Grape Flavonoid Evolution and Composition Under Altered Light and Temperature Conditions in Cabernet Sauvignon (Vitis vinifera L.).

Erna H Blancquaert,Jorge M Ricardo-Da-Silva,Anita Oberholster,Alain J Deloire

doi:10.3389/fpls.2019.01062

Abstract

The evolution of flavonoids under altered temperature and light conditions in the fruit zone was followed in Cabernet Sauvignon (Vitis vinifera L.) grapes during ripening. The study was conducted over two consecutive seasons in 2010/2011 and 2011/2012 comprising two main treatments in which the light quantity was manipulated in the bunch zone: (1) standard (STD) with no lateral shoot or leaf removal and (2) leaf removal west (LRW) treatment with leaf removal on the western side of the bunch zone. Furthermore, the light quality was altered by installing ultraviolet B-suppression sheets within the bunch zone in both seasons. Tannin evolution was dependent on the prevailing light quality/quantity and temperatures during berry development in a particular season. Grape seed tannin accumulation coincided with seed development and commenced at the early stages of berry development. Seed proanthocyanidin composition was not influenced by the treatments. The largest impact on proanthocyanidin accumulation and structure in the skin was due to seasonal variations highlighting the complex interaction between light quality and/or quantity across the two growing seasons and eventually the complex interaction with temperature. Flavonol accumulation was significantly influenced by the light quality, which is known to be the main abiotic driver of flavonol biosynthesis regulation. Anthocyanin concentration and content were largely dependent on the temperature and light quality in a particular season. Anthocyanin composition was altered by the season rather than the treatment.

Highlights

Cabernet Sauvignon (Vitis vinifera L. cv.) is one of the most planted red grape cultivars globally, which is true for the Stellenbosch Wine of Origin District in South Africa South African Wine Industry Statistics (SAWIS, 2016)
This study highlighted the complexity of working under vineyard conditions to investigate the complex interaction of abiotic factors on berry metabolites
The novelty of our study involves the work being conducted under actual vineyard conditions in South Africa, which experiences high levels of UV radiation, while other studies were based on experimental setups (Spayd et al, 2002; Berli et al, 2008)

Summary

Introduction

Cabernet Sauvignon (Vitis vinifera L. cv.) is one of the most planted red grape cultivars globally, which is true for the Stellenbosch Wine of Origin District in South Africa South African Wine Industry Statistics (SAWIS, 2016). Despite the importance of this variety for winemaking, there are still important research questions that should be addressed One such question is about the impact. Flavonoids perform major roles in plants such as pollen fertilization, auxin transport regulation, pigmentation, defense against pathogens and pests, and protection from ultraviolet (UV) radiation (Ribereau-Gayon and Glories, 1986; Santos-Buelga and Scalbert, 2000; Winkel-Shirley, 2001; Adams, 2006). Flavonoids are important in wine because of their contribution to color, taste, mouthfeel, and the potential beneficial role in human health (Ribereau-Gayon and Glories, 1986; Santos-Buelga and Scalbert, 2000; Winkel-Shirley, 2001; Adams, 2006). The three main groups of flavonoids identified in red grape berries are flavan-3-ols (tannin), anthocyanin, and flavonols

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