''Exserohilum'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

fungi 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. These organisms are classified as a kingdom, separately from ...

in the family

Pleosporaceae Pleosporaceae is a family of sac fungi. The taxonomic relationship of this family to associated genera is still not determined. Genera As accepted by GBIF; * '' Acrothecium'' (13) * ''Alternaria'' Nees ex Wallroth, 1816 (841) * '' Alternariast ...

. The ''Exserohilum'' species are known for causing blight and human immune system diseases. The sexual reproductive (or ascigerous) states of Exserohilum species are known as Setosphaeria. The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

is ''

Exserohilum turcicum ''Setosphaeria turcica'' (anamorph ''Exserohilum turcicum''; formerly known as ''Helminthosporium turcicum'') is the causal agent of northern corn leaf blight in maize. It is a serious fungal disease prevalent in cooler climates and tropical hig ...

''. This genus is among three

dematiaceous “Black yeasts”, sometimes also black fungi, dematiaceous fungi, microcolonial fungi or meristematic fungi is a diverse group of slow-growing microfungi which reproduce mostly asexually (fungi imperfecti). Only few genera reproduce by budding ...

that are categorized for containing

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

s leading to diseases like

phaeohyphomycosis Phaeohyphomycosis is a diverse group of fungal infections, caused by dematiaceous fungi whose morphologic characteristics in tissue include hyphae, yeast-like cells, or a combination of these. It can be associated an array of melanistic filamento ...

Morphology

''Exserohilum'' is an asexual organism that reproduces through

spores In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...

. These one-celled reproductive units are concave and can be seen in the suspensor.

Taxonomy

''Exserohilum'' was

circumscribed In geometry, the circumscribed circle or circumcircle of a polygon is a circle that passes through all the vertices of the polygon. The center of this circle is called the circumcenter and its radius is called the circumradius. Not every polyg ...

by K. Leonard and Edna Suggs in 1974 to contain species formerly placed in ''

Bipolaris ''Bipolaris'' is a genus of fungi belonging to the family Pleosporaceae. It was circumscribed by mycologist Robert A. Shoemaker in 1959. Species *''Bipolaris australis'' *'' Bipolaris brizae'' *'' Bipolaris buchloës'' *''Bipolaris cactivora'' ...

'' with distinctly protruding hila. Exsero which means stretch out and hilum which refers to the part of the organism. The truncate hila or hilum, protrudes from its distinct

conidia A conidium ( ; ), sometimes termed an asexual chlamydospore or chlamydoconidium (), is an asexual, non-motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also called mitospores due to the ...

which are

ellipsoid An ellipsoid is a surface that may be obtained from a sphere by deforming it by means of directional scalings, or more generally, of an affine transformation. An ellipsoid is a quadric surface; that is, a surface that may be defined as the ...

al and distoseptate (forming a layer). Colonies of ''Exserohilum'' range from the color grey to blackish-brown. The texture varies from suede-like to floccose in texture. The species also have an olivaceous to black reverse. The conidia from which the hilum extends, are either straight, curved, slightly bent or ellipsoidal to fusiform. and are formed on the top through a pore (poroconidia) on an elongated

sympodial Sympodial growth is a bifurcating branching pattern where one branch develops more strongly than the other, resulting in the stronger branches forming the primary shoot and the weaker branches appearing laterally. A sympodium, also referred to a ...

angled

conidiophore A conidium ( ; ), sometimes termed an asexual chlamydospore or chlamydoconidium (), is an Asexual reproduction, asexual, non-motility, motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are al ...

. The strong, protruding truncate hilum and the septum above is normally thick and dark. The end cells are paler and the walls finely roughened. The conidial germination of ''Exserohilum'' is bipolar.

Habitat and distribution

''Exserohilum'' has a

cosmopolitan distribution In biogeography, cosmopolitan distribution is the term for the range of a taxon that extends across all or most of the world in appropriate habitats. Such a taxon, usually a species, is said to exhibit cosmopolitanism or cosmopolitism. The ext ...

, with its species found naturally in warm,

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

, and

subtropical The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Geographical z ...

locations. They live on plant material like grasses, rotten wood and in the soil.

Species

Index Fungorum ''Index Fungorum'' is an international project to index all formal names ( scientific names) in the fungus kingdom. the project is based at the Royal Botanic Gardens, Kew, one of three partners along with Landcare Research and the Institute of M ...

lists 26 valid species of ''Exserohilum'': *'' Exserohilum antillanum'' R.F.Castañeda, Guarro & Cano 1995 – Cuba *'' Exserohilum curvatum'' Sivan. & Muthaiyan 1984 – Venezuela *'' Exserohilum curvisporum'' Sivan., Abdullah & B.A.Abbas 1993 – Iraq *'' Exserohilum echinochloae'' Sivan. 1984 – Bangladesh *'' Exserohilum frumentacei'' (Mitra) K.J.Leonard & Suggs 1974 –

Andhra Pradesh Andhra Pradesh (, abbr. AP) is a state in the south-eastern coastal region of India. It is the seventh-largest state by area covering an area of and tenth-most populous state with 49,386,799 inhabitants. It is bordered by Telangana to the ...

