Effects of Kaolin and Shading Net on the Ecophysiology and Berry Composition of Sauvignon Blanc Grapevines

Rising temperatures in most viticultural regions are associated with a higher incidence of drastic weather circumstances such as heatwaves. The consequences are reflected in qualitative and quantitative white grapes characteristics. In fact, there is an enhancement in alcohol content and a jeopardized reduction in the aromatic potential. We performed a scientific test to assuage the bump of heatwaves and exposure of grapes on Vitis vinifera cv. “Sauvignon Blanc” with exposed vines (untreated) or with kaolin foliar treatment or with partial fruit-zone shading (shading net 30 and 70%). This work aimed to evaluate the effects of shading net (SD-30% and SD-70%) and foliar kaolin (K) treatment on physiology, technological maturity, and thiolic precursors in Italy during the 2020–2021 seasons. For this purpose, four treatments were established: SD-30% (green artificial shading net at 30%), SD-70% (green artificial shading net at 70%), K (foliar kaolin), and CTRL (no application). During the two vintages, single-leaf gas exchange appraisal, leaf temperature, berry temperature, chlorophyll fluorescence, pre-dawn, and leaf water potential were measured. Moreover, berry weight, pH, °Brix, acidity (technological maturity specifications), and the following thiolic precursors were analyzed: 3-S-glutathionylhexan-1-ol (Glut-3MH), S-4-(4-methylpentan-2-one)-L-cysteine (Cys-4MMP), and 3-S-cysteinylhexan-1-ol (Cys-3MH). SD-70% and K denoted less negative water potential, a lower berry temperature, and a higher level of all precursors than the other treatments. Acidity and sugar parameters indicated significant differences among treatments. The lower berry weight and the lower tartaric acidity were found in the CTRL treatment. In comparison, SD-70% and K showed lower and more balanced sugar contents. As a result of global warming, color shading net and kaolin have been demonstrated to be good practices to counterpoise the divergence between aromatic and technological maturity in Sauvignon Blanc grapevines

Regulation of secondary metabolism in Vitis vinifera by an extract of A.nosodum effects of physiology and grape quality

Heat and drought are major abiotic stresses that impact on many Vitis vinifera physiological processes and berry development, especially as global climate change is speeding up the expected frequency and severity of both stress factors. Nevertheless, seaweed extracts might represent a strategy to confer to treated plants the capability to be more prone to counteract short-term periods of severe stresses. In this paper, we report the effects of foliar treatments with an Ascophyllum nodosum extract on physiological and biochemical parameters of grapevine. In our study performed in the 2016 season in open field in Tuscany, we assessed differences in leaf gas exchanges, chlorophyll fluorescence and midday stem water potential between treated and untreated vines. In addition, the in-depth analysis of anthocyanins and flavonols in berries presented within the work adds significantly to our knowledge of the influence of seaweed extract on the phenylpropanoid pathway. Moreover, our work witness the treatment-promoting greater tolerance to stress in vines, and support previous studies that hypothesize an influence of treatments with algae extracts on qualitative characteristics in V.vinifera

Sustainable Viticulture: Effects of Soil Management in Vitis vinifera

Soil management in vineyards is of fundamental importance not only for the productivity and quality of grapes, both in biological and conventional management, but also for greater sustainability of the production. Conservative soil management techniques play an important role, compared to conventional tillage, in order to preserve biodiversity, to save soil fertility, and to keep vegetative-productive balance. Thus, it is necessary to evaluate long-term adaptation strategies to create a balance between the vine and the surrounding environment. This work sought to assess the effects of following different management practices on Vitis vinifera L. cv. Cabernet Sauvignon during 2017 and 2018 seasons: soil tillage (T), temporary cover cropping over all inter-rows (C), and mulching with plant residues every other row (M). The main physiological parameters of vines (leaf gas exchange, stem water potential, chlorophyll fluorescence, and indirect chlorophyll content) as well as qualitative and quantitative grape parameters (technological and phenolic analyses) were measured. Significant differences in gas exchanges related to the different season and inter-row management were observed. C showed more negative values of water potential, due to the grass–vine competition, especially when water availability was lower. The competition exerted by C led to differences in fruit setting with impact on yield; therefrom, significant differences also in sugar and anthocyanic content were observed

