Hairy root disease of dicot plants is caused by-

Options

A. Agrobacterium tumefacians
B. Agrobacterium rhizogene
C. Bacillum thuriengiensis
D. Melodogyne incognita

Answer

To solve the question regarding the cause of hairy root disease in dicot plants, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the causative agent of hairy root disease specifically in dicot plants.

2. **Identifying the Options**: The options provided are:
- A) Agrobacterium tumefaciens
- B) Agrobacterium rhizogenes
- C) Bacillus thuringiensis
- D) Meloidogyne incognita

3. **Analyzing Each Option**:
- **A) Agrobacterium tumefaciens**: This bacterium is known to cause crown gall disease in dicot plants, not hairy root disease.
- **B) Agrobacterium rhizogenes**: This bacterium is specifically known to cause hairy root disease in dicot plants. It induces the formation of hairy roots by transferring a part of its DNA into the plant cells.
- **C) Bacillus thuringiensis**: This bacterium is used as a biological pesticide and does not cause hairy root disease.
- **D) Meloidogyne incognita**: This is a nematode that causes root knot disease, not hairy root disease.

4. **Conclusion**: Based on the analysis, the correct answer is **B) Agrobacterium rhizogenes**, as it is the causative agent of hairy root disease in dicot plants.

### Final Answer:
The hairy root disease of dicot plants is caused by **Agrobacterium rhizogenes**.

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