''Fusarium oxysporum'' (Schlecht as emended by Snyder and Hansen), an ascomycete fungus, comprises all the species, varieties and forms recognized by Wollenweber and Reinking within an infrageneric grouping called section Elegans. It is part of the family

Nectriaceae The Nectriaceae comprise a family of fungi in the order Hypocreales. It was circumscribed by brothers Charles and Louis René Tulasne Louis René Étienne Tulasne, a.k.a. Edmond Tulasne (12 September 1815 – 22 December 1885) was a French b ...

. Although their predominant role in native soils may be as harmless or even beneficial plant

endophyte An endophyte is an endosymbiont, often a bacterium or fungus, that lives within a plant for at least part of its life cycle without causing apparent disease. Endophytes are ubiquitous and have been found in all species of plants studied to date; h ...

s or soil saprophytes, many strains within the ''F. oxysporum'' complex are soil borne pathogens of plants, especially in agricultural settings.

Taxonomy

While the species, as defined by Snyder and Hansen, has been widely accepted for more than 50 years, more recent work indicates this

taxon In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

is actually a genetically heterogeneous polytypic morphospecies, whose strains represent some of the most abundant and widespread microbes of the global soil microflora.

Genome

The ' family of

transposable element A transposable element (TE, transposon, or jumping gene) is a nucleic acid sequence in DNA that can change its position within a genome, sometimes creating or reversing mutations and altering the cell's genetic identity and genome size. Transp ...

s was first discovered by Daboussi ''et al.'', 1992 in several ''formae speciales'' and Davière ''et al.'', 2001 and Langin ''et al.'', 2003 have since found them in most strains at copy numbers as high as 100.

Habitat

These diverse and adaptable fungi have been found in soils ranging from the

Sonoran Desert The Sonoran Desert ( es, Desierto de Sonora) is a desert in North America and ecoregion that covers the northwestern Mexican states of Sonora, Baja California, and Baja California Sur, as well as part of the southwestern United States (in Arizona ...

, to tropical and

temperate forest A temperate forest is a forest found between the tropical and boreal regions, located in the temperate zone. It is the second largest biome on our planet, covering 25% of the world's forest area, only behind the boreal forest, which covers abou ...

, grasslands and soils of the tundra. ''F. oxysporum'' strains are ubiquitous soil inhabitants that have the ability to exist as saprophytes, and degrade

lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity ...

and complex carbohydrates associated with soil debris. They are pervasive plant

s that can colonize plant roots and may even protect plants or form the basis of disease suppression. Because the hosts of a given ''

forma specialis ''Forma specialis'' (plural: ''formae speciales''), abbreviated f. sp. (plural ff. spp.) without italics, is an informal taxonomic grouping allowed by the International Code of Nomenclature for algae, fungi, and plants, that is applied to a par ...

'' usually are closely related, many have assumed that members of a ''forma specialis'' are also closely related and descended from a common ancestor. However, results from research conducted on ''Fusarium oxysporum'' f. sp. ''cubense'' forced scientists to question these assumptions. Researchers used anonymous, single-copy restriction fragment length polymorphsims (RFLPs) to identify 10 clonal lineages from a collection of ''F. oxysporum'' f.sp. ''cubense'' from across the world. These results showed that pathogens of

banana A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large herbaceous flowering plants in the genus ''Musa''. In some countries, bananas used for cooking may be called "plantains", distinguis ...

causing

Panama disease Panama disease (or Fusarium wilt) is a plant disease that infects banana plants (''Musa'' spp.). It is a wilting disease caused by the fungus ''Fusarium oxysporum'' f. sp. ''cubense'' (Foc). The pathogen is resistant to fungicides and its cont ...

could be as closely related to other host's pathogens, such as melon or tomato, as they are to each other. Exceptional amounts of genetic diversity within ''F. oxysporum'' f.sp. ''cubense'' were deduced from the high level of chromosomal polymorphisms found among strains, random amplified polymorphic DNA fingerprints and from the number and geographic distribution of vegetative compatibility groups.

