Gibberella zeae is a fungus belonging to a group of fungi called Ascomycetes. This group are defined by production of spores after meiosis in microscopic sacs (ascus is Greek for sac). It is typical of this group of fungi to also have asexually produced spores that are distinct and, in some cases, identified separately, and given distinct names. The asexual stage of this Gibberella zeae is Fusarium graminearum. Although formal nomenclature protocol requires naming a fungus by its sexual stage either name is commonly used to identify this same fungal species.
This fungus receives nutrition from weakened or dead plant tissues, primarily grasses. Often initial invasion of the tissue is initiated by the spores (conidia) of the Fusarium portion of the life cycle. The fungus quickly produces more spores on corn debris, spreading readily in a corn field. Spores landing on exposed silks germinate and grow down the silk channel into the tissue within and around the kernels. As the kernels develop within the moist environment of the tight husks, the fungus spreads to appear as a pink mold. Haploid nuclei within the Fusarium hyphae fuse to form a brief diploid nucleus. This causes the fungus to produce a new structure, called a perithecium, a distinctive black body on the surface of the infected host. Within the perithecium, meiosis occurs, resulting in haploid ascospores within the ascus. Ascospores are released, perhaps in the following season. These infections result in the fungus further reproduction and spread of the fungus.
Gibberella stalk rot and ear rot are usually identified presence of the perithecia, rough black structures produced on the outside of the stalk or kernel tissues. Kernel infections often are also a concern because this fungus tends to produce chemicals such as zearalenone and deoxynivalenol (DON). This probably the most significant concern of problems from this fungus. The stalk phase is more of a secondary invasion of dying stalk tissue because of senescence of plant tissue because of the balance of carbohydrates within the maturing corn plant. These can be some satisfaction in having a name for the fungus, but analysis of the cause is more significant to reducing the future problems.
About Corn Journal
The purpose of this blog is to share perspectives of the biology of corn, its seed and diseases in a mix of technical and not so technical terms with all who are interested in this major crop. With more technical references to any of the topics easily available on the web with a search of key words, the blog will rarely cite references but will attempt to be accurate. Comments are welcome but will be screened before publishing. Comments and questions directed to the author by emails are encouraged.