Author
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Shellie, Krista |
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BOWEN, PATRICIA - Agri Food - Canada |
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Submitted to: Irrigation Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 12/1/2013 Publication Date: 3/1/2014 Citation: Shellie, K., Bowen, P. 2014. Indicators of plant water status in deficit irrigated grapevines and their relationships to yield and berry composition. American Journal of Enology and Viticulture. 32(2):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 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: The relationships between indicators of water status, yield and berry attributes at harvest were evaluated over four seasons in field-grown Cabernet Sauvignon and Malbec grapevines under sustained levels of water deficit to identify options for optimizing irrigation strategies under arid conditions. Vines of each cultivar were drip-irrigated with a standard or reduced amount of water that supplied 70 or 23% of estimated full vine evapotranspiration. Our results show that both grape cultivars adapted sufficiently to produce ripe fruit under a substantial reduction in water supply; however, the yield and berry fresh weight of Malbec, with its near-isohydric response to water stress, was less affected by water deficit than that of Cabernet Sauvignon. Cabernet Sauvignon, with its near-anisohydric response to water stress, maintained a lower midday leaf water potential than Malbec and displayed less increase in soluble solids, anthocyanin, and total phenolics than Malbec under increasing severity of water stress. Predawn and midday leaf water potential were found to be similarly related in each cultivar; however, the relationships between midday leaf water potential, stomatal conductance and soil moisture reflected each cultivars’ near-anisohydric or isohydric behavior. 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. |
