Sporisorium reilianum (J.G. Kühn) Langdon & Full.

Synonyms

Cintractia reiliana (J.G. Kühn) G.P. Clinton
Sorosporium holci-sorghi (Rivolta) Moesz
Sorosporium holci-sorghi f. sorghi (Geschele) Savul.
Sorosporium reilianum (J.G. Kühn) McAlpine
Sphacelotheca holci-sorghi (Rivolta) Cif.
Sphacelotheca reiliana (J.G. Kühn) G.P. Clinton
Sporisorium holci-sorghi (Rivolta) Vánky
Ustilago holci-sorghi Rivolta
Ustilago reiliana J.G. Kühn
Ustilago reiliana f. sp. sorghi Geschele
Ustilago reiliana f. zeae Pass.

Description

Sori in inflorescences that are usually ±completely destroyed and transformed into blackish brown granular-powdery spore masses; sometimes only single flowers are attacked and, rarely, the panicle rachis and leaves are infected. Sori initially covered by a white to light brown peridium of fungal origin which ruptures irregularly and flakes away to expose the mass of spore balls mixed with groups of sterile cells and numerous columellae (remnants of vascular bundles and fungal elements). Columellae long, sinuous or stout, thread-like.

Spore balls 60–100 µm long, composed of numerous loosely connected spores.

Spores globose, subglobose to ovoid or slightly irregular, 10.5–14.5 × 10–13 µm, light olivaceous brown, densely and minutely echinulate.

Sterile cells in irregular persistent groups, rounded on the free surface, flattened on the contact surfaces, 8–16 µm long, hyaline to yellow-tinted, smooth, with a few oil droplets in each cell.

Spore germination resulting in 4-celled basidia on which lateral and terminal basidiospores are produced.

Hosts
   
Host family: Poaceae
   
Host species: Chionachne hubbardiana Henrard
Sorghum x almum Parodi
Sorghum bicolor (L.) Moench
Sorghum halepense (L.) Pers.
Zea mays L.

Distribution

States & Territories: NSW, QLD, SA, VIC

Comments

Sporisorium reilianum causes head smut of cultivated sorghum and maize. Infection is initiated by soil-borne spores that germinate and directly penetrate emerging seedlings and young plants. Infection is systemic, and the mycelium of the fungus occupies areas near the apical meristem of its host. In Australia, head smut of sorghum and maize is readily controlled by planting resistant hybrids.

A smut fungus on the native grass Chionachne hubbardiana from Queensland has spore morphology very similar to Sporisorium reilianum. The specimen is fragmentary and over seventy years old, which makes it unsuitable for further study using molecular methods. The three host genera in Australia, Chionachne, Sorghum and Zea, are classified in three different subtribes in the Tribe Andropogoneae.