Pathogen

Presented with the wide-ranging occurrence of ''F. oxysporum'' strains that are nonpathogenic, it is reasonable to conclude that certain pathogenic forms were descended from originally nonpathogenic ancestors. Given the association of these fungi with plant roots, a form that is able to grow beyond the cortex and into the xylem could exploit this ability and hopefully gain an advantage over fungi that are restricted to the cortex. The progression of a fungus into vascular tissue may elicit an immediate host response, successfully restricting the invader; or an otherwise ineffective or delayed response, reducing the vital water-conducting capacity and induce wilting. On the other hand, the plant might be able to tolerate limited growth of the fungus within xylem vessels, preceded by an endophytic association. In this case, any further changes in the host or parasite could disturb the relationship, in a way that fungal activities or a host response would result in the generation of disease symptoms. Pathogenic strains of ''F. oxysporum'' have been studied for more than 100 years. The

host range In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include a ...

of these fungi is broad and includes animals, ranging from

arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...

s to humans, as well as plants, including a range of both

gymnosperm The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, cycads, ''Ginkgo'', and gnetophytes, forming the clade Gymnospermae. The term ''gymnosperm'' comes from the composite word in el, γυμνό� ...

s and

angiosperm Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

s. While collectively, plant pathogenic ''F. oxysporum'' strains have a broad host range, individual isolates usually cause disease only in a narrow range of plant species. This observation has led to the idea of "special form" or ''

'' in ''F. oxysporum''. ''Formae speciales'' have been defined as "…an informal rank in Classification… used for parasitic fungi characterized from a physiological standpoint (e.g. by the ability to cause disease in particular hosts) but scarcely or not at all from a morphological standpoint." Exhaustive host range studies have been conducted for relatively few ''formae speciales'' of ''F. oxysporum''. For more information on ''Fusarium oxysporum'' as a plant pathogen, see

Fusarium wilt Fusarium wilt is a common vascular wilt fungal disease, exhibiting symptoms similar to Verticillium wilt. This disease has been investigated extensively since the early years of this century. The pathogen that causes Fusarium wilt is ''Fusarium o ...

and

Koa wilt Koa wilt is a relatively new disease to Hawaii, discovered in 1980. Koa wilt is caused by a forma specialis of the fungus ''Fusarium oxysporum'', which is now abundant in Hawaiian soils and infects the native Acacia koa tree, a once-dominant spec ...

. Different strains of ''F. oxysporum'' have been used for the purpose of producing nanomaterials (especially

Silver nanoparticles Silver nanoparticles are nanoparticles of silver of between 1 nm and 100 nm in size. While frequently described as being 'silver' some are composed of a large percentage of silver oxide due to their large ratio of surface to bulk silve ...

"Agent Green" in Colombia

In 2000, the government of

Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...

proposed dispersing strains of '' Crivellia'' and ''Fusarium oxysporum'', also known as Agent Green, as a

biological weapon A biological agent (also called bio-agent, biological threat agent, biological warfare agent, biological weapon, or bioweapon) is a bacterium, virus, protozoan, parasite, fungus, or toxin that can be used purposefully as a weapon in bioterroris ...

to forcibly eradicate coca and other illegal crops. The weaponized strains were developed by the US government, who originally conditioned their approval of

Plan Colombia Plan Colombia was a United States foreign aid, military aid, and diplomatic initiative aimed at combating Colombian drug cartels and left-wing insurgent groups in Colombia. The plan was originally conceived in 1999 by the administrations of Col ...

on the use of this weapon, but ultimately withdrew the condition. In February 2001, the EU Parliament issued a declaration specifically against the use of these biological agents in warfare.

Gold interactions

The fungus has the ability to dissolve

gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile met ...

, then precipitate it onto its surface, encrusting itself with gold. This phenomenon was first observed in Boddington, West Australia. As a result of this discovery, ''F. oxysporum'' is currently being evaluated as a possible way to help detect hidden underground gold reserves. It also is used to manufacture gold nanoparticles.

''Formae speciales''

* ''

Fusarium oxysporum f.sp. albedinis ''Fusarium oxysporum'' f.sp. ''albedinis'' is a fungus, fungal plant pathology, plant pathogen that causes a disease known as Bayoud disease or fusarium wilt primarily on date palm. Genome Fernandez ''et al.'', 1998 identify the ''Fot1'' (''F.o ...

Fusarium oxysporum f.sp. nicotianae ''Fusarium'' 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 mi ...

'' * '' Fusarium oxysporum f.sp. niveum'' * '' Fusarium oxysporum f.sp. palmarum'' * '' Fusarium oxysporum f.sp. passiflorae'' * '' Fusarium oxysporum f.sp. perniciosum'' * '' Fusarium oxysporum f.sp. phaseoli'' * '' Fusarium oxysporum f.sp. pisi'' * '' Fusarium oxysporum f.sp. radicis-lycopersici'' * '' Fusarium oxysporum f.sp. ricini'' * '' Fusarium oxysporum f.sp. strigae'' * '' Fusarium oxysporum f.sp. tuberosi'' * '' Fusarium oxysporum f.sp. tulipae'' * ''

Fusarium oxysporum f.sp. vasinfectum ''Fusarium oxysporum'' f.sp. ''vasinfectum'' is a fungal A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. T ...

References

{{Taxonbar, from=Q139958 oxysporum Plant pathogens and diseases Agricultural soil science Soil biology