From the Green Revolution to tissue culture — how biology feeds the world. This chapter covers animal husbandry, plant breeding, single cell protein, and biotechnology-based strategies that increase food production.
Before diving in, here's the entire chapter on one page. Two main approaches to increase food production: traditional (animal husbandry, plant breeding) and modern (tissue culture, single cell protein, transgenic).
To feed a growing population, we use two strategies: (1) traditional — animal husbandry (dairy, poultry, apiculture, aquaculture) and plant breeding (selection, hybridization, mutation breeding, green revolution, biofortification); (2) modern — single cell protein (SCP), plant tissue culture (micropropagation, somatic hybridization), and transgenic animals/plants. All aim to improve yield, quality, and disease resistance.
Animal husbandry: The agricultural practice of breeding and raising livestock — cattle, buffalo, sheep, goats, pigs, poultry, fish, bees — for food, fiber, and other products.
Goals:
Dairy farm management: Managing dairy cattle and buffaloes to maximize milk yield and quality.
Key aspects:
Crossbreeding: Indigenous × exotic breeds → improved milk yield. Example: Karan Swiss (Brown Swiss × Sahiwal), Karan Fries (Holstein-Friesian × Tharparkar).
Poultry: Birds reared for eggs and meat — chicken, ducks, turkeys, quails.
Poultry farm management:
Broiler vs Layer:
Apiculture: Rearing of honeybees for honey, beeswax, propolis, and pollination.
Species: Apis indica (Indian), Apis mellifera (Italian, most common), Apis dorsata (rock bee), Apis florea (dwarf bee).
Products:
Additional benefit: Pollination of crops — bees are critical for food crops (almonds, apples, cucumbers). ~1/3 of global food production depends on pollinators.
Bee dance: Honeybees communicate the location of food via "round dance" and "waggle dance."
Aquaculture: Cultivation of aquatic organisms (fish, prawns, mollusks, seaweed) under controlled conditions.
Types:
Composite fish culture: Raising multiple species together (surface, column, and bottom feeders) to use all food resources in a pond efficiently. Example: Catla (surface), Rohu (middle), Mrigal (bottom).
Problems: Inbreeding, disease, water quality, food availability. Solution: Induced breeding (hypophysation — using pituitary extract to induce spawning).
Fisheries: Capture or culture of fish and other aquatic animals — inland (rivers, ponds) or marine (sea).
India: 2nd largest fish producer in the world (after China). Major sources: marine (coastal), inland (rivers, lakes, ponds), aquaculture.
Hilsa, sardines, mackerel, Bombay duck — important marine species. Rohu, catla, mrigal — important freshwater species.
Animal husbandry: dairy (cattle, buffalo — Holstein-Friesian, Jersey, Sahiwal), poultry (chicken, ducks — broilers, layers), apiculture (honeybees — honey, beeswax, pollination), aquaculture (fish — catla, rohu, mrigal), fisheries. Composite fish culture and crossbreeding improve yields. India is world leader in milk production.
Plant breeding: The science of manipulating plant species to produce desired traits — higher yield, better quality, disease resistance, pest resistance, drought tolerance.
Purpose: Improve food crops to feed growing populations.
Green Revolution: The dramatic increase in food production (especially wheat and rice) in the 1960s–1970s due to improved varieties, fertilizers, pesticides, and irrigation.
Key figure: Dr. Norman Borlaug (Nobel Peace Prize 1970) — developed semi-dwarf, high-yielding wheat varieties (Mexico).
In India: Dr. M.S. Swaminathan led the Green Revolution. Wheat production increased from 11 million tonnes (1960) to over 100 million tonnes (today).
Key varieties:
Components of Green Revolution:
1. Hybridization:
2. Mutation breeding: Using chemicals (EMS, colchicine) or radiation (X-rays, gamma rays) to induce mutations. Select for useful traits.
3. Polyploidy breeding: Increasing chromosome number (triploid, tetraploid) — sometimes improves yield. Example: triploid seedless watermelon, tetraploid cotton.
4. Somatic hybridization (cell fusion): Fusion of somatic cells from different plants (after removing cell walls) → hybrid cell → new plant. Useful for crossing plants that can't be crossed normally (e.g., potato + tomato = "pomato" — not yet successful).
Disease resistance: Plants bred to resist pathogens (bacteria, fungi, viruses).
Examples:
How resistance is developed: Cross with resistant wild varieties, select offspring with resistance genes.
