
''Fusarium solani'' is a species complex of at least 26 closely related filamentous fungi in the division
Ascomycota
Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The def ...
, family
Nectriaceae.
It is the
anamorph of ''
Nectria haematococca
''Fusarium solani'' is a species complex of at least 26 closely related filamentous fungi in the division Ascomycota, family Nectriaceae. It is the anamorph of '' Nectria haematococca''. It is a common soil inhabiting mold. ''Fusarium solani' ...
''.
It is a common soil inhabiting mold.
''Fusarium solani'' is implicated in plant diseases as well as in serious human diseases such as
fungal keratitis.
History and taxonomy
The genus ''
Fusarium
''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 s ...
'' was described in 1809 by Link.
In the 1930s, Wollenweber and Reinking organized the genus ''Fusarium'' into sections, including ''Martiella'' and ''Ventricosum,''
which were collapsed together by Snyder and Hansen in the 1940s to form a single species, ''Fusarium solani;''
one of nine ''Fusarium'' species they recognized based on morphological features.
The current concept of ''F. solani'' is as a
species complex
In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...
consisting of multiple, closely related and morphologically poorly distinguishable, "cryptic" species with characteristic genetic differences.
There is a proposed concept for the entire genus - widely subscribed by specialists - that would include this complex.
However, there is a smaller counterproposal that radically refiles the genus including making this complex into a genus ''Neocosmospora''.
The fungus is allied with the sexual species, ''Nectria haematococca'', in the family Nectriaceae (phylum Ascomycota).
Growth and morphology
Like other species in its genus, ''Fusarium solani'' produces colonies that are white and cottony. However, instead of developing a pink or violet centre like most ''Fusarium'' species,
''F. solani'' becomes blue-green or bluish brown.
On the underside, they may be pale, tea-with-milk-brown, or red-brown.
However, some clinical isolates have been blue-green or ink-blue on the underside.
''F. solani'' colonies are low-floccose, loose, slimy, and sporadic.
When grown on
potato dextrose agar (PDA), this fungus grows rapidly, but not as rapidly as ''
Fusarium oxysporum
''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 ...
''.
In PDA, ''F. solani'' colonies reach a diameter of 64–70 mm in 7 days.
''F. solani'' has aerial
hypha
A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium.
Structure
A hypha consists of one o ...
e that give rise to
conidiophore
A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an Asexual reproduction, asexual, non-motility, motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word f ...
s laterally.
The conidiophores branch into thin, elongated monophialides that produce
conidia
A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an asexual, non- motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also ...
.
Phialides that produce
macroconidia
A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an Asexual reproduction, asexual, non-motility, motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word f ...
are shorter than those that produce
microconidia.
The macroconidia produced by ''F. solani'' are slightly curved, hyaline, and broad,
often aggregating in fascicles.
Typically the macroconidia of this species have 3 septa but may have as many as 4–5.
Microconidia have thickened basal cells and tapered, rounded apical cells.
However, some ''F. solani'' isolates have pointed, rather than rounded, macroconidia.
Microconidia are oval or cylindrical, hyaline, and smooth.
Some microconidia may be curved.
Microconidia typically lack septa, but occasionally they may have up to two.
''Fusarium solani'' also forms
chlamydospores most commonly under suboptimal growth conditions.
These may be produced in pairs or individually.
They are abundant, have rough walls, and are 6-11 μm.
''F. solani'' chlamydospores are also brown and round.
Ecology
''F. solani'' is found in soil worldwide.
However, a given species within the complex may not be as widespread
and may not have the same ecology as others in the complex.
In general, as a soil fungus, ''F. solani'' is associated with the roots of plants
and may be found as deep in the ground as 80 cm.
It is frequently isolated in tropic, subtropic, and temperate locations, and less frequently isolated from alpine habitats.
The pH of soil does not have a significant effect on ''F. solani'', however, soil fumigation causes an increase in occurrence.
