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 Scale bar indicates number of substitutions per site.(Martin, Blair and Coffey, unpublished).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 psychrophila T. Jung & E.M. Hansen 2002 (Oomycetes, Pythiales)
Notes: Closely related to Phytophthora ilicis (Cooke et al. 2000), but morphologically distinct (Jung et al. 2002). Reported in older literature as Phytophthora species 2 (Jung et al. 2002).
Distribution: Europe (France, Germany, UK).
Substrate: Soil.
Disease Note: Only weakly pathogenic in soil infestation tests, but capable of producing necrotic bark lesions on suberized tap roots of Quercus robur seedlings (Jung et al. 2002).
Host: Infects Ilex aquifolium and Quercus spp. in inoculation tests.
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
Jung, T., Hansen, E.M., Winton, L., Obwald, W. , and Delatour, C. 2002. Three new species of Phytophthora from European oak forests. Mycol. Res. 106: 397-411
Updated on Jun 26, 2006
Phytophthora psychrophila T. Jung & E.M. Hansen was recovered from soil underneath declining oak trees in Bavaria and Southern France. In phylogenetic analysis P. psychrophila is in clade 3 closely related to P. nemorosa and P. ilicis.
1. Sporangia
Semi-papillate, sometimes bipapillate, sporangia are formed abundantly in liquid culture but also on solid agar, and even submerged in the agar medium; some of them are caducous with pedicel lengths less than 5 µm. In general, sporangia are variable in shape and size. Usually, they are ovoid to obpyriform with a rounded base, but sporangia with unusual features such as curved apices, lateral displacement of the papilla, lateral attachment of the sporangiophore, short hyphal projections, or a conspicuous basal plug, are common in all isolates. Sporangia average 58 ± 10.3 x 39 ± 5.9 µm with isolate means of 52-67 x 35-41 µm (type isolate : 56 ± 10.4 x 41 ± 5.5 µm); length:breadth ratio is about 1.5. Sporangia proliferate only externally, and form on unbranched sporangiophores or in lax or dense sympodia. Direct germination of sporangia, usually by 2 germination hyphae, was commonly observed in liquid cultures which were older than 3 days. As in P. quercina, primary hyphae sometimes show sympodial branching with the mother hyphae ending in a short projection.
2. Chlamydospores
Chlamydospore mean diameters range from 18.4 - 29.8 µm.
3. Sex Organs
Phytophthora psychrophila is homothallic. Oogonia from 5 isolates averaged 37 ± 3.8 µm with isolate means ranging from 34-39 µm (type isolate : 39 ± 3.7 µm). Oogonial walls are often markedly thicker than oospore walls. Antheridia are exclusively amphigynous, 1-celled, and average 15 ± 2.2 x 13 ± 1.5 µm (type isolate : 16.5 ± 2.8 x 13.4 ± 1.9). Oospores usually fill the oogonia, but can be markedly aplerotic in oogonia with distorted shapes. Oogonia with two oospores are occasionally found in some isolates. Oospore diameter average 29 ± 3.0 µm with isolate means ranging from 27 to 30 µm (type isolate : 30 ± 3.0 µm); oospore walls average 2.4 ± 0.5 µm in diameter, sometimes turning golden yellow when aging. Oospore abortion can be found in all isolates.
4. Growth Temperatures
P. psychrophila grows on average 3.3 mm/day and 4.2 mm/day in colony radius at optimum temperature (about 15 - 17° C) on CMA and V8A, respectively. Maximum temperature for growth is slightly below 25° C with minimal growth at 3.5° C.
5. Growth Characteristics in Culture
Colonies are uniform without distinct growth pattern on all four agar media. Colonies exhibit sparse aerial mycelium on CMA, and are dome shaped and fluffy on V8A and MEA; they are appressed felty and dome shaped on PDA. On CHT agar all isolates produced dark brown to black pigments. The closely related P. ilicis shows yellow pigmentation on CHT agar, and forms a faint petaloid growth pattern with sparse aerial mycelium on CMA, and a petaloid to broad-lobed growth pattern on MEA and V8A. Growing cultures on V8A have a broad appressed to submerged margin, whereas at the periphery of older cultures a ring of aerial mycelium is produced. Cultures on PDA show an irregular to stoloniferous pattern with appressed to submerged growth.
6. Distinguishing Characteristics
P. psychrophila belongs to Waterhouse's morphological Group IV which comprises homothallic species with amphigynous antheridia and semi-papillate sporangia. P. psychrophila shares many morphological and growth features with P. ilicis, but is distinguished by having significantly larger sporangia with more variable shapes and with shorter pedicels (!5 µm) when caducous, by its larger oogonia and oospores, the occurrence of sympodially branched hyphae, by its lower optimum temperature for growth, different colony morphologies on all four agar media tested and different pigmentation on CHT agar. Furthermore, P. ilicis occurs only on above-ground parts of Ilex aquifolium. P. psychrophila isolate IFB-PSY2 comes from southern France, in the same climatic region as P. hibernalis, another low-temperature species belonging to Group IV. The latter can be distinguished from P. psychrophila by the occasional occurrence of paragynous antheridia, the production of smaller sporangia (average 40¬19 µm) with less variable shapes (usually ellipsoid to pyriform) and a tapering base, and with longer pedicels (23 ± 73 µm) when caducous, by different colony growth patterns, and by putatively different host ranges. P. psychrophila and P. quercina exhibit similar growth patterns on all four agar media tested. However, P. quercina can easily be separated from P. psychrophila by having paragynous antheridia, distinctly papillate sporangia, and higher optimum and maximum temperatures for growth. Furthermore, P. quercina is an aggressive fine root pathogen of oaks. P. psychrophila is reported as Phytophthora ` species 2' in previous works.
P. psychrophila was recovered by baiting with oak leaflets from soil collected beneath declining mature Q. robur, Q. petraea and Q. ilex in Bavaria and Southern France. It was only isolated from non-hydromorphic soils. With its low cardinal temperatures and the limitation of successful isolations to the cool season, P. psychrophila is a typical low-temperature species, well adapted to activity in winter and springtime, and not active during summertime. In the soil infestation test with Q. robur seedlings, P. psychrophila was nearly non-pathogenic with damage not significantly different from control inoculations, in contrast to several other Phytophthora species recovered from oak forests. This may be due to the incubation temperature of 18-22° C, which is higher than the optimum temperature for hyphal growth, and therefore certainly higher than the optimum temperature for sporangia formation. In another soil infestation test with an incubation temperature of 12-20° C during the growing season and a 3-month winter period at 5° C three isolates of P. psychrophila were able to produce necrotic bark lesions on suberized tap roots of some Q. robur seedlings. P. psychrophila is unable to cause decay in apple fruit.
Jung, T., M. Hansen, E. M., Winton, L., Oswald, W. and Delatour, C. 2002. Three new species of Phytophthora from European oak forests Mycol. Res. 106: 397-411
Nomenclature information was provided by the the Systematic Botany and Mycology Laboratory in USDA-ARS. This species page was adapted from Jung et al. (2002).
Isolate list