Question

Biological control agent is obtained from

• A. $Agrobacteriumtumefaciens$
• B. $E.coli$
• C. $Meloidogyneincognita$
• D. $Bacillusthuringiensis$

Answer 1

The correct option is D $Bacillusthuringiensis$

Definition of biocontrol agents
Biocontrol agents or biopesticides are biological agents like microbes that are used for the control of pests and pathogens.

Significance of Bacillus thuringiensis
$Bacillusthuringiensis$ produces a toxin which is lethal to certain insects, such as caterpillars of butterflies and moths.

The endotoxin, when consumed by the caterpillar, gets activated at an alkaline pH in the gut of the insects due to solubilisation of the crystal. The active Bt toxin then causes the perforation in the midgut epithelium of the insects. This results in cell swelling followed by lysis eventually leading to the death of the insect.

Hence, the gene encoding the toxin, called cry gene, is introduced to the plants to make them resistant against the pests.

Significance of $E.coli$
$E.coli$ is a bacterium that is found in the intestine of humans and has an important use in biotechnology.

Significance of $Agrobacteriumtumefaciens$
$Agrobacteriumtumefaciens$ causes crown gall disease. It has the ability to transfer a piece of DNA from Ti plasmid to the host genome. Hence, it is modified and used as a vector for introducing foreign DNA into the plants.

Significance of $Meloidogyneincognita$
$Meloidogyneincognita$ is a parasitic roundworm that causes the formation of galls on the roots of its host. Tobacco plants are one of the hosts of this roundworm.
Final answer
(A) $Bacillusthuringiensis$