Fusion between two morphologically similar but physiologically and genetically different thali of opposite strains in fungus is known as

Options

A. homothallism
B. anisogamous
C. heterothallism
D. isogamous

Answer

To answer the question regarding the fusion between two morphologically similar but physiologically and genetically different thalli of opposite strains in fungi, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Terminology**:
- The term "thallus" refers to the non-differentiated plant body of fungi. It is important to differentiate between thalli and gametes.

2. **Analyze the Options**:
- **Homothalism**: This refers to a condition where both male and female reproductive structures are present on the same thallus.
- **Anisogamous**: This describes a type of sexual reproduction involving the fusion of two gametes that are of different sizes and forms.
- **Heterothalism**: This involves the requirement of two compatible partners for mating, where the sexes are present in different individuals.
- **Isogamous**: This refers to a type of reproduction where the male and female gametes are morphologically similar.

3. **Identify the Key Characteristics**:
- The question specifies that the fusion occurs between two thalli that are morphologically similar but physiologically and genetically different, and they are of opposite strains.

4. **Eliminate Incorrect Options**:
- Homothalism can be eliminated because it involves a single thallus.
- Anisogamous is not applicable here as it refers to gametes, not thalli.
- Isogamous can also be ruled out since it involves gametes that are similar, not different thalli.

5. **Select the Correct Answer**:
- The correct answer is **Heterothalism**, as it involves the fusion of two different thalli of opposite strains, which aligns with the description provided in the question.

### Final Answer:
The fusion between two morphologically similar but physiologically and genetically different thalli of opposite strains in fungi is known as **heterothalism**.