Fusarium graminearum is an ascomycete fungus that causes head blight in wheat and ear rot in corn. Crop damage in the United States over the last decade due to this fungus is estimated at several billion dollars, making it a significant plant pathogen. Additionally, F. graminearum produces mycotoxins known to be hazardous to humans and livestock.
The Fusarium genus, which includes two other species closely related to F. graminearum, has been the target of a comparative genomics project by the Broad Institute because it includes plant pathogens that cause disease in almost every economically important crop. Fusarium species are difficult to combat because of their worldwide distribution, persistence in the soil, and genetic plasticity, which allows them to evolve quickly in the face of resistant cultivars.
- Broad Institute. (2010). Fusarium Comparative Database. Retrieved from the Broad Institute website: http://www.broadinstitute.org/annotation/genome/fusarium_group/MultiHome.html
- Nafady, N.A. 2008. Ecological, physiological and taxonomical studies on the genus Fusarium in Egypt. MSc thesis, Faculty of Science, Assiut University, Egypt.
Hyaline septate hyphae, conidiophores, phialides, macroconidia, and microconidia are observed microscopically. Macroconidia are two to multicelled, are sickle-shaped, and have a distinct basal foot cell and pointed distal ends. Fusarium grow rapidly on Sabouraud dextrose agar at 25°C and produce woolly to cottony, flat, spreading colonies.From the front, the color of the colony may be white, cream, tan, salmon, cinnamon, yellow, red, violet, pink, or purple. From the reverse, it may be colorless, tan, red, dark purple, or brown.
The teleomorph of this organism is Gibberella zeae, and is characterized by purple to black perithecia.
Fusarium conidia are very distinctive; “banana-shaped” is one of the terms commonly used to describe them. Fusarium graminearum/Gibberella zeae produces only one kind of conidia – macroconidia – and these possess three septa at maturity as well as the classic Fusarium “foot cell” (see the little knob that looks like the heel of a boot? – That’s the foot cell; it originates as the point by which the conidium is attached to the conidiophore). Several Fusarium species produce small, single-celled microconidia as well as the macroconidia, and this can be used as an identifying feature. As in many Fusarium species, the conidia of F. graminearum are pink.
The sexual state, Gibberella zeae, is characterized by purple to black perithecia – a distinguishing feature of the genus Gibberella. The ascospores, like the conidia, are septate, usually with three septa. In a mixed culture, where both ascospores and conidia are present, you can tell them apart because the ascospores are slightly shorter and fatter than the conidia, and the ascospores lack the foot cells. The spores are shot out of the ascus at 870,000 times the force of gravity; the most powerful acceleration yet known from a biological system.
Molecular Biology and Genetics
Barcode data: Fusarium graminearum
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
Statistics of barcoding coverage: Fusarium graminearum
Public Records: 1
Specimens with Barcodes: 1
Species With Barcodes: 1
Relevance to Humans and Ecosystems
This ascomycete fungus is the causal agent of head blight of wheat and, as such, has caused an estimated several billion dollars worth of damage in the US alone over the past decade. Plant pathologist study plant diseases in an effort to be able to control them. Every crop plant has a cadre of diseases that affect the way it can be used by people or at least affect its yield.
F. graminearum is a plant pathogen and soil saprophyte. This organism causes wheat headblight disease and ear rot of corn. Fusarium head blight causes significant losses in yield and quality. The common symptom is the blighted or bleached heads. Partially blighted heads are most common, and the head blight symptom is most easily recognized in wheat. The symptoms are more difficult to recognize in barley. The grains in blighted heads often do not fill properly. Kernels can be shriveled and bleached, and these Fusarium damaged kernels, or FDK, are also known as tombstone kernels.
Fusarium graminearum also produces mycotoxins which can be harmful to human and animals that ingest contaminated wheat. The two main mycotoxins are deoxynivalenol (DON), also known as vomitoxin, and zearalenone. DON inhibits protein biosynthesis and zearalenone is an estrogen analog. These mycotoxins can contaminate food and when ingested by humans can cause vomiting and liver damage. Reproductive defects are also seen in livestock. In farm animals, zearalenone has been known to cause abortions in pregnant females, and feminization of males.
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