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 Scale bar indicates number of substitutions per site.(Martin, Blair and Coffey, unpublished).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 alni subsp. multiformis Brasier & S.A. Kirk 2004 (Oomycetes, Pythiales)
Notes: Probably a recent hybrid between Phytophthora cambivora and a Phytophthora close to Phytophthora fragariae (Brasier et al. 2004). Brasier et al. (2004) discuss nomenclatural issues associated with hybrids. Brasier et al. recognize several closely related varients within subsp. multiformis.
Distribution: Europe (Germany, the Netherlands, UK).
Substrate: Roots, collar.
Disease Note: Aggressive root and collar rot of riparian, nursery, and shelterbelt alders.
Host: Alnus spp. (alder, Betulaceae).
Supporting Literature:
Brasier, C.M., Kirk, S.A., Delcan, J., Cooke, D.E.L., and Jung, T. 2004. Phytophthora alni sp. nov. and its variants: designation of emerging heteroploid hybrid pathogens spreading on Alnus trees. Mycol. Res. 108: 1172-1184.
Updated on Jun 26, 2006
Phytophthora alni subsp. multiformis Brasier & S. A. Kirk is a subspecies of the hybrid species P. alni that is responsible for declining stands of Alnus species in Europe. The Dutch, UK and German variant types of P. alni are collectively designated as P. alni subsp. multiformis. P. alni subsp. multiformis comprises a range of forms with rather different phenotypes, yet with close molecular affinities (see Dutch, German and UK variants below). Chromosome numbers range from ca n=14 to n=17. Characteristic monomorphic ITS sequence, GenBank accession AF139368, AY689136–7. Isozyme alleles at the Mdh-1, Mdh-2 and GPI loci characteristic viz. Mdh-1: 100/100; Mdh-2: 94/94; Gpi: 85/100. Mdh-1 locus sometimes lacking enzyme product (see German variant, below). The Dutch, German and UK variants are informally described here as representative phenotypic subpopulations within P. alni subsp. multiformis. While the parentage of P. alni hybrids was thought to be species closely related to P. cambivora and P. fragariae, more recent analysis suggests that P. alni subsp. alni is derived from several hybridization events between P. alni subsp. uniformis and P. alni subsp. multiformis (Ioos et al. 2006, 2007). Phylogenetic analysis places P. alni subspecies in clade 7a with P. cambivora and P. fragariae.
1. Sporangia
Sporangia not seen on CA. Produced sparsely in pea broth or when plugs from margins of actively growing cultures on CA or oatmeal agar are partially submerged in Petri’s solution, fresh, unsterile pond water or unsterile soil leachate. Borne singly on long sporangiophores, ellipsoid, non-papillate, noncaducous, with a broad exit pore. Sporangial length: range of means 48–59.8 µm; overall range ca 35–70 µm. Sporangial width: range of means 31.3–42.8 µm; overall range ca 27.5–50 µm. Sporangial length:width ratio: range of means 1.32–1.62. After zoospore release showing nested and extended internal proliferation.
2. Chlamydospores
No chlamydospores observed.
3. Sex Organs
Homothallic. A wide variety of different oogonial forms occurs, from near smooth to extremely ornamented. Oogonial diameters commonly ca 50–60, range ca 45–65 µm. A wide variety of antheridial types also occurs, from single celled to two celled amphigynous and occasionally or sometimes predominantly paragynous.
4. Growth Temperatures
Among different subpopulations upper temperature limits for growth on CA vary from ca 27° to ca 32° C.
5. Growth Characteristics in Culture
Colonies on CA irregular, often with moderate to dense aerial mycelium.
6. Distinguishing Characteristics
Dutch variant
Colonies tend to be irregular, sometimes mainly submerged and sometimes with dense white aerial mycelium, often failing to grow to the edge of the Petri dish. More gametangia are usually formed at the edge than in the centre of the colony. Oogonia often extremely ornamented with coralloid outgrowths. Oogonia often highly distorted. Within one colony, most oogonia have single-celled amphigynous antheridia but some may have two-celled antheridia. Scarce paragynous antheridia also occur. A high proportion of oogonia (<90%) usually with normal looking oospores. Oogonial diameter, range of isolate means (two isolates) 50–54.3 µm; overall range 45–60 µm. Oospore diameter : range of isolate means 40.3–43.5 µm; overall range ca 35–47.5 µm. Antheridial length: range of isolate means 19–25.8 µm; overall range ca 15–32.5 µm.
