Symptom not seen in plants due to viruses is

Options

A. Mosaic formation
B. Leaf rolling and curling
C. Yellowing, vein clearing
D. Root knot

Answer

To determine the symptom not seen in plants due to viruses, we need to analyze the symptoms associated with viral infections in plants and identify one that is not caused by a virus.

### Step-by-Step Solution:

1. **Identify Common Viral Symptoms**:
- Viral infections in plants often lead to symptoms such as mosaic formation, leaf rolling, curling, yellowing, and vein clearing.

2. **Examine Each Symptom**:
- **Mosaic Formation**: This is caused by the Tobacco Mosaic Virus (TMV), which affects tobacco plants and leads to a characteristic mottled appearance on the leaves.
- **Leaf Rolling and Curling**: This symptom is commonly seen in tomato plants due to viral infections. Viruses can cause leaves to curl and roll.
- **Yellowing and Vein Clearing**: This symptom is also associated with viral infections, where leaves turn yellow and veins become more prominent.

3. **Identify the Outlier**:
- **Root Knot**: This symptom is not caused by a virus. Instead, root knot disease is caused by nematodes, which are parasitic worms that infect the roots of plants, leading to the formation of galls or knots.

4. **Conclusion**:
- The symptom not seen in plants due to viruses is **root knot**.

### Final Answer:
The symptom not seen in plants due to viruses is **root knot**.

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