Location: Horticultural Crops Research
2009 Annual Report
This is our second year of validation of inoculum detection for timing fungicide applications in commercial vineyards. Results are similar to 2008 where 2-3 fungicide applications were not made with no difference in disease development between reduced application and growers standard fungicide program.
We have developed SSR markers for describing the Phragmidium violaceum population and demonstrated that U.S. population is more diverse than the Australian population and is more closely related to the European population. These data indicate that P. violaceum was either introduced in to the United States several years prior to its discovery in 2005, or numerous introductions from different inoculum sources were made.
Modifications to the Gubler/Thomas model for infection risk of grape powdery mildew to more accurately reflect the impact of high temperature on disease development are being tested in the field for a second year. Efforts to test a blackberry rust model have been hampered by the lack of favorable weather epidemic development for the past three years; however, the model has correctly indicated that conditions were unfavorable. Based on an analysis of climate data and discussion with stakeholders, this research is being terminated to pursue other research directions that will yield greater benefit.
Objective 3 is currently being validated at 5 vineyards locations across the Willamette valley Oregon as well as at 9 other locations in Oregon and Washington by cooperators.
We developed a new technique for examining microbial colonization of leaf surfaces. We demonstrated that a focus ion beam can be used to cut samples placed in scanning electron microscope to examine the 3-D structure of microbial biofilms.
Substantial progress has been made on several project plan objectives. We described the evolution and population structure of Phytophthora ramorum documenting migration of novel clones in the United States and demonstrated that the three known clonal lineages of P. ramorum evolved in geographic isolation over long evolutionary times predating the emergence of agriculture before they emerged as significant pathogens in the United States. An interactive, searchable database documents emergence of new P. ramorum outbreaks and reports genotype and placement into clonal lineage.
Progress has been made in terms of documenting the existence of two distinct small RNA classes describing previously unknown genetic mechanisms in the genus Phytophthora.
We continue to determine leaf wetness and temperature conditions under which P. ramorum can infect viburnum and lilac. Variation in resistance in viburnum and lilac to P. ramorum has been characterized and scientists continue to study the diversity of Phytophthora spp. in nursery environments as a function of plant genotype, season, and cultural practice.
Peetz, A., Mahaffee, W.F., Gent, D.H. 2009. Effect of temperature on the sporulation and infectivity of Podosphaera macularis on Humulus lupulus. Plant Disease. 93:281-286.
Gent, D.H., Turechek, W., Mahaffee, W.F. 2008. Spatial and Temporal Stability of the Estimated Parameters of the Binary Power Law. Phytopathology. 98:1107-1117.
Mahaffee, W.F., Pethybridge, S.J.,Gent, D.H. editors. 2009. Compendium of hop diseases and pests. St. Paul, MN: APS Press. 93 p.
Mahaffee, W.F., Pethybridge, S. 2009. The genus Humulus. In: Mahaffee, W.F., Pethybridge, S.J., and Gent, D.H. editors. Compendium of Hop Diseases and Pests. St. Paul, MN: APS Press. p. 1-5.
Mahaffee, W.F., Englhard, B. 2009. Gray mold. In: Mahaffee, W.F., Pethybridge, S.J., and Gent, D.H. editors. Compendium of Hop Diseases and Pests. St. Paul, MN: APS Press. p. 24-25.
Mahaffee, W.F., Englhard, B., Gent, D.H. 2009. Powdery mildew. In: Mahaffee, W.F., Pethybridge, S.J., and Gent, D.H. editors. Compendium of Hop Diseases and Pests. St. Paul, MN: APS Press. p. 25-31.
Mahaffee, W.F. 2009. Cone early maturity. In: Mahaffee, W.F., Pethybridge, S.J., and Gent, D.H. editors. Compendium of Hop Diseases and Pests. St. Paul, MN: APS Press. p. 73-74.
Mahaffee, W.F., Pethybridge, S., Gent, D.H. 2009. Nutrient imbalances. In: Mahaffee, W.F., Pethybridge, S.J., and Gent, D.H. editors. Compendium of Hop Diseases and Pests. St. Paul, MN: APS Press. p. 75-77.
Mahaffee, W.F., Pethybridge, S., Gent, D.H. 2009. Injuries caused by environmental factors. In: Mahaffee, W.F., Pethybridge, S.J., and Gent, D.H. editors. Compendium of Hop Diseases and Pests. St. Paul, MN: APS Press. p.77-78.
Gent, D.H., Pethybridge, S., Mahaffee, W.F. 2009. Chemical injury. In: Mahaffee, W.F., Pethybridge, S.J., and Gent, D.H. editors. Compendium of Hop Diseases and Pests. St. Paul, MN: APS Press. p. 78-80.
Grunwald, N.J., Goss, E.M. 2009. Evolution and genetics of the invasive sudden oak death pathogen Phytophthora ramorum. In: Lamour, K. and Kamoun, S. editors. Oomycete Genetics and Genomics: Diversity, Interactions, and Research Tools. Hoboken, NJ. John Wiley and Sons Inc. p.179-196.
Grunwald, N.J., Davis, E.A., Rolfe, K.J. 2009. Efficacy of registered and unregistered fungicides for control of ramorum blight on camellia. Plant Disease Management Reports. 2:OT015. Grunwald, N.J., Goss, E.M., Press, C.M. 2008. Phytophthora ramorum: A pathogen with a remarkably wide host range causing sudden oak death on oaks and ramorum blight on woody ornamentals. Molecular Plant Pathology. 9(6):729-740.
Grunwald, N.J., Goss, E.M., Ivors, K., Garbelotto, M., Martin, F.N., Prospero, S., Hansen, E., Bonants, P., Hamelin, R., Chastagner, G., Werres, S., Rizzo, D.M., Abad, G., Beales, P., Bilodeau, G.J., Blomquist, C., Brasier, C., Briere, S., Chandelier, A., Davidson, J.M., Denman, S., Elliott, M., Fichtner, E.J., Frankel, S.J., Goheen, E.M., De Gruyter, H., Heungens, K., James, D., Kanaskie, A., Mcwilliams, M., Moralejo, E., Osterbauer, N.K., Palm, M.E., Parke, J.L., Shamoun, S.F., Shishkoff, N., Tooley, P.W., Vettraino, A., Webber, J., Widmer, T.L. 2009. Standardizing the nomenclature for clonal lineages of the sudden oak death pathogen, Phytophthora ramorum. Phytopathology. 99:792-795.
Malvick, D.K., Grunwald, N.J., Dyer, A.T. 2009. Population structure, races, and host range of Aphanomyces euteiches from alfalfa production fields in the central U.S.A. European Journal of Plant Pathology. 123(2):171-182.
Prospero, S., Grunwald, N.J., Winton, L.M., Hansen, E.M. 2009. Migration patterns of the emerging plant pathogen Phytophthora ramorum on the west coast of the United States of America. Phytopathology. 99:739-749.
Elliott, M., Sumampong, G., Varga, A., Shamoun, S.F., James, D., Masri, S., Briere, S.C., Grunwald, N.J. 2009. PCR-RFLP markers identify threelineages of the North American and European populations of Phytophthora ramorum. Forest Pathology. 39:266-278.