Effect of Agronomic Techniques on Aroma Composition of White Grapevines: A Review

Climate change with rising temperatures and the unpredictability of rainy events during ripening leads to tough challenges for the winemakers in preserving the quality of white grape varieties. Grape quality is a complex concept that mainly refers to berry chemical composition, including secondary metabolites such as aroma compounds that in white berries play a key role in the identity of the wine. Terpenes, thiols, C13-norisoprenoids, methoxypyrazines, and nonterpenic alcohols are the most important aroma compounds in white grapes and several of them can be found as free volatiles or bound as glycoconjugate molecules. Agronomic practices in vineyards, such as biostimulant application, irrigation, defoliation, training systems, foliar fertilization, and bunch thinning, can have a positive effect on their concentration. This review aims to highlight the aromatic characteristics of the most utilized white grape cultivars and focus on agronomic techniques in the vineyard to enhance, implement, and intensify their aromatic characteristics. The purpose of this review paper is therefore to investigate the state of the art regarding the exaltation of aroma in white grapes in the scientific literature through sustainable agronomic techniques, but further future investigations are considered necessary given the uncertainty concerning some mechanisms of biosynthesis and their correlation with such agronomic practices

Influence of water stress on grape quality and aroma precursors in Sauvignon Blanc grown in Bolgheri area (Tuscany)

Climate change has a direct impact on the phenological stages of the grapevine, with consequences on the anticipation of aging and on the qualitative characteristics of the grapes. In fact, there is a decrease in the skin/pulp ratio, with possible reduction of the aromatic potential. This work was aimed at assessing the effects of water stress on technological maturity and thiol precursors of Sauvignon Blanc grapes in two vineyards of Bolgheri. To this purpose, 3 theses have been established: WW, well watered; WS, moderate stress; CTRL, control. During the season, measurements of single leaf gas exchange, stem water potential were made; moreover parameters of technological maturity (° Brix, acidity, pH and berry weight) and thiol precursors were analyzed. As expected, the water potential was less negative in the irrigated thesis due to the greater availability of water, as well as the highest rates of photosynthesis, transpiration and stomatal conductance. Technological analyses showed no significant differences among the treatments. The analysis of the 3MH/3-mercaptoesan-1-ol precursors showed that the WW had a greater accumulation than the other theses. These results suggest that lower water stress favors a better aromatic content

Effects of different types of shelter on physiology and growth of Sangiovese vines during the first year after planting

In the early stages of planting, the shelter can provide for young vines protection against damage of various kinds. Despite their widespread use, few surveys have been devoted to the study of innovative shelter types and the possible influence of these protections on the physiology and development of plants. In the present experiment, which took place in 2017 in a Tuscan winery, the effects of vine protections by the company OSO (Prato) on single leaf gas exchanges and on the shoot growth in the first year of planting were studied. Three types of shelters with a circular section (completely perforated, partially perforated and closed) have been compared with the traditional full-wall shelters with square section. During the growing season, sprout growth measures, leaf area, leaf gas exchanges and water potential were carried out on the young vines. At the end of the season, shoots were sampled to measure the dry matter accumulated during the season. Among the shelters taken into consideration, it emerges that the completely perforated type guarantees the best development, with differences that are almost always significant for most of the measured parameters with traditional shelters. On the contrary, the closed typology has led to a reduction in growth, in gas exchanges and in water potential. In conclusion, the type completely perforated could constitute a valid alternative to the traditional one because, besides being a useful means for the protection of the vine, it could benefit the development of the root system in the early stages of growth