Covered smut of Barley

Ustilago hordei is a fungal pathogen that causes covered smut or loose smut in barley (Hordeum vulgare). Covered smut is a significant disease that can lead to yield losses and reduce the quality of barley grains. Here is an overview of Ustilago hordei, including its appearance, symptoms, identification, and management:

1. Symptoms:

• Smutted Heads: The primary symptom of covered smut is the replacement of barley grains with masses of dark teliospores, forming smutted heads. The teliospores are covered by a thin membrane that ruptures, releasing the spores during harvest.

• Powdery Mass: As the teliospores are released, they form a powdery, dark mass on the surface of the barley heads, giving them a distinctive appearance.

2. Disease Cycle:

• Infection: The fungus infects barley plants during the flowering stage. The pathogen can enter the plant through the floral organs, and the infection becomes systemic, affecting the developing grains.

• Teliospore Formation: Inside the infected grains, the fungus forms teliospores, replacing the normal endosperm.

• Spore Dispersal: At maturity, the teliospores are released when the barley heads break open during harvesting, threshing, or other handling processes.

3. Identification:

• Visual Inspection: Identification is typically based on visual inspection of barley heads. Smutted heads will have a powdery mass of dark teliospores.

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

4. Management:

• Resistant Varieties: Planting barley varieties that are resistant to covered smut is an effective strategy for disease management.

• Seed Treatment: Treating barley seeds with fungicides before planting can help protect against covered smut. Seed treatments are commonly employed to reduce the risk of introducing the pathogen into new fields.

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

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

• Early Planting: Early planting can help avoid the period when the pathogen is most active, reducing the risk of infection.

5. Importance:

• Covered smut can lead to significant economic losses by reducing the yield and quality of barley grains. The presence of teliospores in harvested barley can also affect the marketability of the crop.