Interannual climatic variability effects on yield, berry and wine quality indices in long-term deficit irrigated grapevines, determined by multivariate analysis

Pascual Romero,1 Jose Ignacio Fernández-Fernández,2 Pablo Botía1 1Department of Natural Resources, Irrigation Group and Physiology of Stress, 2Department of Viticulture, The Murcian Institute of Agri-Food Research and Development (IMIDA), Murcia, Spain Abstract: The effects of climatic factors on yield and berry and wine quality for long-term (7 years) deficit-irrigated (DI) Monastrell wine grapes under the semiarid conditions of southeast Spain were analyzed. The relationships between climatic variables and the yield, and novel technological berry quality (QItechnologicalberry), phenolic berry quality (QIphenolicberry), overall berry quality (QIoverallberry), and wine quality (QIwine) indices confirmed that the most important climatic factors were rainfall, temperature, and radiation. Climate was more influential in determining yield, berry, and wine composition in some important physiological periods such as early season (budburst–fruit set) and ripening (véraison–harvest). In general, climate had more influence on berry quality than on wine quality indices and greater QIoverallberry was also reflected in greater QIwine. According to the stepwise multiple regression, the best fitted models for the partial root-zone drying irrigation (PRI) system were less complex (with a lower number of climatic variables) than for the regulated deficit irrigation (RDI) system, suggesting that PRI is less influenced by climatic factors than RDI. For PRI, the models for yield, berry and wine quality were explained by three climatic factors (rainfall, Tª, and radiation), whereas for RDI, more climatic factors came into play (number of hours of sunshine, evapotranspiration, and vapor pressure deficit). According to these models, in RDI, a sunny and drier pre-véraison period followed by higher soil water availability and associated greater crop evapotranspiration during ripening favored final berry and wine quality. In contrast, in PRI, greater rainfall during the growing season and greater solar radiation during ripening were the main climatic factors that positively influenced the yield response, berry and wine quality. Besides, berry quality in PRI was more affected (negatively) by high temperatures (high Tªmax and Tªmin) during the growing season than in RDI and SDI, indicating that cooler and humid years may favor the PRI response more. These results suggest that years with a cool, wet winter followed by a mild, wet spring and early summer (April–June) and a mild fruit set–véraison period (June–July), and then greater solar radiation during ripening (August–mid-September) provide adequate growth potential and increase the likelihood of higher berry and wine quality in PRI. Besides, more irrigated SDI vines were less sensitive to high temperatures and low soil water content during ripening than RDI and PRI vines. Keywords: berry quality indices, climatic factors, multivariate analysis, deficit irrigation techniques, wine quality index, yiel