Nigrocornus scleroticus (Pat.) Ryley

Synonyms

Epichloë sclerotica Pat.
Hypocrella axillaris
Cooke
Epichloë oplismeni Henn.
Epichloë schumanniana Henn.
Epichloë volkensii Henn.
Hypocrea axillaris (Cooke) Massee
Ophiodothis volkensii (Henn.) Sacc.
Ophiodothis oplismeni (Henn.) Henn.
Ophiodothis sclerotica (Pat.) Henn.
Ophiodothis schumanniana (Henn.) Henn.
Ophiodothis vorax var. paspali Henn.
Ophiodothis arundinellae Henn.
Ophiodothis paspali Henn.
Balansiopsis schumanniana (Henn.) Höhn.
Balansia sclerotica (Pat.) Höhnel
Balansia axillaris (Cooke) Petch
Balansia cynodontis Syd.
Balansia volkensii (Henn.) E. Castell. & Cif.
Balansia trachypogonis Doidge
Balansia sclerotica var. deformans Govindu & Thirum.
Balansia madagascariensis
Viennot-Bourgin
Parepichloë cynodontis (Syd.) J.F.White & P.V.Reddy
Parepichloë oplismeni (Henn.) J.F.White & P.V.Reddy
Parepichloë sclerotica (Pat.) J.F.White & P.V.Reddy
Parepichloë volkensii
(Henn.) J.F.White & P.V.Reddy

Description

Conidial fructifications effuse, epiphytic, ephemeral hyphal layers covering the adaxial surfaces of leaves in the upper parts of infected culms.

Conidia of one type

  • conidia developing on the epiphytic hyphal layer from simple, occasionally branched conidiophores, narrowly obclavate, 13-29 x 1-1.5 µm, hyaline, aseptate, multiguttulate. 

Ascostromata occurring singly at nodes of culms and enclosing axillary buds, dimensions variable dependant on host, at maturity from 3-5 x 1-1.5 mm on Triodia triandra to 10-30 x 2-3 mm on Sorghum leiocladum, corniform to flattened subglobose, black, papillate, closely associated with the protophyll of axillary bud, internally three distinct zones, rind, outer cortex and inner cortex.

Perithecia immersed in periphery of ascostromata, lageniform-obpyriform, 180-540 x 70- 180 µm and somewhat dependant on host, with ostiolar periphyses and a basal cluster of aparaphysate asci.

Asci cylindrical, single walled, with a hemispherical apical cap perforated by a fine pore, 150-240 x 3-7 µm and somewhat dependant on host.

Ascospores 8 per ascus, filiform, 120-210 x 1-1.5 µm, hyaline, 7-septate, breaking into two almost equal 3-septate parts after germination.

Hosts
   
Host family: Poaceae
   
Host species:

Bothriochloa ewartiana
Chrysopogon fallax
Cymbopogon refractus
Entolasia stricta
Eragrostiella bifaria
Eremochloa bimaculata
Eriachne mucronata
Ischaemum sp.
Oplismenus hirtellus
Panicum sp.
Paspalidium criniforme
Paspalidium distans
Paspalidium sp.
Paspalum scrobiculatum
Sarga timorense
Schizachyrium pachyarthron
Sorghum leiocladum
Sorghum plumosum
Themeda triandra
Triodia basedowii
Triodia bitextura
Triodia burbidgeana
Triodia bynoei
Triodia epactia
Triodia procera
Triodia pungens
Triodia shinzii


Distribution

NSW, NT, QLD, WA

Comments

Nigrocornus is a monospecific genus found on grasses mostly belonging to the subfamily Panicoideae in the tropical and subtropical regions of Australia, Asia and Africa. The asexual state of N. scleroticus has many characteristics typical of Ephelis, the asexual state of Balansia. The fungus is a systemic epiphyte of its perennial grass hosts, causing suppression of inflorescence development, a reduction in culm length and thickness, an increase in culm node number, a proliferation of branching in some hosts, and several types of tiller abnormality. Hyphae of Nigrocornus surround the subterranean tiller buds of  host plants over their dormant period (winter) resulting in the production of Nigrocornus-infected tillers year after year. Hypocrella axillaris, a synonym of N. scleroticus, was listed in Cooke’s (1892) Handbook of Australian Fungi, having been found on grasses in Queensland.

Two hyperparasites have been found on living ascostromata of N. scleroticus in Australia. The first, identified as a species of Bionectria, was found on Nigrocornus ascostromata colonising plants of Oplismenus imbecillis and Entolasia stricta at Mt Tomah, New South Wales, in May-June 1977. The asexual state, characteristic of Clonostachys, consisted of light brown-yellow sporodochia scattered or clustered over the surface of the Nigrocornus stromata, with light green, ellipsoidal-narrowly clavate conidia produced on penicillate conidiophores arranged in a palisade over the surface of the sporodochia. The sexual state consisted of globose-subglobose, yellow-orange perithecia on the surface of the Nigrocornus stromata, and in which there were clavate asci, each with 8 ellipsoidal, 1-septate, hyaline ascospores. The second hyperparasite, with characteristics of Nectriella balansiae (Arnold 1967), was found on Nigrocornus ascostromata on Cymbopogon refractus at one locality in southern Queensland. Its spherical perithecia were immersed separately in the Nigrocornus ascostromata and contained clavate-oblong asci with fusiform-elliptical, 1-septate, hyaline ascospores.

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Nigrocornus scleroticus on Sarga sp.
Scale bar = 2 cm.
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Nigrocornus scleroticus on Sarga sp.
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Nigrocornus scleroticus on Sarga sp.
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Nigrocornus scleroticus on Sarga sp.
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Nigrocornus scleroticus on Sarga sp.
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Nigrocornus scleroticus on Sarga sp.
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Nigrocornus scleroticus on Sarga sp.
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Nigrocornus scleroticus on Unknown host.
Scale bar = 1 cm.
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Nigrocornus scleroticus on Unknown host.
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Nigrocornus scleroticus on Unknown host.
Scale bar = 100 µm.
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Nigrocornus scleroticus on Unknown host.
Scale bar = 100 µm.
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Nigrocornus scleroticus on Unknown host.
Scale bar = 100 µm.
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Nigrocornus scleroticus on Unknown host.
Scale bar = 20 µm.
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Nigrocornus scleroticus on Unknown host.
Scale bar = 10 µm.
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Nigrocornus scleroticus on Unknown host.
Scale bar = 10 µm.
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Nigrocornus scleroticus on Unknown host. Scale bar = 10 µm.
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Nigrocornus scleroticus on Unknown host.
Scale bar = 10 µm.
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Nigrocornus scleroticus on Unknown host.
Scale bar = 10 µm.
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Nigrocornus scleroticus on Unknown host. Scale bar = 10 µm.
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Nigrocornus scleroticus on Unknown host.
Scale bar = 10 µm.
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Nigrocornus scleroticus perithecia.
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Bionectria sp. on Nigrocornus scleroticus - DAR 30009. Scale bar = 1 mm.
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Bionectria sp. on Nigrocornus scleroticus - DAR 30009. Scale bar = 500 µm.