Thecaphora solani (potato smut)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- Risk of Introduction
- Habitat List
- Hosts/Species Affected
- Host Plants and Other Plants Affected
- Growth Stages
- List of Symptoms/Signs
- Biology and Ecology
- Means of Movement and Dispersal
- Pathway Causes
- Pathway Vectors
- Plant Trade
- Impact Summary
- Economic Impact
- Risk and Impact Factors
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Gaps in Knowledge/Research Needs
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Thecaphora solani (Thirum & M.J. O'Brien) Mordue 1988
Preferred Common Name
- potato smut
Other Scientific Names
- Angiosorus solani Thirum & M.J. O'Brien
International Common Names
- English: smut of potato; thecaphora smut
- Spanish: carbón de la patata; el carbon de la papa; gangrena de la papa
- French: charbon de la pomme de terre
Local Common Names
- Germany: Kartoffel-Brand
- Peru: la gangrena
- Venezuela: buba
- THPHSO (Thecaphora solani)
Summary of InvasivenessTop of page
T. solani is a smut fungus attacking tubers and underground stems of Solanum, including potato [Solanum tuberosum] and tomato [Solanum lycopersicum], in the Andean region of South America. It is not restricted to the higher, cooler elevations, but has been a problem in coastal Peru (Bazan de Segura 1960; Zachmann and Baumann, 1975) and also occurs in Mexico. It may be transported in infected tubers and planting material and, very likely, on their surfaces if they become contaminated with the spores. The fungus survives in the soil and is difficult to eradicate; it can infect at least one common solanaceous weed. Losses of 80% or more have been reported in susceptible varieties. EPPO lists it as an A1 plant pest (OEPP/EPPO, 1979).
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Fungi
- Phylum: Basidiomycota
- Subphylum: Ustilaginomycotina
- Class: Ustilaginomycetes
- Order: Urocystidiales
- Family: Glomosporiaceae
- Genus: Thecaphora
- Species: Thecaphora solani
Notes on Taxonomy and NomenclatureTop of page
Barrus (1944) originally named the fungus, but because no Latin description was provided, the combination T. solani Barrus is invalid (Mordue, 1988). Regardless, O’Brien and Thirumalachar (1972) created a species for it in a new genus, Angiosorus, because the spores in spore balls were separable, rather than fused as in some Thecaphora spp. Duran (1987) considered this insufficient justification for a new genus. Mordue (1988) later transferred the species validly to Thecaphora, noting the range of spore ball types in that genus. Based on the high similarity of sequences of the LSU region of rDNA, Andrade et al. (2004) placed T. solani with other Thecaphora species.
Furthermore, the concept of the genus Thecaphora has been enlarged. Vánky and Lutz (2007) merged the smut genus Sorosporium with Thecaphora. The genera Kochmania and Glomosporium are also found to be synonyms of Thecaphora within the Glomosporiaceae (Vánky et al., 2008). Vánky (1999) placed Glomosporium (the type genus of the family) in the Ustilaginales, but the results of Andrade et al. (2004) and Vánky et al. (2008) put it in a clade with the Urocystales (Urocystidales).
DescriptionTop of page
Sori locular, 1-4 mm, in galls on stems, stolons and tubers. Sporiferous hyphae lining locules, producing spore balls to interior. Immature locules surrounded by brown corky tissue of potato [Solanum tuberosum].
Mature spore balls comprised of two to eight teliospores rarely one, cinnamon to rust-brown, 15-50 x 12-40 µm diameter. Spores pressed together, but can often be teased apart, globose to angular, smooth on contiguous side and densely verrucose on free side, 7.5-20 x 8-18 µm.
DistributionTop of page
T. solani is indigenous to the Andean region of South America, but also occurs in Mexico (UK CAB International, 1993; Andrade et al., 2004). Although it has been reported from Panama (McGuire and Crandall, 1967), its status in Central America is not clear (Piepenbring, 2001; 2006). It has not spread to any other part of the world.
