American Journal of Potato Research

, Volume 86, Issue 4, pp 315–326 | Cite as

Metalaxyl-M-Resistant Pythium Species in Potato Production Areas of the Pacific Northwest of the U.S.A.

  • Lyndon D. Porter
  • Philip B. Hamm
  • Nicholas L. David
  • Stacy L. Gieck
  • Jeffery S. Miller
  • Babette Gundersen
  • Debra A. Inglis


Several Pythium species causing leak on potato are managed by the systemic fungicide metalaxyl-M. Metalaxyl-M-resistant (MR) isolates of Pythium spp. have been identified in potato production areas of the U.S.A., but information is lacking on the distribution of MR isolates in the Pacific Northwest. Soil samples from numerous fields (312) cropped to potatoes in Idaho (140), Oregon (59), and Washington (113) were assayed using metalaxyl-M-amended agar for the presence of MR isolates of Pythium in 2004 to 2006. Altogether, 1.4%, 42.4% and 32.7% of the fields from these states, respectively, were positive for MR Pythium. Isolates of Pythium ultimum that were highly resistant to metalaxyl were recovered from 53 fields representing ID, OR, and WA. Greater than 50% of the Pythium soil population consisted of MR isolates in ten of 64 fields from Oregon and Washington. Nine species of Pythium were recovered from soil samples, of which MR P. ultimum and P. spinosum were identified. Isolates of MR P. ultimum recovered from soil were pathogenic on potato tubers and may pose a serious threat to the management of Pythium leak and seed rot of diverse crops rotated with potato.


Mefenoxam Fungicide resistance Pythium paroecandrum Pythium inflatum 


Varias especies de Pythium que causan la pudrición acuosa en papa son controladas por el fungicida sistémico metalaxilo-M. Cepas de metalaxilo-M-resistente (MR) de Pythium spp. han sido identificadas en áreas de producción de papa de los Estados Unidos, pero no hay información de la distribución de cepas MR en el Pacifico Noroeste. Muestras de suelo de numerosos campos (312) cultivados con papa, en Idaho (140), Oregon (59), y Washington (113) fueron ensayadas utilizando agar metalaxilo-M-enmendado para la presencia de Pythium MR del 2004 al 2006. En total, 1.4%, 42.4% y 32.7% de los campos de estos estados, respectivamente, dieron positivo a Pythium MR. Cepas de Pythium ultimum altamente resistentes al metalaxilo fueron recuperadas de 53 campos representando a Idaho, Oregon y Washington. Más del 50% de la población de Pythium del suelo, consistió de cepas MR en 10 de los 64 campos de Oregon y Washington. Nueve especies de Pythium fueron recuperadas de muestras de suelo, de las cuales fueron identificadas P. ultimum y P. spinosum MR. Cepas de P. ultimum resistente al metalaxilo-M recuperadas del suelo fueron patogénicas en tubérculos de papa y pueden representar una seria amenaza en el manejo de la pudrición acuosa por Pythium y la pudrición de la semilla en diversos campos rotados con papa.



The authors would like to thank the National Potato Council for funding this research project, and Steve James Casey Royer, Brian Charlton and Mike Nielsen for collecting soil. The experiments associated with this research were in compliance with the laws of the U.S.A.


