Macalpinomyces brachiariae Vánky, C. Vánky & R.G. Shivas

Description

Sori in some ovaries of an inflorescence, ovoid, c. 1.0 mm long and 0.7 mm wide, hidden by the floral envelopes, covered by a dark brown peridium that ruptures irregularly exposing the blackish brown agglutinated to granular mass of irregular groups of spores mixed with sterile cells.

Spores subglobose, broadly ellipsoidal or slightly irregular, rounded-subpolyhedral,
7–11 × 7.0–9.5 µm, reddish brown; wall uniformly 0.5–1.0 µm thick, densely low verruculose-echinulate; spore profile ±smooth to finely wavy.

Sterile cells single or in small loose groups; individual cells subglobose, ovoid or slightly irregular, larger than the spores, 13–22 × 11–20 µm, yellowish to light reddish brown; wall 1.0–1.5 µm thick, smooth.

Hosts
   
Host family: Poaceae
   
Host species: Brachiaria holosericea (R.Br.) Hughes subsp. holosericea

Distribution

States & Territories: NT

Comments

Macalpinomyces brachiariae is one of the most cryptic species of smut fungi. Most sori are only visible after dissection of symptomless spikelets under a stereo microscope. The sori are restricted to some ovaries in an inflorescence and, in one case, only one of two seeds in a spikelet was infected.