Phytophthora has been rebuilt to fix security-related problems and to restore GIS tools. These tools allow users to visualize the geospatial, temporal, and environmental contexts of Phytophthora discoveries. The next phase is to update species information and add data derived from large-scale surveys. If you have suggestions and requests to make the database better, please contact Seogchan Kang (sxk55@psu.edu).
Genus wide phylogeny for Phytophthora using four mitochondrial loci (cox2, nad9, rps10 and secY; 2,373 nucleotides). Maximum likelihood branch lengths shown. Numbers on nodes represent bootstrap support values for maximum likelihood (top), maximum parsimony (middle) and Bayesian posterior probabilities as percentages (bottom). Nodes receiving significant support (>95%) in all analysis are marked with an asterisk (*). Scale bar indicates number of substitutions per site.(Martin, Blair and Coffey, unpublished).
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Phytophthora pseudotsugae Hamm & E.M. Hans. 1983 (Oomycetes, Pythiales)
Notes: Close to Phytophthora cactorum based on molecular analysis (Kroon 2004).
Distribution: North America (USA: WA, OR).
Substrate: Roots.
Disease Note: Root rot.
Host: Pseudotsuga menziesii (Douglas-fir, Pinaceae).
Supporting Literature:
Erwin, D.C., and Ribeiro, O.K. 1996. Phytophthora Diseases Worldwide. APS Press, St. Paul, Minnesota, 562 pages.
Hall, G. 1989. Phytophthora pseudotsugae. C.M.I. Descript. Pathog. Fungi Bact. 978: 1-2
Kroon, L.P.N.M., Bakker, F.T., van den Bosch, G.B.M., Bonants, P.J.M., and Flier, W.G. 2004. Phylogenetic analysis of Phytophthora species based on mitochondrial and nuclear DNS sequences. Fungal Genet. Biol. 41: 766-782
Updated on Jun 12, 2006
P. pseudotsugae is classified in group I (Stamps et al. 1990) and briefly described in G. Hall (1989a). Morphology is shown in Figure 1. See Tables 4.2 and 4.3 in Phytophthora Diseases Worldwide (Erwin and Ribeiro 1996) for tabular keys. Distribution is in the northwestern United States (Washington and Oregon) (CMI Distribution Maps of Plant Diseases 600).
1. Sporangia
Sporangia are spherical to ovoid, sometimes obturbinate or ampulliform, and distinctly papillate. Sporangia are seldom formed on solid media but are formed when colonies grown on pea broth are washed and incubated in distilled water or soil extract at 10 or 20oC. Sporangia formed at 10oC within 1 to 2 days and averaged 49 39 µm (range 42 to 51 32 to 43 µm) but at 20oC were smaller and averaged 39 32 µm (range 34 to 45 28 to 35 µm). The length-breadth ratios, average 1.23:1 (range 1.18 to 1.27:1), were similar at 10 and 20oC. Sporangia are persistent on simple, long (29 to 632 µm) sporangiophores. Intercalary sporangia are formed by some isolates but not by others.
2. Chlamydospores and Hyphal Swellings
Hyphal swellings occur on some isolates (Hamm and Hansen 1983). Irregular hyphal swellings are illustrated by G. Hall (1989a).
3. Sex Organs
P. pseudotsugae produces sex organs in single culture (homothallic) in cornmeal agar, lima bean agar, pea broth, and V8 juice agar. Average diameter of oogonia on V8 juice agar and lima bean agar is 35 µm and on cornmeal agar and pea broth 31 µm. On V8 juice agar, the diameter ranges from 24 to 45 µm, with isolate means ranging from 32 to 40 µm. Oogonia are spherical and smooth walled (about 1.2 µm thick) and borne terminally on stalks varying from 20 to 120 µm in diameter, widening to 5.8 µm at the point of oogonial attachment.
Antheridia are hyaline and usually spherical or club shaped. Dimensions range from 6 to 21 10 to 24 µm (average 11 15 µm). Antheridia are predominantly paragynous and attached to the oogonia at a point near the oogonial stalk; occasionally antheridia are amphigynous (Figure 1).
Oospores are pigmented, spherical, smooth walled, and aplerotic but nearly fill the oogonium. Diameters of oospores ranged from 27 to 33 µm, averaging 24 µm, on V8 juice agar. Hamm and Hansen (1983) noted that most oospores were reported to be abortive.
4. Growth Temperatures
Growth occurs at temperatures ranging from 2 to 30oC with an optimum at 20 to 25oC.
5. Distinguishing Characteristics
P. pseudotsugae lacks any uniquely diagnostic characteristic but can be readily separated from P. cactorum. P. pseudotsugae produces long and loosely branched sporangiophores unlike those produced by P. cactorum or P. iranica. Both P. cactorum and P. iranica produce chlamydospores, but P. pseudotsugae does not. P. cactorum produces caducous sporangia, but P. pseudotsugae does not (Hamm and Hansen 1983). P. pseudotsugae differs from P. iranica by production of smaller sporangia and from P. clandestina by the absence of subterminal antheridia and markedly aplerotic oospores (G. Hall 1989a). Protein patterns were similar for several isolates of P. pseudotsugae and differed distinctly from those of P. cactorum (also classified in group I).
Nomenclature information was provided by the the Systematic Botany and Mycology Laboratory in USDA-ARS.
Isolate list