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 Scale bar indicates number of substitutions per site.(Martin, Blair and Coffey, unpublished).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. alni Brasier & S.A. Kirk 2004 (Oomycetes, Pythiales)
≡Phytophthora alni Brasier & S.A. Kirk 2004 Note: See type subspecies.
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.
Distribution: Europe.
Substrate: Roots, collars.
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. alni Brasier & S. A. Kirk is a subspecies of the hybrid species P. alni that is responsible for declining stands of Alnus species in Europe. While the parentage of these 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). Previously known as the standard hybrid alder Phytophthora, this subspecies has a higher level of virulence on Alnus species and is recovered more frequently than subsp. multiformis or subsp. uniformis. 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, gametangia usually frequent to abundant (some cultures gradually lose fertility). A proportion of oogonia are larger or more mature. These oogonia with tapered stalks, variably warty with bullate protuberances (similar to those of P. cambivora). Range of isolate means for diameter of mature oogonia 42.8–50 µm; overall range 37–55 µm. A further proportion of oogonia rather small with diameters ca 25–35 µm, others only partially developed; some distinctly comma-shaped; some distorted or with beak-like or tube-like protuberances. A high proportion of oogonia, common range ca 36–70%, with either fully aborted or with thin-walled oospores. Viability (not germinability) of normal-looking oospores (tetrazolium method) usually low, ca 31– 36%. Oospore diameters in larger oogonia range of isolate means 33.3–43.5 µm; overall range 27.5–50 µm. Antheridia predominantly two-celled and amphigynous. A small proportion may be one-celled, or with a basal septum that is difficult to observe. Antheridial lengths: range of isolate means (mature oogonia only) 23.5–27 µm; overall range 20–30 µm. Antheridial widths, range of means 18.5–19.5 µm; overall range 15–20 µm.
4. Growth Temperatures
Optimum temperature for growth on CA, ca 23–25° C. Upper limit for growth on CA approximately 29° C with minimal growth at 3° C. Radial growth at 25° C on CA approximately 4.1–7.5 mm/d (mean 5.9 mm/d).
5. Growth Characteristics in Culture
Colonies on CA (10 d at 25 x in darkness) usually uniform, appressed-felty with no or very sparse aerial mycelium; sometimes appressed with a little uniform woolly overgrowth close to the colony surface. Colonies often irregular in outline, sometimes with faster or slower growing areas.
6. Distinguishing Characteristics
While oospore morphology may be similar with P. cambivora, P. alni subsp. alni is homothallic and has a high level of oogonial abortion compared to the heterothallic P. cambivora.
Chromosome number at first metaphase division ca 18–22 (approximately 4n). Meiotic failures common. Sequence of the ITS region of the rDNA unique, with dimorphic bases at up to eleven polymorphic sites (GenBank accession nos AF139366, AY689131–3). A unique combination of isozyme migration bands of the Mdh-1, Mdh-2 and Gpi enzyme loci viz. Mdh-1: 87/100; Mdh-2: 94/100; and Gpi: 85/93/100, with a characteristic 5-banded allele pattern at this dimeric locus.
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 UK, Ireland, France, Belgium, The Netherlands, Sweden, Germany, Austria, and Hungary. Probably present in or spreading to other parts of Europe. In some locations, overlapping with other Phytophthora alni subspecies and variants
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