Australian Journal of Grape and Wine Research最新文献

Background and Aims. High temperatures during grape ripening have a negative effect on the winemaking characteristics of musts. The crop forcing technique delays ripening to a period when temperatures are lower. The objective of this study is to provide information to winemakers and grape growers on how the delay in ripening caused by crop forcing can affect berry performance. Methods and Results. This study of 3 growing seasons (2017–2019) analyzes the effect of this technique in a vineyard of the Vitis vinifera L. cv. Tempranillo in Extremadura, together with two irrigation strategies. The grapevines were forced 4 and 22 days after anthesis (F1 and F2, respectively), compared to a treatment without crop forcing techniques (NF). Each treatment was subjected to two irrigation strategies: to cover the water needs of the plants (C) and deficit irrigation during preveraison (RI). Crop forcing delayed the harvest between 32 and 56 days on average in relation to NF. Crop forcing and irrigation strategy modified berry composition at harvest: C-F1 and C-F2 had higher total polyphenol and anthocyanin concentrations, total acidity, malic acid content, and lower pH relative to C-NF; RI-NF increased total anthocyanin concentration and pH and decreased titratable acidity value. Conclusions. Crop forcing is able to delay grape ripening to lower temperature periods. This is a promising technique for restoring the coupling between phenolic and technological ripeness. The combination of both crop forcing and deficit irrigation strategy maintains the berry quality while improving water use efficiency. Significance of the Study. The present work shows how the “crop-forcing” technique is effective in modifying the relationship between different parameters that determine the characteristics of berries throughout ripening as a raw material for winemaking, compared to vines with traditional winter pruning, under different irrigation strategies.

To the memory of Jordi Marsal

Authentication of grapevine cultivars, Vitis vinifera L., is difficult, especially when analytical specimens lack diagnostic ampelographic characters, which prevents the verification of traceability systems aimed at guaranteeing varietal integrity. This issue is problematic when viticultural strategies and regulations associated with high-value wine-producing geographical areas rely on extensive control and monitoring of valuable cultivars. Varietal identification based on grapevine molecular markers is a standardized methodology that requires a specialised laboratory for its application. In contrast, the use of loop-mediated isothermal amplification (LAMP) allows DNA markers to be characterized quickly and easily, without the need for skilled personnel, allowing implementation in-situ or in-the-field. Simultaneous identification of the chlorotype and the interrogation of a single SNP using a portable device have allowed the first discrimination in-the-field of grafted grapevines, without appreciable ampelographic characters, as belonging to the valuable “Albariño” cultivar. This methodology constitutes a valuable tool for cultivar discrimination and can be efficiently implemented in the traceability of valuable grapevine genetic resources.

Background and Aims. An OIV resolution provides guidelines on using glutathione as a prefermentation additive when the amount of yeast assimilable nitrogen (YAN) of a juice or must is adequate, to avoid the metabolism of glutathione by the yeast. The effect of YAN concentration on glutathione metabolism by yeast had not been determined. This study explored whether nitrogen management could be used to control glutathione consumption during fermentation. Methods and Results. An HPLC-UV method was developed to quantify reduced L-glutathione (GSH) and oxidised glutathione (GSSG) and used to monitor yeast GSH metabolism during alcoholic fermentation with two yeast strains (AWRI 1688 and AWRI 2861). The addition of GSH had no impact on the fermentation rate of the chemically defined medium, even in a limited YAN environment; however, a decrease in glutathione concentration occurred regardless of YAN concentration. The effect of GSH on volatile sulfur compound formation was yeast strain-dependent. Conclusions. Increasing the YAN status of a chemically defined medium led to a decrease in GSH consumption during fermentation, but the loss of GSH could not be prevented entirely, even with a low initial GSH concentration and high initial YAN. Significance of the Study. In the presence of higher concentrations of GSH during fermentation, there is a risk of forming undesirable fermentative sulfur compounds that are not mitigated through nitrogen supplementation. Thus, it seems unlikely that an argument could be made for the inclusion of GSH in relevant food standards codes as a wine additive especially if a lack of GSH metabolism was a criterion.

Consumers are more and more oriented towards the purchase of safer food and beverages, which is pushing the wine sector to find alternatives to the use of sulfur dioxide. Ozone (O₃) is already applied in the wine industry to produce sulfur dioxide-free wines through the patented method Purovino®. The aim of this two-year study was that of evaluating whether the postharvest treatment of grapes with ozone affects volatile organic compounds (VOCs) and polyphenol profile in berries, and in turn, wine composition. Grape bunches (Vitis vinifera L.) of cv Sangiovese were fumigated overnight with gaseous ozone (max 20 g·h⁻¹ with 6% w.w⁻¹ of ozone) in a cold room at 4°C (±0.5). After treatment, grapes were processed into wine. In grapes, ozone treatments increased total polyphenol and flavonoid content and upregulated specific genes (phenylalanine ammonia lyase, VvPAL, flavanol synthase 1, and VvFLS1) involved in polyphenol biosynthesis. Wine obtained from ozone-treated grapes had higher flavanol content than the control. Fumigation only slightly affected the different VOC classes of grapes and wine, including aroma compounds derived from the lipoxygenase (LOX) pathway. Although a season-dependent effect was observed, results showed that postharvest ozone treatments applied to avoid the use of sulfur dioxide introduced limited but, in general, positive modifications to grape and wine composition. This information provides assurance to winemakers that the maintenance of wine quality and typicity will be guaranteed when using ozone treatments.

