Question

Bt-toxin genes have been expressed in plants in order to provide resistance against:
• [(i)] lepidopterans and fungi
• [(ii)] animals and bacteria
• [(iii)] coleopterans and dipterans
• [(iv)] lepidopterans

• A. (ii) and (iii)
• B. (i), (ii) and (iv)
• C. (iii) and (iv)
• D. (ii) and (iv)

Hint:

Bt targets LCD: - Lepidopterans (moths/budworms) - Coleopterans (beetles) - Dipterans (flies/mosquitoes) It is an insect-specific toxin!

Answer 1

The Correct Option is C

Concept: The bacterium Bacillus thuringiensis produces specific insecticidal crystalline proteins (Cry proteins) during its sporulation phase. These Bt-toxins are highly specific and target particular insect orders upon ingestion, while remaining completely harmless to humans, birds, and other animals. The main target insect groups include:
• Lepidopterans: Tobacco budworm, armyworm, butterflies, and moths.
• Coleopterans: Beetles.
• Dipterans: Flies and mosquitoes.

Step 1: Review statements for target scope.
Bt-toxins do not target fungi, bacteria, or higher animals. This immediately rules out options containing statements (i) and (ii).

Step 2: Evaluate valid target insect orders.
Statement (iii) names coleopterans and dipterans, which are classic target groups for specific Bt crystal proteins. Statement (iv) mentions lepidopterans, which represents the primary group targeted by genes like cryIAc and cryIIAb (used in Bt cotton).

Step 3: Select matching option combinations.
Since statements (iii) and (iv) describe target insects, they form the correct pair. This corresponds to Option (C).