Spanish Viticulturists Working with WSU Scientists to Further Understanding of Vineyard Irrigation Management
Pascual Romero, a visiting scientist at WSU’s Irrigated Agriculture Research and Extension Center in Prosser, is the lead author of this year’s Best Paper in Viticulture award from the American Journal of Enology and Viticulture.
Romero shares the award with co-authors and researchers Jose Ignacio Fernández-Fernández and Adrián Martinez-Cutillas of Instituto Murciano de Investigación y Desarrollo Agrario y Alimentario, for their paper titled “Physiological Thresholds for Efficient Regulated Deficit-Irrigation Management in Winegrapes Grown under Semiarid Conditions.”
The subject of the paper, deficit irrigation, highlights the fact that a new leaf is being turned in our understanding of how irrigation affects the physiology of grapevines. In much of Europe, it’s still illegal to irrigate wine grapes after veraison. Veraison, originally a French term, refers to the change of color that occurs in grape berries as they begin to ripen. Because of ancient traditions, rather than science, growers aren’t allowed to irrigate post-veraison for fear of diluting Brix (the measure of the fruit’s sugar content).
For over 20 years, the working assumption has been that berries are hydraulically isolated after veraison, that is, that no water from the roots enters the berries. Recent research by Chateau Ste. Michelle Distinguished Professor of Viticulture Markus Keller and others at WSU’s Irrigated Agriculture Research and Extension Center in Prosser, though, proves that berries are not isolated and that late-season irrigation does not dilute Brix. In fact, Keller said, if done correctly, irrigation accelerates ripening.
“That said, we need lots more research on the effects of irrigation on grapevine physiology,” Keller said.
Romero and his colleagues’ paper begins to address precisely that need. Building on research conducted by Keller and many others, the Spanish scientists found that regulated deficit irrigation (RDI) requires a thorough understanding of “several threshold values for plant stress indicators.” The goal of their two-year RDI project was to gain some insight into how much water could be applied, and when, to “control excessive vegetative development, reduce berry size, and to stimulate the direct accumulation of anthocyanins and other phenolic compounds by post-veraison water deficit.”
To that end, Romero and his collaborators investigated two RDI regimes in order “to identify physiological thresholds for efficient long-term RDI strategies for premium red wines and to improve water use efficiency under semiarid conditions.” They found that a moderate RDI regime was beneficial for factors such as increased Brix and phenolic composition while a much stricter one seriously stressed the plants. The stricter regime reduced fruit quality and actually damaged the vines. This research proposed a range of optimum values of several physiological indicators in order to avoid severe vine damage and to improve phenolic composition and water use efficiency in Mourvedre grapevines. Dangerous thresholds of these physiological parameters were also identified for this variety.
Better knowledge of the contribution of late-season irrigation and water stress to variations in berry size and fruit quality will lay the foundation for better vineyard irrigation management. In semiarid regions like Spain and eastern Washington, that is crucial information because water use affects producers’ economic bottom line.
Now, Romero and Keller are working together to further their understanding of irrigation management in vineyards. “During my year at WSU, my main goal is to learn more about grapevine water relations, especially hydraulic limitations and grape water relations, and deficit irrigation in this dry climate that is so conducive to irrigation viticulture,” Romero said. “I want to study the techniques, tools and approaches used in Keller’s lab to measuring the vines’ responses to water deficit.”
In addition, Romero will participate in ongoing irrigation research in collaboration with Keller’s graduate students, WSU enologist Jim Harbertson, and researchers at Ste. Michelle Wine Estates, which seeks to fine-tune deficit irrigation in order to maximize fruit and wine quality. Romero said that another goal is to initiate some collaborative research between Washington and Spain, both of which have many similar issues in terms of water deficit and irrigation and grapes.
Read the award-winning paper by Pascual Romero et alia in the American Journal of Enology and Viticulture: http://ajevonline.org/cgi/reprint/61/3/300.
Read an article about water use in vineyards by Markus Keller in the Spring 2008 issue of the WSU Wine and Grape Research and Extension Newsletter at http://bit.ly/cwPSMu. In the article, Keller makes some recommendations for growers.
Read an article about irrigation research conducted by Keller and his former graduate student, Marco Biondi, in the Feb. 2008 issue of Voice of the Vine: http://bit.ly/gOCW0W.
Like Spain and eastern Washington, Argentina grows grapes in arid conditions. Read “The Mendoza Connection” to learn about a visiting Argentinian student’s research conducted in collaboration with Keller: http://bit.ly/fx0WGN.
A Successful Celebration
Thank you to everyone who contributed to making the 10th anniversary of the Celebrate Washington Wine gala and auction a success — the attendees, the donors and our sponsors.
The event last month at the Chateau Ste. Michelle Winery in Woodinville netted nearly $120,000 to support the WSU Viticulture and Enology Program. Over its ten year history the event has brought in nearly $1.4 million for the program!
Special thanks to the more than 200 restaurants across the state and in northern Idaho who participated in Chateau Ste. Michelle’s annual “Raise a Glass — Fund a Scholarship” promotion last fall, and to the 10 grocery chains who took part in the spring promotion. Your participation contributed $40,000 in scholarship funding to this year’s auction total.
For a complete list of participating restaurants and supermarkets, please visit http://bit.ly/hnoS5b.
More WAWGG, Less Bark!
WSU faculty and students, with collaboration from USDA ARS scientists, scored big at the poster session at the annual meeting of the Washington Association of Wine Grape Growers a couple weeks ago in Kennewick. Here’s a list of all the awards they won:
- First Prize – Impacts of grapevine leafroll disease on an own-rooted wine grape cultivar by Olufemi J. Alabi, Linga R. Gutha, Luis Casassa, James F. Harbertson, Maria Mireles, Joan Davenport and Naidu A. Rayapati
- Second Prize – A computer model for predicting grapevine cold hardiness by John C. Ferguson, Lynn J. Mills, Julie M. Tarara, Gary G. Grove, Gerrit Hoogenboom, and Markus Keller
- Third Prize – Understanding genetic diversity among grapevine viruses helps to develop robust diagnostics and sound management strategies by Naidu A. Rayapati, Olufemi J. Alabi, Sridhar Jarugula, Linga Gutha, Tefera Mekuria, Sudarsana Poojari and Robert R. Martin
Graduate Student Category
- First Prize – Development of highly sensitive molecular diagnostic assays for the detection of grapevine leafroll associated viruses by Sudarsana Poojari, Patricia Okubara, Olufemi J Alabi and Naidu A. Rayapati
- Second Prize – Know thy enemy: Recreating a virus for R&D applications in grape virology by Sridhar Jarugula, Siddarame Gowda, William O. Dawson and Naidu A. Rayapati
- Third Prize – Unraveling the effects of extended maceration in Merlot wines with different ethanol levels by Federico Casassa, Maria Mireles, Eric Harwood and James F. Harbertson
Undergraduate Student Category
- First Prize – Studies on epidemiology of the grapevine leafroll disease by Elizabeth L. Swanson, Olufemi J. Alabi and Naidu A. Rayapati
- Second Prize – Epidemiology of the grapevine leafroll disease in Washington vineyards by Andrew L. Schultz and Naidu A. Rayapati
- Third Prize – Do state laws affect wine sales? by Carlye Rice and Dennis Reynolds
Learm more about the research behind the growing reputation of Washington wines by visiting the WSU Viticulture and Enology web site at http://bit.ly/bScehw.
Learn more about the Washington Association of Wine Grape Growers’ annual meetings by visiting http://bit.ly/6XuEvg.