A toxic chemical against nematode is secreted by

Options

A. Tagetes
B. Black walnut
C. Penicillum
D. Gravillea robusta

Answer

To solve the question "A toxic chemical against nematode is secreted by," we will analyze the options provided and identify which plant or organism is known for producing such chemicals.

### Step 1: Understand the question
The question asks for the source of a toxic chemical that is effective against nematodes. Nematodes are a type of roundworm, and controlling their population is important in agriculture.

### Step 2: Analyze the options
The options given are:
- a. Tagetes
- b. Black Walnut
- c. Penicillium
- d. Gravelia Robusta

### Step 3: Research each option
1. **Tagetes**: This is a genus that includes marigold plants. Marigolds are known to secrete bioactive chemicals that can effectively control root-knot nematodes.

2. **Black Walnut**: This tree produces a chemical called juglone, which can be toxic to some plants, but it is not specifically known for targeting nematodes.

3. **Penicillium**: This is a genus of fungi known for producing antibiotics, but it is not specifically associated with nematode control.

4. **Gravelia Robusta**: This is a plant species, but there is limited information regarding its effectiveness against nematodes.

### Step 4: Identify the correct answer
Based on the information gathered, **Tagetes (marigold)** is known for secreting bioactive chemicals that effectively control nematode populations, particularly root-knot nematodes. Therefore, the correct answer is:

**Option A: Tagetes**

### Conclusion
A toxic chemical against nematodes is secreted by Tagetes.

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