Sporisorium porosum (Langdon) McTaggart & R.G. Shivas


Ustilago porosa Langdon


Sori destroying the entire inflorescence, leaving the axis and primary branches of the inflorescence intact, transforming partial inflorescences into irregular cylindrical acuminate rarely branching dark brown porous bodies 10–20 mm long and 1–2 mm wide, filled with a dusty mass of spores. Following spore dispersal a grey porous structure remains composed of remnants of host tissues and the apex of the spikelets as a long central irregular flagelliform often branched columella.

Spores globose, subglobose, ellipsoidal, elongate, rarely acuminate, tear-shaped or irregular, 5.5–9.0 (–10) × 5–7 µm, olivaceous brown, much darker on one side, pale yellowish brown on the other; wall uneven; in LM smooth, 0.7–1.0 µm thick on the dark side, c. 0.2 µm on the paler side; in SEM surface rough.

Sterile cells absent.

Host family: Poaceae
Host species: Sarga intrans (F.Muell.) Spangler
Sarga plumosum (R.Br.) Spangler
Sarga timorense (Kunth) Spangler


States & Territories: NT, QLD, WA


Sporisorium porosum occurs on native species of Sarga across northern Australia. It appears to be most common on annual sorghum (S. timorense), although the accurate identification of host species is difficult as the smut destroys the entire inflorescence. The essential difference between S. plumosa and S. timorense is that the former is a perennial and the latter is an annual. Spangler (2003) suggested that these two taxa may represent a polyploidy complex of a single highly variable species.