Question

Given below are two statements :
Statement (I) : RNA is the only genetic element in plant viruses.
Statement (II) : RNA viruses are known to cause crop losses.
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both Statement (I) and Statement (II) are correct.
• B. Both Statement (I) and Statement (II) are incorrect.
• C. Statement (I) is correct but Statement (II) is incorrect.
• D. Statement (I) is incorrect but Statement (II) is correct.

Hint:

To classify plant viruses by their genome types:
- Most plant viruses ($75\%$) are ssRNA (+) genomes (e.g., TMV, Potyviruses).
- DNA plant viruses are less common but highly destructive (e.g., Geminiviruses causing cotton leaf curl and mungbean yellow mosaic diseases).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Plant viruses are sub-microscopic infectious entities composed of genetic material enclosed in a protective protein coat (capsid).
Unlike cellular organisms, viruses can utilize different types of nucleic acids as their genetic material, which varies among different viral families.

Step 2: Detailed Explanation:
Let us analyze both statements individually:
Statement (I): "RNA is the only genetic element in plant viruses."
This statement is incorrect.
While the majority of plant viruses (about $75\%$) are RNA viruses, carrying either single-stranded RNA (e.g., Tobacco Mosaic Virus, TMV) or double-stranded RNA, they are not the only type.
Several major plant virus families contain DNA as their genetic material.
These include:
- Geminiviruses (single-stranded DNA, e.g., Tomato Yellow Leaf Curl Virus).
- Caulimoviruses (double-stranded DNA, e.g., Cauliflower Mosaic Virus).
The word "only" makes the statement false.
Statement (II): "RNA viruses are known to cause crop losses."
This statement is correct.
RNA viruses are highly destructive agricultural pathogens.
Examples such as Potato Virus Y (PVY), Barley Yellow Dwarf Virus (BYDV), and Cucumber Mosaic Virus (CMV) infect major food crops worldwide, causing symptoms like leaf mosaic, stunting, and malformation, which leads to massive economic losses.

Step 3: Final Answer:
Statement (I) is incorrect, but Statement (II) is correct.
This corresponds to Option (D).