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Background and Aim: Reduced rainfall during vine dormancy and supplementary irrigation during winter or at spring impact on vine growth partitioning. We assess the implications that induced changes on canopy growth due to soil moisture availability in spring have on fruit and wine composition. Methods and Results: Irrigation strategies were assessed in a vineyard where winter rainfall was excluded and irrigation was applied during winter or at spring during three seasons. Reduced soil moisture in spring increased canopy porosity from flowering and increased the concentration of phenolic substances in the fruit and wine. Colour, aroma intensity and fruit attributes typical of Barossa Shiraz wines were enhanced under more open canopies. When soil moisture was restored in spring by natural rainfall or by supplementary irrigation, vines developed denser canopies and phenolic substances were reduced in the fruit and wines. Irrigation at spring following a dry winter altered wine style and was associated with some negative attributes. Conclusions: Smaller canopies due to reduced water availability at spring improved fruit and wine composition at the expense of yield. Irrigation in spring following a dry winter promoted canopy growth over yield, and impacted negatively on fruit and wine composition. Significance of the Study: These results stress the importance that soil water availability in spring has on defining wine style, and establishes a framework for the adoption of irrigation strategies that may maintain regional style in a context of a changing climate. These responses can be expected in regions with a Mediterranean climate experiencing a reduction in winter rainfall. [ABSTRACT FROM AUTHOR]

Background and Aims: Declining autumn and winter rainfall increasingly limits soil moisture availability at the onset of the growing season in southern Australia. We studied the consequences of reduced rainfall during dormancy on vine growth, and explored irrigation strategies to maintain yield following dry winters. Methods and Results: The effect of the timing and method of irrigation during dormancy on vine performance was investigated for three seasons in a Shiraz vineyard where late autumn and winter rainfall was excluded using shelters. Reduced soil moisture in spring delayed the time of budburst. A reduction in rain to approximately one third of the historical average reduced yield (24–42%) and canopy size (16–31%). Natural rain (Control) or equivalent sprinkler irrigation, providing water during winter, resulted in a higher yield: pruning mass ratio, but reduction in yield was still observed when drip irrigation was used to replace winter rain. Refilling the soil profile in spring after dry winters favoured growth partitioning towards canopy and roots, increased carbohydrate reserves in the trunk, but reduced yield (−10 to −32%). Conclusions: Irrigation during winter did not fully offset the decline in production. Refilling the soil profile at the end of winter increased vigour, and reduced yield. Reduced soil moisture prior to spring delayed the time of budburst. Significance of the Study: Vineyard management aiming to sustain yield under a changing climate will need to incorporate winter irrigation. Models predicting the time of budburst under a changing environment could be fine‐tuned by incorporating soil moisture availability. [ABSTRACT FROM AUTHOR]

Background and Aims Interactions are the main causes of complexity in field experiments; however, no studies have combined water and temperature regimes in field-growing vines. Here we assessed grape and wine attributes from a field trial where these factors were directly manipulated. Methods and Results The experiment consisted of Shiraz vines grown in a 22 factorial experiment with two temperature (control and heated) and two water regimes (deficit and irrigated) during two seasons (2010/11 and 2011/12). The sensory and compositional characteristics of grapes and wines were assessed in both seasons, whereas a detailed profile of the phenolic substances was determined by spectrophotometry in 2011/12. We found additive effects (i.e. lack of interaction) between temperature and water for berry mass and components, fruit composition (titratable acidity and pH), grape phenolic substances (12.5% ethanol-extracted and most of the 70% acetone-extracted), wine phenolic substances (chemical age 2), and wine sensory traits (floral aromas and berry flavours). Significantly, previously unrecorded interactions between temperature and water were found for grape phenolic substances (70% acetone-extracted skin and seed tannins and total phenolic substances per berry), wine phenolic substances (colour density, tannins and phenolic substances) and wine sensory traits (floral aromas, cooked fruit flavours and tannin structure). Conclusion The effect of water deficit leading to colourful and flavoursome wines rich in phenolic substances may not be held under high temperature. Significance of the Study Our study anticipates the drier and hotter climate of the Barossa Valley, and provides industry with indications of a shift in wine profiles that would require technological innovation to maintain the identity of Barossa Shiraz. [ABSTRACT FROM AUTHOR]

