Which one of the following is not a biofertlizer

Options

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

Answer

To determine which of the following options is not a biofertilizer, we need to first understand what biofertilizers are and then analyze each option provided.

### Step-by-Step Solution:

1. **Definition of Biofertilizers**:
- Biofertilizers are substances that contain living microorganisms which promote plant growth by increasing the availability of nutrients to the plants. They can help in nitrogen fixation, phosphate solubilization, and enhancing soil fertility.

2. **Review the Options**:
- **Option A: Agrobacterium**
- **Option B: Rhizobium**
- **Option C: Nostoc**
- **Option D: Mycorrhizae**

3. **Analyze Each Option**:
- **Agrobacterium**:
- This is a genus of bacteria known for causing crown gall disease in plants. It is primarily used in genetic engineering for gene transfer and expression. Therefore, it does not function as a biofertilizer.
- **Rhizobium**:
- This is a type of bacteria that forms symbiotic relationships with legumes, fixing atmospheric nitrogen into a form that plants can use. It is a well-known biofertilizer.
- **Nostoc**:
- Nostoc is a type of blue-green algae (cyanobacteria) that can fix nitrogen and is used as a biofertilizer.
- **Mycorrhizae**:
- These are fungi that form symbiotic relationships with plant roots, enhancing nutrient uptake, particularly phosphorus. They are also classified as biofertilizers.

4. **Conclusion**:
- Based on the analysis, **Agrobacterium** is the only option that is not a biofertilizer because it is associated with disease rather than promoting plant growth.

### Final Answer:
**Agrobacterium (Option A) is not a biofertilizer.**

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