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 Scale bar indicates number of substitutions per site.(Martin, Blair and Coffey, unpublished).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 clandestina P.A. Taylor, Pascoe & F.C. Greenh. 1985 (Oomycetes, Pythiales)
Distribution: Australia.
Substrate: Roots.
Disease Note: Major root rot pathogen of subterranean clover (Erwin & Ribeiro 1996).
Host: Trifolium subterraneum (subterranean clover, Fabaceae); Medicago spp. are also susceptible (Erwin & Ribeiro 1996).
Supporting Literature:
Erwin, D.C., and Ribeiro, O.K. 1996. Phytophthora Diseases Worldwide. APS Press, St. Paul, Minnesota, 562 pages.
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. clandestina is classified in group I (Stamps et al. 1990) because it produces papillate sporangia; however, the production of both amphigynous and paragynous antheridia is an exception for this group. See Tables 4.2 and 4.3 in Chapter 4 in Phytophthora Diseases Worldwide (Erwin and Ribeiro 1996) for tabular keys. Morphology is described by P. A. Taylor et al. (1985) and is shown in Figure 1, Figure 2, and Figure 3. A summary is provided by Hall (1991a).
1. Sporangia
Papillate sporangia (often two or three papillae) are produced most abundantly on infected roots incubated in water but are also produced on solid lima bean media. The apical thickening is about 4 to 6 µm deep with an exit pore about 6 to 7 µm wide. Sporangia are broadly ellipsoid to ovoid, sometimes subglobose, 16 to 66 µm (
11 µm) long, and 15 to 44 µm (mean 32 11 µm) wide and have a length-breadth ratio of 1.35:1 (range 1.2 to 1.4:1). A conspicuous dome-shaped or broadly conical basal plug protrudes into the sporangium. Sporangia are caducous and do not readily separate from sporangiophores at first but become deciduous after zoospores have been emitted. The sporangial pedicel is 1 to 6 µm in length. Sporangia are formed sympodially on sporangiophores.
2. Chlamydospores
Chlamydospores have not been seen.
3. Sex Organs
Oogonia, which are usually terminal, have a diameter of 21 to 36 µm (mean 30 3 µm). Both paragynous and amphigynous antheridia are formed in host tissue, in which they are predominately paragynous (70 to 90%), but in lima bean agar they are more frequently amphigynous (50 to 60%). Antheridia are terminal or subterminal, occasionally intercalary, and variable in shape. The diameter ranges from 9 to 45 µm (mean 18 5 µm) to 4 to 17 µm (mean 11 3 µm). Antheridia are delimited by thick septa. Oospores are markedly aplerotic with diameters of 18 to 31 µm (mean 25 2 µm) and a wall thickness of 0.3 to 3.6 µm (mean 1.4 1.0 µm).
4. Growth Temperature
P. clandestina grows slowly; e.g., on lima bean agar, growth is about 1.5 to 2.0 mm per day at 25oC. The optimum temperature for growth is 25oC, minimum is 5oC, and maximum is 31oC (P. A. Taylor et al. 1985a). Growth is maximum at a pH of 6.0 at 25oC. Survival in soil is best at 5 to 10oC (Wong et al. 1986).
5. Distinguishing Characteristics
P. clandestina differs from other members of group I because of its slow growth rate, characteristic production of hyphal swellings, and subterminal or digitate antheridia. A distinct basal plug in sporangia of P. clandestina is also unique. Unlike P. cactorum, P. clandestina produces a large proportion of amphigynous antheridia, and unlike P. pseudotsugae and P. iranica, it produces aplerotic oospores (P. A. Taylor et al. 1985).
Nomenclature information was provided by the the Systematic Botany and Mycology Laboratory in USDA-ARS.
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