Common bunt of wheat

Systematic position and pathogen type. The causal agent of common bunt of wheat is the fungus Tilletia caries (syn. Tilletia tritici). It belongs to the kingdom Fungi, phylum Basidiomycota, class Ustilaginomycetes, and order Ustilaginales. As an obligate parasite, it is a specialized pathogen that infects cereal crops, causing a systemic disease that leads to significant agricultural losses.

Diseases and host crops. The fungus causes common bunt (also known as stinking smut) primarily in wheat. The pathogen infects the developing grain within the ear. Instead of normal kernels, the plant produces bunt balls or sori filled with a dark, powdery mass of teliospores. These spores release a pungent, fishy odor due to the presence of trimethylamine, which taints the entire harvest.

Biology and lifecycle. The infection cycle begins with teliospores surviving on seed surfaces or in the soil. Infection occurs at the seedling stage when the germinating grain is attacked by the fungus. The mycelium grows systemically within the plant, eventually reaching the head. During grain development, the fungus colonizes the ovary and replaces the internal tissues with a mass of dark, dormant spores.

Conditions for development and spread. The fungus thrives in cool, moist soil conditions, with an optimal temperature range of +5°C to +15°C. These conditions perfectly align with the autumn planting of winter wheat. During harvest, the mechanical rupture of bunt balls releases spores into the air and onto the threshing equipment, ensuring contamination of healthy seeds for the following season.

Damage and control measures. Common bunt causes severe economic loss by reducing yields and rendering grain unusable for milling due to its foul smell and spore contamination.

• Seed treatment with systemic fungicides is the most critical management practice.
• Planting certified, disease-free seed is essential.
• Selection of resistant wheat cultivars.
• Adjusting sowing dates to avoid soil temperatures that favor pathogen germination.
• Practicing good crop rotation to minimize spore accumulation in the soil.