Common wheat bunt

Tilletia caries

Tilletia caries is a fungus that causes common bunt or stinking smut of wheat (Triticum aestivum) and other cereal crops. Common bunt is a seed-borne disease that can lead to significant economic losses by reducing grain quality and overall crop yield. Here's an overview of Tilletia caries, its appearance, symptoms, identification, and management:

1. Appearance and Symptoms:

  • Smell: The characteristic feature of common bunt is the foul or fishy odor emitted by infected heads of wheat, especially during the harvesting and threshing processes. This smell is one of the reasons the disease is also called "stinking smut."

  • Black Spore Mass: Infected wheat heads contain a mass of dark brown to black teliospores. These teliospores replace the normal seeds and are surrounded by a thin membrane.

  • External Symptoms: Externally, infected plants may not show clear symptoms until the plants head out and produce spikes with smutted kernels.

2. Disease Cycle:

  • Infection: The fungus infects the developing wheat seedlings at the time of germination. The spores enter the plant through the soil and colonize the developing seed.

  • Teliospore Formation: Inside the infected seed, the fungus forms teliospores, which replace the normal endosperm.

  • Spore Dispersal: Infected seeds release spores when they come into contact with healthy seeds, spreading the disease during planting.

3. Identification:

  • Odor: The foul odor emitted by infected wheat heads during threshing is a distinctive characteristic.

  • Internal Examination: Opening individual kernels and examining them for the characteristic dark spore mass is a diagnostic feature.

  • Laboratory Analysis: For definitive identification, laboratory analysis may involve extracting and examining teliospores under a microscope.

4. Management:

  • Seed Treatment: Treating seeds with systemic fungicides is a common practice to control common bunt. Seed treatments are typically applied before planting to protect emerging seedlings.

  • Hot Water Treatment: Hot water treatment of seeds is another method used to kill the teliospores on the seed surface. This can be effective in reducing the incidence of common bunt.

  • Crop Rotation: Implementing a crop rotation strategy can help reduce the inoculum in the soil.

  • Resistant Varieties: Planting wheat varieties that are less susceptible to common bunt is an effective strategy for disease management.

  • Sanitation: Removing and destroying infected crop residues can help minimize the source of inoculum.

5. Importance:

  • Common bunt can lead to significant economic losses by reducing grain quality and affecting marketability. The presence of the foul odor in harvested wheat can also affect the milling and baking quality of the flour.