Claviceps gigantea (horse's tooth)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- Risk of Introduction
- Hosts/Species Affected
- Growth Stages
- List of Symptoms/Signs
- Biology and Ecology
- Means of Movement and Dispersal
- Seedborne Aspects
- Pathway Vectors
- Plant Trade
- Impact Summary
- Risk and Impact Factors
- Detection and Inspection
- Prevention and Control
- Gaps in Knowledge/Research Needs
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Claviceps gigantea SF Fuentes, Isla, Ullstrup & AE Rodr 1964
Preferred Common Name
- horse's tooth
Other Scientific Names
- Sphacelia sp. SF Fuentes, Isla, Ullstrup & AE Rodr 1964
International Common Names
- English: ergot of maize; maize ergot
- Spanish: cornezuelo del maíz; diente de caballo
- French: ergot du maïs
Local Common Names
- Germany: Mutterkorn: Mais
- CLAVGI (Claviceps gigantea)
Summary of InvasivenessTop of page
This pathogen only occurs in certain high humid valleys of Mexico and is apparently not adapted to surrounding drier areas where maize [Zea mays] is certainly grown. Its host range and environmental tolerances have not been determined, so that the risk that would result from an introduction to distant regions cannot be known. Human mistakes, such as the transport of contaminated maize seed, would be the most likely means by which it could bypass ecological and geographic barriers to reach other humid parts of the world, where it might be a problem on maize. In Mexico, it can reduce yield of a maize ear by 50% (Fucikovsky and Moreno, 1971), so preventing its spread is a serious consideration.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Fungi
- Phylum: Ascomycota
- Subphylum: Pezizomycotina
- Class: Sordariomycetes
- Subclass: Hypocreomycetidae
- Order: Hypocreales
- Family: Clavicipitaceae
- Genus: Claviceps
- Species: Claviceps gigantea
Notes on Taxonomy and NomenclatureTop of page Fuentes et al. (1964) identified C. gigantea as the cause of horse's tooth of maize [Zea mays]. They pointed out that a maize disease with ergot symptoms had been mentioned in 1829 by Roullin and that maize had been listed as a host of Claviceps purpurea by Zopf in 1890. However, no evidence could be found in the early literature to prove this relationship.
Fuentes et al. (1964) clearly described both the symptoms of horse's tooth and the morphology of the causal organism, C. gigantea. They also demonstrated that C. gigantea, but not C. purpurea, is pathogenic to maize.
DescriptionTop of page
Sclerotia initially white to cream, 5-8 x 2-5 cm, soft, sticky and hollow, later becoming hard and horny, white to brown, with pink to lavender centres, often comma-shaped, resembling a horse's tooth.
Stromata long-stalked, stalks 26-58 x 2-3.5 mm diameter, pink to reddish-brown, heads capitate or globose, 32–55 mm diameter, pink, sticky.
Perithecia flask-shaped, 338-444 x 152-164 µm, in large numbers within stroma, ostioles visible as darker spots on the stroma surface.
Asci cylindrical, 187-201 x 4.5-4.7 µm, eight-spored.
Ascospores filiform, hyaline, aseptate, 176-186 x 1.5 µm.
Conidiogenous cells in palisades on sclerotium surface and lining walls of cavities, proliferating percurrently, 8-17 x 2-3 µm.
Macroconidia ellipsoidal, 8.3-27 x 4.2-5.8 µm. Microconidia ovoid, 4.2-6.7 x 2.5-3.3 µm. Both hyaline, aseptate (Fuentes et al., 1964).
Distribution TableTop of page
Risk of IntroductionTop of page C. gigantea is of low economic importance, has moderate seedborne incidence and is seed transmitted. Although, where it occurs, the disease can be quite severe, it has such a narrow ecological niche that it poses a very low threat to maize [Zea mays]-growing regions throughout the world.
Hosts/Species AffectedTop of page Fuentes et al. (1964) demonstrated that C. gigantea is pathogenic to maize [Zea mays] and that C. purpurea is not pathogenic to maize.
Growth StagesTop of page Fruiting stage
SymptomsTop of page Sclerotia that replace the kernels are initially white to cream, 5-8 x 2-5 cm, soft, sticky and hollow. Mature sclerotia are comma-shaped, resembling a horse's tooth, and white to greyish-brown. Those beneath the husks are lighter in colour. Each ear may contain one to several sclerotia. The 'honeydew' of the sclerotia is filled with small, hyaline ovoid to ellipsoidal spores (Fuentes et al., 1964).
List of Symptoms/SignsTop of page
|Inflorescence / black fungal spores|
|Inflorescence / honeydew or sooty mould|
Biology and EcologyTop of page
ClimateTop of page
|Cw - Warm temperate climate with dry winter||Preferred||Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)|
Means of Movement and DispersalTop of page
Local dispersal is natural, by means of airborne ascospores, and possibly by means of insect-borne conidia (White, 1999), or accidental, by transportation of sclerotia in harvested ears or in soil.
