The Role of Different Cultural Practices on Polyphenols Evolution During Ripening and on Wine Taste in Black and White Vitis Vinifera Varieties Under Global Warming Scenario.

The researches carried out during the PhD were focused on the effects of different cultural techniques on the phenolic compound of Vitis vinifera L., under the ongoing climate change scenario that has been causing negative effects on grape composition and sensory attributes of wines. In the first trial was evaluated the effectiveness of the delayed winter spur pruning after budburst to slow down sugar accumulation in cv. Merlot, with the aim to reduce the decoupling between technological and phenolic maturity. This technique, if applied in a particular period, resulted able to slow down sugar accumulation without negative effects on berry flavonoids and with acceptable loss of yield. Since the topic of the phenolic maturity became important in the evaluation of the effects that global warming and cultural techniques have on black berry varieties, in the second experiment were investigated the changes that occurs on berry flavonoids and in the properties of skin cell wall material during the last part of ripening in cv. Merlot. Total and extractable anthocyanins increased until harvest, as well as the affinity of cell wall material for the commercial seed tannin. This latter aspect might be correlated to the decrease of astringency during ripening. In the third experiment was investigated the role that sunlight incidence on clusters of cv. Grechetto gentile plays on grape composition and on the phenolic tastes of the resulting wines. Increased light incidence determined higher concentration of flavonols in grape and wine and that was correlated to the greater perception of astringency and bitterness of the wines. The set of results of the present PhD enhanced the knowledge on the behavior of grape flavonoids under the current global warming scenario and proposed innovative approaches in the study of the phenolic maturity

Vine Physiology, Yield Parameters and Berry Composition of Sangiovese Grape under Two Different Canopy Shapes and Irrigation Regimes

Vitis vinifera L. adapts well to a scarce availability of water in the soil. However, in recent decades, the combination of thermal stress with prolonged water scarcity could have dramatic consequences on the vine’s physiological status. In this paper, we evaluated the effects of two canopy shapes and two irrigation regimes at veraison on vine physiology, yield parameters and grape composition through biochemical and molecular approaches. The water shortage strongly influenced the physiology of Sangiovese only when the stress was moderate to severe. Neither the water stress limited to veraison nor the canopy shape were able to influence the yield parameters and sugar content, and a strong induction of the expression of the genes involved in the biosynthesis of anthocyanins was recorded only in conditions of moderate-to-severe stress. This phenomenon led to an increase in the anthocyanin content in berry skins until the end of veraison. Conversely, no significant effects occurred in terms of biochemical and molecular performance after re-watering and at harvest. Though the shape of the canopy could play a role only under elevated temperature and prolonged drought, severe water stress can affect the vine physiology and berry ripening during the veraison stag

Late trimming delays sugar accumulation in grapes

Background and Aims Climate change can alter the synchronous accumulation of sugar and other main berry compounds during ripening. The aim of this study was to determine whether post-veraison trimming could delay sugar accumulation and influence the production of anthocyanins and seed tannins in Sangiovese grapes. Methods and Results Shoots were trimmed in 2009, 2010 and 2011 when the berry total soluble solids (TSS) reached 15–17°Brix, leaving eight nodes on each main shoot. The accumulation of TSS, anthocyanins and seed tannins was measured during ripening, and yield parameters were recorded at harvest. Grapes from trimmed vines contained a lower TSS in 2009 and 2010, but there was no impact on the concentration of anthocyanins and seed tannins. In 2011, leaf area limitation was insufficient to reduce TSS accumulation, because yield constraints were observed and the leaf area/yield ratio was within the optimal range. Conclusions The lower rate of TSS accumulation in berries had no impact on the concentration of anthocyanins and seed tannins, suggesting that this approach could produce grapes with a lower TSS at harvest or delay harvest. In low-vigour vines suffering from water deficit, the post-veraison trimming repeated over the years could reduce yield, which may be responsible for the lack of TSS reduction compared with that of control vines. Significance of the Study Our study provides insight into the relationship between TSS accumulation and the production of anthocyanins and seed tannins in the berry in response to post-veraison leaf area reduction

Zeolite application and irrigation during ripening reduced berry sunburn damage and yield loss in cv. Sangiovese (Vitis vinifera L.)

Climate change poses significant challenges to the grapevine cultivation for wine production. In the last years, the occurrence of extreme weather events such as intense heat waves and prolonged period of drought increased sunburn damage with negative consequences to yield and berry composition. Short-term adaptation strategies are urgently needed to mitigate these effects. In this light, our study aimed to evaluate the efficacy of zeolite application on the canopy and irrigation during ripening on sunburn damage, yield, and berry composition in cv. Sangiovese (Vitis vinifera L.). Over 3 years (2021–2023), canopy management and irrigation treatments were arranged in a strip-plot design. Canopy management treatments included leaf removal on the cluster zone, with and without zeolite application, and no defoliated control; irrigation treatments comprised irrigation from berry softening and no irrigation. Both zeolite application and irrigation reduced sunburn damage, thus mitigating yield loss. Regarding berry composition, zeolite application did not alter the main parameters whereas irrigation led to reductions in sugar and anthocyanin concentrations. These findings suggest that zeolite application and irrigation during ripening represent promising and cost-effective solutions for grape growers facing climate change-induced challenges. However, further studies are necessary to optimize timing of irrigation to avoid detrimental effects on anthocyanin accumulation

Prediction of berry sunburn damage with machine learning: Results on grapevine (Vitis vinifera L.)