  1. Broders, K.D., P.E. Lipps, P.A. Paul, and A.E. Dorrance. 2007. Characterization of Pythium spp. associated with corn and soybean seed and seedling disease in Ohio. Plant Disease 91: 727–735.CrossRefGoogle Scholar
  2. Bruin, G.C.A., and L.A. Edgington. 1981. Adaptive resistance in Peronosporales to metalaxyl. Canadian Journal of Plant Pathology 3: 201–206.Google Scholar
  3. Café-Filho, A.C., and J.B. Ristaino. 2008. Fitness of isolates of Phytophthora capsici resistant to mefenoxam from squash and pepper field in North Carolina. Plant Disease 92: 1439–1443.CrossRefGoogle Scholar
  4. Chauhan, V.B., and U.P. Singh. 1987. A naturally occurring resistant forma specialis of Phytophthora drechsleri to metalaxyl. Journal of Phytopathology 120: 93–96.CrossRefGoogle Scholar
  5. Chellemi, D.O., D.J. Mitchell, M.E. Kannwisher-Mitchell, P.A. Rayside, and E.N. Roskopf. 2000. Pythium spp. associated with bell pepper production in Florida. Plant Disease 84: 1271–1274.CrossRefGoogle Scholar
  6. Cook, R.J., B.X. Zhang, and A. Doerr. 1983. Failure of metalaxyl to control all of the Pythium population pathogenic on roots of Pacific Northwest wheat. (Abstr.). Phytopathology 73: 957.Google Scholar
  7. Crute, I.R., and J.M. Harrison. 1988. Studies on the inheritance of resistance to metalaxyl in Bremia lactucae and on the stability and fitness of field isolates. Plant Pathology 37: 231–250.CrossRefGoogle Scholar
  8. Davidse, L.C. 1981. Resistance to acylalanine fungicides in Phytophthora megasperma f. sp. medicaginis. Netherlands Journal of Plant Pathology 87: 11–24.CrossRefGoogle Scholar
  9. Davidse, L.C., A.E. Hoffman, and G.C.M. Velthuis. 1983. Specific interference of metalaxyl with endogenous RNA polymerase activity in isolated nuclei from Phytophthora megasperma f. sp. medicaginis. Experimental Mycology 7: 344–361.CrossRefGoogle Scholar
  10. Davis, R.M., and J.J. Nunez. 1999. Influence of crop rotation on the incidence of Pythium- and Rhizoctonia- induced carrot root dieback. Plant Disease 83: 146–148.CrossRefGoogle Scholar
  11. Deahl, K.L., D.A. Inglis, and S.P. De Muth. 1993. Testing for resistance to metalaxyl in Phytophthora infestans isolates from northwestern Washington. American Potato Journal 70: 779–795.CrossRefGoogle Scholar
  12. Dowley, L.J., and E. O’Sullivan. 1981. Metalaxyl-resistant strains of Phytophthora infestans (Mont.) de Bary in Ireland. Potato Research 24: 417–421.CrossRefGoogle Scholar
  13. Dowley, L.J., D. Griffin, and E. O’Sullivan. 2002. Two decades of monitoring Irish populations of Phytophthora infestans for phenylamide resistance. Potato Research 45: 79–84.CrossRefGoogle Scholar
  14. Erwin, D.C., and O.K. Ribeiro. 1996. Phytophthora diseases worldwide. St. Paul, MN: APS.Google Scholar
  15. Falloon, R.E., G.B. Follas, R.C. Butler, and D.S. Goulden. 2000. Resistance in Peronospora viciae to phenylamide fungicides: reduced efficacy of seed treatments of pea (Pisum sativum) and assessment of alternatives. Crop Protection 19: 313–325.CrossRefGoogle Scholar
  16. Ferrin, D.M., and J.N. Kabashima. 1991. In vitro insensitivity to metalaxyl of isolates of Phytophthora citricola and P. parasitica from ornamental hosts in southern California. Plant Disease 75: 1041–1044.Google Scholar
  17. Gent, D.H., M.E. Nelson, and G.G. Grove. 2008. Persistence of phenylamide insensitivity in Pseudoperonospora humuli. Plant Disease 92: 463–468.CrossRefGoogle Scholar
