Crop forcing technique and irrigation strategy modified the content and phenolic profile of cv. Tempranillo grape berries grown in a semi-arid climate.

BACKGROUND: Climate change modifies the content and phenolic profiles of grapes and wines. It is known that high temperatures, related to climate change, reduce anthocyanins and procyanidin (catechin and tannin) compounds accumulated in the berries. In recent years, with the aim of improving the phenolic composition of the berries, the technique of crop forcing has been proposed to delay grape ripening to a more favourable period of temperatures. RESULTS: In this study, crop forcing was applied to cv. Tempranillo vines on two different dates, after flowering (F1) and after fruit set (F2), and compared to a treatment control (NF, without forcing). Additionally, as a secondary factor, two irrigation strategies were established in each treatment: irrigation with no water stress, and a pre-veraison deficit irrigation. The study was carried out in three consecutive years (2017-2019). For most of the parameters analysed, no interaction was found. Therefore, for these parameters, the effect of each of these techniques was investigated independently. Regardless of the irrigation strategy, F2 berries achieved higher contents of catechins and anthocyanins than NF berries. Each year, regardless of the irrigation strategy, crop forcing increased the content of monoglucoside forms, and had a positive effect on the total content of malvidin, petunidin, delphinidin, peonidin and malvidin derivatives, but only affected acetyl and coumaryl forms in 2017. However, the effect of irrigation strategy was less significant and consistent, being more dependent on the vintage. CONCLUSION: Regardless of vine water status, crop forcing technique applied after fruit set could be used by vine growers to delay ripening of the grapes and thus achieve an increase in the anthocyanin characteristics of the grapes. © 2023 Society of Chemical Industry.

Improving the Phenolic Content of Tempranillo Grapes by Sustainable Strategies in the Vineyard.

Wine phenolics are of considerable interest due to their implication in the organoleptic appreciation of wines and due to their bioactive functions as antioxidants. In this work, the effects of sustainable strategies in the vineyard, regulated deficit irrigation treatments (RDI) and crop load level (CL) on Tempranillo grape phenolics over two seasons was studied. Rainfed (T), early (EDI) and late (LDI) regulated deficit irrigation was applied. Cluster thinning (TH) and control (C) without cluster removal were also applied under each irrigation treatment. The effect of CL remained independent of RDI for all compounds, except for phenolic acids. The RDI influence on the grape skin phenolic profile was higher than CL in the dry season (2009); however, in 2010, the effect of CL was greater. In 2009, a tendency to increase anthocyanin and hydroxycinnamic acid content in grape skins was registered in EDI with respect to T. However, significant decreases in hydroxycinnamic and flavanol compounds were found in LDI. In 2010, the wettest year, CL increased all phenolic families' content. Thus, it can be concluded that the effects of RDI and cluster thinning treatments depend on the family of compounds considered and the meteorological conditions of the year.

Vine Irrigation through Two Shoot Densities in Flavonoid and Non-Flavonoid Compounds in 'Tempranillo' Grapes.

This study aims to analyze the effects of non-limiting irrigation (I) vs. rainfed (R) through two different shoot densities, high-load (H) and low-load (L), on vegetative growth, agronomic parameters, flavonoid and non-flavonoid polyphenol substances of cv. Tempranillo grown in a semi-arid climate during three consecutive seasons (2014-2016). Under these conditions, in the 2015 and 2016 seasons, irrigation showed significant increases in berry weight (14.7% and 13.4% in H and L, respectively, in 2015, and 35.6% and 23.5% in the same treatments in 2016) and yield (66.7% and 48.5 in 2015; 27.9% and 177.5% in 2016). Additionally, a general decreasing trend is observed in anthocyanins with the exception of peonidin derivates, almost all flavonol compounds, cinnamic acid and resveratrol values with different degrees and statistical significance depending on the shoot density of the vines. A slight variation is observed in 2014 in these parameters. On the other hand, no general trends are established either in flavanol compounds or hydroxybenzoic acid. Thus, the effect of irrigation depends on the parameter considered, the shoot density of the vine and the season considered.

Effect of the timing of water deficit on the must amino acid profile of Tempranillo grapes grown under the semiarid conditions of SW Spain.

