Interactive Effect of Ethephon and Shading on the Anthocyanin Composition of Vitis vinifera L. cv. Crimson Seedless

The Vitis vinifera cultivar Crimson Seedless primarily accumulates the anthocyanin peonidin-3-glucoside. Theresearch undertook the study of two factors which could influence the accumulation of anthocyanin in grape berryskins: ethephon application and shade. Ethephon treatment at 200ppm applied one week post-véraison significantlyincreased the concentration of all anthocyanins in berry skins. Peonidin-3-glucoside was found to increase mostsignificantly in response to ethephon application, and was increased 150% compared with an untreated control. Theproportion of 3‑monoglucoside anthocyanins increased in response to ethephon application. A shading treatment didnot affect total anthocyanin concentration in berry skins, but the anthocyanin cyanidin-3-glucoside was decreasedsignificantly by shade. Its content was 50% of a sun-exposed control. The observed effects were found to occur attwo sites at which the experiment was performed in the Hex River and Paarl regions. Colour development in theVitis vinifera cultivar Crimson Seedless does not appear to be influenced significantly by bunch shading. The use ofcommercial growth regulators like ethephon exert a strong influence on anthocyanin production in grape skins ofthis cultivar, and are therefore a more likely solution to overcome poor colour development in its production

The Interactive Effect of Pruning Level and Irrigation Strategy on Grape Berry Ripening and Composition in Vitis vinifera L. cv. Shiraz

A partial rootzone drying (PRD) irrigation technique (0.5 ML/ha) was compared with a standard irrigation treatment(1 ML/ha) at three different pruning levels of 30, 60 and 120 nodes per grapevine in Vitis vinifera L. cv Shiraz. Berrysize was found to decrease as node number per grapevine increased, but was not significantly altered by the PRDtreatment. The influence of these treatments on the accumulation of total soluble solids per berry was investigatedduring berry ripening and was shown to be reduced at higher node number (120 nodes). There was no effect ofPRD on the accumulation of total soluble solids. Juice titratable acidity and the concentration (per g) and content(per berry) of grape anthocyanins and phenolics were compared between treatments at harvest. In one season ofthe study, juice titratable acidity, anthocyanin and phenolic concentration was unaltered by the PRD treatment. Ina further season, juice titratable acidity was decreased in response to the PRD treatment and was associated withincreases in grape anthocyanin and phenolic concentration in response to PRD. Where there was a small increasein anthocyanin concentration in response to PRD, this was found to be independent of berry size. In addition, linearregression analysis showed a poor relationship between berry size and anthocyanin concentration, but a significantrelationship was found between berry size and anthocyanins per berry

The Interactive Effect of Pruning Level and Irrigation Strategy on Water Use Efficiency of Vitis vinifera L. cv. Shiraz

A partial rootzone drying (PRD) irrigation technique (0.5 ML/ha) was compared with a standard irrigation treatment(1 ML/ha) at three different pruning levels of 30, 60 and 120 nodes per grapevine in Vitis vinifera L. cv Shiraz. The PRDirrigation technique was applied to a single side of the grapevine rootzone at a time, 45 cm from the trunk, and the sideswere switched in 10-day cycles. For the standard irrigation treatment, both sides of the grapevine were irrigated. At theend of an irrigation cycle, the PRD treatment resulted in reduced midday readings of stomatal conductance and stem (ψS)and leaf (ψL) water potential relative to the control treatment. During the switch between irrigation cycles, when the soilwater profile of both the ‘wet’ and ‘dry’ sides of the PRD-treated grapevines was refilled, stomatal conductance, ψS andψL were restored to the same levels as for the control experiment. As node number per grapevine increased, berry size andwinter pruning weight were reduced and yield increased. In the first season of the experiment, the PRD treatment did nothave a significant effect on berry size, yield and pruning weight, although shoot length was reduced in response to PRD forall the pruning treatments. In a subsequent season, PRD was found to reduce yield, primarily through a reduction in berryset. Water use efficiency measured as t/ML irrigation water applied was increased significantly as crop load increased, andwas enhanced in response to the PRD irrigation technique

Tissue discs as an experimental system for metabolic flux analysis in the sugarcane culm

