Crown gall disease in plants is caused by :

Options

A. Ti plasmid
B. Pi plasmid
C. Bacteria
D. Virus

Answer

**Step-by-Step Solution:**

1. **Understanding Crown Gall Disease**: Crown gall disease is a plant disease characterized by abnormal growth and cell division, leading to the formation of galls. These galls can appear on various parts of the plant, including roots, twigs, and leaves.

2. **Identifying the Cause**: The disease is caused by a specific type of bacteria. To understand the nature of this bacteria, we need to consider its classification and characteristics.

3. **Bacterial Classification**: The bacteria responsible for crown gall disease is classified as a gram-negative bacterium. This means it does not retain the crystal violet stain used in the Gram staining procedure.

4. **Specific Bacteria**: The specific bacterium that causes crown gall disease is known as *Agrobacterium tumefaciens*. This bacterium is known for its ability to induce tumor formation in plants.

5. **Conclusion**: Therefore, crown gall disease in plants is caused by the bacterium *Agrobacterium tumefaciens*.

**Final Answer**: Crown gall disease in plants is caused by the bacterium *Agrobacterium tumefaciens*.

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