The genetically modified food is the produce of genetically modified (transgenic) crops. Technology used during production of transgenic crops involves the use of antibiotic and antibiotic resistance genes. Their persistence is GM food in fraught with danger:
(1) GM foods possess transgenic proteins and related metabolites which may cause toxicity and allergies.
(2) Enzyme for antibiotic resistance would cause allergen reactions.
(3) The bacteria present in the alimentary’ canal of the humans could take up the antibiotic resistance gene that is present in the GM food.
It will make the disease resistant to many antibiotics. So these bacteria could become difficult to manage.
Successful management of resources for the purpose of agriculture to satisfy the changing human needs along with maintenance and enhancement of the quality of environment and conservation of natural resources.
Sustainable agriculture would primarily use renewable resources, would cause the minimum pollution and maintain the optimum yield level. Biotechnology is advantageous to sustainable agriculture in following ways-
Microorganisms which bring about nutrient enrichment of soil enhancing the availability of such nutrients e.g., nitrogen (N) and phosphorus (P).
Biofertilizers are low cost input, renewable, reduced dependence on chemical fertilizers and donot pollute the environment. Some examples are:
(a) Free living nitrogen fixing bateria-e.g., Clostridium, Chromatium, Azotobacter etc.
(b) Free living nitrogen fixing cyanobacteria-e.g., Anabaena, Nostoc, Tolypothrix etc.
(c) Symbiotic nitrogen fixing bacteria-e.g., Rhizobium in root nodules of legumes.
(d) Symbiotic nitrogen fixing cyanobacteria-e.g., Anabaena azollae in small aquatic fan Azolla pinnata often inoculated in rice fields.
(e) Phosphate bacteria-e.g., Bacillus megatherium var. phosphaticum.
(f) Phyllosere and Rhizosphere nitrogen fixing bacteria-e.g., Azospirillum, Beijerinckia.
(g) Mycorrhiza-Symbiotic association of fungus and plant roots. These are of irregular shapes often coralloid with wooly covering and absence of root hair and root cap. These fungi solubilise phosphorus, produce plant growth promoting substances and protect host plant from soil pathogens.
Biofertilizers do not produce quick and spectacular results but are slow and take time to become effective.
i. The biological agents that are used to control weeds, insects and pathogens are called biopesticides.
ii. The biological agents which are used as biopesticides are viruses, bacteria, fungi,protozoa and mites.
iii. Insect pest can be overcome by the use of azadirachtin (from Neem) due to its antifeedanl characteristic, predators (e.g., Preying mantis, lady bird beetle), parasites, parasitoids, pathogens of insects, pyrethrin, thurioside etc.
iv. Weeds are controlled by the use of predator herbivore, smoother crops and mycoherbicides.
v. Fungus Trichoderma is used in biocontrol of fungal pathogens by its ability to secrete chitinase.
vi. Sporeine was the first bioinsecticide.
vii.The first bioherbicide was mycoherbicide (based on the fungus Phytophthora palmivora) and was developed in 1981. It is used to control the growth of milk weed in citrus orchards.
viii. The bacterium, Bacillus thuringiensis produces protein toxins. One of these, thurioside is active against different groups of insects. The toxins accumulate as crystals inside the bacteria during speculation. On being ingested by insects, these are converted into active form and kill them by inhibiting ion transport in the midgut.
ix. Due to use of biopesticides, the application of chemicals to control the diseases, insect pest and weeds is reduced which are the source of widespread pollution.
3. Disease and Insect-Resistant Varieties
Genetic engineering has enabled the development of crop varieties resistant to certain insects and diseases. The disease resistant genes are isolated and transferred to high yielding susceptible plants to produce pathogen-free plants. Several disease resistant somaclones have been identified for resistance to early blight of potato caused by Alternaria solani.
Progress in engineering insect resistance in transgenic plants has been made through the expression of insect toxin gene of Bacillus thuringiensis in plants by transferring the viral genes of coat proteins. The technique has been used to produce a virus-resistant variety of squash.
Development of disease and insect resistant varieties would minimise the use of pesticides, prevent pollution, reduces yield losses due to insects and diseases and enhance agricultural production.
4. Single cell protein (SCP):
Microorganisms (e.g., Algae, filamentous fungi, bacteria, yeast etc.) which can be cultured on a commercial scale in a fermenter, treated in various ways dried and used as food source or as animal feed are called single cell protein (SCP). In SCP, biomass is obtained not only from unicellular organisms but also from multicellular organisms.
CO2 produced from industry effluents and materials like saw dust and paddy straw are being used for production of many types of single cell proteins. SCP contain very high amount of proteins with little quantity of fats.
Some microorganisms which lend themselves to biotechnological processing belong to-Algae (e.g., Chlorella, Scenedesmus)\ Filamentous fungi (e.g., Fusarium gramineranum, Chaetomium cellulolyticum); bacteria (e.g., Methylopphilus methylatrophus, Brevibacterium sp. etc.); cyanobacteria (e.g., Spirulina sp.); yeasts (e.g., Saccharomyces cerevisiae, Candida utilis etc.) Processing is required to remove contaminants and excess nucleic acids. Besides providing the much needed proteins, single cell protein is beneficial in reducing environmental pollution by managing industrial and agricultural wastes.