Phenomenon of heterothallism was first observed in Mucorales by

Options

A. K.C. Mehta
B. Alexopoulos
C. Blakeslee
D. de Bary

Answer

### Step-by-Step Solution:

1. **Understanding Heterothallism**:
- Heterothallism is a phenomenon in fungi where two or more genetically different mating types are required for sexual reproduction. This means that for successful reproduction, individuals of different mating types must come together.

2. **Historical Context**:
- The phenomenon of heterothallism was first observed in the group of fungi known as Mucorales. This group includes several genera, one of which is Rhizopus.

3. **Key Scientist**:
- The scientist who first described heterothallism was a geneticist named Blackslee. He made this observation in the year 1903.

4. **Example of Heterothallism**:
- In his studies, Blackslee specifically noted the different mating types in the species of Rhizopus. He identified two mating types, commonly referred to as the plus strain and the minus strain.

5. **Formation of Zygospore**:
- When the mycelium of these two mating types interacts, they can form a zygospore, which is a thick-walled resting spore that can develop into a new organism.

6. **Conclusion**:
- Therefore, the correct answer to the question "Phenomenon of heterothallism was first observed in Mucorales by" is **Blackslee**.

### Final Answer:
Blackslee

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