T.O.Diener discovered a:

Options

A. Free infectious RNA
B. Free infectious DNA
C. Infectious protein
D. Bacteriophage

Answer

**Step-by-Step Solution:**

1. **Identify the Scientist and Year of Discovery**: The question asks about T.O. Diener and his discovery. T.O. Diener made his discovery in the year 1971.

2. **Nature of the Discovery**: Diener discovered an infectious agent that caused disease in plants. Specifically, he observed that this agent caused spindle tuber disease in potato plants.

3. **Characteristics of the Infectious Agent**: Upon studying this infectious agent, Diener found that it was a very short infectious entity. Its genetic material was identified as single-stranded RNA (SS-RNA).

4. **Absence of Protein Coat**: A significant characteristic of this infectious agent is that it lacked a protein coat, meaning there was no capsid surrounding its genetic material. This distinguishes it from typical viruses.

5. **Comparison with Viruses**: Diener noted that this infectious agent was smaller than viruses, which is an important aspect of his discovery.

6. **Conclusion**: Based on the information gathered, the infectious agent discovered by T.O. Diener is a type of pathogen that is characterized by its single-stranded RNA and absence of a protein coat. This agent is known as a viroid.

7. **Correct Answer**: The correct answer to the question is that T.O. Diener discovered a viroid.

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