Claviceps pusilla Ces.

Synonym

Hypocrea pusilla Ces.

Description

Sclerotia formed in the fertile florets of spikelets and replacing the ovaries, cylindrical, variable but approximately the length of the spikelet of the host, tapering slightly and rounded at the ends, dark brown-black, surface minutely wrinkled, with several shallow longitudinal furrows.

Conidia of two types

  • microconidia formed on narrow, flask-shaped terminal conidiogenous cells on the sphacelium and later immersed in honeydew, subglobose-globose, 4-5 μm in diameter, hyaline, aseptate.
  • macroconidia formed on narrow, flask-shaped terminal conidiogenous cells on the sphacelium and later immersed in honeydew, mostly triangular, some ellipitical, 10-16 x 5-7.5 μm, hyaline, asepatate, sometimes biguttulate.

Ascostromata one to several per sclerotium, each consisting of a globose capitulum, 0.5-1.0 mm diameter, dark straw coloured, prominently papillate, a collar-like appendage surrounds the base of the capitulum at its junction with the stipe, borne on a slender stipe 3-15 mm and occasionally up to 30 mm long, pale straw coloured, glabrous, with waxy appearance, tufts of white hyphae persistent round the base.

Perithecia subglobose, 220-300 x 125-165 μm.

Asci cylindrical, 55-160 μm, hyaline, rounded at the apex, attenuated at the base.

Ascospores 8 per ascus, filiform, almost equalling the ascus in length, hyaline.

Hosts
   
Host family: Poaceae
   
Host species: Arundinella nepalensis
Bothriochloa biloba
Bothriochloa bladhii

Bothriochloa decipiens
Bothriochloa erianthoides
Bothriochloa ewartiana
Bothriochloa glabra
Bothriochloa insculpta

Bothriochloa macra
Bothriochloa pertusa
Capillipedium spicigerum
Chrysopogon filipes
Cymbopogon refractus
Dichanthium annulatum
Dichanthium aristatum
Dichanthium caricosum
Dichanthium sericeum
Heteropogon contortus
Hyparrhenia hirta
Sarga leiocladum
Sarga plumosum
Themeda triandra
Urochloa sp.

Distribution

ACT, NSW, NT, QLD

Comments

This is a relatively common ergot, being found widely on a range of tropical and subtropical grasses. Although the triangular shape of the macroconidia distinguishes C. pusilla from all other described species of Claviceps, there is considerable variation in dimensions of conidia in Australian isolates. Pažoutová et al. (2004) also stated that C. pusilla produced secondary conidia when macroconidia were germinated in vitro, but did not provide any details on their morphology. Secondary conidiation may be a rare event in nature, because they were not found in any Australian specimen of C. pusilla.

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Claviceps pusilla on Dichanthium sp.
Scale bar = 1 mm.
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Claviceps pusilla on Dichanthium sp.
Scale bar = 500 µm.
Highslide JS
Claviceps pusilla on Unknown host.
Scale bar = 500 µm.
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Claviceps pusilla on Unknown host.
Scale bar = 250 µm.
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Claviceps pusilla on Unknown host.
Scale bar = 100 µm.
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Claviceps pusilla on Unknown host.
Scale bar = 40 µm.
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Claviceps pusilla on Unknown host.
Scale bar = 20 µm.
Highslide JS
Claviceps pusilla on Unknown host.
Scale bar = 20 µm.
Highslide JS
Claviceps pusilla on Unknown host.
Scale bar = 20 µm.
Highslide JS
Claviceps pusilla on Unknown host.
Scale bar = 20 µm.