Potato leaf-roll disease is caused by

Options

A. Mycoplasma
B. Virus
C. Microspores
D. Bacterium

Answer

**Step-by-Step Solution:**

1. **Understanding the Disease**: Potato leaf-roll disease is a condition that affects potato plants, characterized by specific symptoms in the leaves. The leaves may appear chlorotic (yellowing) and can sometimes exhibit a purple discoloration.

2. **Identifying the Causative Agent**: To determine what causes potato leaf-roll disease, we need to analyze the options provided:
- Option 1: Microplasma
- Option 2: Virus
- Option 3: Microspore
- Option 4: Bacterium

3. **Analyzing the Symptoms**: The symptoms of potato leaf-roll disease include upward rolling of leaves, stunted growth of the plant, and stiff upright growth. These symptoms suggest a viral infection, as viruses are known to cause such changes in plant morphology.

4. **Confirming the Causative Agent**: The specific virus responsible for potato leaf-roll disease is known as the Potato Leaf Roll Virus (PLRV). It belongs to the genus Polerovirus and is classified as a positive-sense RNA virus.

5. **Selecting the Correct Option**: Based on the information gathered:
- Microplasma is not the causative agent.
- Virus (specifically PLRV) is the correct answer.
- Microspore is unrelated to the disease.
- Bacterium is also not responsible for this disease.

Thus, the correct answer is **Option 2: Virus**.

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