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 Scale bar indicates number of substitutions per site.(Martin, Blair and Coffey, unpublished).
[ Click the tree to enlarge it. ]
Phytophthora infestans (Mont.) de Bary 1876 (Oomycetes, Pythiales)
Botrytis infestans Mont. 1845
Peronospora infestans (Mont.) Casp. 1854
= Botrytis fallax Desm. 1846
= Peronospora fintelmannii Casp. 1852
= Botrytis solani Harting 1846
= Phytophthora thalictri G.W. Wilson & Davis 1907
Phytophthora infestans f. sp. thalictri (G.W. Wilson & Davis) G.M. Waterhouse 1963
= Peronospora trifurcata Unger 1847
Notes: The original name applied to this oomycete was Gangraena tuberum solani, by Martius in 1842. After a period of debate (see Erwin & Ribeiro 1996), it was described by Montagne in 1845 and given the name Botrytis infestans. It has received much renown as the cause of the great Irish potato famine of the 1840s, and it is the type of the genus Phytophthora. The name Botrytis devastatrix (alternate spelling vastatrix or devastrix) Lib. 1845 was published previous to Botrytis infestans, and has been listed as a synonym by various authors (e.g. Waterhouse 1963, Erwin & Ribeiro 1996) . If this were true, the epithet vastatrix would have priority for this species. Waterhouse (1970) retained the name Phytophthora infestans, arguing incorrectly that Botrytis vastatrix was an invalid name because it was published in a newspaper, but this is permitted by the Code previous to 1953 (Art. 30.3). While it is in fact valid, Botrytis vastatrix is an illegitimate superfluous name; Libert published it as a replacement name for Botrytis farinosa Fr.:Fr. 1829. Therefore the name Botrytis vastatrix must be typified by Botrytis farinosa (=Peronospora farinosa), and refers to a different species than Phytophthora infestans (Art. 7.4).
Distribution: Cosmopolitan.
Substrate: Tubers, leaves, haulms of potato and tomato. Also stems, flowers, fruits, buds on other hosts.
Disease Note: Late blight of potato and tomato. Overwinters in tubers. Several races occur. Also causes leaf blights and, rarely, damping off, flower, and fruit blight in a wide range of hosts.
Host: Principal hosts are Solanaceae including Solanum spp. (potato) and Lycopersicon esculentum (tomato). Also occurs on hosts in 15 other genera and in ten other families (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
Puttemans, A. 1936. Reivindicacao visando a denominacae scientifica da doenca da batateira Phytophthora infestans (Mont.) de Bary. Rodriguesia 2: 341-350
Stamps, D.J. 1985. Phytophthora infestans. C.M.I. Descript. Pathog. Fungi Bact. 838: 1-2
Tucker, C.M. 1931. Taxonomy of the genus Phytophthora de Bary. Univ. Missouri Agric. Exp. Sta. Bull. 153: 1-208
Updated on May 04, 2006
P. infestans is classified in group IV (Stamps et al. 1990). See Tables 4.2 and 4.3 for tabular keys and Appendix 4.9 for a dichotomous key (Ho 1992) in Phytophthora Diseases Worldwide (Erwin and Ribeiro 1996). Morphology is shown in Figure 1 below and 4.12G. in Phytophthora Diseases Worldwide (Erwin and Ribeiro 1996). See Fry et al. (1993) and Hooker (1981) for photomicrographs of spore structures.
1. Sporangia
Sporangia are ovoid, ellipsoid to limoniform, tapering at the base, caducous (pedicel <3 µm), and semipapillate. Average size of sporangia ranges from 36 x 22 µm (Tucker 1931) to 29 x 19 µm (Waterhouse 1963). These dimensions are similar to those of de Bary (1876), Rosenbaum (1917), Haskell (1921), K. O. Müller (1928), and Leonian and Greer (1929). Sporangiophores are compound sympodial (Figure 4.5B in Phytophthora Diseases Worldwide [Erwin and Ribeiro 1996]) with a small characteristic swelling just below the sporangium (Figures 4.5C and 4.6).
