The smuts are multicellular fungi, that are characterized by their large numbers of teliospores. The smuts get their name from a Germanic word for dirt because of their dark, thick-walled and dust-like teliospores. They are mostly Ustilaginomycetes (of the class Teliomycetae, subphylum Basidiomycota) and can cause plant disease. The smuts are grouped with the other basidiomycetes because of their commonalities concerning sexual reproduction.
Smuts are cereal and crop pathogens that most notably affect members of the grass family (Graminaceae). Economically important hosts include maize, barley, wheat, oats, sugarcane, and forage grasses. They eventually hijack the plants' reproductive systems, forming galls which darken and burst, releasing fungal teliospores which infect other plants nearby. Before infection can occur, the smuts need to undergo a successful mating to form dikaryotic hyphae (two haploid cells fuse to form a dikaryon).
Sugarcane smut or Ustilago scitaminea Sydow is caused by the fungus Sporisorium scitamineum; previously known Ustilago scitaminea. The smut 'whip' is a curved black structure which emerges from the leaf whorl, that aids in the spreading of the disease. Sugarcane smut causes significant losses to the economic value of a sugarcane crop. Sugarcane smut has recently been found in the eastern seaboard areas of Australia, one of the world's highest-yielding sugar areas.
For the sugarcane crop to be infected by the disease, large spore concentrations are needed. The fungi uses its smut-whip to ensure that the disease is spread to other plants, which usually occurs over a time period of three months. As the inoculum is spread, the younger sugarcane buds just coming out of the soil will be the most susceptible of all the crops. Because water is necessary for spore germination, irrigation has shown to be a factor in spreading the disease. Therefore special precautions need to be taken when irrigated the areas of the crop to prevent spreading of the smut.
Another way to prevent the disease from occurring in the sugarcane is to use fungicide. This can be done by either pre-plant soaking or post-plant spraying with the specific fungicide. Pre-plant soaking has been proven to give the best results in preventing the disease, but post-plant spraying is a practical option for large sugarcane cultivations.
Corn smut (Ustilago maydis) infects maize and is a delicacy in Mexico, where it was historically enjoyed by the Aztecs. It grows in the ears of the corn crops and converts the kernels into black, powdery fungal tissues. The smut is sold in the markets in Mexico while other parts of the world (including the United States) continue to reject it as an ingredient for food dishes. The corn smut is currently referenced as huitlacoche to the Mexicans, and the Aztecs formerly called it cuitlacoche. Investigators have recently found that the amount of protein in the corn smuts is said to be greater than the corn, oats and clover hay.
Huitlacoche is used for some of the several recipes including soups, stews, steak sauces and crepes.
- Covered smut Tilletia tritici (syn. T. caries) and T. laevis (syn. T. foetida)
- Ergot, which includes the species Claviceps purpurea
- Loose smut, Ustilago nuda
- TCK smut Tilletia controversa
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