Markus Keller

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.

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 physiologistDr. Bhaskar Bondada 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.

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.

Cold hardiness
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 State Grape and Wine Research Program and the Washington State Concord Grape Research Council.

Staff and Students

• Zilia Khaliullina – Scientific Assistant
• Alan Kawakami – Agr. Research Technician II
• Nataliya Shcherbatyuk – Postdoctoral Research Associate
• Charles Obiero – Postdoctoral Research Associate
• Rosbelys Geraldine Diverres Naranjo – Ph.D. student
• Pierre Davadant – Ph.D. student
• Steven M Jachym – M.S. student

Selected Publications

 

Frost S.C., D.J. Fox, M. Keller, T.S. Collins and J.F. Harbertson. 2023. Freeze-killed leaf material causes atypical aromas and astringency in Cabernet Sauvignon. Am. J. Enol. Vitic. 74: 0740005.

Groenveld T., C. Obiero, Y. Yu, M. Flury and M. Keller. 2023. Predawn leaf water potential of grapevines is not necessarily a good proxy for soil moisture. BMC Plant Biol. 23: 369.

Hewitt S., E. Hernández-Montes, A. Dhingra and M. Keller. 2023. Impact of heat stress, water stress, and their combined effects on the metabolism and transcriptome of grape berries. Sci. Rep. 13: 9907.

Kang C., G. Diverres, M. Karkee, Q. Zhang and M. Keller. 2023. Decision-support system for precision regulated deficit irrigation management for wine grapes. Comput. Electron. Agric. 208: 107777.

Kang C., G. Diverres, A. Paudel, M. Karkee, Q. Zhang and M. Keller. 2023. Estimating soil and grapevine water status using ground-based hyperspectral imaging under diffused lighting conditions: addressing the effect of lighting variability in vineyards. Comp. Electron. Agric. 212: 108175.

Keller M., L.J. Mills and A.K. Kawakami. 2023. Optimizing irrigation for mechanized Concord juice grape production. Am. J. Enol. Vitic. 74: 0740008.

Londo J.P., M.M. Moyer, M. Mireles, L. Mills, M. Keller, B.A. Workmaster, A. Atucha and A.P. Kovaleski. 2023. Evaluation of sample preparation practices common with differential thermal analysis of grapevine bud cold hardiness. Am. J. Enol. Vitic. 74: 0740002.

Müller K.K., M. Keller, M. Stoll and M. Friedel. 2023: Wind speed, sun exposure and water status alter sunburn susceptibility of grape berries. Front. Plant Sci. 14: 1145274.

Saxena A., P. Pesantez-Cabrera, R. Ballapragada, K.H. Lam, M. Keller and A. Fern. 2023. Grape cold hardiness prediction via multi-task learning. Proc. AAAI Conference on Artificial Intelligence 37: 15717-15723.

Chandel A.K, M.M. Moyer, M. Keller, L.R. Khot and G.A. Hoheisel. 2022. Soil and climate geographic information system data-derived risk mapping for grape phylloxera in Washington state. Front. Plant Sci. 13: 827393.

Keller M., R. Scheele-Baldinger, J.C. Ferguson, J.M. Tarara and L.J. Mills. 2022. Inflorescence temperature influences fruit set, phenology, and sink strength of Cabernet Sauvignon grape berries. Front. Plant Sci. 13: 864892.

Lehr P., E. Hernández-Montes, J. Ludwig-Müller, M. Keller and C. Zörb. 2022. Abscisic acid and proline are not equivalent markers for heat, drought, and combined stress in grapevines. Aust. J. Grape Wine Res. 28: 119-130.

Thapa S., C. Kang, G. Diverres, M. Karkee, Q. Zhang and M. Keller. 2022. Assessment of water stress in vineyards using on-the-go hyperspectral imaging and machine learning algorithms. J. ASABE 65: 949-962.

Zhang Y., B.M. Chang, B. Burdet, Z. Dai, S. Delrot and M. Keller. 2022: Apoplastic sugar may be lost from grape berries and retrieved in pedicels. Plant Physiol. 190: 592-604.

Zhou Z., G. Diverres, C. Kang, S. Thapa, M. Karkee, Q. Zhang and M. Keller. 2022: Ground-based thermal imaging for assessing crop water status in grapevines over a growing season. Agronomy 12: 322.

