Q. 53 Explain with the help of one example how genetically modified plants can
(a) Reduce usage of chemical pesticides.
(b) Enhance nutritional value of food crops.

(a) Genetically modified plants can reduce the usage of chemical pesticides by introducing pest resistant plants.

e.g., There are several nematodes that parasitie, a wide variety of plants and animals including human beings. A nematode Meloidogyne incognita infects the roots of tobacco plants and causes a great reduction in yield. A novel strategy was adopted to prevent this infestation which was based on the process of RNA interference (RNAi)

Using Agrobacterium vectors, nematode-specific genes were introduced into the host plant. The introduction of DNA was such that it produced both sense and antisense RNA in the host cells.

These two RNA's being complementary to each other formed a double stranded RNA that initiated RNAi and thus, silenced the specific mRNA of the nematode. The consequence was that the parasite could not survive in a transgenic host expressing
specific interfering RNA.

(b) Genetically modified plants can enhance nutritional value of food crops. e.g., ‘Golden rice’ developed at Swiss Federal institute of technology is an example of nutritionally modified crop. It is rich in vitamin-A ($\beta$-carotene), The rice grains are golden-yellow in colour. It contains ‘beta-carotene’ gene from daffodil plant and also from
some bacteria. Golden rice can prevent child blindness which is caused due to the deficiency of vitamin-A.