The smut of maize is caused by

Options

A. Claviceps
B. Alternaria
C. Phytophthora
D. Ustilago

Answer

### Step-by-Step Solution:

1. **Understanding the Disease**: The question asks about the cause of smut in maize. Smut is a type of fungal disease that affects various plants, including maize.

2. **Identifying the Options**: The options provided in the question include different organisms:
- Claviceps
- Alternaria
- Phytophthora
- Eustelago

3. **Analyzing Each Option**:
- **Claviceps**: This is an ascomycete fungus known for causing powdery mildew, particularly in peas. It does not cause smut in maize.
- **Alternaria**: This is a deuteromycete fungus that causes leaf blight disease, primarily in sunflowers. It is not related to smut in maize.
- **Phytophthora**: Although often confused with fungi, Phytophthora is classified as an algae. It does not cause smut diseases.
- **Eustelago**: This is a basidiomycete fungus specifically known for causing smut diseases, including the smut of maize.

4. **Conclusion**: After analyzing all the options, the correct answer to the question "The smut of maize is caused by" is **Eustelago**.

### Final Answer:
The smut of maize is caused by **Eustelago**.

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