Chang B.M. and M. Keller. 2021: Cuticle and skin cell walls have common and unique roles in grape berry splitting. Hort. Res. 8: 168.

Hernández-Montes E., Y. Zhang, B.M. Chang, N. Shcherbatyuk and M. Keller. 2021: Soft, sweet and colorful: Stratified sampling reveals sequence of events at the onset of grape ripening. Am. J. Enol. Vitic. 72: 137-151.

Hoff R.T., B.R. Bondada and M. Keller. 2021: Onset and progression of the berry shrivel ripening disorder in grapes. Aust. J. Grape Wine Res. 27: 280-289.

Keller M. and L.J. Mills. 2021. High planting density reduces productivity and quality of mechanized Concord juice grapes. Am. J. Enol. Vitic. 72: 358-370.

Camargo-Alvarez H., M. Salazar-Gutiérrez, M. Keller and G. Hoogenboom. 2020: Modeling the effect of temperature on bud dormancy of grapevines. Agric. For. Meteorol. 280: 107782.

Chang B.M., Y. Zhang and M. Keller. 2020. Grape berry splitting is not limited to humid climates. Acta Hort. 1276: 155-161.

Galat Giorgi E., M. Keller, V.O. Sadras, F.A. Roig and J. Perez Peña. 2020. High temperature during the budswell phase of grapevines increases shoot water transport capacity. Agric. For. Meteorol. 295: 108173.

Gonzalez Antivilo F., R.C. Paz, J. Tognetti, M. Keller, M.G. Cavagnaro, E.E. Barrio and F. Roig Juñent. 2020: Winter injury to grapevine secondary phloem and cambium impairs budbreak, cambium activity, and yield formation. J. Plant Growth Regul. 39: 1095-1106.

Keller M. 2020: The Science of Grapevines. 3rd Edition. Elsevier Academic Press, London, UK.

Peña Quiñones A.J., G. Hoogenboom, M.R. Salazar-Gutiérrez, C. Stöckle and M. Keller. 2020. Comparison of air temperature measured in a vineyard canopy and at a standard weather station. PLOS One 15: e0234436.

Chang B.M., Y. Zhang and M. Keller. 2019: Softening at the onset of grape ripening alters fruit rheological properties and decreases splitting resistance. Planta 250: 1293-1305.

Galat Giorgi E., V.O. Sadras, M. Keller and J. Perez Peña. 2019: Interactive effects of high temperature and water deficit on Malbec grapevines. Aust. J. Grape Wine Res. 25: 345-356.

Gohil H., L.J. Mills and M. Keller. 2019: Cordon renewal strategies for declining Merlot grapevines. Catalyst 3: 1-7.

Peña Quiñones A.J., B. Chaves Cordoba, M.R. Salazar Gutierrez, M. Keller and G. Hoogenboom. 2019: Radius of influence of air temperature from automated weather stations installed in complex terrain. Theor. Appl. Climatol. 137: 1957-1973.

Peña Quiñones A.J., M. Keller, M.R. Salazar Gutierrez, L. Khot and G. Hoogenboom. 2019: Comparison between grapevine tissue temperature and air temperature. Sci. Hort. 247: 407-420.

Badr G., G. Hoogenboom, M. Abouali, M. Moyer and M. Keller. 2018: Analysis of several bioclimatic indices for viticultural zoning in the Pacific Northwest. Clim. Res. 76: 203-223.

Badr G., G. Hoogenboom, M. Moyer, M. Keller, R. Rupp and J. Davenport. 2018: Spatial suitability assessment for vineyard site selection based on fuzzy logic. Precision Agric. 19: 1027-1048.

Camargo Alvarez H., M. Salazar-Gutiérrez, D. Zapata, M. Keller and G. Hoogenboom. 2018: Time-to-event analysis to evaluate dormancy status of single-bud cuttings: An example for grapevines. Plant Meth. 14: 94.

Gonzalez Antivilo F., R.C. Paz, M. Echevarria, M. Keller, J. Tognetti, R. Borgo and F. Roig Juñent. 2018: Thermal history parameters drive changes in physiology and cold hardiness of young grapevine plants during winter. Agric. For. Meteorol. 262: 227-236.

Halldorson M.M. and M. Keller. 2018: Grapevine leafroll disease alters leaf physiology but has little effect on plant cold hardiness. Planta 248: 1201-1211.

