Read the given statements that describe certain infectious particle.
(i) It was discovered T.O. Diener and was found to be smaller than viruses.
(ii) It causes potato spindle tuber disease.
(iii) It is a free RNA particle which lacks the protein coat.
(iv) It has low molecular weight RNA as genetic material.
Which of the following is referred to here?

Options

A. Virus
B. Viroid
C. Virion
D. Bacteriophage

Explanation

To solve the question regarding the infectious particle described in the statements, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Discoverer**: The first statement mentions that the particle was discovered by T.O. Diener and is smaller than viruses. This indicates that we are looking for a particle that is not a typical virus.

**Hint**: Consider the significance of the discoverer's name and the size comparison to viruses.

2. **Disease Association**: The second statement states that this particle causes potato spindle tuber disease. This is a specific disease associated with certain pathogens.

**Hint**: Think about plant diseases and which pathogens are known to cause them.

3. **Characteristics of the Particle**: The third statement indicates that it is a free RNA particle that lacks a protein coat. This is a crucial characteristic that differentiates it from viruses, which typically have a protein coat.

**Hint**: Reflect on what types of infectious agents can exist without a protein coat.

4. **Genetic Material**: The fourth statement specifies that it has low molecular weight RNA as genetic material. This reinforces the idea that we are dealing with a simple RNA-based infectious agent.

**Hint**: Consider the types of RNA that are known to exist in infectious agents and their characteristics.

5. **Conclusion**: Based on the information from the statements, we conclude that the infectious particle being referred to is a "Viroid." Viroids are indeed smaller than viruses, consist of free RNA without a protein coat, and are known to cause diseases such as potato spindle tuber disease.

**Final Answer**: The infectious particle referred to in the statements is a **Viroid**.