Influence of foliar fertilization with P and K on chemical constituents of grape cv. 'Cardinal'

Effects of foliar-sprayed potassium dihydrogen phosphate on accumulation of flavonoids in Cabernet Sauvignon (Vitis vinifera L.)

BACKGROUND

In current vineyards, potassium dihydrogen phosphate (KH₂ PO₄ ) is a common foliar fertilizer with the lowest salt index. It is employed to improve the transportation and distribution of grape photosynthetic products, but the mechanism of its effect on fruit flavonoid synthesis is unclear.

RESULTS

This study investigated the effects of foliar spraying of KH₂ PO₄ at different developmental stages (1 week before veraison; the end of veraison (EV)) on flavonoid metabolites and related gene expression of 'Cabernet Sauvignon' grape for two consecutive vintages. High-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry technology was used to identify 6 flavan-3-ols, 11 flavonols, and 16 anthocyanins. KH₂ PO₄ influenced anthocyanins content, especially when applied at the EV stage, the content of anthocyanins was significantly higher than that of the control. Further, quantitative polymerase chain reaction analysis showed that KH₂ PO₄ treatment applied at the EV stage can increase the expression of anthocyanin synthesis genes and accelerate anthocyanin synthesis. In particular, the expression of VviGST in EV treatment was significantly higher than that of the control during the development process.

CONCLUSION

These findings have enhanced our understanding of the effect of KH₂ PO₄ treatment on grape flavonoids. Among them, EV treatment can significantly increase anthocyanins content. © 2023 Society of Chemical Industry.

Physico-Chemical Properties Prediction of Flame Seedless Grape Berries Using an Artificial Neural Network Model

The grape is a very well-liked fruit that is valued for its distinct flavor and several health benefits, including antioxidants, anthocyanins, soluble sugars, minerals, phenolics, flavonoids, organic acids, and vitamins, which significantly improve the product’s overall quality. Today’s supply chain as a whole needs quick and easy methods for evaluating fruit quality. Thus, the objective of this study was to estimate the quality attributes of Flame Seedless grape berries cultivated under various agronomical management and other practices using color space coordinates (berry L*, berry a*, and berry b*) as inputs in an artificial neural network (ANN) model with the best topology of (3-20-11). Satisfactory predictions based on the R² range, which was 0.9817 to 0.9983, were obtained for physical properties (i.e., berry weight, berry length, and berry diameter as well as berry adherence strength) and chemical properties (i.e., anthocyanin, total soluble solids (TSS), TSS/titratable acidity, total sugars, titratable acidity, reducing sugars, and non-reducing sugars). Meanwhile, we also performed a contribution analysis to analyze the relative importance of CIELab colorimeter parameters of berries L*, a*, and b* to determine the main fruit quality. In terms of relative contribution, berry b* contributed relatively largely to berry weight, berry adherence strength, TSS, TSS/titratable acidity, titratable acidity, total sugars, reducing sugars, and non-reducing sugars and a* contributed relatively largely to anthocyanin, berry length, and berry diameter. The developed ANN prediction model can aid growers in enhancing the quality of Flame Seedless grape berries by selecting suitable agronomical management and other practices to avoid potential quality issues that could affect consumers of them. This research demonstrated how color space coordinates and ANN model may well be utilized to evaluate the Flame seedless grape berries’ quality.

Non-destructive fluorescence sensing for assessing microclimate, site and defoliation effects on flavonol dynamics and sugar prediction in Pinot blanc grapes

In an era of growing international competition in modern viticulture, the study and implementation of innovative technologies to increase the production of high-quality grapes and wines are of critical importance. In this study, the non-destructive portable sensor Multiplex, based on fluorescence sensing technique, was applied to evaluate grape maturity parameters and flavonol content of the understudied Pinot blanc variety. The effects of environmental and agronomical factors on flavonol content of Pinot blanc grapes were investigated in eight vineyards characterised by different microclimatic and agronomic conditions. Furthermore, the direct impact of canopy management treatment on the flavonol dynamics of the grapes oriented in the four cardinal directions was assessed. Results highlight the positive role of moderate temperatures and direct sunlight exposure on Pinot blanc flavonol content; however, no direct vineyard-elevation effect was observed. The ability to modulate and evaluate the flavonol content in field represent crucial factors because of their potential effect on flavonoids-dependent wine characteristics, such as stability and ageing. In the present study, for the first time, two calibration curves were reported for pre- and post-veraison periods between flavonol indices and the berry skin flavonol content and a good correlation was observed between Multiplex measurement and the total polyphenolic content of grape juice. Moreover, the strong correlation between the chlorophyll index with grape juice sugar content and titratable acidity revealed the practical application of non-destructive sensors to predict the optimal harvest time for Pinot blanc grapes. In conclusion, the non-destructive fluorescence sensor Multiplex is a high-potential tool for innovative viticulture, for evaluating grape skin composition variables in white grape varieties.

Effects of Girdling and Foliar Fertilization with K on Physicochemical Parameters, Phenolic and Volatile Composition in ‘Hanxiangmi’ Table Grape

Aroma is one of the most important indicators of grape quality. Girdling and foliar fertilization with K (K2O) are common agronomic practices applied to improve berry quality in grape production. However, little is known about its effect on the accumulation and biosynthesis of the entire aromatic profile. Our study was aimed to explore the influences of girdling and foliar fertilization with K (alone or in combination) on the general properties, phenolic composition, volatile free aroma compounds, spatial and temporal expression of terpene-related genes and sensory properties in ‘Hanxiangmi’ table grape. In this study, we found that girdling and foliar fertilization with K (alone or in combination) facilitated fruit enlargement and increased the accumulation of phenolic compounds in skin. The combination treatment of girdling and foliar fertilization with K significantly promoted the concentrations of total soluble solids (TSS) in the pulp and proanthocyanidins in the berry skin, and had a lower titratable acidity (TA) compared to those of the control. In contrast, girdling treatment alone increased the concentrations of titratable acidity. Volatile free aroma composition analysis revealed that the combination treatment increased the volatile compounds and concentrations significantly, most notably in terpenes, such as nerol, citronellol and linalool. Spatial and temporal expression analysis showed that the expression level of VvDXS was significantly correlated with linalool and total terpenes concentrations, as a result of which, we speculated that VvDXS is the candidate gene for the regulation of important grape terpenes. We hope that our results can direct farmers to better apply girdling and foliar fertilization with K in grape production.

Detailed chemical composition of juice from autochthonous pomegranate genotypes (Punica granatum L.) grown in different locations in Montenegro

The first detailed phytochemical screening was performed on juices prepared from arils of wild pomegranate fruits taken from several locations in Montenegro with the aim of their future valorization. Particular attention is paid to the effect of pomegranate growth conditions on the juice quality. In addition to the basic parameters of pomegranate fruits and juices, nine primary metabolites (sugars, organic acids and vitamin C) were determined in the juices. Among 97 phenolic compounds, 23 anthocyanins and their derivatives, 33 ellagitannins and derivatives of ellagic acid, 12 flavanols, 4 flavonol glycosides, 1 flavone, 17 hydroxybenzoic acids and 7 hydroxycinnamic acids and their derivatives, were identified. Flavanols (1137-4424 mg/L) as well as ellagitannins and ellagic acid derivatives (1849-2991 mg/L) had the highest concentrations in pomegranate juices. Juices from the pomegranates grown on two soil types had total analyzed phenolics ranging from 4387 mg/L (Eutric Cambisol) up to 8461 mg/L (Terra Rossa).