Arturo Calderon-Orellana,* Kasandra Ibarra, Ignacio Serra, and Alvaro Peña-Neira
*Universidad de Concepcion, Vicente Medenz 595, 3780000, Chile 
(arcalderon@udec.cl)

Vines from the Itata Valley, in the Ñuble region of Chile, are head-trained and not irrigated during the growing season. This means that severe water stress often occurs from veraison to harvest, which may compromise fruit quality and carbohydrate accumulation in roots and shoots. Muscat of Alexandria vines from this viticultural region exhibit low vegetative growth, inducing over-exposition of berries to high solar radiation and elevated air temperature. High percentages of sunburn-damaged clusters are usually observed at harvest (±50%), which may impact wine quality. Severe pruning could increase shoot length, reducing the amount of intercepted solar radiation and affecting plant water status and fruit and wine quality. A study was conducted in a non-irrigated Muscat of Alexandria vineyard under the traditional cultural management of the Itata Valley. Three pruning intensities (mild, moderate, and severe, leaving 21, 16, or 12 buds per plant, respectively) were applied in the vineyard. Reproductive growth and development, plant water status, microclimate conditions, and fruit and wine chemical quality were evaluated during the 2020 to 2021 season. At harvest, all vines showed severe levels of water stress, but pruning treatments had no effect on plant water status parameters. Pruning severity changed sunlight penetration at the fruit zone before veraison, which was probably responsible for treatment differences in sunburn incidence and severity. Greater severity of sunburn was associated with a lower concentration of herbaceous aroma compounds. These results indicated that sunburn in berries may be induced by pruning at different severities, generating important changes in the aromatic profile of berries and wines. Consequently, changing pruning practices may be a practical tool to face the consequences of global warming and water scarcity in commercial winegrape production. 

Funding Support: “Centro de Extensión Vitivinícola del Sur” and the “Cooperativa Agrícola y Vitivinícola Cerro Negro – Quillón Ltda (COOVICEN)”