Impact of Cluster Thinning on Quality of “Malbec” Grapes in Encruzilhada do Sul-RS

Abstract

The cultivar Malbec has been present's good performance and quality in the South Half of Rio Grande do Sul (RS). In this context, we aimed to evaluate the quality of "Malbec" grapes in relation to the phytotechnical, physicochemical parameters and bioactive compounds under different intensities of cluster thinning in Encruzilhada do Sul-RS. The experiment was carried out in a commercial vineyard in the 2015/16 with the cultivar Malbec (Vitis vinifera L.) under rootstock "1103 Paulsen", with spacing of 2.2 m between rows and 1.1 m between plants. The experimental design was of randomized complete blocks with five replications. The treatment factor tested was the cluster thinning, with four levels (0%, 10%, 30% and 50%), performed in véraison. The evaluated phytotechnical variables were cluster length, cluster fresh weight, berries fresh weight, number of berries, rachis fresh weight. Also what were determined are the number of clusters, production and Ravaz index. The physicochemical variables verified were pH, soluble solids (SS), titratable acidity (TA) and SS/TA ratio. The bioactive compounds were total polyphenols index and total anthocyanins. The appropriate balance between source and sink, by the Ravaz index, occurs to zero and 10% of cluster thinning. The "Malbec" grapes present an increase of the maturation index (SS/TA) at 50% of cluster thinning, due to the low titratable acidity at this level. The total polyphenols index has a larger increment when the plants are submitted to the cluster thinning of 10%, providing a larger quality to the fruits. At all the levels of cluster thinning tested, when compared to the control, there was a greater contribution of total anthocyanins in the berries.

The impact of cluster thinning and leaf removal timing on the grape quality and concentration of monomeric anthocyanins in Cabernet-Sauvignon and Probus (Vitis vinifera L.) wines

“…CT can increase total soluble solid concentration (TSS) (Reynolds et al, 1994;Valdes et al, 2009) and pH (Valdes et al, 2009) of the grape juice. It can also speed up ripening (Barros et al, 2018), which could be useful especially in regions with unfavourable conditions during grape ripening. This technique also increases ethylene production in some fruits, indicating advance maturity (Lopez et al, 2011).…”

Impact of Cluster Thinning on Wine Grape Yield and Fruit Composition: A Review and Meta-Analysis

“…Our meta-analysis revealed no overall signifcant increase in the concentration of anthocyanin and phenolics due to CT; however, many individual studies indicated a positive efect of CT on berry anthocyanin and phenolic concentration. Increases in anthocyanins were observed in studies performed in various wine regions that considered multiple varieties, including Nebbiolo [97], Tempranillo [51,[98][99][100][101], Syrah [100,102], Sangiovese [15], Grenache [91], Pinot Noir [10,34,46,103], Cabernet Sauvignon [27,32,39,46,104], Merlot [31], Malbec [36], Refosco [105], Tannat [92], and Cabernet Franc [8,104]. Te observed increases in grape and wine anthocyanin concentration might be determined by the increases in sugars determined by CT. Anthocyanin and sugar accumulation at the onset of ripening are strongly related [106]; however, uncoupling efects between anthocyanin and sugars may be observed during ripening when grapes are subjected to environmental stresses, such as drought or heat stress [107][108][109].…”

“…Reščič et al [42] also revealed a more consistent impact of thinning at 50% at reducing TA than 25%. Mota et al [39] compared 50% and 75% cluster thinning and showed no consistent pattern of either one treatment improving anthocyanin concentration across two years in Merlot, while in another study, thinning at 10%, 30%, and 50% increased anthocyanin concentration consistently [36].…”

“…Grape producers often remove one cluster per shoot to facilitate ripening, leading to the greater proportion of researchers evaluating cluster thinning near 33-50% severity. Multiple studies have compared thinning at diferent severities [36][37][38][39][40][41][42][43][44][45]. Ough and Nagaoka [40] compared 33% and 66% thinning across multiple years and observed a signifcant decrease in yield in both treatments.…”

Utilization of different yield regulation methods of the vine for production of wines of higher designation protected of origin

“…The given fact relates to a looser arrangement of berries in the bunch, especially when using a cluster tipping method [6], [7]. A smaller grape crop improves grape ripening [8][9][10]. It can improve grape quality and wine quality parameters [11].…”