Effects of vine top shading on the accumulation of C6/C9 compounds in 'Cabernet Sauvignon’ (Vitis vinifera L.) grape berries in northwestern China

Abstract

BACKGROUND: The Xinjiang Uygur Autonomous Region is an arid and semi-arid region with low rainfall and strong sunlight; thus, grape berries in this region accumulate sugar content rapidly, and the ripening process is shorter than that in other regions. Although previous studies illustrated that altered sunlight conditions could influence the aroma profiles of grape berries, less attention has been paid to the effect of vine top shading on volatile compounds under a dry-hot climate.RESULT: We focused on the effects of vine top shading on the concentrations of linolenic and linoleic acids, as well as their metabolites, the C6/C9 compounds, in grape berries. Four vine top shading treatments at veraison (ripening onset) and post-veraison (skin full coloration) were performed by reducing solar exposure to the grapevines by 20% and 50% respectively. Apart from (E)-2-hexenal in the 20% shading treatment of 2016, (E)-2-hexenal were not promoted by the 50% shading and 20% shading treatments during veraison to harvest in both of the vintages. By contrast, the influence of vine top shading from post-veraison till harvest was different between the two vintages; these C6 compounds were decreased in both of the shading treatments in 2016, whereas most of them were promoted in 2017, possibly related to daily sunshine hours in this period. In addition, the C9 compound nonanal with very low concentration exhibits a significant difference among various treatments by two-factor analysis of variance. As for linolenic acid and linoleic acid, two types of C6 compound biosynthetic precursors, four shading treatments all reduced their concentration, except for linolenic acid in the 50% shading treatment of 2016. Moreover, it appeared to have no apparent correlation between the variations of two precursors and their volatile metabolites, indicating that there is a complex impact of vine shading on C6 compound biosynthesis.CONCLUSION: Vine top shading at veraison can reduce the accumulation of some C6 compounds in grape berries, but no consistent consequence was attained for the vine shading at pre-veraison. The findings indicate the significance of grapevine solar exposure management at veraison in controlling the level of C6 compounds in a dry-hot region like Xinjiang.

Effects of Kaolin and Shading Net on the Ecophysiology and Berry Composition of Sauvignon Blanc Grapevines

“…There is an important impact of vine shading on C6/C9 compound biosynthesis (products of the lipoxygenase pathway) and on the concentrations of linolenic and linoleic acids. Under detected high temperatures, the outflow of isoprene, monoterpenes, and C6 elements can balance photosynthetic membranes, preserving the photosynthetic apparatus from lipid peroxidation damage [57]. In addition, shading of the 'Muscat' bunch and leaves from the berry setting to harvest enhanced the concentration of hexanal (C 6 H 12 O) and (E)-2-hexenal compounds [58].…”

Comparative Analysis of the Evolution of Green Leaf Volatiles and Aroma in Six Vitis vinifera L. Cultivars during Berry Maturation in the Chinese Loess Plateau Region

“…A comparison with existing literature reveals that the presence and concentration of C9 aldehydes in grapes are influenced by a multitude of factors, including genetic varietal characteristics, viticultural practices, and, notably, climatic conditions [27,28]. Studies have highlighted the sensitivity of C9 aldehyde synthesis to environmental factors, suggesting that variations in temperature, sunlight exposure, and rainfall can significantly affect their accumulation in grapes [29]. The meteorological data presented for the vintages 2019 and 2020 (Table S1) provide critical insights into the climatic backdrop against which these aromatic compounds developed.…”

Shading Treatment Reduces Grape Sugar Content by Suppressing Photosynthesis-Antenna Protein Pathway Gene Expression in Grape Berries

“…The results showed that shading had significant effects on leaf growth and photosynthetic characteristics, but there were differences among species [18]. In the study of grape berries, the impact of shading during berry ripening on the tannin structure-activity relationship of berry skin extracts was examined, as well as the effect of vine roof shading on C6/C9 compound accumulation in the northwest grape variety 'Cabernet Sauvignon' (V. vinifera L.) [19]. The berries were the main focus of the study.…”