Which one of the following is not a biofertiliser?

Options

A. Agrobacterium
B. Rhizobium
C. Nostoc
D. Mycorrhiza

Answer

To determine which of the following options is not a biofertilizer, we can analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understand Biofertilizers**: Biofertilizers are substances that contain living microorganisms, which help in enhancing the availability of nutrients to plants. They can fix atmospheric nitrogen, solubilize phosphorus, and promote plant growth.

2. **Identify the Options**: The question mentions four options, but we will focus on the key ones mentioned in the transcript: Agrobacterium, Rhizobium, and Mycorrhiza.

3. **Analyze Agrobacterium**:
- Agrobacterium is a genus of bacteria that is primarily known for causing crown gall disease in plants.
- It is widely used in genetic engineering for transferring genes into plants but does not function as a biofertilizer.

4. **Analyze Rhizobium**:
- Rhizobium is a genus of bacteria that forms symbiotic relationships with legumes.
- It fixes atmospheric nitrogen into a form that plants can use, making it a classic example of a biofertilizer.

5. **Analyze Mycorrhiza**:
- Mycorrhiza refers to a symbiotic association between fungi and plant roots.
- This relationship enhances nutrient uptake, particularly phosphorus, and is also considered a biofertilizer.

6. **Conclusion**: Since Agrobacterium is responsible for causing disease and does not provide benefits as a biofertilizer, it is the correct answer to the question.

### Final Answer:
**Agrobacterium is not a biofertilizer.**

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