Abstract
Monoterpenes are crucial to floral and fruit aromas in grapes and wines. Cluster thinning is a common practice for improving grape quality. Using Vitis vinifera cv. Muscat Hamburg, the effects of three cluster-thinning regimes on the biosynthesis and accumulation of monoterpenes from véraison to harvest were investigated at the transcriptomics and targeted metabolomics levels. It was observed that more intense thinning produced higher concentrations of total monoterpenes, particularly in their bound forms. The numbers of differentially expressed genes among the three treatments were 193, 200, and 238 at the three developmental stages. In total, 10 modules were identified from a weighted gene correlation network analysis, and one module including 492 unigenes was associated with monoterpene metabolism. These findings provide new insights into the molecular basis of the relationship between cluster thinning and monoterpene biosynthesis in Muscat Hamburg grape. Cluster thinning could be carefully considered for its application in production.
Highlights
High-quality grapes usually produce low to moderate yields, and over-cropping reduces grape and wine quality level [1]
Cluster thinning is a vineyard practice used worldwide to regulate vine yields by removing whole-grape clusters [2]. This practice results in improved conditions for the retained grapes by changing the source/sink ratio and the leaf area/fruit weight ratio, thereby regulating secondary metabolite synthesis and accumulation [3,4]
The experiment was conducted during the 2018 season on ‘Muscat Hamburg’ (Vitis vinifera L.) vines located in the Sino-French Joint Venture Dynasty Winery (116◦ 230 E, 39◦ 540 N; Tianjin, China)
Summary
High-quality grapes usually produce low to moderate yields, and over-cropping reduces grape and wine quality level [1]. Cluster thinning is a vineyard practice used worldwide to regulate vine yields by removing whole-grape clusters [2]. This practice results in improved conditions for the retained grapes by changing the source/sink ratio and the leaf area/fruit weight ratio, thereby regulating secondary metabolite synthesis and accumulation [3,4]. The change in the source/sink ratio resulting from cluster thinning enhances the accumulation of secondary metabolites such as anthocyanins and favonols [5]. Cluster thinning affects berry ripening, which influences the acid, sugar, aroma, and polyphenol contents of the harvested grapes and resulting wines [6,7]. Cluster thinning increases the anthocyanin contents in ‘Cabernet Franc’, ‘Sangiovese’, ‘Cabernet
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