T.O.Diener discovered a new infectious agent called viroids :

Options

A. that are larger than viruses
B. that causes potato spindle tuber disease
C. that lack RNA
D. that have high molecular weight RNA

Answer

**Step-by-Step Solution:**

1. **Identify the Discoverer**: The question states that T.O. Diener discovered a new infectious agent called viroids. This is the starting point of our answer.

2. **Define Viroids**: Viroids are known to be infectious agents that are smaller than viruses. They are unique because they consist solely of a short strand of circular RNA without any protein coat.

3. **Characteristics of Viroids**: Viroids are characterized by their low molecular weight RNA. Unlike viruses, they do not have a protective protein shell, which makes them distinct.

4. **Associated Diseases**: One of the most notable diseases caused by viroids is the potato spindle tuber disease. This disease affects potato plants and leads to significant agricultural losses.

5. **Conclusion**: Based on the information provided, the correct answer to the question is that viroids cause potato spindle tuber disease.

**Final Answer**: Viroids cause potato spindle tuber disease.

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