  18. Gisi, U., and Y. Cohen. 1996. Resistance to phenylamide fungicides: a case study with Phytophthora infestans involving mating type and race structure. Annual review of Phytopathology 34: 549–572.PubMedCrossRefGoogle Scholar
  19. Goodwin, S.B., and M.T. McGrath. 1995. Insensitivity to metalaxyl among isolates of Phytophthora erythroseptica causing pink rot of potato in New York. Plant Disease 79: 967.Google Scholar
  20. Goodwin, S.B., and A. Drenth. 1997. Origin of the A2 mating type of Phytophthora infestans outside Mexico. Phytopathology 87: 992–999.PubMedCrossRefGoogle Scholar
  21. Hamm, P.B., B.A. Fry, and J. Jaeger. 1994. Occurrence and frequency of metalaxyl insensitivity and mating types of Phytophthora infestans in the Columba Basin of Oregon and Washington. (Abstr.). Phytopathology 84: 1123.Google Scholar
  22. Hamm, P.B., D.A. Inglis, R. Finn, and G. Olaya. 2004. Resistance to mefenoxam in isolates of Pythium ultimum from potato in Oregon. Potato Research 81: 64.Google Scholar
  23. Hansen, E.M., D.D. Myrold, and P.B. Hamm. 1990. Effects of soil fumigation and cover crops on potential pathogens, microbial activity, nitrogen availability, and seedling quality in conifer nurseries. Phytopathology 80: 698–704.CrossRefGoogle Scholar
  24. Henderson, D., C.J. Williams, and J.S. Miller. 2007. Forecasting late blight in potato crops of southern Idaho using logistic regression analysis. Plant Disease 91: 951–956.CrossRefGoogle Scholar
  25. Hendrix Jr, F.F., and W.A. Campbell. 1973. Pythiums as plant pathogens. Annual review of Phytopathology 11: 77–98.CrossRefGoogle Scholar
  26. Herzog, J., and H. Schuepp. 1985. Three types of sensitivity to metalaxyl in Plasmopara viticola. Phytopathologische Zeitschrift 114: 90–93.CrossRefGoogle Scholar
  27. Higginbotham, R.W., T.C. Paulitz, and K.K. Kidwell. 2004. Virulence of Pythium species isolated from wheat fields in eastern Washington. Plant Disease 88: 1021–1026.CrossRefGoogle Scholar
  28. Hollowell, J.E., B.B. Shew, M.K. Beute, and Z.G. Abad. 1998. Occurrence of pod rot pathogens in peanuts grown in North Carolina. Plant Disease 82: 1345–1349.CrossRefGoogle Scholar
  29. Hubele, A., W. Kunz, W. Eckhart, and E. Sturm. 1983. The fungicidal activity of acylalanines. In Pesticide chemistry, human welfare and the environment, ed. J. Miyamoto, P.C. Kearing, P. Doyle, and T. Fujita, 233–242. New York: Pergamon.Google Scholar
  30. Johnson, D.A., T.F. Cummings, P.B. Hamm, R.C. Rowe, J.S. Miller, R.E. Thornton, G.Q. Pelter, and E.J. Sorensen. 1997. Potato late blight in the Columbia Basin: An economic analysis of the 1995 epidemic. Plant Disease 81: 103–106.CrossRefGoogle Scholar
  31. Johnson, D.A., T.F. Cummings, and P.B. Hamm. 2000. Cost of fungicides used to manage potato late blight in the Columbia Basin: 1996 to 1998. Plant Disease 84: 399–402.CrossRefGoogle Scholar
  32. Kadish, D., and Y. Cohen. 1989. Population dynamics of metalaxyl-sensitive and metalaxyl-resistant isolates of Phytophthora infestans in untreated crops of potato. Plant Pathology 38: 271–276.CrossRefGoogle Scholar
  33. Kadish, D., and Y. Cohen. 1992. Fitness of metalaxyl-sensitive and metalaxyl-resistant isolates of Phytophthora infestans in potato tubers. Phytopathology 82: 887–889.CrossRefGoogle Scholar
  34. Kraft, J.M., and D.W. Burke. 1971. Pythium ultimum as a root pathogen on beans and peas in Washington. Plant Disease Reporter 55: 1056–60.Google Scholar