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.Last updated: 23 Apr 2020
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|Panama||Present||Native||Piepenbring (2006) cites this report only|
|United States||Absent, Intercepted only||Interceptions from Mexico|
|Uruguay||Absent, Confirmed absent by survey|
IntroductionsTop of page
Risk of IntroductionTop of page
T. solani belongs to the group of pathogens on South American potato [Solanum tuberosum], still confined to that continent, which present a high risk to commercial potato-growing areas around the world. The particular risk factors for T. solani are that it attacks tubers directly with immediate effect on yield and quality, that no potato disease resembling it occurs elsewhere in the world, and that it can readily contaminate tuber consignments in the form of latent infections or surface contamination by teliospores. It is soil-borne, therefore it would be virtually impossible to eradicate once established. On the other hand, its potential economic importance in intensive potato production is not clear nor is it certain under what climatic conditions it could establish and, therefore, which areas are the most threatened.
It has mostly been reported from the Andean region, for example, above 3000 m in Venezuela (O'Brien and Thirumulachar, 1972) or from the mountains in Peru (Abbott, 1932). However, Abbott (1932) also mentions its presence at sea level in Peru, and high losses occurred in some cultivars in coastal areas (Bazan de Segura, 1960; Zachmann and Baumann, 1975). Its establishment in countries producing seed potatoes would pose considerable problems for their export certification.
Habitat ListTop of page
|Terrestrial||Managed||Cultivated / agricultural land||Present, no further details||Harmful (pest or invasive)|
Hosts/Species AffectedTop of page
The principal host is potato [Solanum tuberosum], but various other tuber-bearing species of Solanum are attacked, particularly Solanum tuberosum subsp. andigenum, as well as Solanum lycopersicum (tomato), and the solanaceous weed, Datura stramonium (Mordue, 1988).
Host Plants and Other Plants AffectedTop of page
|Datura stramonium (jimsonweed)||Solanaceae||Wild host|
|Solanum (nightshade)||Solanaceae||Wild host|
|Solanum lycopersicum (tomato)||Solanaceae||Other|
|Solanum stoloniferum||Solanaceae||Wild host|
|Solanum tuberosum (potato)||Solanaceae||Main|
|Solanum tuberosum subsp. andigenum||Solanaceae||Other|
|Solanum x chaucha||Solanaceae||Other|
Growth StagesTop of page
SymptomsTop of page
No symptoms are visible above ground. Infected tubers are misshapen or have warty swellings on the surface, and are hard. The whole or only part of the tuber may be infected. Numerous brown-black specks, interspersed with lighter-brown specks, can be seen in the flesh. The specks (spore sori) are 1 to 4 (or more) mm diameter and are filled with rusty brown spore balls. Completely infected tubers later become dry brown powdery masses of numerous spores. Galls resembling deformed tubers develop on the stems or stolons underground, often encircling them. Roots are not infected. On tomato [Solanum lycopersicum], galls develop particularly at the junction of the stem and roots.
List of Symptoms/SignsTop of page
|Stems / galls|
|Vegetative organs / internal rotting or discoloration|
Biology and EcologyTop of page
T. solani survives in soil or tuber debris (O'Brien and Thirumalachar, 1972) and the spores are thought to be long-lived. Torres (2001) stated that the fungus can persist for up to 7 years in gall fragments. Nothing is known of the infection process. It is thought that all underground stem organs, but not roots, can be infected, with each gall on a tuber or shoot corresponding to a separate infection. It is not clear whether there can be systemic infection. Disease incidence is increased in the absence of crop rotation and is favoured by high humidity and saline soils (Torres, 2001).
Essential basic investigation of the fungus was performed by Andrade et al. (2004). Isolates of the fungus were grown in pure culture at 18-20°C on ordinary laboratory media, including potato dextrose agar and malt-yeast-peptone agar, although the teliospores of some isolates did not grow and germination levels for those yielding successful cultures were less than 1%. Germination did not involve the production of basidia and basidiospores or growth of a yeast-like anamorph. Mycelium grew slowly and produced both teliospores and chlamydospore-like structures.
In Peru, spores did not germinate in water, soil extract, potato root extract, in the vicinity of growing roots, or on internal tissue of tubers of a susceptible variety (Zachmann and Baumann, 1975).
