Potato tuber spindle disease is caused by

Options

A. virus
B. viroid
C. prion
D. satellite virus

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the causative agent of potato tuber spindle disease. We need to identify whether it is caused by a virus, viroid, prion, or satellite virus.

2. **Identifying the Disease**: Potato tuber spindle disease is a specific condition that affects potato plants. It is important to know the characteristics of this disease to determine its cause.

3. **Researching Causative Agents**:
- **Virus**: A virus is a microscopic infectious agent that can replicate only inside the living cells of an organism.
- **Viroid**: A viroid is a small, circular piece of RNA that can cause disease in plants.
- **Prion**: A prion is a type of infectious agent composed of protein that can cause neurodegenerative diseases.
- **Satellite Virus**: Satellite viruses are dependent on other viruses for their replication.

4. **Linking the Disease to the Causative Agent**: Research indicates that potato tuber spindle disease is specifically caused by a viroid known as potato spindle tuber viroid (PSTVD). This viroid leads to symptoms such as stunting of the plant and malformation and cracking of tubers.

5. **Selecting the Correct Answer**: Based on the information gathered, the correct answer to the question is option B, which states that potato tuber spindle disease is caused by a viroid.

**Final Answer**: Potato tuber spindle disease is caused by **B) viroid**.

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