Search on : Taxa descriptions

 


   
Literature:
 
Remarks (public):For a complete description including images see www.cababstractsplus.org/dfb 
Remarks (internal):The sheathless spores are small compared with the sheathed spores of Tilletia controversa Kuhn and reticulate, not smooth, as in T. foetida (CMI Descriptions 720) or coarsely verrucose as in T. indica Mitral. Tilletia caries can be grown in culture in the dikaryotic state where it produces mycelium and secondary sporidia (48, 2894), and can be isolated from infected plant parts (52, 1500). A wheat based medium is best for teliospore production from cultures (54, 1227). Germination of teliospores is enhanced by light plus Ca(NO3) or presence of NO3 ion, (52, 2238); blue light was also effective (47, 1838), and by substances (e.g. enzymes) which increase the permeability of the spore wall (53, 904). Various biochemical studies have been made (48, 2869; 49, 1601) and pyrolysis gas liquid chromatography has been used to distinguish this species from T. foetida. Hybrids with T. controversa occur (44, 669) and dual infection and hybridization also occur with T. foetida (54, 798). The infection process has been studied (42, 539); the mycelium of the pathogen must reach the growing point of the young plant before elongation of the internodes occurs. Environmental factors can influence the disease until that stage, those factors which are unfavourable to rapid growth of the plant predispose to infection. Temperature, light and soil moisture are known to influence disease incidence (42, 673; 46, 1966) and planting winter wheat earlier when soil temperatures are higher leads to less infection (48, 424). Control measures are based on seed applied chemicals and resistant varieties. Organo-mercurials were largely replaced by chlorinated hydrocarbons (44, 1509) and more recently by systemic compounds such as carboxin (48, 1140), benomyl (51, 2371), thiabendazole (51, 1351) and triadimenol (59, 3576). There is an extensive literature on fungicide screening for bunt control. Biological control has been achieved by dusting with Trichoderma viride (58, 2706), Penicillium spp. (49, 3107), Bacillus spp. (56, 3988) and Actinomyces umbicatus (56, 5559). There is also much literature on varietal screening for resistance (59, 1206; 56, 4458; 54, 5384). Pathogenicity in T. caries is thought to be controlled by multiple factors (48, 423), but various genes for resistance in wheat have been indentified (51, 2370; 52, 4015; 57, 1682).
 
Description type:Non-original description 
Description:Tilletia caries (DC.) Tul., Annales des Sciences naturelles Bot., Ser. 3 7: 113, 1847.
Uredo caries DC., Flore francaise 6: 78, 1815.
Tilletia tritici (Berk.) Wolf, 1874.
Sori in the ovaries filling the grain with spores, partly concealed by the glumes, 4-8 mm long, of similar diameter to uninfected grain. Spore mass powdery, reddish-brown to blackish, foetid, composed of spores and sterile cells. Sterile cells (intermixed with spores) globose, hyaline, thin-walled, smooth 10-20 µm (mostly about 13 µm) diam.; few present in some collections. Spores without sheath, globose or subglobose to ovoid, light brown to reddish-brown, 14-23 (mean 18,0) µm diam., walls reticulate; reticulations polygonal (occasionally cerebriform), 0,5-1,5 µm deep and mostly less than 3 µm wide.
Hosts: On Aegilops, Agropyron, Bromus, Elymus, Hordeum, Poa, Secale, Sitanion, Triticum, Triticale.
Disease: Causes common bunt (stinking or covered smut) of wheat. Tilletia foetida (CMI Descriptions 720) causes a virtually identical disease known by the same name. The grain tissues inside the pericarp are converted to a mass of black teliospores producing a 'bunt ball' as the head matures. Diseased plants may be slightly stunted, infected ears ripen slower and the glumes project more than in healthy ears. Losses are caused both by direct loss of grain and by spoilage of grain and flour by contamination with the bunt spores which are released when the crop is harvested. Bunt spores release trimethylamine which has an odour of decaying fish.
Geographical distribution: Widespread, occurs in most countries where wheat is arown (CMI Map 294, ed. 3, 1978).
Physiologic specialization: Exists in a number of physiologic races. Seventeen races based on reaction to 7 differential wheat varieties arranged in 6 groups according to their reaction to 6 accepted resistance types were proposed in the USA (41, 142). Tilletia caries f.sp. monoccoci was proposed for a form that infected Triticum monoccocum (48, 1619). The spectrum of races has also been investigated in Germany (46, 97), Turkey (52, 3636), USSR (54, 408). The occurrence of new pathogenic races has been noticed (43, 1612; 46, 2215; 57, 4890) and 39 pathogenic races of the bunt fungi (which include T. foetida and T. controversa as well) based on combinations of 8 virulence genes are now recognised in the USA. There is a differential infection response among races at different temperatures.
Transmission: Spores are released when the grain is harvested and are dispersed by air to contaminate healthy grain and soil. Spores germinate in moist soil to produce a basidium and acicular basidiospores (primary sporidia). These fuse to produce a dikaryotic mycelium which may directly infect host seedling coleoptiles or produce further secondary sporidia.
Literature: Duran & Fischer, The Genus Tilletia, Washington State University, 1961; Holton & Heald, Bunt or Stinking Smut of Wheat, Burgess, Minneapolis, 1941 (review of earlier literature); Fischer & Holton, Biology and Control of the Smut Fungi, Ronald Press, New York, 1957; Moore & Kuiper, Agricultural Gazette of New South Wales 85: 16-17, 1974 (recent control methods).

 
Taxon name: