Fusarium /fjuˈzɛəriəm/  is a large genus of filamentous fungi, part of a group often referred to as hyphomycetes, widely distributed in soil and associated with plants. Most species are harmless saprobes, and are relatively abundant members of the soil microbial community. Some species produce mycotoxins in cereal crops that can affect human and animal health if they enter the food chain. The main toxins produced by these Fusarium species are fumonisins and trichothecenes. Despite most species apparently being harmless (some existing on the skin as commensal members of the skin flora), some Fusarium species and subspecific groups are among the most important fungal pathogens of plants and animals. The name of Fusarium comes from Latin fusus, meaning a spindle. Taxonomy
The taxonomy of the genus is complex. A number of different schemes have been used, and up to 1,000 species have been identified at times, with approaches varying between wide and narrow concepts of speciation (lumpers and splitters).Phylogenetic studies indicate seven major clades within the genus.There is a proposed concept – widely subscribed by specialists – that would include essentially the genus as it now stands, including especially all agriculturally significant Fusaria. There is a counterproposal (unrelated to Watanabe 2011) that goes far in the other direction, with seven entirely new genera. Subdivision
Various schemes have subdivided the genus into subgenera and sections. There is a poor correlation between sections and phylogenetic clades.Sections previously described include:

Species
Selected species include:

Etymology
The name of Fusarium comes from Latin fusus, meaning a spindle.
T cell deficiency, often causes secondary disorders such as acquired immune deficiency syndrome (AIDS). Granulocyte deficiency, including decreased numbers of granulocytes (called as granulocytopenia or, if absent, agranulocytosis) such as of neutrophil granulocytes (termed neutropenia). Granulocyte deficiencies also include decreased function of individual granulocytes, such as in chronic granulomatous disease. Asplenia, where there is no function of the spleen
Complement deficiency is where the function of the complement system is deficientIn reality, immunodeficiency often affects multiple components, with notable examples including severe combined immunodeficiency (which is primary) and acquired immune deficiency syndrome (which is secondary). Primary or secondary
The distinction between primary versus secondary immunodeficiencies is based on, respectively, whether the cause originates in the immune system itself or is, in turn, due to insufficiency of a supporting component of it or an external decreasing factor of it. Primary immunodeficiency
A number of rare diseases feature a heightened susceptibility to infections from childhood onward. Primary Immunodeficiency is also known as congenital immunodeficiencies. Many of these disorders are hereditary and are autosomal recessive or X-linked. There are over 95 recognised primary immunodeficiency syndromes; they are generally grouped by the part of the immune system that is malfunctioning, such as lymphocytes or granulocytes.The treatment of primary immunodeficiencies depends on the nature of the defect, and may involve antibody infusions, long-term antibiotics and (in some cases) stem cell transplantation.