''F. solani'' is typically sensitive to soil fungicides.
''F. solani'' has been found in ponds, rivers, sewage facilities, and water pipes.
It has also been found in larvae and adults of the
picnic beetle, is a symbiote of the
ambrosia beetle
Ambrosia beetles are beetles of the weevil subfamilies Scolytinae and Platypodinae (Coleoptera, Curculionidae), which live in nutritional symbiosis with ambrosia fungi. The beetles excavate tunnels in dead or stressed trees into which they introduc ...
.
Life cycle
''F. solani'' can be found in soils worldwide, where its chlamydospores overwinter on plant tissue/seed or as mycelium in the soil.
The pathogen enters hosts through developing roots, where it can infect the host. After infection, F. ''solani'' produces asexual macro and microconidia which are dispersed through wind and rain. The pathogen can persist in the soil for a decade, and if left unchecked can cause complete crop loss.
Physiology and biochemistry
''F. solani'' have 5-13 chromosomes,
with a genome size of about 40 Mb.
The
GC-content
In molecular biology and genetics, GC-content (or guanine-cytosine content) is the percentage of nitrogenous bases in a DNA or RNA molecule that are either guanine (G) or cytosine (C). This measure indicates the proportion of G and C bases out of ...
of its DNA is 50%.
Mycelium of ''F. solani'' is rich in the amino acid
alanine
Alanine (symbol Ala or A), or α-alanine, is an α-amino acid that is used in the biosynthesis of proteins. It contains an amine group and a carboxylic acid group, both attached to the central carbon atom which also carries a methyl group sid ...
, as well as a range of fatty acids including δ-aminobutyric-,
palmitic-,
oleic-, and
linolenic acid
Linolenic acid is a type of naturally-occurring fatty acid. It can refer to either of two octadecatrienoic acids (i.e. with an 18-carbon chain and three double bonds, which are found in the '' cis'' configuration), or a mixture of the two. Lino ...
s.
''Fusarium solani'' requires
potassium
Potassium is a chemical element; it has Symbol (chemistry), symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to ...
for growth,
and develops a feathery pattern when potassium levels are below 3 mM.
In culture the following disaccharides are utilized (from most- to least preferential):
mannose
Mannose is a sugar with the formula , which sometimes is abbreviated Man. It is one of the monomers of the aldohexose series of carbohydrates. It is a C-2 epimer of glucose. Mannose is important in human metabolism, especially in the glycosylatio ...
,
rhamnose
Rhamnose (Rha, Rham) is a naturally occurring deoxy sugar. It can be classified as either a methyl- pentose or a 6-deoxy- hexose. Rhamnose predominantly occurs in nature in its L-form as L-rhamnose (6-deoxy-L- mannose). This is unusual, since mo ...
and
sorbose.
This species can decompose
cellulose
Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important s ...
at an optimal pH of 6.5 and temperature of 30 °C.
It can also metabolise
steroid
A steroid is an organic compound with four fused compound, fused rings (designated A, B, C, and D) arranged in a specific molecular configuration.
Steroids have two principal biological functions: as important components of cell membranes t ...
s and
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 rigidit ...
,
and reduce Fe
3+ to Fe
2+.
''Fusarium solani'' produces
mycotoxin
A mycotoxin (from the Greek μύκης , "fungus" and τοξικός , "poisonous") is a toxic secondary metabolite produced by fungi and is capable of causing disease and death in both humans and other animals. The term 'mycotoxin' is usually rese ...
s like
Fusaric acid and
naphthoquinone
Naphthoquinones constitute a class of organic compounds structurally related to naphthalene. Two isomers are common for the parent naphthoquinones:
* 1,2-Naphthoquinone
* 1,4-Naphthoquinone
Natural products
* Alkannin
* Hexahydroxy-1,4-nap ...
s.
