Ustilago (Pers.) Roussel

Type

Ustilago hordei (Pers.: Pers.) Lagerh. on Hordeum [distichon or vulgare]

Synonyms

Mycosarcoma Bref.
Uredo subgen. Ustilago Pers.

Description

Sori in various parts of the hosts in the Poaceae, at maturity bursting and exposing blackish or olivaceous brown usually powdery or agglutinated spore masses; sterile cells absent.

Spores solitary, small to medium-sized, brown (without violet tint), usually ornamented (verruculose, echinulate, irregularly verrucose-reticulate, etc.), rarely smooth.

Spore germination resulting in phragmobasidia bearing terminal and lateral basidiospores (sporidia) or infection threads (hyphae).

Host-parasite interaction by intracellular hyphae, coated by an electron-opaque matrix.

Septa poreless at maturity.

Comments

The delimitation of Ustilago from Sporisorium and some related genera is not always clear, and the morphological characters used to separate species is dependent on the anatomy and morphology of the host (Holton et al., 1968) as well as being highly variable or convergent (Vánky, 1998). Stoll et al. (2003, 2005) used DNA sequence analysis to reveal three major phylogenetic groups, viz. Sporisorium, Ustilago s. lat. and a monophyletic assemblage comprising both Sporisorium and Ustilago species. Although the monophyly of Ustilago s. lat. was ambiguous, Stoll et al. (2005) demonstrated that it could be further divided into three groups: (1) one that attacked mainly chloridoid grasses; (2) one that could not be reconciled with host preference or morphological traits; and (3) one that attacked mostly pooid grasses with a subgroup on chloridoid grasses.

Additional research is required to resolve the classification of grass-infecting smut fungi that have been assigned to Ustilago and related genera. The genus contains about 230 species of which 36 occur in Australia, including 16 endemic taxa.

Species in Australia
 
Ustilago agropyri
Ustilago avenae
Ustilago bromivora
Ustilago bullata
Ustilago chloridis
Ustilago comburens
Ustilago crameri
Ustilago curta
Ustilago cynodontis
Ustilago distichlidis
Ustilago enneapogonis
Ustilago hordei
Ustilago latzii
Ustilago lepturi-xerophili
Ustilago maydis
Ustilago neurachnis
Ustilago nuda
Ustilago radulans
Ustilago schmidtiae
Ustilago scitaminea
Ustilago serena
Ustilago sparsa
Ustilago spinificis
Ustilago striiformis
Ustilago syntherismae
Ustilago tepperi
Ustilago trichophora
Ustilago tritici
Ustilago valentula
Ustilago xerochloae

Key based on host taxonomy
 
On ArrhenatherumUstilago avenae
On Austrodanthonia1
1.  Spores less than 5.0 µm diameter, smoothUstilago comburens
Spores 9.5-13.5 µm diameter, finely echinulateUstilago agropyri
On Avena1
1.  Sori in leaves forming striate; spores 9-15(-16) µm longUstilago striiformis
Sori in all spikelets of a spike, spores ca. 5-9 µm long2
2.  Spores smoothUstilago hordei
Spores minutely echinulateUstilago avenae
On BrachypodiumUstilago bromivora
On BrizaUstilago striiformis
On BromusUstilago bromivora
On ChlorisUstilago chloridis
On CynodonUstilago cynodontis
On DactylisUstilago striiformis
On Dactyloctenium1
1.  Sori in distal part of the shoots. Spores 10-14.5(-15) µm longUstilago radulans
Sori in ovaries. Spores 7-9.5(-10.5) µm longUstilago sparsa
On DigitariaUstilago syntherismae
On DiplachneUstilago serena
On DistichlisUstilago distichlidis
On EchinochloaUstilago trichophora
On ElymusUstilago bullata
On Enneapogon1
1.  Sori in the whole inflorescenceUstilago enneapogonis
Sori in some ovaries of an inflorescenceUstilago schmidtiae
On EnteropogonUstilago valentula
On FestucaUstilago bromivora
On HolcusUstilago striiformis
On Hordeum1
1.  Spores smoothUstilago hordei
Spores minutely echinulateUstilago nuda
On LepturusUstilago lepturi-xerophili
On LoliumUstilago striiformis
On Neurachne1
1.  Spores (6.5-)7-9(-9.5) µm long, verrucoseUstilago neurachnis
Spores 13-17(-18.5) µm long, echinulateUstilago tepperi
On NotodanthoniaUstilago agropyri
On PlectrachneUstilago triodiae
On PoaUstilago striiformis
On SaccharumUstilago scitaminea
On SetariaUstilago crameri
On SpinifexUstilago spinificis
On TripogonUstilago curta
On TriraphisUstilago latzii
On TriticumUstilago tritici
On XerochloaUstilago xerochloae
On ZeaUstilago maydis
On ZygochloaUstilago spinificis