Zachmann and Baumann (1975) observed tubers infected with both the smut fungus and root-knot nematodes. Also, because spores did not germinate under various simple conditions, they suggested a possible requirement for interaction with nematodes.
ClimateTop of page
|A - Tropical/Megathermal climate||Preferred||Average temp. of coolest month > 18°C, > 1500mm precipitation annually|
Means of Movement and DispersalTop of page
The fungus has a very low natural dispersal potential. Field observations (Abbott, 1932) indicate that seed tubers transmit the disease. Since 1984, T. solani has been intercepted by the USDA over 125 times in tubers of Solanum tuberosum and Solanum stoloniferum, almost all from Mexico (JF Bischoff, USDA/APHIS/PPQ, personal communication, 2009). Soil from infected areas could also carry the fungus, therefore, agents that move soil, such as irrigation water and livestock (Torres, 2001), as well as tools and equipment, can spread it.
Pathway CausesTop of page
Pathway VectorsTop of page
Plant TradeTop of page
|Plant parts liable to carry the pest in trade/transport||Pest stages||Borne internally||Borne externally||Visibility of pest or symptoms|
|Bulbs/Tubers/Corms/Rhizomes||hyphae; spores||Yes||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Stems (above ground)/Shoots/Trunks/Branches||hyphae; spores||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Plant parts not known to carry the pest in trade/transport|
|Fruits (inc. pods)|
|Growing medium accompanying plants|
|True seeds (inc. grain)|
Impact SummaryTop of page
Economic ImpactTop of page
T. solani is reported to cause serious disease (Bazan de Segura, 1960). Losses of up to 80% have been known in the very susceptible potato [Solanum tuberosum] cultivar, Peruanita (Abbott, 1932). The pathogen directly infects the tubers, reducing the quantity and quality of the yield. Gregory (1979) noted that potato smut used to be disregarded as 'a threat mainly to primitive cultivars grown at high altitudes', but it has also caused serious losses to potato at low altitudes in Peru. Little was published on the disease in the 20 years after Gregory’s observation (see citations in Torres, 2001), but spread of the fungus in Chile, where yield losses often exceeded 90%, stimulated the essential work of Andrade et al. (2004).
Risk and Impact FactorsTop of page
- Invasive in its native range
- Proved invasive outside its native range
- Has high reproductive potential
- Has propagules that can remain viable for more than one year
- Reproduces asexually
- Host damage
- Negatively impacts agriculture
- Negatively impacts livelihoods
- Highly likely to be transported internationally accidentally
- Difficult to identify/detect as a commodity contaminant
- Difficult/costly to control
DiagnosisTop of page
Sequences of the ITS and LSU regions of rDNA of this species are available for comparison in GenBank (NCBI, 2009).
Detection and InspectionTop of page
Although malformed tubers are conspicuous (see Symptoms) and the spore sori are distinctive, there is no reliable inspection method to detect spores of T. solani on healthy tubers. A quarantine period is necessary to ensure that tubers are free of the fungus.
Similarities to Other Species/ConditionsTop of page
In South America, the smut fungus, Polysaccopsis hieronymi, on wild Solanum species, has similar sori, but the spore balls produced are black and consist of viable spores surrounded by sterile cells, as in Urocystis (O’Brien and Thirumalachar, 1972).
Root-knot nematodes also cause galling on potato tubers, the size of the galls varying with the cultivar (Santo, 2001). Nematode galls will lack the spore-filled locules, but tubers with mixed infections have been reported (Zachmann and Baumann, 1975).
Prevention and ControlTop of page
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
As for other South American pathogens of potato [Solanum tuberosum], the recommended procedure for other parts of the world is post-entry quarantine of planting material, together with equivalent checks before export (OEPP/EPPO, 1979). Only material for scientific purposes should normally be imported from countries where the smut is known to occur.
Consignments from areas in which the disease occurs can carry infection at undetectable levels or spores on the surface of healthy tubers. Inspections cannot be fully reliable and there is no alternative to a quarantine period to ensure that tubers are free of the fungus.