;

Bihar Bihar (; ) is a state in eastern India. It is the 2nd largest state by population in 2019, 12th largest by area of , and 14th largest by GDP in 2021. Bihar borders Uttar Pradesh to its west, Nepal to the north, the northern part of West Be ...

;

Botswana Botswana (, ), officially the Republic of Botswana ( tn, Lefatshe la Botswana, label=Setswana, ), is a landlocked country in Southern Africa. Botswana is topographically flat, with approximately 70 percent of its territory being the Kalahar ...

;

Ethiopia Ethiopia, , om, Itiyoophiyaa, so, Itoobiya, ti, ኢትዮጵያ, Ítiyop'iya, aa, Itiyoppiya officially the Federal Democratic Republic of Ethiopia, is a landlocked country in the Horn of Africa. It shares borders with Eritrea to the ...

;

Sabah Sabah () is a States and federal territories of Malaysia, state of Malaysia located in northern Borneo, in the region of East Malaysia. Sabah borders the Malaysian state of Sarawak to the southwest and the North Kalimantan province of Indone ...

*'' Exserohilum fusiforme'' Alcorn 1991 – Queensland *'' Exserohilum gedarefense'' (El Shafie) Alcorn 1983 – Egypt; Sudan *'' Exserohilum heteromorphum'' G.Y.Sun 2005 *'' Exserohilum heteropogonicola'' Sivan. 1984 –

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 ...

;

Uttaranchal Uttarakhand ( , or ; , ), also known as Uttaranchal ( ; the official name until 2007), is a state in the northern part of India. It is often referred to as the "Devbhumi" (literally 'Land of the Gods') due to its religious significance and ...

*'' Exserohilum inaequale'' Sivan. 1984 – Nigeria *'' Exserohilum israeli'' Steiman, Guiraud, Seigle-Mur. & Sage 2000 – Israel *'' Exserohilum longirostratum'' (Subram.) Sivan. 1984 – Andhra Pradesh;

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

; France; Haryana; Madhya Pradesh; Nigeria; Northern Territory;

Puerto Rico Puerto Rico (; abbreviated PR; tnq, Boriken, ''Borinquen''), officially the Commonwealth of Puerto Rico ( es, link=yes, Estado Libre Asociado de Puerto Rico, lit=Free Associated State of Puerto Rico), is a Caribbean island and Unincorporated ...

;

Rajasthan Rajasthan (; lit. 'Land of Kings') is a state in northern India. It covers or 10.4 per cent of India's total geographical area. It is the largest Indian state by area and the seventh largest by population. It is on India's northwestern si ...

; Sudan; Uttar Pradesh; Zambia *'' Exserohilum longisporum'' G.Y.Sun 1997 – China *'' Exserohilum mcginnisii'' A.A.Padhye & Ajello 1986 *'' Exserohilum minor'' Alcorn 1986 *'' Exserohilum neoregeliae'' Sakoda & Tsukib. 2011 *'' Exserohilum oryzae'' Sivan. 1987 – Macedonia *'' Exserohilum oryzicola'' Sivan. 1984 *'' Exserohilum oryzinum'' Sivan. 1984 – Egypt *'' Exserohilum parlierense'' W.Q.Chen & Michailides 2002 *'' Exserohilum paspali'' J.J.Muchovej & Nesio 1987 –

Minas Gerais Minas Gerais () is a state in Southeastern Brazil. It ranks as the second most populous, the third by gross domestic product (GDP), and the fourth largest by area in the country. The state's capital and largest city, Belo Horizonte (literally ...

*'' Exserohilum phragmitis'' W.P.Wu 1990 *'' Exserohilum protrudens'' Alcorn 1988 *'' Exserohilum psidii'' Sivan. 1992 – Andhra Pradesh *'' Exserohilum sodomii'' Guiraud, Steiman, Seigle-Mur. & Sage 1997 – Israel *'' Exserohilum sorghicola'' Sivan. 1987 – Ethiopia

Clinical significance

Infection cases caused by exposure to ''Exserohilum'' are rare, but it's the most well studied detail of the fungi. The three species of ''Exserohilum'' that are identified as human pathogens are: ''

Exserohilum Rostratum ''Setosphaeria rostrata'' is a heat tolerant fungus with an asexual reproductive form (anamorph) known as '' Exserohilum rostratum''. This fungus is a common plant pathogen, causing leaf spots as well as crown rot and root rot in grasses. It is ...

'', '' Exserohilum longirostratum'' and '' Exserohilum mcginnisii''. Prevailing infections include sinusitis, skin infection and in some rare cases, cerebral abscesses, keratitis, osteomyelitis, prothetic valve endocarditis, and disseminated infection. Reports of human infection by ''Exserohilum'' mainly come from warm, tropical and subtropical locations such as southern United States, India, and Israel.

References

External links

{{Taxonbar, from=Q10493219 Dothideomycetes genera Pleosporaceae