Gibberella moniliformis

Ear and stalk rot

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cellular organisms - Eukaryota - Fungi/Metazoa group - Fungi - Dikarya - Ascomycota - Pezizomycotina - Sordariomycetes - Hypocreomycetidae - Hypocreales - Nectriaceae - Gibberella - Gibberella moniliformis

Brief facts

• Gibberella moniliformis (also, Fusarium moniliforme) is a biological species of the mating populations within Gibberella fujikuroi species complex.
• This fungus is primarily a pathogen of maize that causes ear and stalk rot, but it can also cause disease in other crop species.
• The species is an example of facultative endophyte, which can exist in the biotrophic endophytic assocoation with maize as well as saprophytically.
• The fungus is transmitted vertically (spread by growing inside the plant and by infected seeds) and horizontally (spread contagiously through the plant debris and insect vectors and infects plant from outside). The former type of transmission is important because it cannot be controlled by seed applications of fungicides, and maintains the reservoir from which the infection takes place in each generation of plants.
• The fungal infection can result in contamination of the grain with mycotoxins (fumonisins) that can cause severe toxicosis and liver and kidney damage in animals and humans upon ingestion of infected grains.
• Parasitic endophytic fungal growth that progresses asymptomatically is considered to be latent which is not the same as dormant. Hyphae are active physiologically and can produce mycotoxins during asymptomatic infection. Control, prevention, and detection of the endophytic infections by G. moniliformis in corn are difficult, especially because kernels appear to be of good quality.

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Developmental stages

The stage on which the fungus produces sexual spores is called the teleomorph (or perfect stage), the other, asexual, stage is called the anamorph (or imperfect stage). Gibberella moniliformis anamorph is known as Fusarium verticillioides.

• Endophytic phase The fungus grows in the biotrophic association with maize; in this stage the fungus is transmitted vertically, through seed stage; the fungus endophytically infects seedling from its systemic infection of the seed, usually by the second day following germination.
  • Asymptomatic
    growth This is a long-term fungus-plant association during which the pathogen grows without doing substantive harm to its host; toxin production is relatively low at this stage. Some isolates enhanced the growth of maize seedlings. The fungus exists intercellularly, although under certain circumstances can become intracellular.
  • Symptomatic
    growth 2-3% seedlings infected through the seed develop the disease and die within 2 to 3 weeks, however, some of them may recover and grow without further symptoms; usually the disease (stalk rot) develops on later stages of the plant growth and induced by conditions that encourage early senescence (water and temperature stress, other diseases); diseased plants take on a grayish green hue then turn tan; pith disintegrates and stalks feel spongy when squeezed.
• Saprophytic phase The fungus grows by using nutrients from decaying debris and soil; on this stage the fungus is spread horizontally, and infection is introduced from outside (through corn silk or injured tissue); this stage can be controlled by application of fungicides.

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Tissues

• Mycelium The vegetative part of a fungus, consisting of a mass of branching, threadlike hyphae.
  • Hypha Threadlike filaments forming the mycelium of a fungus; the fungal hyphae localize mostly intercellularly during asymptomatic endophytic phase and are not disruptive to the structure of the host's cells (although systemic morphology and histology of the plant is changing); hyphae of disease-causing strains are found in both intercellular and intracellular sites.
    • Conidiophore A specialized hypha that produces conidia. Each conidiophore is ended with a multinucleate vesicle. In G. moniliformis conidiophores are single or branched. Phialides are spherical protuberances that arise from the surface of the vesicle. G. moniliforme is monophialide. Nuclei migrate into the phialides and each mature phialide contains a single nucleus. Phialides produce conidiospores (conidia).
• Conidium A mononucleate vegetative spore; this type of spores is produced by the fungus in saprophytic stage of its growth; conidia serve for asexual reproduction and distribution of the fungus horizontally. There are three types of conidia. Conidia are formed on conidiophore. On Petri dishes G. moniliformis conidia appear purple gray or pink-purple in color.
  • Microconidium Microconidia form chains 5-12 μm in length and 1.5-2.5 μm in width.
  • Mesoconidium Short 1-3 septate conidium (may not be observed in G. moniliformis).
  • Macroconidium Microconidia form chains approx. 31 μm in length and 3.7 μm in width.

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References

• Bacon CW et al. Biological control of Fusarium moniliforme in maize. Environ Health Perspect. 2001 May;109 Suppl 2:325-32. PMID: 11359703
• Morales-Rodríguez I et al. Biodiversity of Fusarium species in Mexico associated with ear rot in maize, and their identification using a phylogenetic approach. Mycopathologia. 2007 Jan;163(1):31-9. PMID: 17216329

Websites

• Yates IE at al. Effects of Endophytic Infection by Fusarium moniliforme on Corn Growth and Cellular Morphology. Plant Disease / July 1997
• Doctor Fungus: Fusarium moniliforme synopsis
• University of Nebraska-Lincoln: Fusarium Stalk Rot

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