Due to climate change, heatwaves and prolonged periods of drought are more frequent and cause serious consequences to yield and berry composition of grapevine (Vitis vinifera L.). In response to this challenge, machine learning model was built to predict sunburn damages on the berries. The trial was conducted over two years (2022–2023) in a not irrigated vineyard of cv. Sangiovese, trained to vertical shoot positioning (VSP) spur pruned cordon. The vineyard was monitored from veraison to harvest with a weather station and thermocouples connected to a wireless sensor network (WSN). The evolution of the sunburn damages was visually evaluated twice a week. The damages appeared soon after veraison and the severity of the symptoms increased when heatwaves occurred. Weather station data including air temperature, solar radiation and relative humidity were analysed and used to build prediction models for sunburn damage. Ten parameters were derived from raw data to supply the prediction models of neural network (NN) and Support Vector Machine (SVM) optimised with gamma tuning. The NN achieved 90.32% accuracy in cross-validation, followed by SVM with 86.22% using radial kernel. The machine learning model was created using TensorFlow framework and it is available in the mobile phone application SHEET which will alert grape growers about the risk of sunburn damages on their orchards

Climate change and vine training systems: the influence different spatial distribution of shoots may have on sugar accumulation in Sangiovese grapevines.

The choice of training system may influence vineyard efficiency in terms of light interception and water consumption, particularly in the current context of climate change. On this basis, during the 2017 season, Sangiovese potted vines were grown outdoors using two different training systems: guyot vertical shoot positioned system (C) and V-shaped open canopy (A). From the end of June until September, vine transpiration was continuously monitored by the gravimetric approach and at different times in the season, the leaf area, light interception, photosynthetic activity and stem water potential were measured. Grape yield and fruit composition were recorded at harvest. C plants did not differ from A in terms of leaf area during the entire season. Light interception was higher in C vines during the early hours of the morning and lower in the central part of the day and the transpiration loss was higher, as was the net photosynthesis detected on some days in August. No differences were detected in terms of yield but a significant increase in soluble solids was found in C compared to A. The open canopy compared to a closed one, in a particularly hot year like 2017, resulted in negative consequences on the accumulation of soluble solids, probably as a result of the radiative stress suffered by the A vines in the middle hours of the day

Whole Plant Temperature Manipulation Affects Flavonoid Metabolism and the Transcriptome of Grapevine Berries

Among environmental factors, temperature is the one that poses serious threats to viticulture in the present and future scenarios of global climate change. In this work, we evaluated the effects on berry ripening of two thermal regimes, imposed from veraison to harvest. Potted vines were grown in two air-conditioned greenhouses with High Temperature (HT) and Low Temperature (LT) regimes characterized by 26 and 21\ub0C as average and 42 and 35\ub0C as maximum air daily temperature, respectively. We conducted analyses of the main berry compositional parameters, berry skin flavonoids and berry skin transcriptome on HT and LT berries sampled during ripening. The two thermal conditions strongly differentiated the berries. HT regime increased sugar accumulation at the beginning of ripening, but not at harvest, when HT treatment contributed to a slight total acidity reduction and pH increase. Conversely, growing temperatures greatly impacted on anthocyanin and flavonol concentrations, which resulted as strongly reduced, while no effects were found on skin tannins accumulation. Berry transcriptome was analyzed with several approaches in order to identify genes with different expression profile in berries ripened under HT or LT conditions. The analysis of whole transcriptome showed that the main differences emerging from this approach appeared to be more due to a shift in the ripening process, rather than to a strong rearrangement at transcriptional level, revealing that the LT temperature regime could delay berry ripening, at least in the early stages. Moreover, the results of the in-depth screening of genes differentially expressed in HT and LT did not highlight differences in the expression of transcripts involved in the biosynthesis of flavonoids (with the exception of PAL and STS) despite the enzymatic activities of PALs and UFGT being significantly higher in LT than HT. This suggests only a partial correlation between molecular and biochemical data in our conditions and the putative existence of post-transcriptional and post-translational mechanisms playing significant roles in the regulation of flavonoid metabolic pathways and in particular of anthocyanins

Increasing the source/sink ratio in Vitis vinifera (cv Sangiovese) induces extensive transcriptome reprogramming and modifies berry ripening

<p>Abstract</p> <p>Background</p> <p>Cluster thinning is an agronomic practice in which a proportion of berry clusters are removed from the vine to increase the source/sink ratio and improve the quality of the remaining berries. Until now no transcriptomic data have been reported describing the mechanisms that underlie the agronomic and biochemical effects of thinning.</p> <p>Results</p> <p>We profiled the transcriptome of <it>Vitis vinifera </it>cv. Sangiovese berries before and after thinning at veraison using a genome-wide microarray representing all grapevine genes listed in the latest V1 gene prediction. Thinning increased the source/sink ratio from 0.6 to 1.2 m²leaf area per kg of berries and boosted the sugar and anthocyanin content at harvest. Extensive transcriptome remodeling was observed in thinned vines 2 weeks after thinning and at ripening. This included the enhanced modulation of genes that are normally regulated during berry development and the induction of a large set of genes that are not usually expressed.</p> <p>Conclusion</p> <p>Cluster thinning has a profound effect on several important cellular processes and metabolic pathways including carbohydrate metabolism and the synthesis and transport of secondary products. The integrated agronomic, biochemical and transcriptomic data revealed that the positive impact of cluster thinning on final berry composition reflects a much more complex outcome than simply enhancing the normal ripening process.</p

Interventi in verde: come eseguirli e renderli efficaci

Per una viticoltura moderna orientata sia ad un miglioramento delle caratteristiche compositive delle uve che ad un incremento della redditività del vigneto, la gestione in verde della chioma rappresenta l’ago della bilancia su cui intervenire per ottenere un giusto equilibrio tra produzione e qualità del prodott