Macalpinomyces sharmae Vánky

Description

Sori in some ovaries of an inflorescence, inconspicuous, hidden by the floral envelopes, ovoid, c. 2 mm long, 0.8–1.0 mm wide, covered by a relatively thick pale to dark brown peridium that ruptures irregularly to expose the blackish brown granular mass of spores mixed with sterile cells. Peridium composed of an external layer of host origin (pericarp) and a thick internal layer of fungal tissue in which the spores differentiate; fungal cells between the spores transformed into sterile cells.

Spores agglutinated in irregular groups, subglobose, ovoid, usually subpolyhedrally irregular, 7.0–10.5 (–11) × 6.5–9.0 µm, yellowish brown; wall thin, c. 0.5 µm, finely and densely punctate-verruculose.

Sterile cells subglobose, ovoid to slightly irregular, larger than the spores, 9–12 × 11–17 µm, solitary or in loose groups, subhyaline to pale yellowish brown; wall c. 1 µm thick, smooth.

Spore germination resulting in 1 or 2 septate basidia 17–35 × 2.0–3.5 µm on which basidiospores are produced laterally and terminally. Basidiospores ovoid to long-ellipsoidal, 3–8 × 1.5–2.5 µm, hyaline, yeast-like.

Hosts
   
Host family: Poaceae
   
Host species: Setaria surgens Stapf

Distribution

States & Territories: NT, QLD

Comments

Macalpinomyces sharmae is one of three species of smut fungus that infect the ovaries of Setaria in Australia. The others, M. neglectus and Sporisorium setariae, can be differentiated in that the former has larger echinulate spores [9–13 (–14) µm], and S. setariae has spore balls.