Which of the following statement is not correct for Viroids?

Options

A. Causes potato spindle tuber disease and tobacco mosaic disease
B. In 1971, TO. Diener discovered these agents
C. Viroid was found to be a free RNA, it lacked the protein coat
D. RNA of viroid was of low molecular weight

Answer

To determine which statement is not correct for viroids, we need to analyze the statements provided regarding viroids and their characteristics. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand what viroids are
Viroids are infectious agents that are smaller than viruses and consist solely of a short strand of circular RNA. They lack a protein coat, which is a characteristic feature of viruses.

### Step 2: Review the discovery of viroids
Viroids were discovered in 1971 by T.O. Diener, who identified them as the causative agents of certain plant diseases, notably potato spindle tuber disease.

### Step 3: Analyze the statements
1. **Statement 1**: "Viroids cause potato spindle tuber disease and tobacco mosaic disease."
- This statement is incorrect because while viroids do cause potato spindle tuber disease, tobacco mosaic disease is caused by the tobacco mosaic virus, which is a virus and not a viroid.

2. **Statement 2**: "In 1971, T.O. Diener discovered these agents."
- This statement is correct as it accurately reflects the historical discovery of viroids.

3. **Statement 3**: "Viroids were found to be free RNA."
- This statement is also correct since viroids consist solely of RNA without any protein coat.

4. **Statement 4**: "RNA of viroids is of low molecular weight."
- This statement is true as viroids are characterized by their low molecular weight RNA.

### Step 4: Identify the incorrect statement
From the analysis, the first statement is the only one that is not correct. Therefore, the answer to the question is that the first statement is incorrect.

### Final Answer
The statement that is not correct for viroids is: "Viroids cause potato spindle tuber disease and tobacco mosaic disease."

---