Abstract

The effects of partial root zone drying (PRD) on the physiology, water status, yield, and wine quality of Vitis vinifera L. cv. Merlot and Carm & eacute;n & egrave;re subjected to a reduction in water supply for irrigation were evaluated during three seasons, although only the data collected in the last two seasons were statistically analyzed because the treatments were only partially implemented in the first season. This study was conducted in two commercial vineyards (Merlot and Carm & eacute;n & egrave;re vineyards) in the central zone of Chile. The plants were subjected to the following treatments: (T0) Control, with conventional irrigation regimes used by local growers; (T1) water shortage equivalent to 50% of T0; and (PRD) the same water supply as T1 but applied with the partial root-drying technique. Across both vineyards, differences were observed in terms of water status variables, where the measures collected under T1 conditions were significantly affected compared with those collected under T0 conditions, whereas stomatal conductance (gs), stem water potential (SWP), chlorophyll fluorescence (Cf), and leaf relative water content (RWC) were strongly mitigated under the PRD treatment. Compared with the T0 treatment, irrigation water use efficiency (IWUE) in both cultivars significantly increased with the PRD treatment. Regarding Merlot, the negative effects of water restriction on yield and physiological performance (gs and SWP) were significantly mitigated under PRD conditions. Conversely, Carm & eacute;n & egrave;re exhibited limited physiological and productive differences among treatments, likely because of the presence of a shallow water table at a depth of approximately 80 cm, which may have buffered the intended water deficit. Additionally, yield losses associated with 50% water restriction were mitigated under PRD conditions, and wine quality improved, as reflected by higher polyphenol content and greater color intensity. These findings highlight PRD as a promising water-saving strategy under commercial conditions, although site-specific factors, such as groundwater availability, can constrain its effectiveness.