Markus Keller, Ph.D.
Chateau Ste. Michelle Distinguished Professor of Viticulture
Education
Ph.D., 1995, Federal Institute of Technology,
Zürich, Switzerland
M.S. (Dipl. Ing. Agr.), 1989, Federal Institute of Technology, Zürich, Switzerland
Research
My research program focuses on developmental and environmental factors and vineyard management practices as they influence crop physiology of wine and juice grapes. As outlined below, my lab investigates scion-rootstock interactions, grape development and water relations during fruit ripening, irrigation and crop load management, yield formation, and cold hardiness.
Rootstock evaluation
This research addresses the needs of both the wine and juice grape industries in Washington. Both industries currently rely almost exclusively on own-rooted plants. Although the occasional cold winters make the use of grafted plants a somewhat risky endeavor, the wine industry wants to be prepared in the event the devastating root aphid phylloxera ever spreads in the state, or if nematode populations increase. While we study the viticultural performance of grafted vines, the collaborating WSU enologist Dr. James Harbertson focuses on fruit composition and wine quality.
The juice grape industry, on the other hand, wrestles with the frequent appearance of lime-induced chlorosis on eastern Washington’s high-pH soils. We are collaborating with the WSU soil scientist Dr. Joan Davenport and the Cornell University plant physiologist Dr. Lailiang Cheng to identify rootstocks and other possible remedies for this chlorosis problem. This work is funded by the Washington wine tax and the juice processors through the Washington State Concord Grape Research Council.
Pre-harvest irrigation
Irrigation during the grapes’ ripening phase is prohibited by law in many European countries and is often discouraged by wineries even in the new world for fear the extra water might be taken up by the grapes and dilute their quality. Surprisingly, there is little scientific evidence that late-season water uptake by the roots is detrimental to fruit quality. We are using innovative techniques to investigate how water moves into and out of grape berries and whether such water movement leads to changes in berry size and solute concentration. This work is done in collaboration with the WSU grape physiologist Dr. Bhaskar Bondada and is funded by the USDA Northwest Center for Small Fruits Research.
Berry shrivel
A relatively new phenomenon is plaguing grape growers up and down western North America from California to British Columbia. Grape berries, especially of the varieties Cabernet Sauvignon and Sauvignon blanc, sometimes appear to stop ripening shortly after veraison and remain sour with low sugar, color and flavor but high astringency. In contrast to the better known bunch-stem necrosis, the rachis tissues remain green until well after the berries have begun to shrivel. The problem is also known in Europe, although often under the name “Zweigelt disease”, because it was first reported on this variety. In collaboration with the WSU grape physiologist Dr. Bhaskar Bondada and the WSU extension viticulturist Dr. Mercy Olmstead we are trying to uncover the causes for this syndrome, so that we may develop potential remedies. This research is funded by the Washington wine tax.
Temperature and fruitfulness
Grapevine yield, which is formed over a two-year period, and fruit composition vary widely from plant to plant, vineyard to vineyard, and season to season. This makes yield estimations and predictions notoriously unreliable and hampers efforts attempting to modify viticultural practices aimed at improving the consistency of grape supply. In collaboration with the USDA-ARS viticulturist Dr. Julie Tarara we are disentangling the effects of temperature from those of sunlight in an effort to uncover the underlying reasons for the variation in vine fruitfulness and yield formation. Funding for this research comes from the USDA Northwest Center for Small Fruits Research.
Planting density
Concord juice producers face stiff competition nationally and internationally, which results in very small profit margins for the growers. We are testing the establishment and performance of Concord grapes planted at various distances both within and between vineyard rows with the aim to consistently maximize crop production while maintaining desirable fruit quality. This project is funded by the juice processors through the Washington State Concord Grape Research Council.
Washington’s occasional cold winters make wind machines or heating devices in vineyards a necessary but costly investment. In extreme cases, not running a wind machine during a cold episode can result in vines being killed to the ground, while running one unnecessarily is a waste of time and money. We test the changes in cold hardiness of buds and cane tissues of a range of grapevine varieties throughout each winter season. The information on critical temperatures is updated weekly, so that growers can use it to determine when frost protection measures should be initiated. Funding for this service activity comes from Washington’s grape growers, winemakers and juice processors through the Washington Association of Wine Grape Growers, Washington Wine Industry Foundation and the Washington State Concord Grape Research Council.