Background and Aims. In ancient grapevine varieties, the experimental design of field trials is crucial to providing a reliable evaluation of quantitative traits. The main purposes of this study are to demonstrate the benefits of the resolvable row-column design (RCD) for quantifying intravarietal variability and performing polyclonal selection and to compare the efficiency of fully and partially replicated designs for quantifying intravarietal variability to implement the latter designs for a preliminary analysis of that variability. Methods and Results. Linear mixed models were fitted to yield data obtained in field trials with fully and partially replicated designs. The results pointed out the importance of the RCD in controlling the spatial variability present in large field trials. Although less precise, a partially replicated design proved to be useful in evaluating intravarietal variability when the average of years was used. Conclusions. The results reinforced the importance of the RCD in increasing the efficiency of intravarietal variability quantification and polyclonal selection. The partially replicated design proved to be useful when the only objective was to perform a preliminary analysis of intravarietal variability. Significance of the Study. Understanding the role of experimental design in grapevine selection field trials will help grapevine breeders enhance their knowledge about variability within ancient varieties and implement more successful polyclonal selection.

Background and Aims. Grapevine is susceptible to several diseases and requires a large use of fungicides. Sustainable alternatives must be safe for humans and the environment and also should not interfere with must fermentation. The aim of this study was to implement the use of a rare sugar, tagatose, against powdery mildew and downy mildew and to assess possible side effects on Saccharomyces cerevisiae fermentation. Methods and Results. Tagatose was evaluated for the suppression of powdery mildew and downy mildew under controlled and field conditions and for its impact on S. cerevisiae fermentation of synthetic and grape musts. Tagatose applied at 8 kg/hareduced powdery mildew and downy mildew severity and incidence on grapevine leaves and bunches under field conditions. Tagatose caused a limited and transient slowdown of the fermentation with no negative impact on yeast viability and wine chemical composition at the end of the fermentation. Conclusions. Tagatose is a promising alternative for sustainable grapevine protection against powdery mildew and downy mildew with no negative impacts on the must fermentation. Significance of the Study. These findings pave the way for grapevine protection strategies based on the use of rare sugars as sustainable fungicides in integration with other plant protection products.

Background and Aims. Vitis vinifera L. is a major global horticulture crop which holds historical connections contributing to the development of human culture. The main objective of the study was to explore the genetic diversity and structure of grapes curated at the germplasm bank of Aragón and link them to cultivar utilization, putative geographic origin, and historical events. Methods and Results. The genetic diversity of the 411 accessions of the Grapevine Germplasm Bank was assessed using 26 SSR markers. SSR markers VVIP31, VMC4F3-1, VVIV67, and VVS2 distinguished the 156 nonredundant genotypes found in the collection. The profiles were compared to the El Encin database, and 105 were identified as known cultivars, of which 93 were Spanish, 12 were from other European origins, and 51 others were not known. The 51 profiles, as they were all collected in Spain, were designated as Spanish unknown for further analysis. To establish a comparative study for principal coordinate analysis (PCoA) and structure, we kept 113 identified genotypes from this collection but added 61 representative genotypes with diverse European and oriental origins. Bayesian analysis and PCoA showed four distinct groups of grape cultivars: (1) traditional Spanish wine grape from Aragón or cultivated along the Ebro River, (2) Spanish wine grape, (3) Spanish and oriental table grape, and (4) Italian, Portuguese, French, and German-Slovenian wine grape varieties. Conclusions. The 51 unknown Spanish genotypes were not registered yet in any European commercial list and are of special interest. These genotypes could be ancient cultivars adapted to local climatic and environmental conditions and probably resilient to face the new conditions derived from climate change.

Background and Aims. The cultivation of grapevines in England is expected to benefit under climate change. Yet assessments of future wine climates remain undeveloped. Accordingly, this study assesses how climate change might modify frost risk for Chardonnay in the Southeast England viticulture region. Methods and Results. Cold-bias-corrected climate projections from the UKCP18 Regional (12 km) perturbed parameter ensemble (PPE) climate model under RCP8.5 are applied with phenological models to determine how frost risk and the timing of key grapevine phenophases might alter under climate change. Notwithstanding the uncertainties associated with projections of key viticulture-related bioclimate variables, the last spring frost was found to advance at a greater rate than budburst, indicating a general decrease in frost risk. Conclusions. Although projections point to an improving climate for viticulture across Southeast England, frost will remain a risk for viticulture, albeit at a reduced level compared to the present. Furthermore, the strong cold-bias found for temperature simulations used in this study needs to be given careful consideration when using the UKCP18 projections for viticulture impact assessments of climate change. Significance of the Study. This study highlights the present sensitivity of viticulture to climate variability and the inherent uncertainty associated with making future projections of wine climate under climate change.

Background and Aims. Cofermentation and blending are traditional winemaking practices. This study reports their comparative chemical and sensory outcomes. Methods and Results. Malbec and Merlot were made into monovarietal wines, cofermented (COF), blended postalcoholic (PAF), and postmalolactic fermentation (PMLF), at a 50/50 proportion. Wines were followed up to 3 years of bottle aging. Tannins were 50% higher in monovarietal Merlot wines, which improved production of large polymeric pigments in Merlot-based cofermented and blended wines. Addition of Malbec favored production of small polymeric pigments. After 3 years of bottle aging, polymeric pigments were higher in cofermented and blended wines. PMLF blended wines showed 15% improved copigmentation and 25% increase in wine colour. The perception of wine length was positively correlated with red fruit aroma (R² = 0.94 and p = 0.006) and negatively correlated with earthy aroma (R² = 0.91 and p = 0.012). Conclusions. Blending postalcoholic fermentation highlighted more of the individual character of each monovarietal wine in the final blend. Cofermentation and postmalolactic fermentation blending tended to equalize the sensory profile of the resulting wines but also showed higher complexity of aromas than monovarietal wines. Significance of the Study. Cofermentation and blending are both suitable winemaking practices for increasing the polymeric pigment content and the sensory complexity of the resulting wines.