Which of the following is commonly present in root ecosystems and control various types of plant pathogens?

Options

A. Rhizobium
B. Bacillus thuringiensis
C. Trichoderma
D. Dragonflies

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which organism is commonly found in root ecosystems and helps control various types of plant pathogens.

2. **Analyzing the Options**:
- **Option 1: Rhizobium** - This is a type of bacteria that forms symbiotic relationships with legumes, primarily aiding in nitrogen fixation, but it is not primarily known for controlling plant pathogens.
- **Option 2: Bacillus thuringiensis** - This bacterium is known for its insecticidal properties and is used in pest control, but it does not specifically target plant pathogens in root ecosystems.
- **Option 3: Trichoderma** - This is a genus of fungi that is commonly found in soil and is known for its ability to suppress various plant pathogens, making it beneficial for plants.
- **Option 4: Dragonflies** - These are insects and not directly involved in controlling plant pathogens in the soil.

3. **Identifying the Correct Answer**: Based on the analysis, Trichoderma is the organism that fits the criteria of being present in root ecosystems and controlling plant pathogens.

4. **Conclusion**: The correct answer to the question is **C, Trichoderma**.

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