Read the passage and answer the following questions:
Genetic modification (GM) has been utilised to create custom-designed plants that serve as alternative resources for industries, producing starches, fuels, and pharmaceuticals. Biotechnology in agriculture has numerous applications, one of which involves developing pest-resistant plants to reduce the reliance on chemical pesticides. This is achieved by introducing the Bt toxin gene from the bacterium Bacillus thuringiensis (Bt) into plants, creating what is known as a bio-pesticide. Notable examples include Bt cotton, Bt corn, rice, tomato, potato, and soybean. Bt toxin is a naturally occurring insecticidal protein produced by certain strains of Bacillus thuringiensis. During a specific phase of their growth, these bacteria form protein crystals containing toxic substances. These crystals harbour inactive protoxins, which, when activated, become lethal to targeted insects. Different Bt toxin genes, such as cryIAc and cryIIAb, have been isolated and introduced into various crop plants, depending on the crop and the specific pests targeted, as Bt toxins are often insect-group specific. By incorporating these genes, plants gain inherent resistance to insects without the need for synthetic insecticides. This advancement in biotechnology has significant implications for sustainable and eco-friendly agricultural practices.
Genetic modification has also increased the efficiency of mineral usage by plants. This helps to prevent:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Early exhaustion of fertility of soil
Plants take up minerals from the soil. If a crop uses the minerals it absorbs more efficiently, it needs to draw less from the soil for the same growth. The soil then keeps its fertility for a longer time. NCERT lists this as one of the gains of genetic modification.
Option (1) Early exhaustion of fertility of soil — Correct. Increased efficiency of mineral usage by plants prevents early exhaustion of fertility of soil. This is the effect given in the book for this use of GM.
Option (2) Infection of the crop by viruses — Incorrect. Freedom from viruses is obtained by a different method: the meristem of an infected plant is free of virus and is grown in vitro. It has nothing to do with mineral usage.
Option (3) Infestation of the roots by nematodes — Incorrect. Protection against the nematode Meloidegyne incognitia in tobacco roots was obtained by RNA interference, not by better use of minerals.
Option (4) Attack of the crop by insect pests — Incorrect. Protection against insect pests comes from Bt toxin genes placed in the crop (pest-resistant crops). Efficient mineral usage does not keep insects away.
NCERT Extract:
Biotechnological Applications in Agriculture – “… Plants, bacteria, fungi and animals whose genes have been altered by manipulation are called Genetically Modified Organisms (GMO). GM plants have been useful in many ways. Genetic modification has:
(i) made crops more tolerant to abiotic stresses (cold, drought, salt, heat).
(ii) reduced reliance on chemical pesticides (pest-resistant crops).
(iii) helped to reduce post harvest losses.
(iv) increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of soil).”