The role of rootstocks in grapevine water use efficiency: impacts on transpiration, stomatal control and yield efficiency

Irrigated agriculture is the world’s largest consumer of fresh water. With a growing global demand for horticultural products and decreasing fresh water availability, improving the water use efficiency of irrigated horticultural crops has clear benefits for industry and society. Rootstocks are used in many crops and offer a potential mechanism to alter canopy processes for a given scion, particularly relevant in viticulture, where the scion is strongly associated with the product. Rootstocks may affect vine canopy function in various ways, most notably by altering scion vigour. Changes in scion growth have a direct impact on whole plant transpiration and yield, with potential effects on fruit quality. Rootstocks may also alter canopy responses to the environment, particularly to soil moisture. Through the use of a field trial with mature vines, we have examined the role rootstock selection has in determining canopy size, plant water use, crop yield and crop quality in winegrapes. We have determined that rootstock selection can alter both crop yield per unit of water transpired (crop water use index: CWUI) and the response of canopy physiology to a given soil environment. Assessment of current rootstocks for specific traits that impact CWUI and targeting future rootstock breeding towards these traits will provide improved rootstocks and improved horticultural practice.