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Proton nuclear magnetic resonance (1H NMR) metabolomics was employed to investigate the impact of water deficit, defoliation, and crop thinning on the chemical composition of must and wines from the cool-climate white grape variety Solaris. The obtained results show that viticultural practices (defoliation and crop thinning) affected the amino acid and sugar content of Solaris must and thereby the quality of the final wine—mainly in terms of compounds normally related to fruity aroma (i.e., isopentanol), non-sugar sweetness (i.e., proline and glycerol), and alcohol content. The content of tyrosol, a natural phenolic antioxidant with a high bioavailability, was increased in the final wine by a combination of defoliation and crop thinning. The results of the metabolomics analysis performed on the must and wine samples from the water stress experiment showed that short-term water deficit significantly affected the concentration of several flavor-related compounds, including glutamate, butyrate and propanol, of the organic acids lactate and fumarate, and of the phenolic compounds caffeic acid and p-coumaric acid. ANOVA simultaneous component analysis showed that the effect of water deficit accounted for 11% (p < 0.001) and 8% (p < 0.001) of the variability in the metabolite concentrations in must and wines, respectively, while viticultural practices accounted for 38% (p < 0.001) and 30% (p < 0.001) of the metabolite variability in must and wines, respectively. [ABSTRACT FROM AUTHOR]

Crop thinning is a common practice performed in the vineyard consisting of whole clusters or individual fruits being removed after flowering is attained. Current studies have reported that unripe grape products as verjuice and sour grape sauce contain high content of bioactive compounds such as polyphenols, sugars, organic acids, nitrogenous compounds and sterols. This mini-review overviewed the bioactive components obtained from thinned unripe grapes such as phenolic compounds, sugars, organic acids, minerals, nitrogen compounds and sterols, and their use as antibrowning and whitening agents, natural catalysts, food preservative and food additive. In addition, their beneficial effects for human health also were reviewed, as well as the practices to maximize the extraction of antioxidant compounds. Therefore, revalorizing the waste from this management practice in viticulture can increase the vineyard sustainability and farmers' economic profits. [ABSTRACT FROM AUTHOR]

Proton nuclear magnetic resonance (1H NMR) metabolomics was employed to investigate the impact of water deficit, defoliation, and crop thinning on the chemical composition of must and wines from the cool-climate white grape variety Solaris. The obtained results show that viticultural practices (defoliation and crop thinning) affected the amino acid and sugar content of Solaris must and thereby the quality of the final wine—mainly in terms of compounds normally related to fruity aroma (i.e., isopentanol), non-sugar sweetness (i.e., proline and glycerol), and alcohol content. The content of tyrosol, a natural phenolic antioxidant with a high bioavailability, was increased in the final wine by a combination of defoliation and crop thinning. The results of the metabolomics analysis performed on the must and wine samples from the water stress experiment showed that short-term water deficit significantly affected the concentration of several flavor-related compounds, including glutamate, butyrate and propanol, of the organic acids lactate and fumarate, and of the phenolic compounds caffeic acid and p-coumaric acid. ANOVA simultaneous component analysis showed that the effect of water deficit accounted for 11% (p < 0.001) and 8% (p < 0.001) of the variability in the metabolite concentrations in must and wines, respectively, while viticultural practices accounted for 38% (p < 0.001) and 30% (p < 0.001) of the metabolite variability in must and wines, respectively.

The training system Semi-Minimal-Pruned Hedge (SMPH) blends features of traditional Vertical Shoot Positioning-type (VSP) trellising systems with the concept of minimal pruning. While saving labor, this training system results in relatively high crop load and a poor leaf area to fruit weight-ratio (LFR), and thus, needs to be able to ripen grapes in a cool to moderate climate. For these reasons the impact of yield regulation strategies, including (i) shoot thinning (Darwin-Rotor), (ii) biotechnological thinning (Gibberellic acid), and (iii) bunch thinning (harvest machine) were trialed in a three year study at Geisenheim, Germany between 2017 and 2019 using Riesling (Vitis vinifera L.). The average yield per vine in SMPH (5.34 ± 1.10 kg) was 61.1% higher with a narrower LFR (14.01 cm2 g−1), compared with VSP (3.32 ± 1.02 kg, LFR: 16.99 cm2 g−1). The yield was successfully reduced and LFR simultaneously increased with shoot thinning (−33.1%, LFR: 19.04 cm2 g−1), biotechnological thinning (−18.3%, LFR: 16.69 cm2 g−1) and bunch thinning (−37.3%, LFR: 21.49 cm2 g−1). Ripening was delayed in SMPH. On average, two maturity thresholds (14.1 °Brix and 18.2 °Brix) were achieved 129 GDD (seven days according to the recorded daily mean temperatures, respectively) and 269 GDD (16 days) later in non-thinned SMPH, compared to VSP. All thinning treatments accelerated maturity progress ranging from 27 GDD (two days) to 58 GDD (three days) for 14.1 °Brix and 59 GDD (three days) to 105 GDD (six days) for 18.2 °Brix. Apart from immediate benefits on the economic efficiency, the adaption of the leaf area to fruit weight ratio using SMPH holds high potential to, (i) produce grapes targeting specific wine profiles and/or (ii) reducing the velocity of ripening under conditions of climatic change. [ABSTRACT FROM AUTHOR]