Biofortification: Breeding crops with higher nutritional content (vitamins, minerals, protein).
Purpose: Address malnutrition (hidden hunger) in developing countries.
Examples:
Plant breeding: germplasm collection → parent selection → hybridization → selection → testing → release. Green Revolution (1960s): semi-dwarf HYV wheat (Sonora-64, Kalyan Sona) and rice (IR-8) with fertilizer → huge production increase. Disease resistance breeding (wheat rust, rice blight). Biofortification (Golden Rice, QPM, iron-rich rice). Mutation breeding (Mung bean YMV resistance).
Somatic hybridization: Fusion of somatic (body) cells from two different plants (after removing cell walls) to produce a hybrid plant.
Steps:
Example: Pomato — hybrid of potato (Solanum tuberosum) and tomato (Solanum lycopersicum), attempted for combined traits (tubers + fruit). Not commercially successful.
Advantages: Overcomes sexual incompatibility (can combine traits from unrelated species).
Limitations: Chromosomal instability, hybrid not always viable.
Mutation breeding: Using physical (X-rays, gamma rays, UV) or chemical (EMS, colchicine) agents to induce mutations, then selecting useful variants.
Advantages: Creates new variation not available in natural populations.
Examples:
Polyploidy: Having more than two sets of chromosomes (3n, 4n, etc.). Some polyploids are larger, more vigorous, higher yielding.
Examples:
Colchicine is used to double chromosome number (induces polyploidy).
| Crop | Key Variety | Feature |
|---|---|---|
| Wheat | Sonora-64, Lerma Rojo | Semi-dwarf, high-yield (introduced from Mexico) |
| Wheat (India) | Kalyan Sona, Sonalika | High-yield, disease-resistant |
| Rice | IR-8 (miracle rice) | Semi-dwarf, high-yield (from IRRI) |
| Rice (India) | Jaya, Padma, Ratna | High-yield, adapted to Indian conditions |
| Rice (aromatic) | Pusa Basmati-1 | Basmati quality + high yield |
Modern breeding methods: somatic hybridization (protoplast fusion — pomato example), mutation breeding (gamma rays — Mung bean YMV resistance), polyploidy breeding (colchicine — triploid seedless watermelon, hexaploid wheat), and genetic engineering (Golden Rice, Bt cotton).
Single Cell Protein (SCP): Protein extracted from single-celled organisms (bacteria, yeast, algae, fungi) used as a protein supplement in human food and animal feed.
Why SCP?
Common example: Spirulina — 60–70% protein, rich in vitamins, minerals, essential fatty acids. Used as dietary supplement. NASA studied it for space missions.
Advantages:
Concerns:
Single Cell Protein (SCP): protein from microbes (bacteria, yeast, algae, fungi) used as food/feed supplement. Spirulina (60-70% protein), Methylophilus methylotrophus (methanol-grown). Fast production, uses waste substrates, less land. Concerns: allergies, nucleic acid content, cost, consumer acceptance. Useful for space and developing countries.
Tissue culture: Growing plant or animal cells/tissues in an artificial medium under controlled conditions (in vitro).
Plant tissue culture: Growing plant cells in a nutrient medium containing sugars, minerals, vitamins, and plant hormones (auxins, cytokinins).
Key concept — totipotency: The ability of a single plant cell to grow into a complete plant (because it has all the genetic information).
Steps:
Micropropagation: Rapid production of many identical plants (clones) using tissue culture.
Advantages:
Examples: Orchids, bananas, sugarcane, potato, tomato, cardamom, date palm, teak.
Somaclones: Plants produced by tissue culture (from somatic cells). Genetically identical to the parent — unless mutations occur (somaclonal variation — can be a source of new variation).
Meristem culture: Using the shoot apical meristem (which is usually free of viruses) to produce virus-free plants.
Why meristem? Viruses usually don't reach the actively dividing meristematic cells. So tissue from meristem is virus-free.
Application: Producing disease-free planting material — banana, potato, sugarcane, citrus, orchids.
(Covered in Section 3.) Removing cell walls from plant cells (using cellulase, pectinase) → protoplasts → fusion → hybrid cell → hybrid plant.
Example: Pomato (potato + tomato).
Animal cell culture: Growing animal cells in vitro — in nutrient medium (serum, amino acids, vitamins, antibiotics).
Uses:
Transgenic animals: Animals whose genome has been altered by introducing foreign genes (via microinjection, viral vectors, or stem cell manipulation).
Uses:
Examples:
Plant tissue culture: micropropagation (rapid clone production from explant), meristem culture (virus-free plants), somaclones (from somatic cells), somatic hybridization (protoplast fusion). Animal cell culture: vaccines, hormones, drug testing. Transgenic animals: disease models, therapeutic proteins (Rosie cow), organ transplants. Also transgenic crops (Bt cotton, Golden Rice).
"D-P-A-A-F" — Dairy, Poultry, Apiculture, Aquaculture, Fisheries
"Collection, Evaluation, Crossing, Selection, Testing"
CECST (like "sect") — collection → evaluation → crossing → selection → testing
"Borlaug — Wheat, Swaminathan — India"
Norman Borlaug (Mexico) → Nobel Peace Prize 1970. M.S. Swaminathan → India.
"Sonora-Kalyan (Wheat), IR-8-Jaya (Rice)"
Wheat: Sonora-64, Kalyan Sona. Rice: IR-8, Jaya.
"Golden Rice-A, Iron Rice, QPM"
Golden Rice (Vitamin A), Iron-rich rice (IR 68144), Quality Protein Maize (QPM).
"Mu-Poly-Somatic" — Mutation, Polyploidy, Somatic hybridization
"Spirulina-Bacteria-Yeast-Fungi"
Spirulina (algae), Methylophilus (bacteria), Candida (yeast), Aspergillus (fungi).
"Explant → Callus → Plantlet"
Explant (starting piece) → Callus (undifferentiated cells) → Plantlet (via hormones).
Key concept: Totipotency — cell can grow into whole plant.
"Rosie Cow, Tracy Sheep, Dolly Clone"
Rosie (human protein in milk), Tracy (alpha-1 antitrypsin), Dolly (first cloned mammal).
Use "DPAAF" for animal husbandry types, "CECST" for plant breeding steps, "Borlaug-Wheat, Swaminathan-India" for Green Revolution names, "Explant → Callus → Plantlet" for tissue culture.
Q1. What is animal husbandry? Give two examples of products obtained from animal husbandry.
Animal husbandry: The agricultural practice of breeding and raising livestock (cattle, buffalo, sheep, goats, pigs, poultry, fish, bees) for food, fiber, and other products.
(1) Milk and milk products — from dairy cattle and buffaloes
(2) Eggs and meat — from poultry
(3) Honey and beeswax — from apiculture (beekeeping)
(4) Fish and fish products — from aquaculture
(5) Wool — from sheep
Q2. What is the significance of meristem culture in plant tissue culture?
Meristem culture is used to produce virus-free plants. The shoot apical meristem is usually free of viruses because viruses don't typically penetrate the actively dividing meristematic cells.
Used to produce disease-free planting material for crops: banana, potato, sugarcane, citrus, orchids. This helps in producing high-quality, virus-free planting stock for agriculture and horticulture.
Q3. What is single cell protein (SCP)? Give its advantages and one example.
Single Cell Protein (SCP) = protein extracted from single-celled organisms (bacteria, yeast, algae, fungi). Used as a protein supplement in human food and animal feed.
(1) Fast production — microbes multiply rapidly
(2) Uses cheap substrates (waste materials, methanol, molasses)
(3) High protein content (50-80% dry weight)
(4) Less land and water needed than conventional protein sources
(5) Useful for space missions and disaster relief
Spirulina (blue-green algae) — 60-70% protein, rich in vitamins and minerals. Sold as dietary supplement.
Methylophilus methylotrophus — grows on methanol, produces ~250,000 tonnes of SCP/year globally (used in Pruteen process for animal feed).
Q4. What is micropropagation? What are its advantages?
Micropropagation: The technique of producing many identical plants (clones) rapidly using tissue culture. A small piece of plant tissue (explant) is grown in a nutrient medium to produce many plantlets.
(1) Rapid multiplication: millions of plants from one explant in a short time
(2) Genetically identical: produces clones of superior plants
(3) Disease-free: especially using meristem culture
(4) Seedless plants: can propagate plants that don't produce viable seeds (banana, orchids)
(5) Space-efficient: small lab produces huge numbers
(6) Year-round production: not seasonal
Examples: Orchids, bananas, sugarcane, potato, tomato, cardamom, date palm.
Q5. Describe the Green Revolution. What were its key components? What role did M.S. Swaminathan and Norman Borlaug play?