Cultural Control and Sanitary Measures
Some control measures recommended by Torres (2001) include the planting of smut-free seed potatoes, long crop rotations, elimination of the weed, Datura stramonium, also reported as a host, and the removal of smutted material from fields after harvest.
Susceptibility of potato cultivars to infection varies (Bazan de Segura, 1960; Zachmann and Baumann, 1975). Screening for resistance is actively carried out at CIP (Centro Internacional de la Papa or International Potato Centre) in Peru (Torres and Martin, 1986). The use of resistant cultivars is strongly recommended (Zachmann and Baumann, 1975; Torres, 2001).
Gaps in Knowledge/Research NeedsTop of page
Not all of the possible means of T. solani persistence have been examined. Other weeds in the family Solanaceae may be hosts. The possibility of biological control by other soil organisms should be explored.
ReferencesTop of page
Abbott EV, 1932. Diseases of cultivated plants in Peru. Estación Experimental Agricultural Molina (Peru) Circular, No. 18.
Andrade O; Muñoz G; Galdames R; Durán P; Honorato R, 2004. Characterization, in vitro culture, and molecular analysis of Thecaphora solani, the causal agent of potato smut. Phytopathology, 94(8):875-882. http://www.apsnet.org/phyto/
Barrus MF; Muller AS, 1943. An Andean disease of potato tubers. Phytopathology, 33:1086-1089.
Bazan de Segura C, 1960. The gangrena disease of potato in Peru. Plant Disease Reporter, 44:257.
BPI (US National Fungus Collections), 2009. Fungal Databases - Specimens. Beltsville, USA: Systematic Mycology and Microbiology Laboratory, Agricultural Research Service, USDA. www.nt.ars-grin.gov/fungaldatabases/specimens/specimens.cfm
EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm
Fajardo L, 1975. [English title not available]. (El carbon de la papa (Thecaphora solani Bar.), una nueva enfermedad fungosa para Chile.) In: Publicaciones Miscelaneas No. 10., Chile: Facultad de Agronomia, Universidad de Chile, unpaginated.
Gregory RH, 1979. Movement of diseases between neighbouring states: some South American examples. In: Ebbels DL, King JE, eds. Plant Health. Oxford, UK: Blackwell Scientific Publications, 269-274.
Santo GS, 2001. Root-knot nematodes. In: Compendium of Potato Diseases, Second edition [ed. by Stevenson, W. R.\Loria, R.\Franc, G. D.\Weingartner, D. P.]. Saint Paul, Minnesota, USA: APS Press, 51-53.
Vánky K; Lutz M, 2007. Revision of some Thecaphora species (Ustilaginomycotina) on Caryophyllaceae. Mycological Research, 111(10):1207-1219. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7XMR-4P2YX2J-6&_user=10&_coverDate=10%2F31%2F2007&_rdoc=7&_fmt=summary&_orig=browse&_srch=doc-info(%23toc%2329677%232007%23998889989%23674586%23FLA%23display%23Volume)&_cdi=29677&_sort=d&_docanchor=&_ct=12&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=9bc0da88d15fd577f03b532c54a73524
BPI (US National Fungus Collections), 2009. Fungal Databases - Specimens., Beltsville, USA: Systematic Mycology and Microbiology Laboratory, Agricultural Research Service, USDA. http://www.nt.ars-grin.gov/fungaldatabases/specimens/specimens.cfm
CABI, Undated. Compendium record. Wallingford, UK: CABI
CABI, Undated a. CABI Compendium: Status as determined by CABI editor. Wallingford, UK: CABI
Fajardo L, 1975. Potato sooty mould (Thecaphora solani Bar.), a new fungal disease for Chile. (El carbon de la papa (Thecaphora solani Bar.), una nueva enfermedad fungosa para Chile.). In: El carbon de la papa (Thecaphora solani Bar.), una nueva enfermedad fungosa para Chile. Chile: Facultad de Agronomia, Universidad de Chile. unpaginated.
OrganizationsTop of page
Peru: Centro Internacional de la Papa (CIP), Apartado 1558, Lima 12, http://www.cipotato.org
ContributorsTop of page
06/11/09 Updated by:
Distribution MapsTop of page
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CABI Summary Records
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