The grapevine is an economically important crop and a model species of long-lived perennials widely used in bioclimatic studies. Ambient temperature modulates berry composition, hence the significant research effort in establishing links between temperature, berry composition and wine attributes. Our current understanding of the effect of temperature on berries and wines has been largely gained from indirect methods or direct methods in controlled conditions. Indirect methods include comparisons of thermally contrasting locations and vintages; this approach is of value but is bound to be inconclusive as the effect of temperature is often confounded with other weather and climate factors (solar radiation, vapour pressure deficit and rainfall), management practices and soils. Direct experimental methods comparing fruit grown at a range of temperature are required to prove cause-and-effect, but attempts to modify the thermal regime of the plant often generate secondary effects. Experimental artefacts in controlled environments often include small soil volume, lack of wind and altered radiation regimes, with direct implications for plant physiology and berry composition. Experiments involving controlled temperature in vineyards aim at a higher degree of realism, but are constrained by cost, issues of scale in space and time, and are not necessarily free from artefacts. Indirect and direct methods are of course non-mutually exclusive but complementary. This review critically assesses the methods used to elucidate the effect of temperature on grape berry composition. It emphasises the limitations of studies where confounded effects are overlooked. With the focus on selected berry traits (total soluble solids, total and titratable acidity and anthocyanins), we analyse the dominant effect of temperature and highlight discrepancies and agreements between indirect and direct research methods. [ABSTRACT FROM AUTHOR]

Background and Aim Berry water loss at late stages of ripening is a cultivar dependent-trait correlated with mesocarp cell death. We tested the hypothesis that elevated temperature anticipates the onset and increases the rate of mesocarp cell death. The implications of these putative effects on the time course of berry shrivel were also investigated. Methods and Results We assessed the progression of mesocarp cell vitality and the degree of shrivelling in berries from a factorial field experiment combining two thermal regimes (elevated temperature and control) and two cultivars ( Shiraz and Chardonnay). A bilinear model was used to objectively discriminate the onset of cell death and to quantify the rates of cell death before and after the inflection point in chronological and thermal scales. Elevated temperature advanced the onset of mesocarp cell death of berries and increased the rate of cell death in the period onset-harvest for both cultivars. There was a close correlation between the proportion of living tissue and shrivel for Shiraz, but no shrivel was observed in Chardonnay despite significant mesocarp cell death. Conclusion Elevated temperature accelerated both mesocarp cell death and berry shrivelling in Shiraz and accelerated mesocarp cell death but had no impact on shrivel in Chardonnay. Mesocarp cell death seems necessary but not sufficient to explain berry shrivelling. Significance of the Study Understanding the functional links between berry shrivel and mesocarp cell death and their responses to environmental drivers would likely contribute to management practices that could reduce the severity of shrivel in a context of warmer conditions. [ABSTRACT FROM AUTHOR]

Background and Aim Thermal decoupling results from the differential effect of temperature on the many components of biological systems from molecular to ecosystem scales. We tested the hypotheses that elevated temperature decouples berry sensory traits, and that this effect is cultivar-dependent. Methods and Results We assessed 20 sensory traits in berries from a factorial field experiment combining two temperature regimes (elevated temperature and control) and four cultivars ( Cabernet Franc, Chardonnay, Semillon and Shiraz) over two thermally contrasting seasons in the Barossa Valley. The thermal response had two elements: offset, which accounts for the average advancement (or delay) across traits, and decoupling, which measures the scatter in the response of the different traits. Large decoupling was generally associated with large offset (e.g. Cabernet Franc), but large decoupling was also observed with minor offset (e.g. Semillon). Two types of decoupling were identified: decoupling mostly driven by differential response between seed and other berry components, and decoupling with a dominant variation in traits within berry parts. Conclusion Elevated temperature decoupled berry sensory traits, and this effect was cultivar- and season-dependent. Significance of the Study Awareness of the magnitude and type of decoupling would likely contribute to viticultural and winemaking adaptations in warmer regimes. [ABSTRACT FROM AUTHOR]