Green Revolution: The dramatic increase in food production (especially wheat and rice) in the 1960s-1970s, resulting from the introduction of high-yielding varieties, fertilizers, pesticides, and irrigation.
(1) High-yielding varieties (HYV): Semi-dwarf wheat (Sonora-64, Lerma Rojo) and rice (IR-8) with high yield and fertilizer responsiveness.
(2) Chemical fertilizers: NPK to support HYV growth.
(3) Pesticides: To control pests and diseases.
(4) Irrigation: Assured water supply.
(5) Modern machinery: Tractors, harvesters.
American agronomist who developed semi-dwarf, high-yield, disease-resistant wheat varieties in Mexico. His varieties spread to India, Pakistan, and other countries. Awarded Nobel Peace Prize in 1970 for his contribution to world food supply.
Indian geneticist, called "Father of Green Revolution in India." He introduced Borlaug's wheat varieties to India, developed high-yielding wheat (Kalyan Sona, Sonalika) and rice (Jaya, Padma, Ratna) varieties adapted to Indian conditions. Wheat production in India increased from 11 million tonnes (1960) to over 100 million tonnes today.
Selected exercise questions from the OLD NCERT Chapter (Strategies for Enhancement in Food Production). Removed from current syllabus but useful for competitive exams.
Answer: Animal husbandry plays a crucial role in human welfare:
(1) Food production: Provides milk, eggs, meat, fish — major protein sources.
(2) Employment: Millions of rural people depend on animal husbandry for livelihood.
(3) Manure: Animal dung used as organic fertilizer and biogas source.
(4) Pollination: Beekeeping helps crop pollination, increasing yields.
(5) Industrial products: Wool, leather, honey, beeswax.
(6) Economic contribution: India's dairy industry is world's largest; India is 3rd in egg and 5th in broiler production.
Methods: (1) Inbreeding: Breeding closely related individuals (father × daughter, brother × sister). Increases homozygosity; fixes desirable traits but can cause inbreeding depression.
(2) Outbreeding: Breeding unrelated individuals. Types: outcrossing (same breed), crossbreeding (different breeds — like Karan Swiss), interspecific hybridization (different species — like mule).
(3) Artificial insemination: Collecting semen from a superior male and artificially transferring it to females. Popular for dairy cattle and buffaloes.
(4) Multiple ovulation embryo transfer (MOET): Hormonal stimulation of a superior female to produce multiple eggs → artificial insemination → embryos collected and transferred to surrogate mothers. Faster than natural breeding.
Best method: MOET + Artificial insemination — best for maximizing genetic gain quickly. It allows rapid multiplication of superior germplasm, eases transport of genetic material, and prevents spread of physical diseases. Widely used in cattle and buffalo breeding in India.
Apiculture: Rearing of honeybees (Apis species) for honey, beeswax, propolis, and pollination. Common species: Apis indica (Indian), Apis mellifera (Italian, most common), Apis dorsata (rock bee), Apis florea (dwarf bee).
Uses of honey:
(1) Food — natural sweetener, energy source
(2) Medicine — antibacterial, wound healing, cough remedy, immune booster
(3) Cosmetics — skin care, hair care
(4) Industrial — flavoring, food preservation
(5) Ayurveda — traditional medicine
Other products: Beeswax (candles, cosmetics, ointments, polishes), propolis (antiseptic), royal jelly (nutritional supplement), bee venom (apitherapy).
Additional benefit: Pollination of crops (almonds, apples, cucumbers, etc.) — bees are critical for food crop production.
Composite fish culture: Raising multiple fish species in the same pond to use all food resources efficiently.
Advantages:
(1) Uses all resources: Different species feed in different zones — surface, column, bottom — so food is used efficiently.
(2) Higher yield: More fish per unit area compared to monoculture.
(3) Ecosystem balance: Fish clean the pond (some eat weeds and snail), improving water quality.
(4) Stable income: Different species have different market value and demand.
(5) Pest control: Some fish eat mosquito larvae — reduce mosquito-borne diseases.
Three species:
(1) Catla catla: Surface feeder — eats planktons at the top
(2) Rohu: Column feeder — eats middle-level vegetation
(3) Mrigal: Bottom feeder — eats detritus at the bottom
Together, they use all food resources of the pond efficiently.
Steps in plant breeding:
(1) Collection of variability: Collection of diverse genetic material (germplasm) from various sources — wild relatives, landraces, modern varieties. Preserved in gene banks.
