Ustilago bromivora (Tul. & C. Tul.) A.A. Fisch. Waldh.

Synonyms

Cintractia patagonica Cooke & Massee
Sorosporium lavrovianum Smarods
Sorosporium maroccanum Unamuno
Ustilago brachypodii-distachyi Maire
Ustilago bromi-arvensis Liro
Ustilago bromi-mollis Liro
Ustilago carbo (DC) Tul. & C. Tul. α vulgaris Tul. & C. Tul. d bromivora Tul. & C. Tul.
Ustilago compacta G.W. Fisch.
Ustilago grossheimii Uljanishchev
Ustilago holwayi Dietel
Ustilago hordeicola Speg.
Ustilago jamalainenii Liro
Ustilago lorentziana Thüm.
Ustilago patagonica (Cooke & Massee) Cif.
Ustilago patagonica (Cooke & Massee) Lavrov
Ustilago pospelovii Uljanishchev
Ustilago zernae Uljanishchev
Yenia bromivora (Tul. & C. Tul.) Liou

Description

Sori in the spikelets, usually destroying the basal parts of the glumes and even the ovaries, bullate, at first agglutinated and covered by the epidermis but becoming dusty, black or blackish brown. Infection systemic; seedlings and older shoots infected.

Spores globose to subglobose, occasionally ovoid or irregularly polyhedral, 8–11 × 6.5–9.5 µm, olivaceous to reddish brown, often with a darker equatorial band; wall uniformly thick to slightly uneven, 1.0–1.5 µm, in LM finely to rather coarsely verrucose, more pronounced on the polar regions, in SEM coarsely verrucose.

Spore germination: spore usually forming a pair of 2-celled basidia (occasionally one 3-celled and one 1-celled) on which terminal and lateral ovoid basidiospores are borne. Sometimes only one 2-celled basidium is produced, the 2 cells conjugating and giving rise to a dikaryotic mycelium or, rarely, to 2 basidiospores.

Hosts
   
Host family: Poaceae
   
Host species: Austrofestuca littoralis (Labill.) E.B.Alexeev
Brachypodium distachyon (L.) P.Beauv.
Bromus arenarius Labill.
Bromus catharticus Vahl
Bromus cebadilla Steud.
Bromus diandrus Roth
Bromus hordeaceus L. subsp. hordeaceus
Bromus hordeaceus subsp. molliformis (Lloyd) Maire & Weiller
Bromus sterilis L.
Festuca arundinacea Schreb.
Lolium rigidum Gaudin

Distribution

States & Territories: ACT, NSW, QLD, SA, TAS, VIC, WA

Comments

The bullate floral smut on Bromus (and some other host genera) has often been treated under Ustilago bullata Berk. s. lat. (Lindeberg, 1959; Vánky, 1985, 1994a; Zogg, 1986). Vánky (2001c) considered U. bullata and U. bromivora to be distinct species that could be separated on sorus and spore morphology. In U. bullata s. str., the sori usually comprise the whole spikelet, often also the whole spike, leaving intact only the tip of some floral envelopes and their awns, and sometimes extending to the distal leaves as striae. However, in U. bromivora the sori are restricted to the basal part of the floral envelopes and to the ovaries. In U. bullata, the spores are uniformly pigmented and are verrucose-echinulate in SEM. By contrast, the spores of U. bromivora often have a dark equatorial band and are verrucose in SEM.

Ustilago bromivora is widespread in Australia with more than 250 collections, mostly on Bromus spp., made since 1910. It is the only smut known to occur on that host in Australia. There is some variation in spore size on different hosts; for example, spores from
B. arenarius are up to 16 µm long with walls to 2.0 µm thick.