Claviceps platytricha Langdon

Description

Sclerotia formed in the fertile florets of spikelets and replacing the ovaries,cylindrical, straight or slightly curved, 9-12 x 1.25-1.5 mm, deep chestnut brown, with tips often narrowing to a projection 1-2 mm long, with longitudinal ridges.

Conidia of two types

  • macroconidia formed on narrow, flask-shaped terminal conidiogenous cells on the sphacelium and later immersed in honeydew, oblong, 7-11 x 3.5-5.5 µm, mostly with sides parallel rarely curved, hyaline, aseptate, biguttulate.
  • secondary conidia developed singly at the tips of sterigmata from germinated macroconidia above the honeydew surface, pyriform, 6-8 x 3-4 µm, hyaline, aseptate.

Ascostromata 5-7 per sclerotium, each consisting of a globose capitulum, 0.6-1.2 mm in diameter, hazel, glabrous, meeting the stipe at approx. 90°, and with perithecial beaks distinctly separated, borne by a slender stipe 5-7 mm long x 0.2-0.4 mm in diameter, dark purple-chestnut, glabrous, with fine longitudional grooves and often thickened at the base.

Perithecia immersed in capitula, pyriform, 180-215 x 110-150 µm.

Asci cylindrical, 65-105 x 4 µm, apex rounded, base attenuated.

Ascospores filiform, nearly equaling the ascus in length, hyaline.

Hosts
   
Host family: Poaceae
   
Host species:

Ischaemum australe
Ischaemum triticeum


Distribution

QLD, WA

Comments

Langdon (1942) distinguished this species from other Claviceps species by the drab colour of the ascostroma, the white hyphae lying flat against the sclerotium at the base of the stipe, and the morphology of the macroconidia. Based on overseas records of Cerebella (a saprophytic fungus which grows on the sphacelia and honeydew of Claviceps) on Ischaemum spp. and the fact that C. platytricha is the only ergot fungus recorded on Ischaemum species, it is highly probable that C. platytricha is not confined to Australia.

Highslide JS
Claviceps platytricha on Ischaemum sp. - BRIP 51832.
Scale bar = 1 cm.
Highslide JS
Claviceps platytricha on Ischaemum sp. - BRIP 51832. Scale bar = 5 mm.
Highslide JS
Claviceps platytricha on Ischaemum australe - BRIP 8104.
Scale bar = 1 mm.
Highslide JS
Claviceps platytricha on Ischaemum triticeum - BRIP 15296.
Scale bar = 10 µm.
Highslide JS
Claviceps platytricha on Ischaemum triticeum - BRIP 15296.
Scale bar = 10 µm.