Other toxins have also been isolated from ''F. solani'', including:
*
Fusarubin
*
Javanicin
*
Marticin
*
Isomarticin - causes
chlorosis
In botany, chlorosis is a condition in which leaves produce insufficient chlorophyll. As chlorophyll is responsible for the green color of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to ...
in citrus
*
Solaniol
*
Neosolaniol
*
T-2 toxin
*
HT-2 toxin
*
Diacetoxyscirpenol
Pathology
Humans
''F. solani'' is largely resistant to typical antifungal agents.
The most effective antifungals in treating ''F. solani'' infections are
amphotericin B
Amphotericin B is an antifungal medication used for serious fungal infections and leishmaniasis. The fungal infections it is used to treat include mucormycosis, aspergillosis, blastomycosis, candidiasis, coccidioidomycosis, and cryptococ ...
and
natamycin
Natamycin, also known as pimaricin, is an antifungal medication used to treat fungal infections around the eye. This includes infections of the eyelids, conjunctiva, and cornea. It is used as eyedrops. Natamycin is also used in the food in ...
; however, these agents have only modest success in the treatment of serious systemic infection.
As of 2006, there has been increasing evidence that ''F. solani'' can act as a causal agent of mycoses in humans.
''F. solani'' has been implicated in the following diseases:
disseminated disease
Disseminated disease can refer to disseminated cancer which is the movement of cancerous cells from the original tumor to other areas of the body, or disseminated infection which is the pathogen's entry into the host, growth, and dissemination ...
,
osteomyelitis
Osteomyelitis (OM) is the infectious inflammation of bone marrow. Symptoms may include pain in a specific bone with overlying redness, fever, and weakness. The feet, spine, and hips are the most commonly involved bones in adults.
The cause is ...
,
skin infection,
fungemia, and
endophthalmitis.
Half of human disease involving ''Fusarium'' is caused by ''F. solani'' and it is involved in most cases of systemic fusariosis and corneal infections.
In immunocompromised patients, ''F. solani'' is one of the most common agents in disseminated and cutaneous infections.
In the southern USA,
fungal keratitis has been most commonly caused by ''F. solani'', as well as ''F. oxysporum''. Cases occur most frequently during harvest season as a result of corneal trauma from dust or plant material. Fungal spores come into contact with the damaged cornea and grow. Without treatment, the hyphae can grow into the cornea and into the
anterior chamber of the eye.
''F. solani'' is also a major cause of fungal keratitis in HIV positive patients in Africa.
As of 2011, ''F. solani'' was implicated in cases of
fungal keratitis involving the
Bausch and Lomb ReNu contact lens solution.
Some strains of ''F. solani'' can produce a biofilm on soft contact lenses. However, when lenses are cleaned correctly with solution, these biofilms are prevented.
Prevention also includes leaving lenses in
polyhexanide biguanide solution overnight to inhibit ''F. solani''.
Other risk factors of contact lens-related ''Fusarium'' keratitis include use of daily-wear lenses beyond the recommended timeline and overnight wear.
An investigation into a meningitis outbreak of 79 cases since October 2022, which had killed 35 people (34 of them women who had undergone cesarean section) in
Durango (city)
Durango (, ) is the capital and largest city of the northern List of states of Mexico, Mexican state of Durango and the seat of the Durango Municipality, municipality of Durango. It has a population of 616,068 as of the 2020 census with 688,697 ...
revealed contamination of
bupivacaine
Bupivacaine, marketed under the brand name Marcaine among others, is a medication used to decrease sensation in a specific small area. In nerve blocks, it is injected around a nerve that supplies the area, or into the spinal canal's epidural ...
with ''Fusarium solani'' in 4 batches, used by an anesthesiologist. US news reported however, that the anesthesiologist used multi-dose vials of morphine, which he would administer in more than one patient for his anesthesias in the 4 private hospitals. As of May 26, 2023 WHO had been asked to declare a public health emergency.