Bondada B., E. Harbertson, P.M. Shrestha and M. Keller. 2017: Temporal extension of ripening beyond its physiological limits imposes physical and osmotic challenges perturbing metabolism in grape (Vitis vinifera L.) berries. Sci. Hort. 219: 135-143.

Bondada B. and M. Keller. 2017: Structural and fruit compositional anomalies related to various shrivel types developing during ripening of grape berries. Acta Hort. 1157: 49-54.

Cragin J., M. Serpe, M. Keller and K. Shellie. 2017: Dormancy and cold hardiness transitions in wine grape cultivars Chardonnay and Cabernet Sauvignon. Am. J. Enol. Vitic. 68: 195-202.

Gonzalez Antivilo F., R.C. Paz, M. Keller, R. Borgo, J. Tognetti and F. Roig Juñent. 2017: Macro- and microclimate conditions may alter grapevine deacclimation: variation in thermal amplitude in two contrasting wine regions from North and South America. Int. J. Biometeorol. 61: 2033-2045.

Keller M. and L.J. Mills. 2017: ‘Sunbelt’ as a possible ‘Concord’ juice grape partner in a warming world. HortTechnology 27: 557-562.

Romero P., P. Botía and M. Keller. 2017: Hydraulics and gas exchange recover more rapidly from severe drought stress in small pot-grown grapevines than in field-grown plants. J. Plant Physiol. 216: 58-73.

Zapata D., M. Salazar-Gutierrez, B. Chaves, M. Keller and G. Hoogenboom. 2017: Predicting key phenological stages for 17 grapevine cultivars (Vitis vinifera L.). Am. J. Enol. Vitic. 68: 60-72.

Zhang Y. and M. Keller. 2017: Discharge of surplus phloem water may be required for normal grape ripening. J. Exp. Bot. 68: 585-595.

Zhang Y., J.C. Perez and M. Keller. 2017: Grape berry transpiration: determinant factors, developmental changes, and influences on berry ripening. Acta Hort. 1188: 51-56.

Bowen P., K.C. Shellie, L. Mills, J. Willwerth, C. Bogdanoff and M. Keller. 2016: Abscisic acid form, concentration, and application timing influence phenology and bud cold hardiness in Merlot grapevines. Can. J. Plant Sci. 96: 347-359.

Keller M., P. Romero, H. Gohil, R.P. Smithyman, W.R. Riley, L.F. Casassa and J.F. Harbertson. 2016: Deficit irrigation alters grapevine growth, physiology, and fruit microclimate. Am. J. Enol. Vitic. 67: 426-435.

Keller M., P.M. Shrestha, G.E. Hall, B.R. Bondada and J.R. Davenport. 2016: Arrested sugar accumulation and altered organic acid metabolism in grape berries affected by berry shrivel syndrome. Am. J. Enol. Vitic. 67: 398-406.

Molitor D. and M. Keller. 2016: Yield of Müller-Thurgau and Riesling grapevines is altered by meteorological conditions in the current and previous growing seasons. OENO One 50: 245-258.

Casassa L.F., M. Keller and J.F. Harbertson. 2015: Regulated deficit irrigation alters anthocyanins, tannins and sensory properties of Cabernet Sauvignon grapes and wines. Molecules 20: 7820-7844.

Keller M. 2015: The Science of Grapevines – Anatomy and Physiology. 2^nd Edition. Elsevier Academic Press, London, UK.

Keller M., L.S. Deyermond and B.R. Bondada. 2015: Plant hydraulic conductance adapts to shoot number but limits shoot vigour in grapevines. Funct. Plant Biol. 42: 366-375.

Keller M., Y. Zhang, P.M. Shrestha, M. Biondi and B.R. Bondada. 2015: Sugar demand of ripening grape berries leads to recycling of surplus phloem water via the xylem. Plant Cell Environ. 38: 1048-1059.

Zapata D.M., M. Salazar, B. Chaves, M. Keller and G. Hoogenboom. 2015: Estimation of the base temperature and growth phase duration in terms of thermal time for four grapevine cultivars. Int. J. Biometeorol. 59: 1771-1781.

Zhang Y. and M. Keller. 2015: Grape berry transpiration is determined by vapor pressure deficit, cuticular conductance, and berry size. Am. J. Enol. Vitic. 66: 454-462.