  35. Levesque, C.A., C.E. Harlton, and A.W.A.M. de Cock. 1998. Identification of some oomycetes by reverse dot blot hybridization. Phytopathology 88: 213–222.PubMedCrossRefGoogle Scholar
  36. Mazzola, M., P.K. Andrews, J.P. Reganold, and C.A. Levesque. 2002. Frequency, virulence and metalaxyl sensitivity of Pythium spp. isolated from apple roots under conventional and organic production systems. Plant Disease 86: 669–675.CrossRefGoogle Scholar
  37. Mendes, M.A.S., V.L. da Silva, J.C. Dianese, et al. 1998. Fungos em Plants no Brasil. Emprapa-Brasilia: SPI/Embrapa-Cenargen.Google Scholar
  38. Molinero-Ruiz, M.L. 2003. First report of resistance to metalaxyl in Downy Mildew of Sunflower caused by Plasmopara halstedii in Spain. Plant Disease 87: 749.CrossRefGoogle Scholar
  39. Njoroge, S.M.C., M.B. Riley, and A.P. Keinath. 2008. Effect of incorporation of Brassica spp. residues on population densities of soilborne microorganisms and on damping-off and Fusarium wilt of watermelon. Plant Disease 92: 287–294.CrossRefGoogle Scholar
  40. Nuninger, C., G. Watson, N. Leadbitter, and H. Ellgehausen. 1996. CGA329341: Introduction of the enantiometric form of the fungicide metalaxyl. Brighton Crop Protection Conference. Pests and Diseases 1: 263–268.Google Scholar
  41. Paulitz, T.C., and K. Adams. 2003. Composition and distribution of Pythium communities in wheat fields in eastern Washington state. Phytopathology 93: 867–873.PubMedCrossRefGoogle Scholar
  42. Peters, R.D., H.W. Platt, and C.A. Lévesque. 2005. First report of Pythium sylvaticum causing potato tuber rot. American Journal of Potato Research 82: 173–177.CrossRefGoogle Scholar
  43. Porter, L.D., J.S. Miller, P. Nolte, and W.J. Price. 2007. In vitro somatic growth and reproduction of phenylamide-resistant and -sensitive isolates of Phytophthora erythroseptica from infected potato tubers in Idaho. Plant Pathology 56: 492–499.CrossRefGoogle Scholar
  44. Powelson, M.L., K.B. Johnson, and R.C. Rowe. 1993. Management of diseases caused by soilborne pathogens. In Potato health management, ed. R.C. Rowe, 149–158. St. Paul MN: APS.Google Scholar
  45. Pscheidt, J.W., and C.M. Ocamb. 2007. Pacific northwest plant disease management handbook. Corvalis, OR: Oregon State University.Google Scholar
  46. Raposo, R., V. Gomez, T. Urrutia, and P. Melgarejo. 2000. Fitness of Botrytis cinerea associated with dicarboximide resistance. Phytopathology 90: 1246–1249.PubMedCrossRefGoogle Scholar
  47. Reuveni, M., H. Eyal, and Y. Cohen. 1980. Development of resistance to metalaxyl in Pseudoperonospora cubensis. Plant Disease 64: 1108–1109.Google Scholar
  48. Salas, B., and G.A. Secor. 2001. Leak. In Compendium of potato diseases, 2nd ed, ed. W.R. Stevenson, R. Loria, G.D. Franc, and D.P. Weingartner, 30–31. St. Paul, MN: APS.Google Scholar
  49. Schettini, T.M., E.J. Legg, and R.W. Michelmore. 1991. Insensitivity to metalaxyl in California populations of Bremia lactucae and resistance of California lettuce cultivars to downy mildew. Phytopathology 81: 64–70.CrossRefGoogle Scholar
  50. Schroeder, K.L., P.A. Okubara, J.T. Tambong, C.A. Levesque, and T.C. Paulitz. 2006. Identification and quantification of pathogenic Pythium spp. from soils in eastern Washington using real-time polymerase chain reaction. Phytopathology 96: 637–647.PubMedCrossRefGoogle Scholar
