Effect of Temporal and Spatial Variations in Soil Moisture on Grapevine Physiology, Productivity and Quality
Creators: name: Diverres Naranjo, R. Geraldine
Publisher: name: Washington State University
Year: 2023
Subjects: Aquaporins
Partial rootzone drying
Regulated deficit irrigation
Riesling
Soil temperature
Wine

description: The response of wine grapes (Vitis vinifera L.) to water stress can be exploited by growers to achieve quality and production goals. Regulated deficit irrigation (RDI) strategically applies controlled water stress during specific growth stages, leading to reduced vine vigor, smaller berries, and increased fruit sun exposure. While RDI benefits red wine production, it may pose challenges for white wine grape cultivars. Water-stressed vines not only yield smaller berries, but greater sun exposure and reduced transpiration result in higher berry temperatures, which impact acid metabolism and overall fruit quality. In contrast, partial rootzone drying (PRD) introduces spatial water deficit by generating wet and dry sections in the soil. PRD could potentially minimize the adverse effects of regulated deficit irrigation on white wine grape production while conserving irrigation water. This study was conducted over three years in a V. vinifera cv. Riesling vineyard in arid southeastern Washington to examine the impact of PRD and RDI on irrigation water use, canopy size, fruit sun exposure, yield, yield components, fruit characteristics, and wine composition. The results were compared to a no-stress control. Preveraison water deficit, whether through RDI or PRD, reduced yield and altered fruit sun exposure through canopy size reduction. While PRD conserved less irrigation water than RDI, it maintained a canopy size similar to the control, limiting fruit sun exposure. Even small differences in preveraison plant water status resulted in notable differences in the profiles of phenolic and volatile compounds in the wines. These results highlight the impact of irrigation strategies in shaping wine styles in the vineyard through temporal and spatial manipulation of soil water availability. Framed within the field irrigation trial, the effect of irrigation on soil temperature at 30 cm depth was assessed by simultaneously tracking the changes in soil moisture and soil temperature during several irrigation events. The application of irrigation water decreased soil temperature. Variances in soil moisture before and after each irrigation event were correlated with differences in soil temperature. In supplemental growth chamber experiments, soil moisture and soil temperature were manipulated in potted V. vinifera cv. Cabernet Sauvignon vines to assess the effect of these factors on gas exchange, water status, and hydraulic conductance. Lower soil moisture and cooler rootzone temperatures resulted in reduced leaf water potential, stomatal conductance, photosynthesis, transpiration, and whole-plant hydraulic conductance. Since membrane water channels termed aquaporins are crucial in controlling water permeability and can adjust hydraulic conductance in response to various stresses, we collected fine root samples and analyzed the relative expression of four aquaporin genes using RT-qPCR. Cooler rootzone temperatures decreased root aquaporin gene expression and whole-plant hydraulic conductance. While the leaf-level responses (leaf water potential, gas exchange) were dominated by the influence of soil moisture, aquaporin gene expression in the roots was dominated by the effects of soil temperature. The results demonstrate that soil temperature plays a significant role in influencing vine physiology. Irrigation practices, such as regulated deficit irrigation and partial rootzone drying, are widely used and can impact vine physiology beyond the expected effects on changes in soil water content.