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 Scale bar indicates number of substitutions per site.(Martin, Blair and Coffey, unpublished).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 porri Foister 1931 (Oomycetes, Pythiales)
Notes: Isolates from the host Brassica are referred to the new species Phytophthora brassicae.
Distribution: Africa (South Africa); Asia (Japan); Australia; Europe; North America (Canada). The report from WI, USA is actually Phytophthora brassicae. The report from Canada may be a distinct species (Erwin & Ribeiro 1996).
Substrate: Leaves, roots, collars, bulbs.
Disease Note: Leaf blight; shanking; white tip disease; leaf dieback; crown collar and root rot.
Host: Principal host: Allium spp. (Liliaceae); also 5 other genera in 5 families. Not on Brassicaceae; this is a distinct species Phytophthora brassicae.
Supporting Literature:
Cooke, D.E.L., Drenth, A., Duncan, J.M., Wagels, G., and Brasier, C.M. 2000. A molecular phylogeny of Phytophthora and related Oomycetes. Fungal Genet. Biol. 30: 17-32
Erwin, D.C., and Ribeiro, O.K. 1996. Phytophthora Diseases Worldwide. APS Press, St. Paul, Minnesota, 562 pages.
Man in \\'t Veld, W.A., de Cock, A.W.A.M., Ilieva, E. , and Levesque, C.A. 2002. Gene flow analysis of Phytophthora porri reveals a new species: Phytophthora brassicae sp. nov. Eur. J. Pl. Pathol. 108: 51-62
Stamps, D.J. 1978. Phytophthora porri. C.M.I. Descript. Pathog. Fungi Bact. 595: 1-2
Updated on Jun 07, 2006
P. porri is classified in group III (Stamps et al. 1990). Morphology is illustrated in Figure 1. See Tables 4.2 and 4.3 in Phytophthora Diseases Worldwide (Erwin and Ribeiro 1996) for tabular keys. A description of P. porri is given by Stamps (1978e) and Holliday (1980). Some isolates are host specific. Isolates from Campanula were not pathogenic on leek and vice versa (Legge 1951).
P. porri, as it is known currently, is not a homogeneous species. Within isolates from leek, cabbage, and carrot from different geographical areas, all of which were considered to be P. porri, de Cock et al. (1992) found variations in temperature-growth relations; sporangial production; oogonium, antheridium, and oospore production; pathogenicity to leek (A. porrum) and cabbage (Brassica oleracea L.); and RFLP of mitochondrial DNA (mtDNA). RFLP patterns were significantly different in isolates from Allium and Brassica. The RFLP patterns of the Allium isolates differed from the Brassica and Daucus isolates, all of which correlated well with differences in growth at temperatures higher than 24 to 27oC (See Fig. 53.2 in Phytophthora Diseases Worldwide [Erwin and Ribeiro 1996]). Isolates from A. porrum produced oogonia consistently, but those from B. oleracea produced oogonia shortly after isolation and only occasionally afterward. Isolates from B. oleracea produced sporangia readily on agar media, but isolates from A. porrum produced sporangia only when transferred to hemp seed-water culture. De Cock et al. (1992) suggested that the isolates from Brassica and Daucus carota (carrot) might represent a different, as yet unnamed, species or possibly a forma specialis because they are host specific. Thus, some isolates recorded from carrot and cabbage in Table 1 may eventually be reclassified.
1. Mycelium
Coiling of mycelium (Figure 4.1B, Chapter 4 in Phytophthora Diseases Worldwide [Erwin and Ribeiro 1996]), and Figure A of Stamps [1978e]) is typical; hyphae measure up to 8 µm in diameter but are not uniform.
2. Sporangia
Sporangia are obpyriform, ovoid, or ellipsoid, occasionally with distorted shapes; semipapillate; persistent on the stalk; nonproliferating; and borne successively. Length-breadth ratio is 1.29 to 1.46. For dimensions of sporangia from different hosts, see Table 1. Sporangiophores are undifferentiated, often with intercalary swellings. Sporangia and zoospores can be induced by incubating fast-growing mycelium with soil extract at 15oC for 2 days followed by replacement of soil extract with cold (3oC) distilled water (Smilde and Van Ness 1992).
3. Hyphal Swellings
Hyphal swellings that are round, ellipsoid, or angular and occurring singly or in chains form abundantly in culture.
4. Chlamydospores
Chlamydospores form in culture media after prolonged incubation in water (8 weeks) and measure 20.8 to 35.3 µm in diameter, average 30.0 µm.
5. Sex Organs
P. porri is homothallic. Globose oogonia and oospores form abundantly in culture. Both amphigynous and paragynous antheridia occur. Oogonia average about 34 µm in diameter. Oospores are spherical and aplerotic and average about 30 µm in diameter. For dimensions of oogonia and oospores from different isolates, see Table 1. Wheat and barley straw was a favorable substrate for production of oospores of isolates from carrot (Thomson et al. 1986). DeCock (1992) noted that most oogonia were abortive. Healthy oospores were rare.
6. Growth Temperatures
Although Foister (1931) originally stated that the maximum temperature for growth of P. porri was <35oC, most investigators (de Cock et al. 1992) now report a maximum temperature of 27oC or less (also reported for a carnation isolate by Kouyeas [1977]). Leonian (1934) also found this to be the case with Foister\'s original isolate. Examples of growth at minimum, optimum, and maximum temperatures (oC) include <5:25:35 (Allium porrum, Foister 1931); <8:20:27 (A. porrum from Foister, Leonian 1934); no data:20:27 (Campanula persicofolia, Legge 1951); 3:21:27 (A. porrum, de Cock et al. 1992); 3:18:27 (A. grayi, de Cock et al. 1992); 3:21:24 and 3:21:27 (B. oleracea) and 3:24:30 (Daucus carota) (de Cock et al. 1992). RFLP patterns of an isolate (366.59) from A. porrum with a maximum growth at 36oC had a greater similarity to P. nicotianae than to P. porri (Figure 53.2). De Cock et al. (1992) concluded that this isolate could not be identified as P. porri.
Nomenclature information was provided by the the Systematic Botany and Mycology Laboratory in USDA-ARS.
Isolate list