  51. Seemuller, E., and C. Sun. 1989. Occurrence of metalaxyl resistance in Phytophthora fragariae. Nachrichtenblatt des Deutschen Pflanzenschutzdienstes 41: 71–73.Google Scholar
  52. Shattock, R.C. 1988. Studies on the inheritance of resistance to metalaxyl in Phytophthora infestans. Plant Pathology 37: 4–11.CrossRefGoogle Scholar
  53. Shew, H.D. 1985. Response of Phytophthora parasitica var. nicotianae to metalaxyl exposure. Plant Disease 69: 559–562.CrossRefGoogle Scholar
  54. Sumner, D.R., R.D. Gitaitis, J.D. Gay, D.A. Smittle, B.W. Maw, E.W. Tollner, and Y.C. Hung. 1997. Control of soilborne pathogenic fungi in fields of sweet onion. Plant Disease 81: 885–891.CrossRefGoogle Scholar
  55. Taylor, R.J., B. Salas, G.A. Secor, V. Rivera, and N.C. Gudmestad. 2002. Sensitivity of North American isolates of Phytophthora erythroseptica and Pythium ultimum to mefenoxam (metalaxyl). Plant Disease 86: 797–802.CrossRefGoogle Scholar
  56. Taylor, R.J., B. Salas, and N.C. Gudmestad. 2004. Differences in etiology affect mefenoxam efficacy and the control of pink rot and leak tuber diseases of potato. Plant Disease 88: 301–307.CrossRefGoogle Scholar
  57. Timmer, L.W., J.H. Graham, and S.E. Zitko. 1998. Metalaxyl-resistant isolates of Phytophthora nicotianae: Occurrence, sensitivity, and competitive parasitic ability on citrus. Plant Disease 82: 254–261.CrossRefGoogle Scholar
  58. USDA National Agricultural Statistics Service. 2008. Crop Production 2007 Summary, 64–65. Beltsville, MD: USDA-NASS.Google Scholar
  59. Wang, P.H., and J.G. White. 1997. Molecular characterization of Pythium species based on RFLP analysis of the internal transcribed spacer region of ribosomal DNA. Physiological and Molecular Plant Pathology 51: 129–143.CrossRefGoogle Scholar
  60. White, J.G., M.E. Stanghellini, and L.M. Ayoubi. 1988. Variation in the sensitivity to metalaxyl of Pythium spp. isolated from carrot and other sources. Annals of Applied Biology 113: 269–277.CrossRefGoogle Scholar
  61. White, T.J., T. Bruns, S. Lee, and J. Taylor. 1990. Amplification and direct sequencing of fungal ribosomal RNA genes for phylogenetics. In PCR protocols, a guide to methods and applications, ed. M.A. Innis, D.H. Gelfand, J.J. Sninsky, and T.J. White, 315–322. San Diego, CA: Academic.Google Scholar
  62. Wiglesworth, M.D., M. Reuveni, W.C. Nesmith, M.R. Siegel, J. Kuc, and J. Juarez. 1988. Resistance of Peronospora tabacina to metalaxyl in Texas and Mexico. Plant Disease 72: 964–967.CrossRefGoogle Scholar
  63. Zhang, B.Q., W.D. Chen, and X.B. Yang. 1998. Occurrence and relative abundance of Pythium species in long- term corn and soybean monoculture and corn/soybean rotation fields. Mycological Research 102: 1450–1452.CrossRefGoogle Scholar

Copyright information

© Potato Association of America 2009

Authors and Affiliations

  • Lyndon D. Porter
    • 1
  • Philip B. Hamm
    • 2
  • Nicholas L. David
    • 3
  • Stacy L. Gieck
    • 2
  • Jeffery S. Miller
    • 4
  • Babette Gundersen
    • 5
  • Debra A. Inglis
    • 5
  1. 1.Vegetable and Forage Crops Research UnitUSDA-ARSProsserUSA
  2. 2.Department of Botany & Plant Pathology, Hermiston Agricultural Research and Extension CenterOregon State UniversityHermistonUSA
  3. 3.Department of Plant SciencesNorth Dakota State UniversityFargoUSA
  4. 4.Miller Research LLCRupertUSA
  5. 5.NWRECWashington State UniversityMount VernonUSA

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