As of June 1, 2023, a multistate outbreak of meningitis due to ''F. solani'' was ongoing among patients who underwent
epidural anesthesia at two clinics in the Mexican city of
Matamoros, Tamaulipas, with a total of 212 residents in 25 US states identified as being at risk, two of whom had died.
Other animals
''F. solani'' is implicated in cutaneous infections of young turtles as well as infections of turtle egg shells.
It has also caused infections in Australian crocodile farms, sea lions and grey seals.
''F. solani'' is a facultative pathogen of the
castor bean tick. It is also lethal to
southern pine beetles.
Plants
''F. solani'' rots the roots of its host plant.
It also causes
soft rot of plant tissues by penetrating plant cell walls and destroying the
torus
In geometry, a torus (: tori or toruses) is a surface of revolution generated by revolving a circle in three-dimensional space one full revolution about an axis that is coplanarity, coplanar with the circle. The main types of toruses inclu ...
.
It is implicated, along with ''
Pythium myriotylum'', in pod rot of the pods of groundnuts.
''F. solani'' can cause damping off, corn rot, and
root rot
Root rot is a condition in which anoxic conditions in the soil or potting media around the roots of a plant cause them to rot. This occurs due to excessive standing water around the roots.-Hydroponics Root Rot: What is It, How To Treat It, How ...
, as well as sudden death of soybeans (SDS). It is a very generalistic fungal species and has been known to infect peas, beans, potatoes, and many types of cucurbits. Symptoms include general plant decline, wilting, and large necrotic spots on tap roots.
Recently the pathogen has also done serious damage to olive trees throughout the mediterranean.
Virulence of this agent in plants is controlled by the
cutinase genes ''cut1'' and ''cut2''. These genes are upregulated by exposure to the plant's cutin monomers.
''F. solani'' is known to cause sudden death syndrome in soybeans, and it is also known to cause disease in other economically important crops such as avocado, citrus, orchids,
passion fruit
''Passiflora edulis'', commonly known as passion fruit, is a vine species of passion flower native to the region of southern Brazil through Paraguay to northern Argentina. It is cultivated commercially in tropical and subtropical areas for its ...
, peas, peppers, potato, and squash.
Management
Agriculture
The ubiquitous nature of ''F. solani'' gives rise to a plethora of management practices developed independently. One particular method is the use of the bacterial complex ''Burkholderia cepacia,'' which is a registered control method. This bacterial complex has been shown to produce several types of antibiotics (depending on the strain), and can act as a substitute for chemical pesticides. Precautionary methods include planting during warm/dry weather, 3 plus years of crop rotation of non host species, and avoiding dense seed planting.
Humans
In the 2023 Matamoros outbreak of F. solani meningitis CDC recommended liposomal amphotericin B and voriconazole,
however, disease progressed on this regimen,
and patients were trialed on
fosmanogepix through a compassionate use authorization.
Biotechnology
''F. solani'' has been investigated as a biological control for certain plants including
leafy spurge,
morning glory
Morning glory (also written as morning-glory) is the common name for over 1,000 species of flowering plants in the family Convolvulaceae, whose taxonomy and systematics remain in flux. These species are distributed across numerous genus, gene ...
,
striga
''Striga'', commonly known as witchweed, is a genus of parasitic plants that occur naturally in parts of Africa, Asia, and Australia. It is currently classified in the family Orobanchaceae, although older classifications place it in the Scrophul ...
,
gourd
Gourds include the fruits of some flowering plant species in the family Cucurbitaceae, particularly '' Cucurbita'' and '' Lagenaria''. The term refers to a number of species and subspecies, many with hard shells, and some without. Many gourds ha ...
, and
water hyacinth
''Pontederia crassipes'' (formerly ''Eichhornia crassipes''), commonly known as common water hyacinth, is an aquatic plant native to South America, naturalized throughout the world, and often invasive species, invasive outside its native rang ...
.
References
{{Authority control
solani
Fungi described in 1881
Fungal plant pathogens and diseases
Fungus species
Animal fungal diseases