowering, and in laminae and grape juice at harvest, in each year of the trial. Vines on all rootstocks accumulated less chloride in either petioles at flowering or in laminae and juice at harvest compared with vines on own roots at all salinity treatments. By inference, all rootstocks behaved as chloride excluders relative to the roots of own‐rooted vines. 1103 Paulsen was the best chloride excluder based on lowest concentrations of accumulated Cl^‐ in petioles, laminae and grape juice at high salinity. Sultana on R3 rootstock at high salinity accumulated more Na+ in both laminae and grape juice (at harvest) than did Sultana on own roots or on any of the other rootstocks. Laminae K+ at harvest time was reduced at high salinity in Sultana on own roots and on all rootstocks. Concentrations of both Cl^‐ and Na+ in petioles at flowering and in laminae and grape juice at harvest showed no significant correlation with either yield (as kg of fresh grapes per vine) or vigour (as measured by fresh weight of one‐year‐old pruning wood per vine) for any salinity treatment. There was however, a strong positive correlation between yield and the subsequent weight of one‐year‐old pruning wood for all salinity treatments. There was also a negative correlation between Na+ concentrations in petioles at flowering and the subsequent weight of one year‐old‐pruning wood from the 0.40 dS/m treatment. Similar negative correlations were found between Na+ concentration in both laminae and grape juice at harvest time, and the subsequent weight of one‐year‐old pruning wood from the 0.40 dS/m treatment (but not from either the 1.75 or 3.50 dS/m treatments). Based on these findings and those from Walker et al. 2002a we conclude that a high innate vigour of a rootstock combined with moderate to high chloride and sodium exclusion ability represents the best combination for salt tolerance in Sultana grapevines as measured by yield at moderate to high salinity.     

Identification and significance of sources of spatial variation in grapevine water status

Background and Aims: Water stress in grapevines is directly linked to grape quality. Differential vine water management should therefore be strongly linked to the water stress in the vine. To do this, an understanding of the dominant drivers and indicators of vine water status are needed from a sub-block to whole vineyard level. This understanding will help generate effective vine water status models for variable rate irrigation systems. Methods and Results: A vineyard in the south of France was sampled for pre-dawn leaf water potential (Ψ_PD) at several dates during the growing season for two consecutive years. Sampling was stratified by soil types and relative within-block vegetative expression. A recursive partitioning analysis identified that cultivar had a dominant effect at low water stress, while vegetative expression and then soil unit effects became dominant as water restriction increased. Variance in Ψ_PD was calculated at difference scales (plant, site, block and vineyard) and Smith's heterogeneity law was used to evaluate the scalar nature of Ψ_PD variance. Spatial heterogeneity increased as the season and water restriction increased. Conclusion: Variance in Ψ_PD changed temporally through a season and the dominant drivers/indicators also changed. The opportunity to spatially manage water stress (irrigation) increased as water restriction increased. Significance of the Study: Managing vine water stress helps optimise production and a Ψ_PD model would be a useful addition to a viticulture decision support system. This study identified how the variance in Ψ_PD evolved during a season and the best ancillary indicators of Ψ_PD for spatial and temporal modelling.     

Effects of site, season and viticultural practices on grape seed development

The effects of vineyard site, season, clone and viticultural management practices were examined as possible sources of variability in seed development between populations of grape berries, cvs Traminer, Riesling and Pinot Noir. Mean values for number and weight of seeds per berry were similar in most seasons and sites, but some were significantly different. In some but not all cases, smaller means for seed number per berry were associated with larger mean weight per seed. Trellising, training, pruning level, canopy manipulation and regulation of bunch number per vine had little effect on seed complement per berry except that mean weight per seed was smaller with minimal pruning. Reduction in water supply imposed after flowering did not alter seed number but reduced seed weight. Berries of boron-deficient vines had fewer and smaller seeds. The implications of seed development for berry development are discussed.