Tilletia nigrifaciens Langdon & Boughton

Description

Sorion the adaxial surface of distal leaves, forming a dark brown powdery covering of spores and sterile cells.

Spores globose or subglobose, rarely ovoid or broadly ellipsoidal, 16.0–22.5 (–24.0) × 16.0–21.0 (–22.5) µm, yellowish to olivaceous brown; wall reticulate, with (5–) 6–7 (–8) polygonal meshes per spore diameter; muri 0.5–1.5 µm high, blunt in optical median view.

Sterile cells globose, ellipsoidal to slightly irregular, 13.5–32.0 × 12–27 µm, subhyaline to pale yellow; wall c. 1 µm thick, smooth.

Spore germination unknown.

Hosts
   
Host family: Poaceae
   
Host species: Phragmites australis (Cav.) Trin. ex Steudel

Distribution

States & Territories: NSW, QLD

Comments

Usually the entire leaf surface is covered by spores but, on rare occasions, the sori extend to the distal part of the leaf sheaths and to parts of the abaxial surface of the leaf blades. Infection is systemic, appearing year after year on the same plant at the end of summer. Infected plants can remain sterile or they can produce normal or greatly reduced and distorted inflorescences.

Tilletia nigrifaciens and T. tumefaciens Syd. & P.Syd. (on Panicum antidotale Retz., in South Asia) are the only species that produce external sori on the leaves of the host. Molecular studies (Cunnington & Shivas, 2004) have confirmed the generic placement of
T. nigrifaciens.