Distinguished from the German variant, which it most closely resembles, in its lower chromosome number of ca 13–15 (inferred karyotype ca 2n+4), its highly ornamented oogonia and its mainly one-celled antheridia. Distribution and ecology: Associated with an aggressive root and collar rot of riparian, nursery and shelterbelt Alnus glutinosa and other Alnus species, including A. incana and A. cordata. Presently known distribution: The Netherlands and Germany. Probably present in or spreading to other parts of Europe. In some locations overlapping with other Phytophthora alni subspecies, and other phenotypic variants of subsp. multiformis.
German variant
Colonies of the German variant on CA usually do not grow to the edge of the Petri dish. With dense, felty white aerial mycelium, sometimes across the whole colony (cf P. cambivora) but sometimes only in the colony centre; often interspersed with sectors of submerged growth. Gametangia usually frequent (some cultures gradually loose fertility). Both colony patterns and fertility can vary widely from one growth test to the next. Oogonia from smooth to moderately warty, often only slightly warty. Antheridia mainly two-celled, occasionally single-celled; very rarely, paragynous. A high percentage (90%+) of oogonia have well formed normal-looking oospores. Oogonial diameter, range of isolate means 56.8–59.5 µm; overall range 52.5–65 µm. Oospore diameter, range of isolate means 50.5 µm; overall range ca 45–55 µm. Antheridial length, range of isolate means 24.8–26 µm; overall range ca 20–30 µm.
Distinguished from the Dutch variant, which it most closely resembles, in its higher chromosome number of ca 16–18 (inferred karyotype ca 2n+7), its less ornamented oogonia and its mainly two celled antheridia. ITS sequence and isozyme alleles at Mdh-2 and GPI as Dutch and UK variants, but lacks a measurable enzyme product at Mdh-1. Distribution and ecology: Associated with an aggressive root and collar rot of riparian, nursery and shelterbelt Alnus glutinosa and A. incana. Presently known distribution: southern Germany. Probably already present in or spreading to other parts of Europe. Overlaps locally with Phytophthora alni subsp. alni and subsp. uniformis. Probably also overlaps with subsp. multiformis Dutch variant.
UK variant
The UK variant often exhibits an irregular striate colony with sexually sterile sectors interspersed with entirely submerged sexually fertile sectors. However, this variant is characteristically highly plastic, being very variable from one single hyphal tip subculture to the next. The combinations of colony patterns, growth rates, upper temperature limits for growth, fertility to sterility and gametangial morphologies produced are remarkable. Oogonia alone may range from large (ca 50>60 µm) smooth-walled to small (40–50 µm) highly coralloid and antheridia from solely single celled paragynous to two celled amphigynous. ITS sequence and isozyme alleles as the Dutch and German variants.
Distinguished from the Dutch and German variants of subsp. multiformis in its more unpredictable and extremely variable colony morphologies, its variable upper temperature limits for growth, its variable fertility and its variable combinations of oogonial forms and antheridial types on CA. Ecology and distribution. Associated with root and collar rot of riparian Alnus glutinosa. Presently only known location: North Yorkshire, UK. Possibly entirely local and unique.
Other phenotypic variants probably also exist within subsp. multiformis. For example, isolates with oogonial ornamentation intermediate between that of the Dutch and German variants, but with predominantly single celled amphigynous antheridia have recently been identified amongst our collections from Germany and France. These isolates also differ from the Dutch and German variants in their RAPD patterns, but are identical to them in their ITS and isozyme alleles at the Mdh-1, Mdh-2 and Gpi loci.
Associated with an aggressive root and collar rot of riparian, nursery and shelterbelt Alnus glutinosa and other Alnus species. See above section on distinguishing characteristics for additional information on each variant.
Brasier, C. M., Kirk, S. A., Delcan, J, Cooke, D. E. L., Jung, T And Man In’t Veld, W. A. 2004. Phytophthora alni sp. nov. and its variants: designation of emerging heteroploid hybrid pathogens spreading on Alnus trees. Mycol. Res. 108: 1172–1184
Ioos, R., Andrieux, A., Marcais, B., & Frey, P. (2006). Genetic characterization of the natural hybrid species Phytophthora alni as inferred from nuclear and mitochondrial DNA analyses. Fungal Genetics and Biology 43:511–529.
Ioos, R., Andrieux, A., Marcais, B., and Frey, P. 2007. New Hypothesis on the origin of the interspecific hybrid Oomycete Phytophthora alni. Pages 61-62. in: Fourth Meeting of the IUFRO Working Party S07.02.09 E. M. Goheen, and S. J. Frankel, eds. USDA-FS PSW-GTR-221, Monterey, CA August, 26, 2007.
This species page was adapted from Brasier et al. (2004).
Isolate list