Claviceps maximensis Theis

Description

Sclerotia formed in the fertile florets of spikelets and replacing the ovaries, straight-slightly curved or twisted, tapering towards the tip usually with a cap of dried sphacelial stage hyphae, 2-9 mm long x 1 mm wide, brown-gray-brown, longitudionally furrowed, host glumes remain attached.

Conidia of two types

  • macroconidia formed on narrow, flask-shaped terminal conidiogenous cells on the sphacelium and later immersed in honeydew, elliptical, 10-30 x 3.5-11 µm, hyaline,aseptate.
  • secondary conidia developed singly at the tips of sterigmata from germinated macroconidia above the honeydew surface, obovoid, 9-17 x 4-8 µm, hyaline, aseptate.

Ascostromata 1-5 per sclerotium, each consisting of a subglobose capitulum 0.7-1 mm in diameter, brown, finely papillate, overlapping at point of attachment with the stipe, borne by a slender, flexous stipe variable in length, 0.4-0.6 mm in diameter, yellow, glabrous.

Perithecia pyriform, immersed in the capitulum and distributed over the entire upper surface, 240-280 µm long x 120-160 µm wide, neck projected slightly above capitulum surface.

Asci cylindrical, 2-3 x 105-139 µm, tapering toward point of attachment, apex with a hyaline cap, 8-spored, hyaline, aparaphysate.

Ascospores filiform, 0.5 x 95-126 µm, hyaline.

Hosts
   
Host family: Poaceae
   
Host species: Megathyrsus maximus

Distribution

QLD

Comments

The first Australian collection of this fungus was in 1980 on the Atherton Tableland in north Queensland, and Ryley (1981) mentioned that infected panicles could be recognised in part by the presence of a white mycelial growth, then though to be due to an unidentified hyphomycete, on the honeydew. It is highly likely that the “white growth” was in fact due to secondary conidiation because that conidium type has since been found on Australian collections of C. maximensis. This ergot is common on guinea grass (Megathyrsus maximus) in Queensland.

Highslide JS
Claviceps maximensis on Megathyrsus maximus - BRIP 39913.
Scale bar = 1 cm.
Highslide JS
Claviceps maximensis on Megathyrsus maximus - BRIP 39913. Scale bar = 1 cm.
Highslide JS
Claviceps maximensis on Megathyrsus maximus - BRIP 39913. Scale bar = 2 cm.
Highslide JS
Claviceps maximensis on Megathyrsus maximus.
Highslide JS
Claviceps maximensis on Megathyrsus maximus.
Highslide JS
Claviceps maximensis on Megathyrsus maximus.
Highslide JS
Claviceps maximensis on Megathyrsus maximus.
Highslide JS
Claviceps maximensis on Megathyrsus maximus.
Highslide JS
Claviceps maximensis on Megathyrsus maximus.
Highslide JS
Claviceps maximensis on Megathyrsus maximus.
Highslide JS
Claviceps maximensis on Megathyrsus maximus - BRIP 39913. Scale bar = 10 µm.
Highslide JS
Claviceps maximensis on Megathyrsus maximus - BRIP 39913.
Scale bar = 10 µm.
Highslide JS
Claviceps maximensis on Megathyrsus maximus - BRIP 39913. Scale bar = 10 µm.
Highslide JS
Claviceps maximensis on Megathyrsus maximus - BRIP 39913.
Scale bar = 10 µm.
Highslide JS
Claviceps maximensis on Megathyrsus maximus - BRIP 39913.
Scale bar = 10 µm.
Highslide JS
Claviceps maximensis on Megathyrsus maximus - BRIP 40393.
Scale bar = 10 µm.
Highslide JS
Claviceps maximensis on Megathyrsus maximus - BRIP 40393.
Scale bar = 20 µm.
Highslide JS
Claviceps maximensis on Megathyrsus maximus.
Scale bar = 10 µm.