Heterothallism in fungi was first discovered by :

Options

A. A. F. Blakeslee
B. C. B. Huggins
C. Alexander Fleming
D. Robert Whittaker

Explanation

To solve the question regarding who first discovered heterothallism in fungi, follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Heterothallism**:
- Heterothallism refers to a condition in fungi where two genetically different mating types are required for sexual reproduction. This is important for genetic diversity.

2. **Identify the Options**:
- The options provided are:
1. A.F. Blackesley
2. C.B. Huggins
3. Alexander Fleming
4. Robert Whittaker

3. **Recall Historical Discoveries in Mycology**:
- Review the contributions of each individual listed in the options to determine who made significant discoveries related to fungi.

4. **Focus on A.F. Blackesley**:
- A.F. Blackesley is known for his work in the field of mycology, specifically related to the study of heterothallism in fungi.

5. **Confirm the Year of Discovery**:
- It is noted that A.F. Blackesley discovered heterothallism in fungi in the year 1904.

6. **Select the Correct Option**:
- Based on the information gathered, the correct answer to the question is Option 1: A.F. Blackesley.

### Final Answer:
The correct answer is **Option 1: A.F. Blackesley**.

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