Tilletia chionachnes Vánky, C. Vánky & R.G. Shivas

Description

Sori in the ovaries, swollen, obovoid with a rounded tip and a narrowing basal part, 8–10 mm long, 5–6 mm wide, initially green, brown at maturity, with a rounded or irregular apical or subapical opening due to the thin covering membrane on this part of the sorus.

Spores globose, subglobose to broadly ellipsoidal, 23–36 × 22–30 µm, yellowish to dark chocolate-brown or opaque; wall 4.5–6.0 µm thick, including the 2.5–4.0 µm high and c. 1 µm wide warts with subacute rounded or flattened tips; in surface view, the darker warts and the paler spaces between them form a finely and irregularly reticulate pattern, 7–14 per spore diameter.

Sterile cells subglobose, ellipsoidal or slightly irregular, 14–28 (–35) × 14–24 (–35) µm, subhyaline; wall 1.5–4.0 (–6.0) µm thick, smooth.

Hosts
   
Host family: Poaceae
   
Host species: Chionachne cyathopoda (F.Muell.) F.Muell. ex Benth.

Distribution

States & Territories: QLD

Comments

The black, semi-agglutinated to powdery mass of spores mixed with sterile cells is successively scattered through the sorus opening. Infected spikelets are typically bent due to the swollen sori situated on one side of the floral axis. As the inflorescence matures, the ±empty sori fall entirely together with the whole spikelet and a rachis segment.

Tilletia chionachnes and T. kimberleyensis both occur on Chionachne cyathopoda in northern Australia. Although they produce similar sori and symptoms in their host, they can be separated by their spore size and spore wall thickness.