Table_1_Photoselective Shade Films Mitigate Heat Wave Damage by Reducing Anthocyanin and Flavonol Degradation in Grapevine (Vitis vinifera L.) Berries.docx

Wine grape production is challenged by forecasted increases in air temperature and droughts due to climate change and photoselective overhead shade films are promising tools in hot viticulture areas to overcome climate change related factors. The aim of this study was to evaluate the vulnerability of ‘Cabernet Sauvignon’ grape berries to solar radiation overexposure, optimize shade film use for preserving berry composition. An experiment was conducted for two years with four shade films (D1, D3, D4, D5) with differing solar radiation spectra transmittance and compared to an uncovered control (C0). Integrals for leaf gas exchange and mid-day stem water potential were unaffected by the shade films in both years. At harvest, berry primary metabolites were not affected by treatments applied in either year. Despite precipitation exclusion during the dormant seasons in shaded treatments, and cluster zone temperatures reaching 58°C in C0, yield was not affected. Berry skin anthocyanin and flavonol composition and content were measured by C18 reversed-phase HPLC. In 2020, total skin anthocyanins (mg·berry-1) in the shaded treatments were 27% greater than C0 during berry ripening and at harvest. Conversely, flavonol content in 2020 decreased in partially shaded grapevines compared to C0. Berry flavonoid content in 2021 increased until harvest while flavonol degradation was apparent from veraison to harvest in 2020 across partially shaded and control grapevines. Untreated control showed lower di- to tri-hydroxylated flavonol ratios closer to harvest. Our results provided evidence that overhead partial shading of vineyards mitigate anthocyanin degradation by reducing cluster zone temperatures and is a useful tool in combatting climate change in hot climate regions.

受气候变化影响，未来气温上升与干旱频发将对酿酒葡萄生产造成严峻挑战；而光选择性顶部遮阴膜则为炎热产区的葡萄栽培应对气候变化相关问题提供了颇具前景的解决方案。本研究旨在评估‘赤霞珠（Cabernet Sauvignon）’葡萄果粒对太阳辐射过度暴露的敏感性，并优化遮阴膜的使用方案以维持果粒的品质组成。本试验为期两年，设置了四种具备不同太阳辐射光谱透过率的遮阴膜处理（D1、D3、D4、D5），并以未遮阴的对照组（C0）作为对照。两年试验中，遮阴膜处理对叶片气体交换参数积分值以及正午茎水势均无显著影响。收获期时，两年试验中各处理对果粒初生代谢产物均无显著影响。尽管遮阴处理组在休眠期排除了自然降水，且对照组（C0）的果簇区域温度最高达58℃，但各处理对产量均无显著影响。本研究采用C18反相高效液相色谱（C18 reversed-phase HPLC）测定了果粒果皮的花色苷与黄酮醇组成及含量。2020年，在果粒成熟阶段及收获期，遮阴处理组的果皮总花色苷含量（mg·berry-1）较对照组（C0）高出27%。与之相反，2020年部分遮阴处理的葡萄植株果皮黄酮醇含量较对照组（C0）有所降低。2021年，果粒总黄酮含量直至收获期均呈上升趋势；而2020年，部分遮阴处理与对照组的葡萄植株均在转色期（veraison）至收获期出现了明显的黄酮醇降解现象。未处理对照组在临近收获期时，二羟基化黄酮醇与三羟基化黄酮醇的比值更低。本研究结果表明，葡萄园顶部部分遮阴可通过降低果簇区域温度缓解花色苷降解，为炎热气候产区应对气候变化提供了可行的实用手段。