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Australian Journal of Grape and Wine Research provides a forum for the exchange of information about new and significant research in viticulture, oenology and related fields, and aims to promote these disciplines throughout the world.
Chief Editor Dr Stefano Poni is Professor of Viticulture at the Faculty of Agriculture, Food and Environmental Sciences at Universita Cattolica del Sacro Cuore, Piacenza. His research focuses on applied vine physiology and sustainable vineyard management in response to climate change.
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Grapes, Wines, and Changing Times: A Bibliometric Analysis of Climate Change Influence
Climatic conditions play a major role in wine production. Given the increasing impacts and risks posed by climate change, it is important to understand the effects it will have on the wine sector and different wine-producing regions worldwide. This study provides an in-depth examination of the scientific discourse on wine and climate change from 2000 to 2022 by conducting a bibliometric analysis of the literature published on the Web of Science database, which included 1,314 publications. The use of quantitative and qualitative methods allows us to investigate how research has evolved over the years. Our analysis uncovers the most productive countries, institutions, and journals leading the research in this domain, while emphasising the multifaceted approach to studying wine and climate change. Nevertheless, numerous research areas are yet to be adequately explored. Through co-citation analysis and bibliographic coupling, we identify dominant thematic clusters in previous and current scientific literature and reveal emerging research trajectories in this field. The main thematic clusters found include the assessment of climate change effects on viticultural regions worldwide, climate change’s impact on grape composition, and the impact on grape phenology. Our results can be useful not only to understand the main themes studied until now but also to orientate researchers towards less explored aspects and disciplines in scientific research.
Underpinning Terroir with Data: Integrating Vineyard Performance Metrics with Soil and Climate Data to Better Understand Within-Region Variation in Marlborough, New Zealand
Background and Aims. Previous work in Australia has demonstrated the value of data-driven approaches to terroir analysis but, like other terroir research, focussed predominantly on the natural resources (soils, topography, and climate) on which winegrowing depends. In only very few cases have metrics of production performance also been considered. In this study, focussed on the Marlborough region of New Zealand, we integrated data pertaining to vineyard performance with biophysical data (soils and climate) describing the conditions under which grapes are grown to give a more holistic indication of regional-scale variation in the terroir of the Marlborough production system. Methods and Results. Digital map layers describing variation in climate, soil properties, and the yield and harvest date of Sauvignon Blanc (Vitis vinifera L.) were assembled and analysed for similarity in their patterns of spatial variation over six vintages (2014–2019) using k-means clustering. The results suggest that the Marlborough region has a characteristically variable Sauvignon Blanc production with crop phenology and harvest date strongly influenced by variation in temperature, and yield variation impacted by soil properties. Spatial variation in seasonal rainfall did not appear to impact on vineyard performance. Importantly, the Wairau and Awatere valleys which, hitherto, have been considered together as parts of a single Marlborough region, are shown to be distinct. Conclusions. This analysis is strongly suggestive of the Marlborough terroir being variable at the within-region scale. It also lends weight to the idea that estimates of vineyard performance in some parts of the region may be used to predict performance in others. Significance of the Study. The results have potentially important implications for the management of both vineyard operations and winery logistics, for wine marketing and for whole-of-industry planning around expansion or contraction. The methods used are free of any bias introduced to many previous studies of terroir zoning through adherence to historical or geopolitical boundaries, expert opinion of wines, and other heuristics.
Effects of the Annual Nitrogen Fertilization Rate on Vine Performance and Grape Quality for Winemaking: Insights from a Meta-Analysis
Sustainability in grapevine cultivation requires the precise use of water and fertilizers, particularly nitrogen (N), to produce grapes of the highest quality for winemaking, while simultaneously avoiding harm to the surrounding waters and atmosphere by reducing NO3− losses and N2O and NH3 emissions from the vineyards. To address the challenge of optimizing N use in viticulture, many N fertilization trials have been carried out over the last decades, and a compilation and analysis of worldwide trials was therefore needed. The present study tackled this challenge through a meta-analysis of published research, which included 374 fertilization trials. From the compiled data, six vine production parameters and eight grape quality traits were extracted and normalized to enable comparisons between experiments. The Mitscherlich law of diminishing returns was able to satisfactorily describe the set of vine production parameters against nitrogen application rate, and the same occurred with the yeast assimilable nitrogen (YAN). In vines, both reproductive and vegetative growth similarly responded to the N application rate. In general, the nitrogen requirements for 95% of the maximum grape yield amounted to rates between 30 and 40 kg·N·ha−1, which increased nitrogen use efficiency (NUE) to values between 0.27 and 0.36 t·kg·N−1. Although several grape quality traits could not be described against the N rate in terms of any mathematical relationship, an N rate between 20 and 25 kg·N·ha−1 could be considered as maximizing grape quality for winemaking. Such N fertilization range increases NUE up to values between 0.41 and 0.47 t·kg·N−1, thus almost doubling the known NUE standards when grape quality is targeted instead of yield, although soil fertility could be exhausted in the mid-to-long term. Whatever the case, anthocyanins and polyphenols are well preserved in red grapes at such low N rates, although YAN is not. The results of this work will be useful for guiding new vine N nutrition research and N nutrition management in vineyards, thus increasing wine growing sustainability.