Must nitrogen is very important for successful fermentation. Irrigation can influence vine nitrogen availability, and therefore must nitrogen content and wine quality. The aim of this work was to assess the effect of vine water status on the nitrogen concentration of cv. Tempranillo grown under semiarid conditions. A rainfed and two regulated deficit irrigation (RDI) strategies, late (LDI) and early deficit irrigation (EDI) were applied during pre- and post-veraison respectively periods over two seasons in Badajoz (Spain). Twenty-eight amino acids, amines and ammonia were determined by high performance liquid chromatography (HPLC) in the must. Results showed an effect of the pre-veraison vine water status on the must amino acid concentration. Higher values of nitrogenous indices were reached in musts from LDI treatments, mainly in the dry year. Significant correlations between pre-veraison stem water potential and 19 amino acid concentrations were observed. Therefore, LDI was a more suitable strategy for increasing the content of nitrogenous substances in the must.

Histochemical and immunohistochemical analysis of enzymes involved in phenolic metabolism during berry development in Vitis vinifera L.

Phenolics are involved in many of plants' biological functions. In particular, they play important roles in determining the quality of grape berries and the wine made from them, and can also act as antioxidants with beneficial effects for human health. Several enzymes are involved in the synthesis of phenolic compounds. Among them, stilbene synthase (STS) is a key to the biosynthesis of stilbenes, which are considered to be important secondary metabolites in plants. Other enzymes, such as polyphenol oxidase (PPO) and peroxidase (POD), are involved in the degradation of phenolics, and become activated during late stages of berry ripening. In the present study, Vitis vinifera L. berries were sampled at eight stages of development, from 10 days after anthesis to late harvest. The PPO and POD enzymatic activities were determined at each stage. The presence of STS, PPO, and POD proteins in the grape exocarp and mesocarp was detected immunohistochemically and histochemically. The amount and intensity of the immunohistochemical and histochemical signals correlate with the variations in enzyme activities throughout fruit development. Strong STS immunoreactivity was detected until the onset of ripening. Labeled tissue increased gradually from mesocarp to exocarp, showing an intense signal in epidermis. At subcellular level, STS was mainly detected in cytoplasm grains and cell walls. The amount of PPO immunoreactivity increased progressively until the end of ripening. The PPO signal was detected in hypodermal layers and, to a lesser extent, in mesocarp parenchyma cells, especially in cytoplasm grains and cell walls. Finally, POD activity was stronger at the onset of ripening, and the POD histochemical signal was mainly detected in the cell walls of both exocarp and mesocarp tissue.

Early leaf removal applied in warm climatic conditions: Impact on Tempranillo wine volatiles.

Defoliation is a cultural practice with demonstrated benefits in grape and wine quality. The objective of this study was to evaluate the effect of early leaf removal applied in warm climatic conditions on volatile composition of Tempranillo wines. During three consecutive vintages (2009-2011) wine volatile compounds (alcohols, C6-compounds, ethyl esters, acetates, volatile acids, lactones and carbonyl compounds) from defoliated and non-defoliated vines were identified and quantified by GC-MS. Early leaf removal induced the increase of the concentration of all families of volatile compound quantified with exception of lactones. Significant increase was observed for 23 out 34 volatile compounds analyzed. The vintage effect also was shown, where the highest effect of defoliation was exhibited in 2009 vintage. Principal component analysis (PCA) showed a good separation of defoliation, non-defoliation and vintage according to wine volatile composition. The analysis of odour activity value (OAV) exhibited an increase of fruity and floral odour on Tempranillo wines when early defoliation was applied.

The Evolution of Total Phenolic Compounds and Antioxidant Activities during Ripening of Grapes (Vitis vinifera L., cv. Tempranillo) Grown in Semiarid Region: Effects of Cluster Thinning and Water Deficit.

A study was made of how water status (rainfed vs. irrigated) and crop load (no cluster thinning vs. cluster thinning) can together affect the grapes of Vitis vinifera cv. Tempranillo vines growing in a semiarid zone of Extremadura (Spain). The grapes were monitored at different stages of ripening, measuring the peroxidase (POX) and superoxide dismutase (SOD) antioxidant activities and the phenolic content (flavonoids and phenylpropanoids), together with other parameters. The irrigation regime was adjusted to provide 100% of crop evapotranspiration (ETc). The findings confirmed previous results that both thinning and water deficit advance ripening, while irrigation and high crop load (no thinning) lengthen the growth cycle. The SOD activity remained practically constant throughout ripening in the thinned treatments and was always lower than in the unthinned treatments, an aspect which could have been the cause of the observed greater level of lipid peroxidation in the water deficit, thinned treatment. The nonspecific peroxidase activity was very low, especially in the thinned treatments. The effect of thinning was enhanced when combined with water deficit, inducing increases in phenylpropanoids and, above all, flavonoids at the harvest stage of ripening, while leaving the polyphenol oxidase activity (PPO) unaffected.