(2) Evaluation and selection of parents: Evaluate collected material for desired traits (yield, disease resistance, quality). Select the best parents for breeding.
(3) Cross hybridization: Cross selected parents to combine desirable traits. May be intervarietal, interspecific, or intergeneric.
(4) Selection and testing of superior recombinants: From the hybrid offspring, select the best ones (superior recombinants). Self-pollinate to stabilize traits.
(5) Testing, release, and commercialization: Multi-location trials for yield, disease resistance, and quality. The best variety is released to farmers.
Biofortification: Breeding crops with higher nutritional content — vitamins, minerals, protein, essential amino acids. Aimed at addressing hidden hunger (micronutrient deficiency).
Examples:
(1) Golden Rice: Transgenic rice producing beta-carotene (Vitamin A precursor) — helps prevent blindness in developing countries.
(2) Atlas 66 wheat: High protein content.
(3) Iron-rich rice (IR 68144): Higher iron content, helps against anemia.
(4) Quality Protein Maize (QPM): Higher lysine and tryptophan (essential amino acids).
(5) Iron-rich pearl millet, wheat: For iron deficiency.
(6) Mustard oil: Low erucic acid (healthy) and high oleic acid.
Somatic hybridization: Fusion of somatic (body) cells from two different plants to produce a hybrid plant. Overcomes sexual incompatibility (can combine traits from species that can't be crossed normally).
Steps:
(1) Isolation of protoplasts: Cell walls of plant cells are removed using cellulase and pectinase → protoplasts (cells without walls).
(2) Fusion of protoplasts: Protoplasts from two plants are fused using polyethylene glycol (PEG), electric field, or Sendai virus.
(3) Culture of hybrid cell: The fused hybrid cell is grown in nutrient medium → callus.
(4) Differentiation: Hormones induce differentiation into roots and shoots → hybrid plantlet.
(5) Acclimatization: Hybrid plantlet transferred to soil.
Example: Pomato — hybrid of potato (Solanum tuberosum) and tomato (Solanum lycopersicum). Not commercially successful but illustrates the technique.
Single Cell Protein (SCP): Protein extracted from single-celled organisms — bacteria, yeast, algae, fungi — used as protein supplement in human food and animal feed.
Advantages:
(1) High protein content (50-80% dry weight).
(2) Microbes multiply rapidly (20 min to a few hours) — fast production.
(3) Uses cheap substrates (waste materials, methanol, molasses) — cost-effective.
(4) Requires less land, water, energy than livestock production.
(5) Environmental-friendly — less greenhouse gas emission.
(6) Useful in space travel and disaster relief (compact, high-protein).
(7) Can be produced year-round, independent of climate.
Examples: Spirulina (algae), Methylophilus (bacteria), Candida (yeast), Aspergillus (fungi).
Concerns: Allergies, nucleic acid content, cost of processing, consumer acceptance.
Micropropagation: Rapid production of many identical plants using plant tissue culture. Small pieces of tissue (explant) are grown in nutrient medium → callus → plantlets.
Why somaclones? Plants produced by micropropagation are called somaclones because:
(1) They are produced from somatic cells (body cells, not gametes).
(2) They are genetically identical to the parent plant (clones) — because they are produced by mitosis (not meiosis + fertilization).
(3) They come from repeated mitotic divisions of somatic cells → same genetic makeup.
Exception: somaclonal variation — sometimes mutations occur during culture and produce variants (can be useful for breeding).
Examples: Orchids, bananas, sugarcane, potato, tomato, cardamom, date palm.
Methods:
(1) Meristem culture: Using the shoot apical meristem (which is usually virus-free) to produce virus-free plants.
(2) Thermotherapy: Heating plants to 35-40°C for several weeks — many viruses are destroyed by heat.
(3) Chemotherapy: Treating plants with antiviral chemicals (less common).
(4) Combination: Meristem culture + thermotherapy — most effective.
Biological principle: The shoot apical meristem contains actively dividing cells. Viruses typically cannot penetrate or multiply in these rapidly dividing meristematic cells. They are present in the older, differentiated tissues. So culturing the meristem gives virus-free plants.
Examples: Banana, potato, sugarcane, citrus, orchids — major crops that use meristem culture for disease-free planting material.
(A) Both true, R explains A. (B) Both true, R does NOT explain A. (C) A true, R false. (D) A false, R true.
All key facts at one place — perfect for quick revision.