Chardonnay shoot emerging from a bud grafted on a green rootstock shoot in the field.
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Pre-harvest irrigation research
on the cover of the Journal of
Experimental Botany
High-precision sensors measure
the changes in grape berry
diameter while a vine's root
system is being pressurized.
Heating dormant grapevine buds
accelerates shoot development
(foreground) while cooling the
buds slowes growth down
(background).
Example of berry shrivel on one
shoot. The top cluster does not
show symptoms, while the lower cluster exhibits shrivel
symptoms.
Layout of a chamber with
thermocouples used to measure
cold hardiness of grapevine buds and cane tissues.
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Selected Publications
Keller M. and L.J. Mills. 2007: Effect of pruning on recovery and productivity of cold-injured Merlot grapevines. Am. J. Enol. Vitic. 58: 351-357.
Ross C., H. Ferguson, M. Keller, D. Walsh, K. Weller and S. Spayd. 2007: Determination of ortho-nasal aroma threshold for multicolored Asian lady beetle in a Concord grape juice. J. Food Quality 30: 855-863.
Tesic D., M. Keller and R. Hutton. 2007: Influence of vineyard floor management practices on grapevine growth, yield, and fruit composition. Am. J. Enol. Vitic. 58: 1-11.
Holzapfel B.P., J.P. Smith, R.M. Mandel and M. Keller, 2006: Manipulating the postharvest period and its impact on vine productivity of Semillon grapevines. Am. J. Enol. Vitic. 57: 148-157.
Keller M., J.P. Smith and B.R. Bondada, 2006: Ripening grape berries remain hydraulically connected to the shoot. J. Exp. Bot. 57: 2577-2587.
Mills L.J., J.C. Ferguson and M. Keller, 2006: Cold hardiness evaluation of grapevine buds and cane tissues. Am. J. Enol. Vitic. 57: 194-200.
Rogiers S.Y., D.H. Greer, J.M. Hatfield, B.A. Orchard and M. Keller, 2006: Mineral sinks within ripening grape berries (Vitis vinifera L.). Vitis 45: 115-123.
Rogiers S.Y., D.H. Greer, J.M. Hatfield, B.A. Orchard and M. Keller, 2006: Solute transport into Shiraz berries during development and late-ripening shrinkage. Am. J. Enol. Vitic. 57: 73-80.
Keller M., 2005: Deficit irrigation and vine mineral nutrition. Am. J. Enol. Vitic. 56: 267-283.
Keller M., L.J. Mills, J.M. Tarara and J. Ferguson, 2005: Effects of budbreak temperature on seasonal shoot and fruit growth in grapevines. Acta Hort. 689: 183-188.
Keller M., L.J. Mills, R.L. Wample and S.E. Spayd, 2005: Cluster thinning effects on three deficit-irrigated Vitis vinifera cultivars. Am. J. Enol. Vitic. 56: 91-103.
Tarara J.M., J.E. Perez Peña and M. Keller, 2005: Using whole-vine photosynthesis to understand the effects of water deficit on premium wine grapes. Acta Hort. 689: 301-307.
Keller M., L.J. Mills, R.L. Wample and S.E. Spayd, 2004: Crop load management in Concord grapes using different pruning techniques. Am. J. Enol. Vitic. 55:
35-50.
Keller M. and N. Torres-Martinez, 2004: Does UV radiation affect winegrape composition? Acta Hort. 640: 313-319.
Rogiers S.Y., J.M. Hatfield and M. Keller, 2004: Irrigation, nitrogen, and rootstock effects on volume loss of berries from potted Shiraz vines. Vitis 43: 1-6.
Rogiers S.Y., J.M. Hatfield, V.G. Jaudzems, R.G. White and M. Keller, 2004: Grape berry cv. Shiraz epicuticular wax and transpiration during ripening and preharvest weight loss. Am. J. Enol. Vitic. 55: 121-127.
Viret O., M. Keller, V.G. Jaudzems and F.M. Cole, 2004: Botrytis cinerea infection of grape flowers: light and electron microscopical studies of infection sites. Phytopathology 94: 850-857.