2. Hyphal Swellings and Chlamydospores
Neither hyphal swellings nor chlamydospores have been reported, except in a paper from Russia by Patrikeyeva (1979), who noted chlamydospores with a two-layer wall after incubation for 4 to 9 months on oat-pea agar at 9 to 10°C.
3. Sex Organs
P. infestans is heterothallic. Antheridia are amphigynous; oogonia are 31 to 50 µm in diameter (average 38 µm); oospores formed in plant leaves are aplerotic, 24 to 35 µm in diameter (average 30 µm); in artificial culture they measure 24 to 56 µm in diameter. Until the early 1980s, A1 was the only mating type found in most of the world, but in central Mexico both A1 and A2 isolates coexisted at a 50:50 ratio (Niederhauser 1991). Inoculation of a leaf with an A2 isolate of P. drechsleri and P. infestans (A1) induced oospore production (Skidmore et al. 1984). Whether or not unique biotypes could arise from unrelated species is unknown. Most likely, formation of oospores results from stimulation by hormonelike substances emitted by the opposite mating type (see Chapter 3 in Phytophthora Diseases Worldwide (Erwin and Ribeiro 1996).
4. Growth Temperatures
The minimum temperature for growth is 4°C, optimum 20°C, and maximum 26°C.
P. infestans affects several hosts in the nightshade family (Solanaceae>). It is a severe pathogen of potato (Solanum tuberosum) and tomato (Lycopersicon esculentum) and can lead to 100% crop loss under conditions favorable for disease development and in the absence of fungicide . Figure 2
P. infestans also infects hairy nightshade (S. sarrachoides), petunia (Petunia hybrida), and bittersweet (S. dulcamara). Generally, all parts of the potato plant including leaves, stems, tubers and flowers are susceptible to infection by P. infestans. Young lesions on leaves appear initially appear as small necrotic spots with collapsed green or chlorotic margins which, under optimal conditions for disease development (wet, cool days), enlarge rapidly. Under wet conditions downy mildew like cottony growth can be observed at the margin of necrotic areas, particularly on the underside of leaves. Stem lesions are characterized by water-soaked dark brown discoloration that can extend up the stem and can also show sporulation. Figure 3
Tuber infection is characterized by reddish-brown discoloration. Once secondary microorganisms infect tubers soft rot can occur.
P. infestans sporulating on bottom side of tomato leaves in NC. Figure 4
P. infestans infecting tomato fruit in NC. Figure 5
Phytophthora ELISA kits can be used to confirm that indeed a Phytophthora species is infecting the plant. Sporulation on tomato or potato plant parts is very diagnostic of this disease. Leaves showing no sporulation can be incubated in a moist chamber for 1-2 days to determine if diagnostic sporulation will occur. Several molecular, PCR-based assays exist.
Potato late blight is managed by integrating several pest management strategies. Sanitation to reduce the amount of initial inoculum is critical. Cultural practices to reduce leaf wetness reduce the number of successful infection events. Use of resistant cultivars is particularly useful in the developing world. Fungicides are used to manage epidemics and should be combined with forecasting systems to minimize the number of sprays. In addition, fungicides with different modes of action should be used in rotation.
P. infestans is best known for causing the Irish potato famine in the 1840s.
[[PAPER:2353|1]]
[[PAPER:2354|1]]
[[PAPER:2355|1]]
[[PAPER:2366|1]]
[[PAPER:2356|1]]
[[PAPER:2357|1]]
[[PAPER:2358|1]]
[[PAPER:2361|1]]
[[PAPER:2362|1]]
[[PAPER:2359|1]]
[[PAPER:2363|1]]
[[PAPER:2364|1]]
[[PAPER:2360|1]]
[[PAPER:2365|1]]
This P. infestans species page was written by Niklaus J. Grunwald (USDA ARS, Corvallis, OR). Pictures specific to this pathogen were provided by N. J. Grunwald and tomato pictures provided by Kelly Ivors (NC State University).
Nomenclature information was provided by the the Systematic Botany and Mycology Laboratory in USDA-ARS.