|BOWEN, PATRICIA - Agriculture And Agri-Food Canada|
Submitted to: Irrigation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2013
Publication Date: 3/1/2014
Citation: Shellie, K., Bowen, P. 2014. Isohydrodynamic behavior in deficit-irrigated Cabernet Sauvignon and Malbec and its relationship between yield and berry composition. Irrigation Science. 32:87-97.
Interpretive Summary: Soil moisture in arid climates is determined by irrigation frequency and amount. Irrigation is used to control water supply and is an important cultural practice in winegrape production because it influences yield and fruit composition at harvest. When the amount of water supplied through irrigation is less than required by the vine, a water deficit is imposed and the vine is under water stress. Water stress related changes in berry composition are desirable for enhancing wine quality; however, reduction in yield and response is inconsistent and often insufficient to enhance crop value. Delineation of desirable water deficit severities is complicated because cultivars of winegrape respond differently to water stress and weather conditions have a strong influence on use of available water. Also, there has been limited investigation of the interrelationships among indicators of vine water status and their relationships with different grape cultivars. In this study, we evaluated the relationships between indicators of vine water status, yield and berry attributes at harvest over four seasons in field-grown Cabernet Sauvignon and Malbec grapevines to identify options for optimizing irrigation strategies under arid conditions. Our results show that the yield and berry fresh weight of Malbec was less affected by water deficit than that of Cabernet Sauvignon and that Cabernet Sauvignon was under greater water stress than Malbec when supplied a similar amount of water. Under increasing severity of water stress, Cabernet Sauvignon displayed less increase in soluble solids, anthocyanin, and total phenolics than Malbec The relative magnitudes of yield decline and changes in berry composition associated with midday leaf water potential under the conditions of this study suggest that Cabernet Sauvignon is best grown under mild water stress whereas Malbec is best grown under moderate water stress.
Technical Abstract: Cabernet Sauvignon and Malbec grapevines were irrigated at 70 or 23% of estimated crop evapotranspiration (ETc) throughout berry development over four growing seasons. Stomatal behavior was characterized by relating predawn leaf water potential and mid-morning stomatal conductance to mid-morning leaf water potential. Seasonal average weekly midday leaf water potential was lower in Cabernet Sauvignon than Malbec despite similar irrigation amounts. Both cultivars exhibited anisohydric behavior with midday leaf water potential decreasing linearly with declining predawn leaf water potential (r2=0.51) and stomatal conductance (r2=0.42). However, both cultivars utilized hydrodynamic mechanisms to maintain a soil-to-leaf water potential gradient of -0.62 (± 0.03) MPa under standard irrigation and -0.75 (± 0.04) MPa under reduced irrigation. Berry fresh weight and titratable acidity decreased and the concentration of total anthocyanins increased in both cultivars in response to decreases in midday leaf water potential. The slope of regression equations for seasonal mean midday leaf water potential were used to estimate cultivar specific levels of water stress associated with changes in berry weight and berry composition at fruit maturity.