Question

Given below are two statements
Statement I: Plant viruses are transmitted by insects.
Statement II: Only sucking insects are capable of transmitting plant viruses.
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:

In biology, absolute words like "only," "always," or "never" are often indicators of an incorrect statement.
Sucking insects (Aphids) are the main vectors, but not the only ones.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question explores the vectors of plant virus transmission, specifically focusing on the role of insects and their feeding mechanisms.

Step 2: Detailed Explanation:

• Analysis of Statement I: A large majority (over 70%) of known plant viruses rely on biological vectors for transmission between hosts because they cannot penetrate the plant cell wall independently.
Insects are the most significant group of vectors. Common examples include aphids, whiteflies, leafhoppers, and beetles.
Therefore, Statement I is Correct.

• Analysis of Statement II: While sucking insects (Order Hemiptera) like aphids are indeed the most prolific vectors due to their stylet-based feeding which allows for precise inoculation into vascular tissues, they are not the only capable insects.
Chewing insects such as beetles (Order Coleoptera) and grasshoppers are also well-documented vectors.
For example, the Bean Leaf Beetle transmits Cowpea Mosaic Virus. They carry the virus in their saliva/regurgitant, which enters the plant through the wounds created while chewing.
The word "Only" in the statement makes it factually incorrect.
Final Answer:
Statement I is a general truth of virology, but Statement II is an overgeneralization that ignores chewing insect vectors.
The correct option is (C).