Question

Genetically modified tobacco plants were produced using Agrobacterium vectors. Which property of Agrobacterium helps in carrying nematode specific genes into the host plant ?

• A. Infectious for monocot plant ; has Ti plasmid
• B. Infectious for dicot plant ; has Ti plasmid
• C. Infectious for plants and animals ; has Ti plasmids
• D. Infectious for monocot and dicot plants ; has cry gene

Hint:

Agrobacterium naturally infects dicots like tobacco and moves T-DNA from its Ti plasmid into the plant genome.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Tobacco plants resistant to the root-knot nematode Meloidogyne incognita were made by RNA interference.
Nematode-specific genes were put into the tobacco genome so that the plant made sense and antisense RNA. The vector was Agrobacterium tumefaciens.

Step 2: What makes Agrobacterium a good vector:
Agrobacterium is a soil bacterium that naturally infects dicot plants such as tobacco and causes crown gall.
It carries a Ti (tumour inducing) plasmid. A piece of this plasmid, the T-DNA, moves into the plant cell and joins the plant chromosome.
Scientists remove the tumour genes and put the useful gene in the T-DNA. So the key properties are: infects dicots, and has the Ti plasmid.

Step 3: Check the options:
(A) is wrong because Agrobacterium does not naturally infect monocots well.
(B) is correct. It says dicot plants and Ti plasmid.
(C) is wrong because it does not infect animals.
(D) is wrong because the cry gene belongs to Bacillus thuringiensis (Bt), not to Agrobacterium, and it is not the property used to carry genes.

Final Answer:
Agrobacterium infects dicot plants and has the Ti plasmid. This is option (B).