Nitrogen deficit affects both crop production and composition, particularly in crops requiring an optimal fruit N content for aroma development. The adaptation of cultural practices to improve N use efficiency (NUE) (i.e. N uptake, assimilation and partitioning) is a priority for the sustainable production of high-quality crops. A trial was set on potted grapevines (Vitis vinifera L. cv. Chasselas) to investigate the potential of crop limitation (via bunch thinning) to control plant NUE and ultimately fruit N composition at harvest. A large crop load gradient was imposed by bunch thinning (0.5–2.5 kg m–2) and N traceability in the plant was realised with an isotope-labelling method (10 atom % 15N foliar urea). The results indicate that the mobilisation of root reserves plays a major role in the balance of fruit N content. Fertiliser N uptake and assimilation appeared to be strongly stimulated by high-yielding conditions. Fertilisation largely contributed to fulfilling the high fruit N demand while limiting the mobilisation of root reserves under high yield conditions. Plants were able to modulate root N reserve mobilisation and fertiliser N uptake in function of the crop load, thus maintaining a uniform N concentration in fruits. However, the fruit free amino N profile was modified, which potentially altered the fruit aromas. These findings highlight the great capacity of plants to adapt their N metabolism to constraints, crop thinning in this case. This confirms the possibility of monitoring NUE by adapting cultural practices. Without fertilisation, plant nutrition can be enhanced to some extent through the optimisation of agricultural practices. In a 15N-labelling experiment, we demonstrate that grapevine has a strong ability to regulate N uptake and reserve mobilisation to maintain a constant fruit N concentration despite changes in crop load. Nitrogen uptake and root N mobilisation were positively correlated with crop load. This result is essential for improving perennial fruit crop production through higher fertilisation efficiency and lower environmental impact. [ABSTRACT FROM AUTHOR]

Background and Aims: Recently, early defoliation (ED) has been used widely to regulate yield and reduce bunch compactness to improve tolerance to bunch rot. The aim of this study was to test ED, as an alternative to the conventional crop thinning (CT), to regulate yield and improve tolerance to bunch rot of the Vitis vinifera L. cv. Aragonez. Methods and Results: Early defoliation and CT were compared with an untreated Control over three consecutive seasons in a commercial vineyard in Portugal. Early defoliation had little effect on tolerance to bunch rot and led to progressive loss of yield reducing fruitset, bunch number, berry number and mass, compared to Control vines. Reduced bunch number is likely to be a function of reduced bud fertility. Crop thinning also reduced yield but, unlike ED, the yield reduction was less and remained constant over the seasons studied. Both ED and CT had little effect on berry composition. Conclusions: Among the two crop‐regulating techniques, CT appears more suitable than ED to control grape yields in regions where yield limitations are imposed. The progressive yield decline caused by ED is likely to be not economically viable in the region studied. Significance of the Study: Early defoliation reduces bud fertility in unirrigated vineyards under Mediterranean conditions. Therefore, this practice should be avoided under those conditions. [ABSTRACT FROM AUTHOR]

The training system Semi-Minimal-Pruned Hedge (SMPH) blends features of traditional Vertical Shoot Positioning-type (VSP) trellising systems with the concept of minimal pruning. While saving labor, this training system results in relatively high crop load and a poor leaf area to fruit weight-ratio (LFR), and thus, needs to be able to ripen grapes in a cool to moderate climate. For these reasons the impact of yield regulation strategies, including (i) shoot thinning (Darwin-Rotor), (ii) biotechnological thinning (Gibberellic acid), and (iii) bunch thinning (harvest machine) were trialed in a three year study at Geisenheim, Germany between 2017 and 2019 using Riesling (Vitis vinifera L.). The average yield per vine in SMPH (5.34 ± 1.10 kg) was 61.1% higher with a narrower LFR (14.01 cm2 g−1), compared with VSP (3.32 ± 1.02 kg, LFR: 16.99 cm2 g−1). The yield was successfully reduced and LFR simultaneously increased with shoot thinning (−33.1%, LFR: 19.04 cm2 g−1), biotechnological thinning (−18.3%, LFR: 16.69 cm2 g−1) and bunch thinning (−37.3%, LFR: 21.49 cm2 g−1). Ripening was delayed in SMPH. On average, two maturity thresholds (14.1 °Brix and 18.2 °Brix) were achieved 129 GDD (seven days according to the recorded daily mean temperatures, respectively) and 269 GDD (16 days) later in non-thinned SMPH, compared to VSP. All thinning treatments accelerated maturity progress ranging from 27 GDD (two days) to 58 GDD (three days) for 14.1 °Brix and 59 GDD (three days) to 105 GDD (six days) for 18.2 °Brix. Apart from immediate benefits on the economic efficiency, the adaption of the leaf area to fruit weight ratio using SMPH holds high potential to, (i) produce grapes targeting specific wine profiles and/or (ii) reducing the velocity of ripening under conditions of climatic change.