Wade J., B. Holzapfel, K. Degaris, D. Williams and M. Keller, 2004: Nitrogen and water management strategies for wine-grape quality. Acta Hort. 640: 61-67.
Keller M., S.Y. Rogiers and H.R. Schultz, 2003: Nitrogen and ultraviolet radiation modify grapevines’ susceptibility to powdery mildew. Vitis 42: 87-94.
Keller M., O. Viret and F.M. Cole, 2003: Botrytis cinerea infection in grape flowers: defense reaction, latency, and disease expression. Phytopathology 93: 316-322.
Keller M., M. Kummer and M.C. Vasconcelos, 2001: Soil nitrogen utilisation for growth and gas exchange by grapevines in response to nitrogen supply and rootstock. Aus. J. Grape Wine Res. 7: 2-11.
Keller M., M. Kummer and M.C. Vasconcelos, 2001: Reproductive growth of grapevines in response to nitrogen supply and rootstock. Aus. J. Grape Wine Res. 7: 12-18.
Rogiers S.Y., J.A. Smith, R. White, M. Keller, B.P. Holzapfel and J.M. Virgona, 2001: Vascular function in berries of Vitis vinifera (L) cv. Shiraz. Aus. J. Grape Wine Res. 7: 47-51.
Keller M., C.C. Steel and G.L. Creasy, 2000: Stilbene accumulation in grapevine tissues: developmental and environmental effects. Acta Hort. 514: 275-286.
Rogiers S.Y., M. Keller, B.P. Holzapfel and J.M. Virgona, 2000: Accumulation of potassium and calcium by ripening berries of field vines of Vitis vinifera (L) cv. Shiraz. Aus. J. Grape Wine Res. 6: 240-243.
Steel C.C. and M. Keller, 2000: Influence of UV-B irradiation on the carotenoid content of Vitis vinifera tissues. In Harwood J.L. and P.J. Quinn (Eds.): Recent Advances in the Biochemistry of Plant Lipids. Portland Press, London, pp. 883-885.
Keller M., R.M. Pool and T. Henick-Kling, 1999: Excessive nitrogen supply and shoot trimming can impair colour development in Pinot Noir grapes and wine. Aus. J. Grape Wine Res. 5: 45-55.
Keller M., K.J. Arnink and G. Hrazdina, 1998: Interaction of nitrogen availability during bloom and light intensity during veraison: I. Effects on grapevine growth, fruit development, and ripening. Am. J. Enol. Vitic. 49: 333-340.
Keller M. and G. Hrazdina, 1998: Interaction of nitrogen availability during bloom and light intensity during veraison: II. Effects on anthocyanin and phenolic development during grape ripening. Am. J. Enol. Vitic. 49: 341-349.
Koblet W., M.C. Candolfi-Vasconcelos und M. Keller, 1996: Stress und Stressbewältigung bei Weinreben. Bot. Helv. 106: 73-84.
Keller M., B. Hess, H. Schwager, H. Schärer and W. Koblet, 1995: Carbon and nitrogen partitioning in Vitis vinifera L.: Responses to nitrogen supply and limiting irradiance. Vitis 34: 19-26.
Keller M. and W. Koblet, 1995: Dry matter and leaf area partitioning, bud fertility and second-season growth of Vitis vinifera L.: Responses to nitrogen supply and limiting irradiance. Vitis 34: 77- 83.
Keller M. and W. Koblet, 1995: Stress-induced development of inflorescence necrosis and bunch stem necrosis in Vitis vinifera L.: Responses to environmental and nutritional effects. Vitis 34: 145- 150.
Keller M. and W. Koblet, 1995: How do grapevines respond to nitrogen supply under limiting irradiance? Acta Hort. 427: 129-131.
Koblet W., M. Keller and M.C. Candolfi-Vasconcelos, 1995: Effects of training system, canopy management practices, crop load and rootstock on grapevine photosynthesis. Acta Hort. 427: 133-140.
Keller M. and W. Koblet, 1994: Is carbon starvation rather than excessive nitrogen supply the cause of inflorescence necrosis in Vitis vinifera L.? Vitis 33: 81-86.
Candolfi M.P., M. Keller and E.F. Boller, 1991: Mite-load function improves precision of feeding damage estimation in Tetranychus urticae. Entomol. Exp. Appl. 58: 289-293.
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