Exserohilum

Exserohilum is a genus of fungi in the family Pleosporaceae. 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 is Exserohilum turcicum. This genus is among three dematiaceous that are categorized for containing pathogens leading to diseases like phaeohyphomycosis.

Exserohilum
Exserohilum turcicum on corn leaf
Scientific classification
Domain:	Eukaryota
Kingdom:	Fungi
Division:	Ascomycota
Class:	Dothideomycetes
Order:	Pleosporales
Family:	Pleosporaceae
Genus:	Exserohilum K.J.Leonard & Suggs (1974)
Type species
Exserohilum turcicum (Pass.) K.J.Leonard & Suggs (1974)

Morphology

Exserohilum is an asexual organism that reproduces through spores. These one-celled reproductive units are concave and can be seen in the suspensor.^[1]

Taxonomy

Exserohilum was circumscribed by K. Leonard and Edna Suggs in 1974 to contain species formerly placed in Bipolaris with distinctly protruding hila.^[2] 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 which are ellipsoidal and distoseptate (forming a layer).^[3]

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 angled conidiophore. 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.^[1]

Habitat and distribution

Exserohilum has a cosmopolitan distribution, with its species found naturally in warm, tropical, and subtropical locations. They live on plant material like grasses, rotten wood and in the soil.^[4]

Species

As of October 2015^[update], Index Fungorum lists 26 valid species of Exserohilum:^[5]

• Exserohilum antillanum R.F.Castañeda, Guarro & Cano 1995 – Cuba^[6]
• Exserohilum curvatum Sivan. & Muthaiyan 1984 – Venezuela^[7]
• Exserohilum curvisporum Sivan., Abdullah & B.A.Abbas 1993 – Iraq^[8]
• Exserohilum echinochloae Sivan. 1984 – Bangladesh^[7]
• Exserohilum frumentacei (Mitra) K.J.Leonard & Suggs 1974 – Andhra Pradesh; Bihar; Botswana; Ethiopia; Sabah
• Exserohilum fusiforme Alcorn 1991 – Queensland
• Exserohilum gedarefense (El Shafie) Alcorn 1983 – Egypt; Sudan^[9]
• Exserohilum heteromorphum G.Y.Sun 2005^[10]
• Exserohilum heteropogonicola Sivan. 1984 – Colombia; Uttaranchal^[7]
• Exserohilum inaequale Sivan. 1984 – Nigeria^[7]
• Exserohilum israeli Steiman, Guiraud, Seigle-Mur. & Sage 2000 – Israel^[11]
• Exserohilum longirostratum (Subram.) Sivan. 1984 – Andhra Pradesh; Florida; France; Haryana;^[12] Madhya Pradesh; Nigeria; Northern Territory; Puerto Rico; Rajasthan; Sudan; Uttar Pradesh; Zambia^[7]
• Exserohilum longisporum G.Y.Sun 1997 – China^[13]
• Exserohilum mcginnisii A.A.Padhye & Ajello 1986^[14]
• Exserohilum minor Alcorn 1986
• Exserohilum neoregeliae Sakoda & Tsukib. 2011
• Exserohilum oryzae Sivan. 1987 – Macedonia^[15]
• Exserohilum oryzicola Sivan. 1984^[7]
• Exserohilum oryzinum Sivan. 1984 – Egypt^[7]
• Exserohilum parlierense W.Q.Chen & Michailides 2002
• Exserohilum paspali J.J.Muchovej & Nesio 1987 – Minas Gerais
• Exserohilum phragmitis W.P.Wu 1990
• Exserohilum protrudens Alcorn 1988^[16]
• Exserohilum psidii Sivan. 1992 – Andhra Pradesh^[17]
• Exserohilum sodomii Guiraud, Steiman, Seigle-Mur. & Sage 1997 – Israel
• Exserohilum sorghicola Sivan. 1987 – Ethiopia^[15]

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, 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.^[3]

References

1. "Fungal Diseases". Centers for Disease Control and Prevention. Retrieved 21 October 2015.
2. Leonard KJ, Suggs EG (1974). "Setosphaeria prolata, the ascigerous state of Exserohilum prolatum". Mycologia. 66 (2): 281–297. doi:10.2307/3758363. JSTOR 3758363.
3. Liu, Dongyou, ed. (2011). Molecular detection of human fungal pathogens. Boca Raton, Fla.: CRC Press. pp. 83–91. ISBN 978-1-4398-1240-2.
4. Therese KL, Madhavan HN (2011). "Exserohilum". In Liu D. (ed.). Molecular Detection of Human Fungal Pathogens. CRC Press. pp. 83–91. ISBN 978-1-4398-1240-2.
5. Kirk PM. "Species Fungorum (version 28th September 2015). In: Species 2000 & ITIS Catalogue of Life". Retrieved 14 October 2015.
6. Castañeda Ruiz RF, Guarro J, Cano J (1995). "A new species of Exserohilum from Cuba". Mycological Research. 99 (7): 825–826. doi:10.1016/S0953-7562(09)80734-X.
7. Sivanesan A. (1984). "New species of Exserohilum". Transactions of the British Mycological Society. 83 (2): 319–329. doi:10.1016/s0007-1536(84)80154-0.
8. Sivanesan A, Abdullah SK, Abbas BA (1993). "Exserohilum curvisporum sp. nov., a new hyphomycetes from Iraq". Mycological Research. 97 (12): 1486–1488. doi:10.1016/S0953-7562(09)80222-0.
9. Alcorn JL. (1983). "Generic concepts in Drechslera, Bipolaris and Exserohilum". Mycotaxon. 17: 1–88.
10. Sun GY, Zhang R, Zhou W, Zhu MQ (2005). "Exserohilum heteromorphum sp. nov., a new helminthosporioid fungus from Echinochloa in China". Mycotaxon. 92: 173–176.
11. Steiman R, Guiraud P, Seigle-Murandi F, Sage L (2000). "Exserohilum israeli, a new species isolated from soil from Timna Park (Israel), and its physiological properties". Antonie van Leeuwenhoek. 78 (2): 153–161. doi:10.1023/A:1026561631387. PMID 11204767. S2CID 1347744.
12. Choudhary, M.; Sardana, H. R.; Bhat, M. N.; Gurjar, M. S. (1 October 2018). "First Report of Leaf Spot Disease Caused by Exserohilum rostratum on Bottle Gourd in India". Plant Disease. 102 (10): 2042. doi:10.1094/PDIS-02-18-0315-PDN. PMID 30088959.
13. Sun GY, Zhang R, Zhu MQ, Zhang TY (1997). "A new species of Exserohilum from China". Mycological Research. 101 (7): 776–778. doi:10.1017/S0953756297003547.
14. Padhye AA, Ajello L, Wieden MA, Steinbronn KK (1986). "Phaeohyphomycosis of the nasal sinuses caused by a new species of Exserohilum". Journal of Clinical Microbiology. 24 (2): 245–249. doi:10.1128/jcm.24.2.245-249.1986. PMC 268883. PMID 3745422.
15. Sivanesan A. (1987). "Graminicolous species of Bipolaris, Curvularia, Drechslera, Exserohilum and their teleomorphs". Mycological Papers. 158: 1–261.
16. Alcorn JL. (1988). "A new species of Exserohilum". Transactions of the British Mycological Society. 90: 146–148. doi:10.1016/s0007-1536(88)80199-2.
17. Sivanesan A. (1992). "New Bipolaris, Curvularia and Exserohilum species". Mycological Research. 96 (6): 485–489. doi:10.1016/S0953-7562(09)81095-2.

External links

Exserohilum in Index Fungorum