Impact of Cluster Thinning and Basal Leaf Removal on Fruit Quality of Cabernet Franc (Vitis vinifera L.) Grapevines Grown in Cool Climate Conditions

Abstract

<jats:p>Achieving desired fruit quality at harvest in cool climate conditions is a challenge, especially for red varieties, and the typical inability of fruit to reach technological maturity is a critical contributing factor requiring examination. To probe this issue, this research investigated the impact of two levels of crop thinning and of basal leaf removal at three phenological stages in the 2011 and 2012 growing seasons in Michigan. Experiments were conducted at the Southwest Michigan Research and Extension Center (SWMREC) in Benton Harbor. Using ‘Cabernet franc’ (<jats:italic>Vitis vinifera</jats:italic> L.) vines, yield components (yield per vine, pruning weight, and cluster and berry weight) and basic fruit composition traits [total soluble solids (TSS), pH, titratable acidity, anthocyanins, and phenolics) were studied to investigate the effect of cluster thinning and basal leaf removal on vine performance and fruit quality at harvest. Neither of the treatments significantly impacted TSS in either of the two seasons. Cluster thinning treatment successfully altered cropload ratio, indexed as Ravaz Index (RI), independently of the time of application. Basal leaf removal increased exposed berry temperature, cluster light exposure, and subsequent anthocyanin and phenolic content of the berry in both seasons, again independent of application date, whereas cluster thinning was effective only in 2012. Crop thinning coupled with basal leaf removal resulted in an increased efficiency in anthocyanin accumulation in relation to TSS accumulation, expressed as anthocyanin:sugar, in both years. This is significant because it offers potential for vineyard management practices aiming to improve fruit quality in cool climates where the onset of anthocyanin accumulation could be reduced and decoupled from sugar accumulation.</jats:p>

Effect of Exogenous Abscisic Acid (ABA), Gibberellic Acid (GA3) and Cluster Thinning on Yield of some Grape Cultivars

“…However, it had a remarkable effect on the cluster weight, but such increase did not completely compensate the decrement in the yield weight. Our results concerning the effect of cluster thinning on yield weight and cluster weight have been confirmed by many workers (Looney and Wood, 1977;Looney, 1981;Kaps and Cahoon, 1989;Ferree et al, 2003;Dami, 2005;Reynolds et al, 2007;Gil-Muñoz et al, 2009;El-salhy et al, 2009;Kamiloglu, 2011;Zhuang et al, 2014 andBogicevic et al, 2015), they found that cluster thinning of grape cultivars reduced yield. Naor et al, 2002;Sun et al, 2012 andRescic et al, 2015 noted that the reduction of yield weight resulted from cluster thinning led to a significant increase of cluster weight.…”

Modeling Land Suitability for Vitis vinifera in Michigan Using Advanced Geospatial Data and Methods

“…The present study was conducted in MI, United States. The region experiences a humid continental climate with warm summers, cold winters [9,13,16,[29][30][31] and a mean growing season temperature range of 13 • C to 15 • C [9]. The region receives consistent precipitation year-round [29,31], estimated at 70-80 mm per month [32].…”

“…Thirdly, Schultze, Sabbatini and Luo [29] report that MI, especially the west coast, receives reliable rainfall all-year round. However, seasonal precipitation peaks coincide with veraison (beginning of fruit ripening) and harvesting periods leading to reduced yields due to increased fruit disease occurrence and failure of the vines to reach full fruit maturity [30]. Lastly, vinifera production is limited by occurrence of very cold winter temperatures [34].…”

Vineyard Floor Management and Cluster Thinning Inconsistently Affect ‘Pinot noir’ Crop Load, Berry Composition, and Wine Quality

“…Many studies have defined wine grape crop load metrics related to basic ripeness, including sugar accumulation, under greenhouse conditions (Jackson, 1986) and primarily in warm, arid regions (Geller and Kurtural, 2013;Jackson and Lombard, 1993;Keller et al, 2005;Kliewer and Weaver, 1971;Uriarte et al, 2016). However, studies that investigated relationships between crop load and wine quality have been inconclusive because of climate, cultural, and cultivar differences (Bravdo et al, 1984(Bravdo et al, , 1985King et al, 2015;Reynolds et al 1994Reynolds et al , 1996Zhuang et al, 2014). Previously defined crop load metrics have not been useful for cool climate 'Pinot noir' production, in part because of limited applicability to the climatic or cultivar constraints.…”