Cepsiclava phalaridis (J. Walker) J. Walker

Synonyms

Claviceps phalaridis J. Walker

Description

Sclerotia formed in the fertile florets of spikelets and replacing the ovaries, spherical to broadly oblong, flattened slightly in plane of the glumes, shape and size vary with host species, up to 6 x 3 mm on cereal hosts and 1-3 x 0.5–1.8 mm on other grass hosts, buff-vinaceous buff, contains mummified anthers within the sclerotia with remnants of ovary and enclosed ovule at base.

Conidia sparse in nature, formed from hyphae on truncated apices of sclerotia, of two types

  • (i) primary conidia formed on narrow, flask-shaped terminal or lateral conidiogenous cells 10–18 x 2 µm, oval-cylindrical-narrowly obclavate 4–14 x 1–3 µm, hyaline, unicellular, very rarely with central septum, holoblastic.
  • (ii) secondary conidia formed initially by germination of primary conidia or ascospores, narrowly cylindrical, tapering to apex which bears 1–3 single or dichotomously branched, thin, straight or slightly curved cellular appendages, 18–40 x 1–2 µm, with 1 or rarely 2 septa, hyaline, holoblastic.

Ascostromata 2–4 per sclerotium, occasionally to 6, each consisting of a globose-subglobose, and slightly dorsi-ventrally flattened capitulum 0.7–1.5 mm in diameter, dark violet, surface papillate, borne on a slender stipe 0.5-7 mm long x 0.25 mm wide, violet.

Perithecia commonly 50–70 embedded in stroma with prominent, bluntly conical to mammiform projecting necks, pyriform, 240–320 × 70–120 µm, neck canal lined with abundant, hyaline, upwardly directed and inwardly curving periphyses 1–2 µm wide.

Asci cylindrical, 130–270 x 4–6 µm, narrowing slightly towards base, apex rounded and containing a hemispherical, slightly refringent cap, pierced centrally by a fine pore channel.

Ascospores filiform 170–240 x 1 µm, rarely with lower length as short as 140 µm, hyaline, with 7 indistinct transverse septa 20–30 µm apart, not separating at septa, each cell germinating by one (rarely two) short, lateral projections 1.5 x 1.5 µm bearing either hyaline, unicellular, narrowly obclavate cells 5–8 x 1–2 µm similar to conidia produced on sclerotium apex, or apically appendaged conidia. Ascospores occasionally germinate in ascus.

Hosts
   
Host family: Poaceae
   
Host species: Austrodanthonia eriantha
Austrostipa variabilis
Avena sativa
Avena strigosa
Bromus diandrus
Dactylis glomerata
Elymus scaber
Holcus lanatus
Hordeum leporinum
Hordeum vulgare
Lolium perenne
Lolium rigidum
Lolium temulentum
Microlaena stipoides
Phalaris aquatica
Phalaris tuberosa
Vulpia bromoides
Vulpia myuros

Distribution

ACT, NSW, SA, TAS, VIC

Comments

Cepsiclava (an anagram of Claviceps) is montoypic and known only on temperate grasses in south-eastern Australia. It is unique amongst clavicipitaceous grass endophytes in producing discrete, deciduous sclerotia, two conidial anamorphs neither of which can be accommodated in Sphacelia (which is the anamorph of Claviceps), preferential invasion of the stamens by systemic hyphae from which hyphae grow out and invade other floral organs, and sclerotia which incorporate mummified floral organs and occasionally sterile floral elements.

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Cepsiclava phalaridis on Phalaris aquatica - DAR 72254.
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Cepsiclava phalaridis on Vulpia sp. - DAR 62080.
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Cepsiclava phalaridis on Phalaris aquatica - DAR 65398.
Highslide JS
Cepsiclava phalaridis on Phalaris aquatica - DAR 65398.
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Cepsiclava phalaridis on Phalaris aquatica - DAR 65398.
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Cepsiclava phalaridis ascrostromata on Phalaris aquatica - DAR 65398.
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Cepsiclava phalaridis on Dactylis glomerata - DAR 15498.
Scale bar = 500 µm.
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Cepsiclava phalaridis on Hordeum vulgare - DAR 55617.
Scale bar = 1 mm.
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Cepsiclava phalaridis on Phalaris aquatica - DAR 72254. Scale bar = 1 mm.