Impact of Leaf Removal, Applied Before and After Flowering, on Anthocyanin, Tannin, and Methoxypyrazine Concentrations in ‘Merlot’ (Vitis vinifera L.) Grapes and Wines

Abstract

ABSTRACT:The development and accumulation of secondary metabolites in grapes determine wine color, taste, and aroma. This study aimed to investigate the effect of leaf removal before flowering, a practice recently introduced to reduce cluster compactness and Botrytis rot, on anthocyanin, tannin, and methoxypyrazine concentrations in 'Merlot' grapes and wines. Leaf removal before flowering was compared with leaf removal after flowering and an untreated control. No effects on tannin and anthocyanin concentrations in grapes were observed. Both treatments reduced levels of 3-isobutyl-2-methoxypyrazine (IBMP) in the grapes and the derived wines, although the after-flowering treatment did so to a greater degree in the fruit specifically. Leaf removal before flowering can be used to reduce cluster compactness, Botrytis rot, and grape and wine IBMP concentration and to improve wine color intensity but at the expense of cluster weight and vine yield. Leaf removal after flowering accomplishes essentially the same results without loss of yield.

Multi-Omics and Integrated Network Analyses Reveal New Insights into the Systems Relationships between Metabolites, Structural Genes, and Transcriptional Regulators in Developing Grape Berries (Vitis vinifera L.) Exposed to Water Deficit

“…Compounds were identified with TargetLynx software based on their reference standard, retention time, and qualifier and quantifier ion, and were accurately quantified by their calibration curve and expressed as mg/Kg of grapes. Anthocyanins were analyzed as described in Sivilotti et al (2016) using a HPLC (Shimadzu) equipped with a diode array detector. The concentration of individual anthocyanins was expressed in oenin chloride equivalents and expressed as mg/Kg of grapes.…”

Transcriptional Responses to Pre-flowering Leaf Defoliation in Grapevine Berry from Different Growing Sites, Years, and Genotypes

“…Among the different operations pertaining to grapevine canopy management, pre-flowering leaf removal is likely the one that has received the greatest interest from the scientific community over the last decade. Starting with the original work (Poni et al, 2006), a number of subsequent studies, representing a broad array of cultivars and environments (Diago et al, 2012; Gatti et al, 2012, 2015; Palliotti et al, 2012; Lee and Skinkis, 2013; Pastore et al, 2013; Risco et al, 2014; Komm and Moyer, 2015; Sternad Lemut et al, 2015; Sivilotti et al, 2016), have confirmed the technique to be valuable and repeatable for: (i) reducing vine yield through a decrease in fruit-set and/or berry size; (ii) decreasing cluster compactness, hence susceptibility to rot diseases, and (iii) improving grape composition in terms of total soluble solids (TSSs), phenolic and aroma compounds. However, it was also observed that the outcome of pre-flowering defoliation (PFD) could be quite variable between consecutive years (Gatti et al, 2015) and that different cultivars or the same cultivar in different environments could be influenced differently by the treatment (Kuhn et al, 2014).…”

Does Full Exposure of Clusters Have Any Negative Effects on Tempranillo (Vitis vinifera L.) Grape Quality in La Rioja, Spain? The Use of Severe Cluster-zone Leaf Removal after Berry Set

“…Mosetti et al (2016) reported that basal LR 25 days after anthesis did not affect berry size. In the study by Sivilotti et al (2016), basal LR failed to change the berry mass, even when performed 15 days after flowering. Nonetheless, in our view, to avoid the risk of yield loss, LR ought not to be conducted within two weeks after fruit set.…”

“…Otherwise it is difficult to evaluate the direct impact of the technique. Martínez de Toda & Balda (2014) and Mosetti et al (2016) report that, at a similar TSS level, LR after berry set reduced juice pH and malic acid, although this reduction in pH was not found in the studies of Lee and Skinkis (2013) and Sivilotti et al (2016). Similarly, regarding TA, the results also differed in previous studies.…”

“…Before flowering, LR tends to lead to a lower yield by reducing the rate of fruit set (Poni et al, 2006;Tardáguila et al, 2010;Sivilotti et al, 2016). Since most berry abscission occurs within two to three weeks after full bloom (CandolfiVasconcelos & Koblet, 1990), LR should be conducted at least two weeks after fruit set if an alteration in yield is unwanted.…”