We have investigated the suitability of tissue discs as an experimental system to determine carbon flux in sugarcane. Whilst the number of cells per tissue disc derived from young and older internodes differed largely, the protein content per cell of the discs was constant and is, therefore, most probably the best unit to accurately express metabolic flux. No significant changes in the glucose, fructose and sucrose pools within the tissue discs occurred during a 3h labelling period, which suggests that the uptake of sugars from the medium was adequate to balance the demand by the tissue. This also suggests that no major disturbances in the in vivo metabolism occurred. During a 3h labelling period the rate of 14CO2 release became linear, indicating that the system was approaching isotopic steady state between the external and internal glucose pool, and the respiratory processes involved in CO2 release. Despite this observation, the specific activity of the internal glucose pool was much lower than that of the external glucose pool. This is probably as a result of the intracellular compartmentation of glucose, with most of it present in a sub-cellular compartment making a small contribution in the provision of substrate for respiration.Articl

Optimization of a method for the extraction and quantification of carotenoids and chlorophylls during ripening in grape berries (Vitis vinifera cv. Merlot)

An extraction method to identify and quantify the carotenoid and chlorophyll profile of lyophilized tissue from unripe (green) to ripe (red) Merlot grape berries was developed. The RP-HPLC method baseline separated all of the carotenoids and chlorophylls and their derivatives. Problems encountered during sample storage and extraction are discussed as well as possible alternative methods. This study confirmed that carotenoids and chlorophylls decreased on a per berry (μg/berry) and concentration (μg/g) basis from veraison to harvest over two growing seasons. The carotenoid 5,8-epoxy-β-carotene was quantified for the first time in grapes and represents a significant amount of the total carotenoids present at harvest. All the carotenoids and chlorophylls except β-carotene appeared to be sensitive to seasonal variation in climatic conditions. Lutein and β-carotene were found to be the most abundant carotenoids present in Merlot grape berries together with chlorophyll a for both seasons studied. © 2010 American Chemical Society.Articl

Retention of proanthocyanidin in wine-like solution is conferred by a dynamic interaction between soluble and insoluble grape cell wall components

Published: September 12, 2016For better understanding of the factors that impact proanthocyanidin (PA) adsorption by insoluble cell walls or interaction with soluble cell wall-derived components, application of a commercial polygalacturonase enzyme preparation was investigated to modify grape cell wall structure. Soluble and insoluble cell wall material was isolated from the skin and mesocarp components of Vitis vinifera Shiraz grapes. It was observed that significant depolymerization of the insoluble grape cell wall occurred following enzyme application to both grape cell wall fractions, with increased solubilization of rhamnogalacturonan-enriched, low molecular weight polysaccharides. However, in the case of grape mesocarp, the solubilization of protein from cell walls (in buffer) was significant and increased only slightly by the enzyme treatment. Enzyme treatment significantly reduced the adsorption of PA by insoluble cell walls, but this effect was observed only when material solubilized from grape cell walls had been removed. The loss of PA through interaction with the soluble cell wall fraction was observed to be greater for mesocarp than skin cell walls. Subsequent experiments on the soluble mesocarp cell wall fraction confirmed a role for protein in the precipitation of PA. This identified a potential mechanism by which extracted grape PA may be lost from wine during vinification, as a precipitate with solubilized grape mesocarp proteins. Although protein was a minor component in terms of total concentration, losses of PA via precipitation with proteins were in the order of 50% of available PA. PA-induced precipitation could proceed until all protein was removed from solution and may account for the very low levels of residual protein observed in red wines. The results point to a dynamic interaction of grape insoluble and soluble components in modulating PA retention in wine.Keren A. Bindon, Sijing Li, Stella Kassara, and Paul A. Smit

Grape seed procyanidin fractions enhance the impact of 5-Fluorouracil chemotherapy on colon cancer cells

NutritionKY Cheah, GS Howarth, KA Bindon, JA Kennedy, SEP Bastia

Oxygen exposure during red wine fermentation modifies tannin reactivity with poly-L-proline

Red wines injected with nitrogen or oxygen during fermentation were used to identify the effect of gas exposure on tannin structure and reactivity with poly-l-proline. Tannin was purified from wine after fermentation and after three years of bottle storage. Tannin from nitrogen-treated wine had a lower percentage of galloylation and were less pigmented than tannin from oxygen-exposed wine. Self-aggregation of tannin was measured by nanoparticle tracking analysis and a larger particle size was observed for the oxidized treatment. The interaction of tannin and poly-l-proline was measured by isothermal titration calorimetry, and involved more hydrogen bonding than hydrophobic interactions in the case of nitrogen-treated wine tannin. Conversely, oxidized tannin was more hydrophobic and the association with poly-l-proline was entropy-driven due to a change of solvation. The results show meaningful changes in the structure and reactivity of tannin as a result of oxygen exposure during fermentation, which may impact astringency perception.Aude A. Watrelot, Martin P. Day, Alex Schulkin, Robert J. Falconer, Paul Smith, Andrew L. Waterhouse, Keren A. Bindo