WSU undergraduate scientist Landon Keirsey won a first place award at the Washington Association of Wine Grape Growers meeting for his research on Rhone-style cofermentation. Keirsey is based at WSU Tri-Cities and is mentored by enologist Jim Harbertson. His research was funded in part by grants from the Rhone Rangers and WSU’s College of Agricultural, Human and Natural Resource Sciences.
PULLMAN, Wash. – Some of wine drinkers’ favorite grape varieties are originally from the Rhone River Valley of France. Now, though, syrah, grenache, viognier and a handful of other varieties are grown in vineyards all over the world, including Washington state.
That’s why a U.S.-based organization, Rhone Rangers, recently helped fund the research of four WSU graduate students working on issues related to Rhone grape varieties:
Katherine Wang, a master’s student at WSU Tri-Cities, is studying drought resistance in grenache. It has long been an economically important variety in California, where it is prized for its ability to stand up to the Central Valley’s hot, dry summers.
In Washington, grenache was one of the first premium varietals to be grown in the Yakima Valley. More recently, it has become a key element in blends modeled on those produced in France’s Chateauneuf-de-Pape region.
Wang plans to compare anatomical and physiological features of drought-stressed grenache vines with those found in cabernet sauvignon and zinfandel vines.
“With global competition for water increasing,” she said, “it is important to understand the adaptive mechanisms in different grape varieties in order to ensure the sustainability of viticulture under challenging conditions.”
At WSU’s research center in Prosser, doctoral student Yun Zhang is continuing her investigation of the biophysics of water movement in grapevines. For her Rhone Ranger project, she is focusing on late-season berry shriveling in syrah.
Zhang estimates that growers can lose up to $400 per acre due to weight loss from shriveling. Regarding economic losses, Zhang said, “That’s the known issue. What is not known is the effect of shriveling on wine quality. And we don’t know if shriveling can be prevented or reduced.
“With this study, we’ll gain a better understanding of how and when berries utilize and transport water,” she said. “More crucially, we should be able to give growers more suggestions regarding how to fine tune irrigation depending on environmental conditions knowledge that will enable growers to optimize yield and maximize fruit quality.”
Rhone Rangers has helped fund this work since 2010. Zhang’s work on this and related issues is also funded by the U.S. Department of Agriculture’s Northwest Center for Small Fruits Research.
Eileen Harbertson, a master’s student based at WSU’s Prosser research center, is investigating a new way to control grapevine vigor. Ideally, grapevines would produce a certain amount of green foliage and then stop sprouting leaves in order to focus their resources on fruit development.
Unfortunately for the fruit, a vine’s capacity for outgrowth is enormous and, ironically, pruning excess growth causes a hormonal cascade that generates even more new shoots.
“It can be a Herculean task to keep a high-capacity vine focused on ripening its fruit,” Harbertson said.
Viticulturists plan carefully to constrain vine vigor through controlled irrigation and matching planting sites with specific varieties and trellis types. But, Harbertson said, most aspects of vineyard infrastructure are capital intensive, and managers are reluctant to change things once they are in the ground.
Instead, she is researching the possibility of using a naturally occurring plant hormone to control vigor.
“My ongoing and future work includes testing strigolactone in combination with various pruning regimes in order to understand what the most effective, practical and economically viable protocol will be,” Harbertson said. “Along the way, I’m going to optimize certain analytical methods that will tell us how much strigolactone is in these plants naturally, as well as where the minimum threshold for effective vigor control lies.”
In Pullman, doctoral student Kathie Nicholson is investigating the possibility of detecting genetic differences in varietals and in clones within those varieties.
“The identification of varieties relies primarily on ampelography, the visual assessment of morphological features of the vine – primarily leaves, but also shoots, inflorescences, clusters and berries,” she said.
“Clonal identification is dependent on precise record keeping and the faith that each cutting from a particular clone is properly labeled and tracked,” she said.
“With ampelography, a lot is left to the subjective interpretation of plant features, while with cloning there is always the possibility of record-keeping errors or of plant material getting switched around,” she said. “So we really need a reliable method for identifying varieties and their clones.”
Faculty mentor grad students
Yun Zhang and Eileen Harbertson are both graduate students mentored by WSU Chateau Ste. Michelle Distinguished Professor of Viticulture Markus Keller. Learn more about research in Keller’s lab at http://bit.ly/kellervit.
Kathleen Wang is a graduate student working with viticulturist and assistant professor Bhaskar Bondada at WSU Tri-Cities. Learn more about Bondada’s work at http://bit.ly/uixMeL.
Kathie Nicholson is a graduate student working under the mentorship of horticultural genomicist Amit Dhingra. Learn more about research in Dhingra’s lab at http://bit.ly/sCRADO.
Nicholson has her work cut out for her. Grape varieties have been successfully distinguished using modern DNA analysis, but the differences among clones are much more subtle. She will have to break new ground to develop a test that can detect minute molecular differences.
Her work is no mere academic exercise, though. As part of her recently completed master’s work, Nicholson surveyed both winemakers and consumers in order to get a picture of how each group ranks their awareness and the importance of clones. Both winemakers and wine drinkers are interested in clonal varieties.
Nicholson suspects that, just as differentiation of variety and vineyard have helped wineries market the distinctiveness of their product from others, clonal varieties will offer consumers new choices and marketers new leverage to expand the rapidly growing industry.