Claviceps cynodontis Langdon

Description

Sclerotia formed in the fertile florets of spikelets and replacing the ovaries, elongate, usually curved, sometimes twisted, distinctly compressed laterally, 2-7 mm long x 1-1.5 mm high x 0.5 mm wide; dark brown–black, surface verruculose, with indistinct longitudional furrows.

Conidia of two types

  • macroconidia formed on narrow, flask-shaped terminal conidiogenous cells on the sphacelium and later immersed in honeydew, predominately reniform, 9-17 x 3-6 µm, hyaline, aseptate.
  • secondary conidia developed singly at the tips of sterigmata from germinated macroconidia above the honeydew surface, ovoid-obovoid, with a slight flattened protrusion at base, 9-12 µm x 4-7 µm, hyaline, aseptate hyaline.

Ascostromata one-several per sclerotium, each consisting of a subglobose capitulum, up to 1 mm in diameter, bright yellow, overlapping at point of attachment with stipe, prominently papillate at maturity, borne by a slender stipe up to 7 mm long x 0.3-0.4 mm wide, narrowing to 0.2 mm at the junction with the capitulum, straw-coloured, smooth except for a few loose white hyphae which persist at the base.

Peritheciapyriform, 220-245 x 110-113 µm, the neck opening at the top of a papilla.

Asci cylindrical, 115-150 x 3-5 µm, unitunicate, attenuated at the base, with a thickened hemispherical apical cap perforated by a fine pore.

Ascospores filiform, 93-133 x 1-2 µm, hyaline.

Hosts
   
Host family: Poaceae
   
Host species: Cynodon dactylon

Distribution

QLD

Comments

Although C. dactylon was collected in Australia in 1802-1805 by the botanist Robert Brown, Langdon (1954b) used mycological evidence to suggest that the grass is not indigenous to Australia, and that it was introduced into Australia in the first decade after European colonisation (1788-1798). There are no records of ergot on C. dactylon in Australia prior to 1998, indicating that C. cynodontis is either a very recent introduction, or that the conditions for infection are very specific and occur only rarely.

Highslide JS
Claviceps cynodontis on Cynodon dactylon - BRIP 43495.
Scale bar = 1 cm.
Highslide JS
Claviceps cynodontis on Cynodon dactylon.
Scale bar = 1 cm.
Highslide JS
Claviceps cynodontis on Cynodon dactylon.
Highslide JS
Claviceps cynodontis on Cynodon dactylon - BRIP 39261.
Scale bar = 20 µm.
Highslide JS
Claviceps cynodontis on Cynodon dactylon - BRIP 39261.
Scale bar = 20 µm.