Sporisorium sorghi Ehrenb. ex Link

Synonyms

Cintractia sorghi (Ehrenb. ex Link) Hirschh.
Cintractia sorghi-vulgaris (Tul. & C. Tul.) G.P. Clinton
Sphacelotheca sorghi (Ehrenb. ex Link) G.P. Clinton
Sphacelotheca sorghicola (Speg.) Zundel
Tilletia sorghi-vulgaris Tul. & C. Tul.
Ustilago sorghicola Speg.
Ustilago tulasnei J.G. Kühn

Description

Sori in spikelets, light brown, ovoid or cylindrical, 3–10 mm long, protruding from the glumes, covered by a well-developed peridium of interwoven hyphae overlain by host tissue, which ruptures irregularly to expose the dark brown powdery spore mass and the central columella composed of host tissues permeated by hyphae; panicles congested and stunted or not.

Spores globose, subglobose, ovoid to slightly irregular, 5.5–8.0 (–8.5) × 5.5–7.0 µm, light olivaceous brown, from apparently smooth to sparsely punctate or very finely verruculose.

Sterile cells somewhat larger than the spores, in irregular groups or chains, hyaline, smooth.

Spore germination resulting in 4-celled basidia (the basal cell usually remains in the spore) producing lateral and apical basidiospores in nutrient media, or infection hyphae in water.

Hosts
   
Host family: Poaceae
   
Host species: Sorghum bicolor (L.) Moench
Sorghum bicolor subsp. drummondii (Nees ex Steud.) de Wet & Harlan
Sorghum caffrorum (Retz.) P.Beauv.

Distribution

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

Comments

Sporisorium sorghi causes covered kernel smut of cultivated sorghum, and it has been recorded in most sorghum-growing regions of Australia. Infection is initiated only by seedborne spores that germinate as soon as soil conditions become favourable to produce basidia and basidiospores. Complementary basidiospores fuse prior to invading young seedlings. Infection is systemic, but symptoms are not usually apparent until the flowering stage. In Australia, covered kernel smut has been virtually eliminated from commercial crops through the use of disease-free seed, the selection of less susceptible varieties and chemical seed treatments.

While S. sorghi occurs on introduced species of Sorghum in Australia, it has not been recorded from native species of Sorghum or the closely related Sarga. Two other important smut fungi, S. cruentum (J.G.Kühn) Vánky which causes loose kernel smut and S. ehrenbergii (J.G.Kühn) Vánky which causes long smut, are absent from Sorghum in Australia.