In plant biotechnology, root tumours are induced by

Options

A. Rhizobium
B. Agrobacterium tumefaciens
C. Agrobacterium rhizogenes
D. Agrobacterium basilis

Answer

To answer the question "In plant biotechnology, root tumours are induced by," we will analyze the options provided and identify the correct one step by step.

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks which organism is responsible for inducing root tumors in plants. This is a specific inquiry into plant biotechnology and the agents that cause such tumors.

2. **Evaluating the First Option - Rhizobium**:
- Rhizobium is a genus of bacteria that forms symbiotic relationships with leguminous plants, leading to the formation of root nodules.
- These root nodules are primarily involved in nitrogen fixation, not tumor formation.
- **Conclusion**: Rhizobium does not induce root tumors, making this option incorrect.

3. **Evaluating the Second Option - Agrobacterium tumefaciens**:
- Agrobacterium tumefaciens is known for causing crown gall disease, which is characterized by tumor formation in plants.
- This bacterium is a rod-shaped, gram-negative bacterium that can transfer a portion of its DNA (T-DNA) into the plant cells, leading to uncontrolled growth and tumor formation.
- **Conclusion**: Agrobacterium tumefaciens is indeed responsible for inducing root tumors, making this option correct.

4. **Final Decision**:
- Since Agrobacterium tumefaciens is the only option that correctly identifies an organism that induces root tumors in plants, we conclude that the answer to the question is **Agrobacterium tumefaciens**.

### Answer:
In plant biotechnology, root tumours are induced by **Agrobacterium tumefaciens**.