A tumour inducing autonomously replicating circular extra - chromosomal DNA widely used in development of transgenic plant is that of

Options

A. Escherichia coli
B. Bacillus thuringiensis
C. Staphylococcus aureus
D. Agrobacterium tumefaciens

Answer

To solve the question regarding the tumor-inducing, autonomously replicating circular extra-chromosomal DNA used in the development of transgenic plants, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for a specific type of DNA that is circular, extra-chromosomal, and capable of autonomous replication, which is associated with tumor induction in plants.

2. **Identifying the Characteristics**:
- The DNA must be circular and extra-chromosomal, meaning it exists outside the main chromosomal DNA of the organism.
- It should replicate independently of the host's chromosomal DNA.
- It should induce tumors in plants.

3. **Reviewing Possible Options**:
- **Escherichia coli**: Known for causing infections but does not induce tumors in plants.
- **Bacillus thuringiensis**: Produces toxins to kill insects but is not related to tumor formation.
- **Staphylococcus aureus**: Affects humans and causes pneumonia, not related to plants or tumor induction.
- **Agrobacterium tumefaciens**: This bacterium is known for inducing tumor formation (galls) in plants through the transfer of its DNA.

4. **Conclusion**: The correct answer is **Agrobacterium tumefaciens**, as it is the only option that fits all the criteria of being a tumor-inducing, autonomously replicating circular extra-chromosomal DNA used in the development of transgenic plants.

### Final Answer:
**Agrobacterium tumefaciens**

---