Ferguson, J.C., M.M. Moyer, L.J. Mills, G. Hoogenboom and M. Keller. 2014. Modeling dormant bud cold hardiness and budbreak in twenty-three genotypes reveals variation by region of origin. Am. J. Enol. Vitic. 65: 59-71.

Keller, M. and P.M. Shrestha. 2014. Solute accumulation differs in the vacuoles and apoplast of ripening grape berries. Planta 239: 633-642.

Casassa, L.F., R.C. Larsen, C.W. Beaver, M.S. Mireles, M. Keller, W.R. Riley, R. Smithyman and J.F. Harbertson. 2013. Impact of extended maceration and regulated deficit irrigation (RDI) in Cabernet Sauvignon wines: Characterization of proanthocyanidin distribution, anthocyanin extraction, and chromatic properties. J. Ag. Food Chem. 61: 6446-6457.

Casassa, L.F., R.C. Larsen, C.W. Beaver, M.S. Mireles, M. Keller, W.R. Riley, R. Smithyman and J.F. Harbertson. 2013. Sensory impact of extended maceration and regulated deficit irrigation on Washington state Cabernet Sauvignon wines. Am. J. Enol. Vitic. 64: 505-514.

Bondada, B.R. and M. Keller. 2012. Not all shrivels are created equal – morpho-anatomical and compositional characteristics differ among different shrivel types that develop during ripening of grape (Vitis vinifera L.) berries. Am. J. Plant Sci. 3: 879-898.

Bondada, B.R. and M. Keller. 2012. Morphoanatomical symptomatology and osmotic behavior of grape berry shrivel. J. Am. Soc. Hort. Sci. 137: 20-30.

Harbertson, J.F. and M. Keller. 2012. Rootstock effects on deficit-irrigated winegrapes in a dry climate: Grape and wine composition. Am. J. Enol. Vitic. 63: 40-48.

Keller, M., L.J. Mills and J.F. Harbertson. 2012. Rootstock effects on deficit-irrigated winegrapes in a dry climate: Vigor, yield formation, and fruit ripening. Am. J. Enol. Vitic. 63: 29-39.

Widrlechner, M.P., C. Daly, M. Keller and K. Kaplan. 2012. Horticultural applications of a newly revised USDA Plant Hardiness Zone Map. HortTechnology 22: 6-19.

Ferguson, J.C., J.M. Tarara, L.J. Mills, G.G. Grove and M. Keller. 2011. Dynamic thermal time model of cold hardiness for dormant grapevine buds. Ann. Bot. 107: 389-396.

Hall, G.E., B.R. Bondada and M. Keller. 2011. Loss of rachis cell viability is associated with ripening disorders in grapes.  J. Exp. Bot. 62: 1145-1153.

Tarara, J.M., J.E. Perez Peña, M. Keller, R.P. Schreiner and R.P. Smithyman. 2011. Net carbon exchange in grapevine canopies responds rapidly to timing and extent of regulated deficit irrigation. Funct. Plant Biol. 38: 386-400.

Keller, M., J.M. Tarara and L.J. Mills. 2010. Spring temperatures alter reproductive development in grapevines. Aus. J. Grape Wine Res. 16: 445-454

Keller, M. 2010.  The Science of Grapevines – Anatomy and Physiology. Elsevier: Academic Press, Burlington, MA.

Keller, M. 2010. Managing grapevines to optimise fruit development in a challenging environment: a climate change primer for viticulturists. Aus. J. Grape Wine Res. 16: 56-69.

Keller, M. and J.M. Tarara. 2010. Warm spring temperatures induce persistent season-long changes in shoot development in grapevines. Ann. Bot. 106: 131-141.

Davenport, J.R., M. Keller, and L.J. Mills. 2008. How cold can you go? Frost and winter protection for grape. HortScience 43: 1966-1969.

Hagen, K.M., M. Keller, and C.G. Edwards. 2008. Survey of biotin, pantothenic acid, and assimilable nitrogen in winegrapes from the Pacific Northwest. Am. J. Enol. Vitic. 59: 432-436.

Keller, M. 2008. Traubenwelke: auch in den USA ungelöst. Schweiz. Z. Obst. Weinbau 144: 6-8.

Keller, M., R.P. Smithyman, and L.J. Mills. 2008. Interactive effects of deficit irrigation and crop load on Cabernet Sauvignon in an arid climate. Am. J. Enol. Vitic. 59: 221-234.

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, and 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.