Reintroducing Autochthonous Minor Grapevine Varieties to Improve Wine Quality and Viticulture Sustainability in a Climate Change Scenario
One of the major challenges that global warming poses to viticulture is the maintenance of adequate acidity at maturity in white grapes for sparkling winemaking. This issue arises from three main occurrences: (i) with higher temperatures, degradation of malic acid is significantly enhanced; (ii) with a general advancement in grapevine phenology, grape maturity may occur under suboptimal climatic conditions; and (iii) harvesting grapes at “traditional” dates results in overripe fruits for sparkling destinations. In this biennial work, we compared the fruit and must composition of a local, widely grown white grape variety in the Colli Piacentini area (cv. Ortrugo, ORT) with those of a minor autochthonous variety, namely, Barbesino (BRB). Furthermore, we compared the composition, aromatic, and sensory profiles of wines obtained from ORT and BRB grapes picked on the same date and, in addition, of a second Barbesino wine from late harvest (BRB-LH). ORT and BRB had a similar sugar accumulation dynamic, whereas BRB exhibited a delayed loss of titratable acidity. In more details, BRB had lower malic acid degradation rates when malate concentration was <9 g/L. As a result, with comparable yield and total soluble solid content (TSS) (∼20°Brix), BRB had a higher berry titratable acidity and malic acid concentration at harvest than ORT. BRB wines showed the highest titratable acidity (TA), while ORT had the lowest TA and a higher pH, and as expected, BRB-LH had the highest pH and a lower TA than BRB although still higher than those of ORT wine. The aroma profiles of wines were mainly characterized by fermentative aromas, including esters, fatty acids, higher alcohols, and C6 compounds, and BRB-LH wines showed the highest concentration of higher alcohols, while the fermentative esters were higher in ORT wines. Panelists considered BRB significantly fresher and with bigger aroma intensity than ORT, confirming that the higher acidity detected in BRB musts is well preserved in final wines. Our work demonstrates that local minor varieties can be reconsidered in light of the new climate change-related issues impairing viticulture sustainability today. In particular, currently neglected cultivars could help preserve must acidity as compared to traditional varieties having early ripening, maintaining the links with terroir and local traditions at the same time.
Arbuscular Mycorrhizal Fungi Enhance Drought Stress Tolerance by Regulating Osmotic Balance, the Antioxidant System, and the Expression of Drought-Responsive Genes in Vitis vinifera L.
Background and Aims. Drought harms the growth and productivity of grapevines; it thus poses a major threat to the development of viticulture in the background of ongoing climate change. Arbuscular mycorrhizal fungi (AMF) can be used to enhance the resistance/tolerance of plants to environmental stress. The effects of AMF on the osmotic regulation, antioxidant substances, and expression of drought-responsive genes in the grapevine Vitis vinifera L. cv. Ecolly were studied. Methods and Results. The experiment was conducted in a greenhouse in a completely randomized block design with four treatments: AMF colonization, well-watered; non-AMF colonization, well-watered; AMF colonization with drought stress; and non-AMF colonization with drought stress. The concentration of sucrose and proline in the leaves was higher in mycorrhizal grapevine than in nonmycorrhizal grapevine under drought stress. The concentration of malonaldehyde, hydrogen peroxide, superoxide anion, and glutathione and the activity of superoxide dismutase and peroxidase activity in leaves were higher in mycorrhizal grapevine than in nonmycorrhizal grapevine under drought conditions. AMF inoculation affected the expression of drought-responsive genes. Mycorrhization upregulated the expression of VvNCED, VvP5CS, VvSIP, VvPIP1;2, and VvTIP2;1 genes under drought stress. Conclusions. AMF could reduce the harm caused by drought stress by regulating osmosis, antioxidant activities, and the expression of key drought-responsive genes and aquaporin genes. Significance of the Study. This work provides insights into the physiological and biochemical activities influenced by AMF on grapevine under drought stress.
The Role of Potent Thiols in “Empyreumatic” Flint/Struck-Match/Mineral Odours in Chardonnay Wine
Background and Aims. A wide range of Chardonnay styles exist on the market, from fruit-forward examples to wines displaying “empyreumatic” aromas such as flint, smoky, mineral, and struck-match. The thiols 2-furylmethanethiol and phenylmethanethiol have been linked to these aromas, and this study aimed to determine the contribution of these compounds to specific sensory properties in Chardonnay wines, as well as the consumer acceptance of wine displaying “empyreumatic” aromas. Methods and Results. Twenty-four Australian and New Zealand Chardonnay wines were selected for volatile analysis and quantitative sensory descriptive analysis. Consumer liking of a subset of six wines was also determined, and a further sensory study involving additions of the thiols to a base wine was conducted. Partial least squares regression showed that flint/struck-match/mineral aromas were related to 2-furylmethanethiol concentration with phenylmethanethiol less well associated. The odorant addition study confirmed that 2-furylmethanethiol directed flint/struck-match/mineral aromas and exerted strong suppression of other aromas while phenylmethanethiol played a lesser role. Consumer acceptance (n = 92) was overall lower for wines displaying high flint/struck-match/mineral aromas, although cluster analysis of the liking scores identified a sizeable consumer group (33%) who preferred wines with this attribute. Conclusions. The potent thiol 2-furylmethanethiol was indicated to be the primary contributor to flint/struck-match/mineral aromas in Chardonnay wines, with phenylmethanethiol playing a subordinate role. Significance of the Study. Increased concentration of 2-furylmethanethiol and the conferred “empyreumatic” odours should be carefully considered when producing wine styles to appeal to consumers.