Question

The choice of the Bt-toxin genes depends upon the

• A. Type of the crop
• B. Type of targeted pest
• C. The type of vector
• D. Both A and B

Answer 1

The correct option is D Both A and B

The cry protein (delta endotoxin) obtained from the cry gene of Bacillus thuringiensis is a protoxin and has insecticidal properties. It gets activated in the alkaline environment of the insect gut and causes perforations in the epithelial lining of the stomach.

Bt toxin is toxic only to the biting and chewing insects. Hence, the larvae of Lepidoptera, Diptera and Coleoptera are affected by it. Thus, tobacco budworm, armyworm (Lepidoptera), flies, mosquitoes (Diptera) and beetles (Coleoptera) are killed by Bt toxin.

Since the pests are usually host-specific, hence, the type of crop also decides the choice of toxin genes.

For example, introduction of cryIAc and cryIIAb genes provides resistance to the cotton plant against cotton bollworms.

Introduction of cryIAb gene provides resistance to the corn plant against corn borers.

Hence the correct option is
d. Both A and B