Name the fungus that causes foolish seedling disease.

Answer

**Step-by-Step Solution:**

1. **Identify the Disease**: The question asks for the fungus that causes "foolish seedling disease." This disease primarily affects rice plants.

2. **Identify the Fungus**: The fungus responsible for causing foolish seedling disease is known as **Gibberella fujikuroi**.

3. **Understand the Role of the Fungus**: This fungus produces a hormone called **gibberellin**. Gibberellin is responsible for the symptoms associated with foolish seedling disease, which include excessive elongation of the seedlings.

4. **Effects of Gibberellin**: Gibberellin plays a significant role in plant growth by promoting cell elongation and breaking dormancy in seeds. It counteracts the effects of another hormone, abscisic acid, which is responsible for maintaining dormancy.

5. **Historical Context**: Gibberellin was first isolated from this fungus in the 1930s in Japan, highlighting its historical significance in plant physiology.

**Final Answer**: The fungus that causes foolish seedling disease is **Gibberella fujikuroi**.

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