Question

Given below are two statements:
Statement I: Most economically important plant viruses have only ssRNA as their genetic material.
Statement II: Viruses with ssDNA as their genetic material cause plant disease epidemics.

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:

Remember the general genomic distribution of plant viruses:
- +ssRNA is the most common genome type in plant viruses.
- Geminiviruses (ssDNA) are the most economically significant DNA viruses, causing major crop losses.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Plant viruses can possess genomes composed of double-stranded DNA (dsDNA), single-stranded DNA (ssDNA), double-stranded RNA (dsRNA), or single-stranded RNA (ssRNA).
The distribution and impact of these genomic groups differ across crops and geographical regions.
Detailed Explanation:
Let us evaluate both statements:
Statement I:
Approximately 75% to 80% of all recognized plant viruses belong to the single-stranded RNA (ssRNA) group, most of which are positive-sense (+ssRNA).
This group includes many of the most economically devastating plant pathogens, such as members of the families Potyviridae (e.g., Potato virus Y), Secoviridae, and Virgaviridae (e.g., Tobacco mosaic virus).
Thus, Statement I is correct.
Statement II:
Single-stranded DNA (ssDNA) plant viruses, primarily belonging to the family Geminiviridae (e.g., Tomato yellow leaf curl virus, Cotton leaf curl virus) and Nanoviridae (e.g., Banana bunchy top virus), are major pathogens.
They are transmitted by insect vectors like whiteflies and aphids and cause widespread, catastrophic epidemics in tropical and subtropical regions.
Thus, Statement II is correct.

Step 2: Final Answer:
Both Statement I and Statement II are correct.
Therefore, the correct option is (A).