Tilletia caries (DC.) Tul. & C. Tul.

Synonyms

Caeoma sitophilum (Ditmar) Link
Lycoperdon tritici Bjerk.
Tilletia tritici (Bjerk.) R. Wolff
Tilletia tritici (Bjerk.) G. Winter
Tilletia sitophila (Ditmar) J. Schröt.
Uredo caries DC.
Uredo sitophila Ditmar

Description

Sori filling the ovaries with a reddish brown to dark brown semi-agglutinated to pulverulent foetid spore mass.

Spores globose to subglobose, (14–) 16–20 (–25) µm diam., light yellow to reddish brown; wall reticulate, 5–8 meshes per spore diameter, 2.5–6.0 µm thick; muri 0.5–1.5 µm high.

Sterile cells globose to subglobose, 10–18 µm diam., hyaline to subhyaline; wall smooth, 0.5–1.5 µm thick. Mycelium mostly intercellular.

Spore germination: aseptate basidia producing 8–16 elongate basidiospores at their apices. Basidiospores fusing to produce a dikaryotic mycelium that can directly infect host seedling coleoptiles or produce further ballistospores (secondary sporidia).

Hosts
   
Host family: Poaceae
   
Host species: Triticum aestivum L.

Distribution

States & Territories: NSW, QLD, SA, VIC

Comments

Tilletia caries and T. laevis are two closely related species that occur worldwide wherever wheat is cultivated, causing the disease ‘common bunt’ or ‘stinking smut’. Both were known to be already widespread in Australia about 100 years ago (McAlpine, 1910: 192, 194).

These smuts share similar life and disease cycles. Spores are released during harvest from ruptured sori (bunt balls) which contaminate healthy seed and the soil. The spores germinate during cool, moist conditions and penetrate the first leaf (coleoptile) of wheat seedlings. The smut fungus is systemic within the host and completely replaces the ovaries with masses of spores producing bunt balls. The bunt balls are easily crushed during harvest, releasing the spores which emit a foul fishy odour attributed to trimethylamine. Common bunt is controlled by chemical seed treatments and sowing resistant varieties.

Tilletia caries can be distinguished from T. laevis by the surface ornamentation of the spores; the spores of T. caries are reticulate and those of T. laevis are smooth. These two smut fungi can hybridise and can be found together in the same sorus.