The nematode that infects the root of tobacco plants and causes a great reduction in its yield is:

Options

A. Ancylostoma duodenale
B. Meloidegyne incognita
C. Wuchereria bancrofri
D. Ascaris lumbricoides

Answer

To solve the question about the nematode that infects the roots of tobacco plants and causes a significant reduction in yield, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for a specific nematode that affects tobacco plants. We need to identify which of the given options is known to infect the roots of tobacco.

2. **Analyzing the Options**: The options provided are:
- A) Cyclostoma duodenale
- B) Malathiogaine incognita
- C) Victoria Bancroftii
- D) Ascaris lumbricoides

3. **Identifying the Correct Nematode**:
- **Cyclostoma duodenale**: This is not known to infect tobacco plants; it is a type of hookworm that affects humans.
- **Malathiogaine incognita**: This nematode is known to infect the roots of various plants, including tobacco, leading to reduced yield.
- **Victoria Bancroftii**: This nematode is associated with other diseases and not specifically with tobacco plants.
- **Ascaris lumbricoides**: This is a human intestinal parasite and does not infect plants.

4. **Conclusion**: Based on the analysis, the nematode that infects the roots of tobacco plants and causes a significant reduction in yield is **Malathiogaine incognita**.

5. **Final Answer**: The correct answer is **B) Malathiogaine incognita**.