Open Access
Source-sink manipulation does not mitigate the effects of grapevine red blotch virus (GRBV) infection on fruit sugar and flavonoid accumulation in Cabernet-Sauvignon
(International Viticulture and Enlogy Society, 2023) Kurtural, Sahap Kaan; Tanner, Justin D.; Mainos, Dimitirios; Yu, Runze; Torres Molina, Nazareth; Martínez-Lüscher, Johann; Agronomía, Biotecnología y Alimentación; Agronomia, Bioteknologia eta Elikadura; Institute for Multidisciplinary Research in Applied Biology - IMAB
Grapevine red blotch virus (GRBV) negatively affects the composition of grapevine (Vitis vinifera L.) berries by reducing total soluble solids and anthocyanins, leading to economic losses for grape producers. Negative effects of GRBV were suspected to be due to impeded carbon translocation from leaves to fruit which limits sugar and flavonoid accumulation in berries. A two-year trial was conducted to determine whether an increase in source: sink ratio may affect sugar allocation and mitigate the effects of GRBV on Cabernet-Sauvignon plants. Experimental design was factorial (2 by 2) with healthy plants that did not have the virus (GRBV (-)) and plants having GRBV (GRBV (+)) and plants were subjected either untreated (UNT) or cluster thinned down to 10 clusters (CT). Effects of cluster thinning and virus status on leaf and shoot total soluble sugars (TSS), plant water status, leaf gas exchange, berry primary and secondary metabolites, and yield components were measured. The TSS in leaves began to accumulate around véraison. In shoot sap, GRBV(-) plants had greater concentration in TSS than GRBV(+) plants. The presence of disease improved plant water status increasing the stem water potential and increasing berry mass. However, juice total soluble solids were consistently lower in GRBV(+) plants despite increasing source: sink ratio by 3× with cluster removal. Likewise, GRBV(+) plants produced berries with lower anthocyanin content at harvest regardless of CT in both years. Our results suggest that GRBV infection severally impeded carbohydrate translocation out of the leaves, and in contrast to healthy plants reducing the number of clusters does not induce a reconcentration of sugars in the remaining clusters.
Open Access
Impacts of leaf removal and shoot thinning on cumulative daily light intensity and thermal time and their cascading effects of grapevine (vitis vinifera L.) berry and wine chemistry in warm climates
(Elsevier, 2020-10-23) Torres Molina, Nazareth; Martínez-Lüscher, Johann; Porte, Etienne; Yu, Runze; Kurtural, Sahap Kaan; Agronomía, Biotecnología y Alimentación; Agronomia, Bioteknologia eta Elikadura
Leaf removal (LR), shoot thinning (ST) and their combination (LRST) are known to increase berry solar exposure affecting berry composition and consequently improving wine quality and antioxidant properties. We hypothesized that LR, ST or their combination (LRST) would affect flavonoid content during berry ripening by means of changes of the berry microclimate (light and temperature) as well as wine composition, quality, and antioxidant properties. Thermal time and sum of light intensity thresholds were different to achieve the maximum berry anthocyanin and flavonol contents. ST mostly affected wine characteristics by increasing alcoholic content, acidity, hue and phenolic substances. Wine antioxidant capacity decreased in ST wines likely by decreases in catechin and quercetin contents. ST and LRST increased proanthocyanidin polymerization and decreased monomeric flavan-3-ols, which may reduce wine bitterness and enhance astringency. Therefore, the management of canopy should take into account the warming trends in viticulture regions, rather than being applied preemptively.

Torres Molina, Nazareth

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