Which of the protein encoded by gene controls corn borer?

The correct answer is Option (1) → cryIAb

Option (1) cryIAb — Correct. Bt toxin genes are insect-group specific. The protein encoded by the gene cryIAb controls the corn borer, while the proteins of cryIAc and cryIIAb control cotton bollworms.

Option (2) CryIAc — Incorrect. Its protein controls the cotton bollworms.

Option (3) CryIIAb — Incorrect. Also controls cotton bollworms.

Option (4) CryIIAc — Incorrect. NCERT does not name this gene.

NCERT Extract:
Biotechnological Applications in Agriculture – “… The choice of genes depends upon the crop and the targeted pest, as most Bt toxins are insect-group specific. The toxin is coded by a gene cryIAc named cry. There are a number of them, for example, the proteins encoded by the genes cryIAc and cryIIAb control the cotton bollworms, that of cryIAb controls corn borer.”