What part of the insect pest does the Bt toxin target?

The correct answer is Option (2) → Midgut

Bt toxin comes from the bacterium Bacillus thuringiensis. The toxin is harmless until an insect eats it; inside the insect’s gut it becomes active and attacks the midgut.

Option (1) Hindgut — Incorrect. The toxin is activated and acts in the midgut, the part of the gut where food is digested and absorbed. The hindgut is not its target.

Option (2) Midgut — Correct. The activated toxin binds to the surface of the midgut epithelial cells and makes pores, which kill the insect.

Option (3) Reproductive system — Incorrect. Bt toxin is taken in with food and acts in the gut. It does not attack the reproductive system.

NCERT Extract:
Biotechnological Applications in Agriculture – “… B. thuringiensis forms protein crystals during a particular phase of their growth. These crystals contain a toxic insecticidal protein. … Actually, the Bt toxin protein exist as inactive protoxins but once an insect ingest the inactive toxin, it is converted into an active form of toxin due to the alkaline pH of the gut which solubilise the crystals. The activated toxin binds to the surface of midgut epithelial cells and create pores that cause cell swelling and lysis and eventually cause death of the insect.”