Seedborne AspectsTop of page
Many seeds on an ear can be replaced by sclerotia (Fuentes et al., 1964).
Effect on Seed Quality
Germination can be reduced by 50% in seeds from ears bearing only one sclerotium (Fucikovsky and Moreno, 1971). Germination is affected more by sclerotia distributed over the cob than by localized sclerotia (Moreno and Fucikovsky, 1972).
Sclerotia that might be planted with seed could be a source of inoculum (Fuentes et al., 1964).
Seed Health Tests
Seedlots can be examined for comma-shaped sclerotia.
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|
|Flowers/Inflorescences/Cones/Calyx||hyphae; sclerotia; spores||Yes||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|True seeds (inc. grain)||sclerotia||Yes||Pest or symptoms usually visible to the naked eye|
|Plant parts not known to carry the pest in trade/transport|
|Fruits (inc. pods)|
|Growing medium accompanying plants|
|Stems (above ground)/Shoots/Trunks/Branches|
Impact SummaryTop of page
ImpactTop of page
The disease is confined to high, humid mountain valleys in central Mexico (Fucikovsky and Moreno, 1971; Ullstrup, 1973). It is endemic in these areas and can infect over 50% of maize [Zea mays] ears (Fucikovsky and Moreno, 1971). A single sclerotium in a maize ear can cause a 50% reduction in seed germination (Fucikovsky and Moreno, 1971).
Alkaloids of the dihydroergoline type are present in sclerotia, but their toxicity to humans and animals is not known (Pazoutova, 2003).
Risk and Impact FactorsTop of page Invasiveness
- Abundant in its native range
- Has propagules that can remain viable for more than one year
- Reproduces asexually
- Host damage
- Negatively impacts agriculture
DiagnosisTop of page
Detection and InspectionTop of page Maize [Zea mays] ears can be examined for comma-shaped sclerotia, resembling a horse's tooth.
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.
Gaps in Knowledge/Research NeedsTop of page
The potential host range and the means of dispersal of conidia outside the ear should be determined, because these are avenues by which the pathogen could be spread naturally beyond its current limited distribution.
ReferencesTop of page
Alvarez MG, 1976. Primer catalogo de enfermedades de plantas Mexicanas. Fitofilo, 71:1-169.
EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm
Fucikovsky L; Moreno M, 1971. Distribution of Claviceps gigantea and its percent attack on two lines of corn in the state of Mexico, Mexico. Plant Disease Reporter, 55:231-233.
Fuentes SF; de la Isla ML; Ullstrup AJ; Rodriguez AE, 1964. Claviceps gigantea, a new pathogen of maize in Mexico. Phytopathology, 54:379-381.
Moreno M; Fucikovsky L, 1972. Effect of position and number of sclerotia of Claviceps gigantea on maize germination. Fitopatologia, 5:7-9.
Pazoutova S, 2003. The evolutionary strategy of Claviceps. In: Clavicipitalean Fungi: evolutionary biology, chemistry, biocontrol and cultural impact [ed. by White Jr JF, Bacon CW, Hywel Jones NL, Spatafora JW] New York, USA: Marcel Dekker Inc, 329-354. [Mycology Series No.19.]
Shurtleff MC, 1980. Compendium of Corn Diseases. St Paul, Minnesota, USA: APS Press, 37.
Tooley PW; Ranajit Bandyopadhyay; Carras MM; Pazoutová S, 2006. Analysis of Claviceps africana and C. sorghi from India using AFLPs, EF-1alpha gene intron 4, and beta-tubulin gene intron 3. Mycological Research, 110(4):441-451. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7XMR-4JJGCC5-1&_user=10&_coverDate=04%2F30%2F2006&_rdoc=11&_fmt=summary&_orig=browse&_srch=doc-info(%23toc%2329677%232006%23998899995%23621877%23FLA%23display%23Volume)&_cdi=29677&_sort=d&_docanchor=&view=c&_ct=19&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=ecadd1112aea577c6faf6b0ba2cdaa98
Ullstrup AJ, 1973. Maize ergot: a disease with a restricted ecological niche. PANS 19:389-391.
Ullstrup AJ, 1973. Maize ergot: a disease with a restricted ecological niche. In: PANS, 19 389-391.
OrganizationsTop of page
Mexico: International Maize and Wheat Improvement Center (CIMMYT), Lisboa 27, Apdo, Postal 6-641, 06600, http://www.cimmyt.org
ContributorsTop of page
10/09/09 Updated by:
Distribution MapsTop of page
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