Question

Choose the correct answer from the options given below:
(A) Certain plant viruses are vectored by insect
(B) Certain plant viruses are transmitted by mechanical means
(C) No plant viruses are vectored by fungi
(D) No plant viruses are vectored by nematodes

• A. (A), (B), (C), (D)
• B. (A), (B), (C) only
• C. (A) and (B) only
• D. (B), (D), (A) only

Hint:

To remember non-insect vectors of plant viruses:
- Nematode vectors: *Xiphinema*, *Longidorus*, and *Trichodorus* (transmit Nepoviruses and Tobraviruses).
- Fungal/Oomycete vectors: *Olpidium*, *Polymyxa* (transmit soil-borne mosaic viruses).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Plant viruses are obligate intracellular parasites that lack the molecular machinery to actively penetrate host plant cell walls on their own.
They rely on vectors (such as insects, nematodes, or fungi) or mechanical contact (wounding) to enter and infect host plant cells.

Step 2: Detailed Explanation:
Let us analyze each of the statements regarding virus transmission:
Statement (A): "Certain plant viruses are vectored by insect"
This statement is correct.
Insects are the most common vectors of plant viruses.
Sap-sucking insects like aphids, whiteflies, leafhoppers, and thrips transmit a wide range of plant viruses (such as Potato Virus Y, Tomato Yellow Leaf Curl Virus) during feeding.
Statement (B): "Certain plant viruses are transmitted by mechanical means"
This statement is correct.
Many highly stable viruses (such as Tobacco Mosaic Virus, TMV) can be transmitted mechanically through direct contact.
The virus is transferred when infected leaves rub against healthy leaves, or via contaminated agricultural tools and hands during farm operations.
Statement (C): "No plant viruses are vectored by fungi"
This statement is incorrect.
Some plant viruses are indeed vectored by soil-borne zoosporic fungi or fungi-like protists.
For example, the Tobacco Necrosis Virus is transmitted by the zoosporic chytrid fungus Olpidium brassicae.
Statement (D): "No plant viruses are vectored by nematodes"
This statement is incorrect.
Certain ectoparasitic nematodes are well-known vectors of plant viruses.
Species of *Xiphinema* (dagger nematodes) and *Longidorus* transmit Nepoviruses (such as Grapevine Fanleaf Virus), while *Trichodorus* species transmit Tobraviruses.
Therefore, only Statements (A) and (B) are correct.

Step 3: Final Answer:
Only Statements (A) and (B) are correct.
This corresponds to Option (C).