Foolish seeding disease is caused by a fungus. This study helped in discovery of

Options

A. Gibberellin
B. Cytokinin
C. ABA
D. Auxin

Answer

### Step-by-Step Solution:

1. **Understanding the Disease**: Foolish seedling disease, also known as bakanae disease, is a condition that affects rice plants. It is caused by a fungus called Gibberella fujikuroi.

2. **Symptoms of the Disease**: The primary symptom of this disease is the abnormal elongation of the rice seedlings. This elongation can be so severe that it may lead to the death of the seedlings.

3. **Discovery Related to the Disease**: The study of foolish seedling disease led to the discovery of a plant hormone known as gibberellin. Gibberellins are responsible for promoting growth and elongation in plants.

4. **Identifying the Correct Answer**: Among the options provided (gibberellin, cytokinin, ABA, auxin), gibberellin is the correct answer as it was discovered through the study of the effects of the fungus on rice plants.

5. **Conclusion**: Therefore, the answer to the question is that the study of foolish seedling disease helped in the discovery of gibberellin.

### Final Answer:
The study of foolish seedling disease helped in the discovery of **gibberellin**.

---