The microbe associated with root nodule formation is

Options

A. Trichoderma
B. Rhizobium
C. Azotobacter
D. Monascus

Answer

**Step-by-Step Solution:**

1. **Identify the Context of the Question**: The question asks about the microbe associated with root nodule formation. This indicates that we are looking for a specific type of microbe that plays a role in this biological process.

2. **Understand Root Nodules**: Root nodules are specialized structures that form on the roots of certain plants, particularly leguminous plants (such as peas, beans, and lentils). These nodules are important for nitrogen fixation, a process that converts atmospheric nitrogen into a form that plants can use.

3. **Identify the Types of Microbes**: The question mentions several microbes:
- **Trichoderma**: A fungus that does not form root nodules.
- **Rhizobium**: A type of bacteria known for forming root nodules in leguminous plants.
- **Azotobacter**: A free-living nitrogen-fixing bacteria that does not form root nodules.
- **Monascus**: A fungus used in food fermentation, not related to root nodules.

4. **Determine the Correct Microbe**: Among the listed options, **Rhizobium** is the only microbe that specifically forms root nodules in leguminous plants and is involved in nitrogen fixation.

5. **Conclusion**: The correct answer to the question is **Rhizobium**, as it is the microbe associated with root nodule formation in leguminous plants.

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