RAS question
Bt cotton, India's only approved GM crop, incorporates genes from which bacterium to confer insect resistance?
Correct answer: (B) Bacillus thuringiensis.
Bt cotton gets its insect resistance from Cry genes taken from the soil bacterium Bacillus thuringiensis.
Explanation
Bt cotton is named after Bacillus thuringiensis, a naturally occurring soil bacterium. It contains Cry genes such as Cry1Ac and Cry2Ab from this bacterium. These genes encode Cry, or crystal, proteins that are toxic to bollworm larvae such as Helicoverpa armigera and thereby make the plant insect-resistant. Bacillus thuringiensis is therefore the source of the insecticidal genes; a gene-transfer vector, a nitrogen-fixing bacterium or a biological-control bacterium plays a different role. An article in Agricultural Economics Research Review, the journal of the Indian Council of Agricultural Research (ICAR), also links Bt cotton with bollworm resistance and identifies it as the only genetically modified crop approved for commercial cultivation in India. Bt cotton was approved in India in 2002.
Why the other options are wrong
- (A) Agrobacterium tumefaciens can be used as a vector to introduce genes into plants, but it is not the source of the insecticidal Cry genes in Bt cotton.
- (C) Rhizobium leguminosarum fixes nitrogen in the root nodules of legumes, so it is not responsible for Bt cotton's bollworm resistance.
- (D) Pseudomonas fluorescens is known as a biological-control agent against fungal pathogens, whereas the insecticidal Cry genes used in Bt cotton come from Bacillus thuringiensis.
Concept
This tests applied biotechnology: how an inserted gene gives a transgenic crop a specific trait. It is relevant to RAS because GM crops, biosafety, agricultural science and India's regulatory position are standard Science and Technology themes.