Application of Biotechnology in Agriculture involves scientific techniques such as Genetically Modified Organisms, Bt Cotton, Pest Resistant Plants. It helps in modifying plants, animals, and microorganisms and improve their agricultural productivity. Techniques like vaccines, tissue culture, genetic engineering are also used.
Before Agricultural Biotechnology
Between the 1930s and 1960s, there was a tremendous increase in food production worldwide, due to the Green Revolution. This revolution basically involved the use of high-yielding crop varieties, increased use of fertilizers and better irrigation methods. Although the green revolution tripled the food supply worldwide, it was still not enough for the growing population.
Farmers have also used agrochemicals (pesticides and fertilizers) to increase crop yield. However, agrochemicals are too expensive for farmers in developing countries. The use of these chemicals also adds to environmental pollution. Moreover, it is difficult to further increase crop yield using existing varieties and conventional breeding.
Is there a way to use our knowledge of plant genetics to produce new varieties and increase yield? Can we minimize the use of pesticides and fertilizers and use a more environment-friendly approach? Yes, agricultural biotechnology has given rise to genetically modified crops that solve all the above problems.
Genetically Modified Organisms
You must have heard the term ‘GMO’ used by people around you or in the news every now and then. What does this mean? GMO stands for ‘Genetically Modified Organisms’. GMOs are plants, animals, bacteria or fungi whose genes have been modified by genetic manipulation. Genetically modified crops or GM crops are used in the following ways:
- They are more tolerant to stresses such as drought, cold, heat etc.
- They are pest-resistant and therefore less dependent on chemical pesticides.
- Genetically Modified crops help to reduce post-harvest losses.
- They help to increase the mineral usage by plants, thereby preventing early exhaustion of soil fertility.
- Genetically modified crops have enhanced nutritional value. Example – Vitamin A enriched rice.
Genetic modifications also help to create tailor-made plants to provide alternative resources to industries, such as fuels, starches, and pharmaceuticals. Let’s look at some examples of GM crops and how they are useful.
This is a genetically modified version of cotton. ‘Bt’ stands for the microbe Bacillus thuringiensis. This microbe produces an insecticidal protein or toxin that kills other insects such as tobacco budworm, flies, mosquitoes, beetles etc. Why is this protein not toxic to the Bacillus itself?
This is because it stays inactive (as protoxin) in the Bacillus. It gets activated only once it comes in contact with the alkaline pH in the insect gut when the insect ingests it. The activated toxin then binds to the surface of epithelial cells and creates pores in it. This causes the cells to swell and lyse, eventually leading to the death of the insect.
Scientists isolated the Bt toxin genes from Bacillus thuringiensis and incorporated it into various crop plants such as cotton. This variety is ‘Bt cotton’. Since most Bt toxins are insect-group specific, the choice of genes to be incorporated depends on the crop and the targeted pest. A gene named cry codes for the toxin protein and there a number of these genes. For example, the genes cryIAc and cryIIAb encode toxins that control cotton bollworms whereas the gene cryIAb controls the insect ‘corn borer’.
Pest Resistant Plants
Several nematodes live as parasites on multiple hosts like plants, animals, and even human beings. A specific nematode ‘Meloidegyne incognitia‘ infects the roots of tobacco plants and causes a great decrease in yield. To prevent this infestation, a novel strategy was adopted which is based on the process of RNA interference (RNAi).
RNAi is a method of cellular defence in all eukaryotes. It involves the silencing of a specific mRNA by a complementary double-stranded (ds) RNA that binds and inhibits the translation of this mRNA. The complementary RNA can come from an infection by viruses that have RNA genomes or genetic elements called ‘transposons’.
Scientists took advantage of this process and introduced nematode-specific genes into host plants using Agrobacterium vectors. The introduced DNA produces both sense and anti-sense strands in the host cells. These complementary strands then produce dsRNA and initiate RNAi and thus silence the specific RNA of the nematode. Consequently, the parasite cannot survive in the host that expresses this RNA, leading to resistance against that parasite.
Solved Example For You
Q: Why is the toxin produced by Bacillus thuringiensis (Bt) toxic to other insects but not to itself?
- Bt has an enzyme that cleaves the toxin.
- The toxin is enclosed in a capsule.
- The toxin is inactive in Bt.
- Bt is resistant to the toxin.
Solution: The answer is ‘c’. The toxin is inactive in Bt which is why it does not produce any effect on it.