Silencing of mRNA has been used in producing transgenic plants which…

The correct answer is Option (2) → Nematodes

RNA interference (RNAi) silences a specific mRNA with a complementary double-stranded RNA. Genes of the nematode Meloidegyne incognitia were put into tobacco plants so that they made dsRNA against the nematode’s own mRNA. The parasite could not survive in such a transgenic host, and the plant was protected.

Option (1) Boll worms — Incorrect. Bollworms are controlled with Bt toxin genes (cryIAc, cryIIAb) in Bt cotton, not with RNAi.

Option (2) Nematodes — Correct. Using RNA interference, a transgenic tobacco plant was made resistant to the nematode Meloidogyne incognita, which infects its roots. The parasite’s own mRNA is silenced, so it cannot survive in the plant.

Option (3) White rusts — Incorrect. White rust is a fungal disease of plants; NCERT does not link RNAi with it.

Option (4) Bacterial blights — Incorrect. Bacterial blight is a bacterial disease, not the case NCERT uses for RNAi.

NCERT Extract:
Biotechnological Applications in Agriculture – “… Pest Resistant Plants: Several nematodes parasitise a wide variety of plants and animals including human beings. A nematode Meloidegyne incognitia infects the roots of tobacco plants and causes a great reduction in yield. A novel strategy was adopted to prevent this infestation which was based on the process of RNA interference (RNAi). RNAi takes place in all eukaryotic organisms as a method of cellular defense. This method involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA (silencing).”