Notes-Part-1-Class-12-Biology-Chapter-11-Enhancement in Food Production-Maharashtra Board

Enhancement in Food Production

Maharashtra Board-Class-12th-Biology-Chapter-11


Topics to be Learn : Part-1

  • Improvement in Food Production
  • Plant breeding
  • Tissue culture
  • Single cell protein (SCP)
  • Biofortification

Topics to be Learn : Part-2

  • Animal husbandry

Topics to be Learn : Part-3

  • Microbes in human welfare
  • Role of Microbes in Industrial Production
  • Microbes in Sewage Treatment
  • Microbes in Energy Generation
  • Role of Microbes as Biocontrol Agents
  • Role of Microbes as Biofertilizers

Improvement in Food Production

Food : It can be defined as anything solid or liquid, which when swallowed, digested and assimilated in the body, keeping us well.

  • It is organic, energy rich, non-poisonous, edible and nourishing substance.
  • It is one of the basic needs.
  • It gives energy for everything to the living things.
  • It keeps us alive, strong and healthy.
  • Green plants synthesize their own food.
  • Animals including humans are dependent on plants for food directly.

Plant breeding :

To meet the increasing demand for food, there is need for improvement of food production, both quantity wise and quality wise (nutritive).

Plant breeding and animal breeding help us to increase the food production.

Plant breeding : Plant breeding involves the improvement or purposeful manipulation in the heredity of crops and the production of new superior varieties of crops. It involves genetic alteration of plants to increase their value and utility.

Objectives of plant breeding :

Objectives of plant breeding:

Primary aim of plant breeding is to obtain a new crop variety superior to the existing type, in all characters.

Some Objectives of plant breeding are common (as given below) and some vary according to type and use of the plant.

  • To increase crop yield.
  • To improve quality of produce.
  • To increase tolerance to environmental stresses.
  • To develop varieties of plants resistant to pathogens and insect pest.
  • To alter the lifespan.


Different methods of plant breeding:

  • Introduction, selection, hybridization, mutation breeding, polyploidy breeding, tissue culture, r-DNA technology, SCP (Single cell protein).
  • The present day crops are the result of domestication and acclimatization.

Hybridization and its technique :

  • Hybridization is an effective means of combining the desirable characters of two or more varieties.
  • New genetic combinations can be created by hybridization.
  • It exploits and utilizes hybrid-vigour.

Types of Hybridization :

  • Intravarietal (between plants of same variety)
  • Intervarietal (between two varieties of the same species)
  • Interspecific (between two species of the same genus)
  • Intergeneric (between two genera of the same family)
  • Wide/distant crosses : Crosses between distantly related parental plants. Interspecific and intergeneric hybrids are rare to occur in the nature.

The main steps of the plant breeding program (Hybridization) :

The main steps of the plant breeding program (Hybridization) :

(1) Collection of variability :

  • Germplasm collection is the entire collection of all the diverse alleles for all genes in a given crop.
  • Wild species and relatives of the cultivated species having desired traits are collected and preserved.

Germplasm conservation can be done in following ways :

  • In situ conservation : It can be done withthe help of forests and Natural Reserves.
  • Ex situ conservation : It is done through botanical gardens, seed banks, etc.

(2) Evaluation and selection of parents :

  • The collected germplasm is evaluated toidentify healthy and vigorous plants with desirable and complementary characters.
  • Selected parents are selfed for three to four generations to increase homozygosity.
  • Only pure lines are selected, multiplied and used in the hybridization.

(3) Hybridization :

  • The variety showing maximum desirable features is selected as female (recurrent) parent and the other variety which lacks good characters found in recurrent parent is selected as male parent (donor).
  • The pollen grains from anthers of male parent are artificially dusted over stigmas of emasculated flowers of female parent.
  • Hybrid seeds are collected and sown to grow F1 geneartion.

(4) Selection and Testing of Superior Recombinants :

  • The F1 hybrid plants which are superior to both the parents and having high hybrid vigour, are selected and selfed for few generations to make them homozygous for the said desirable characters.
  • This ensures that there is no further segregation of the characters.

(5) Testing, release and commercialization of new cultivars :

  • The newly selected lines are evaluated for the productivity and desirable features like disease resistance, pest resistance, quality, etc.
  • They are initially grown under controlled conditions of water, fertilizers, etc. and their performance is recorded.
  • The selected lines are then grown for at least three generations in natural field, in different agro climatic zones.
  • Finally variety is released as new variety for use by the farmers.
Steps of Hybridization technique :

Collection of variability from germ plasm/ gene bank

→ Evaluation and selection of parents

→ Selection of parent plants with different qualities

→ Selected parents selfed for three to four generations to make them homozygous or true breeding

→ Identification of parents as male parent (donor) and female parent (recurrent)

→ Collection of pollen grains from the flowers of male parent

→ Removal of stamens from the flowers of the female parent (emasculation)

→ Artificial cross pollination by using pollen grains collected from male parent

→ Bagging, tagging of the emasculated flower of female parent

→ Development of fruit and seed representing F1 (hybrid)generation

→ Selection and testing of F1 hybrid for combination of desirable characters

→ Field trials for yield (productivity)

→ Testing and the release of variety


Green revolution :

Many high yielding, hybrid varieties of rice, wheat, sugarcane, millets, developed through hybridization, have helped farmer community to attain record agricultural production in India since 1961. This is called green revolution.

  • Basic elements for Green revolution : The use of seeds of improved varieties of crops for cultivation, expansion of land for cultivation (farm land), optimum use of pesticides and fertilizers, multiple cropping system, modern farm machinery and proper irrigation system.
  • Dr. Norman E. Borlaug was awarded the Nobel prize for developing the semi-dwarf varieties of wheat at international centre for wheat and maize.

Indian Hybrid Crops :

Indian Hybrid Crops :

Wheat and Rice :

  • Hybrid wheat varieties in India : Sonalika and Kalyan Sona
  • Semi-dwarf rice varieties in India: Jaya, Padma and Ratna
  • Semi-dwarf rice varieties were developed from IR—8 (International Rice Research
  • Institute] and Taichung native—I (from Taiwan) and introduced in India.

Sugar cane :

  • Saccharum barberi : Native of North India and it has poor yield and sugar content.
  • S.officinarum : Grown in South India, has thicker stem and high sugar contents, but it does not grow Well in North India.
  • Hybrid varieties developed by crossing these two species have desirable combinations of characters like high sugar content, thicker stem and the ability to grow in North India.
  • Sugar cane varieties developed at Coimbatore, Tamil Nadu : CO-419, 421, 453

Millets : Hybrid maize (Ganga-3), Jowar (CO-12) and Bajra [Niphad) : These varieties are high yielding and resistant to water stress.


Plant Breeding for Disease Resistance :

  • The basic objective is to develop inherent quality in the plant to prevent the pathogen from causing the disease.
  • It is carried out by hybridization process.

Some pathogens and plant diseases :

Some of the plant diseases are as follows :

Pathogen Plant disease
Fungi Brown rust of wheat

Red rot of sugarcane

Late blight of potato

Bacteria Black rot of crucifers
Viruses Tobacco mosaic virus


Some developed disease resistant plants : :

Some disease resistant plants developed are :

Crop Variety Resistant to Disease
Wheat Himgiri Leaf and stripe rust, hill bunt
Brassica Pusa Swarnim White rust
Cauliflower Pusa Shubra Black rot and Curl blight black rot
Chilli Pusa Sadabahar Chilli mosaic virus, Tobacco mosaic virus and leaf curl


Mutation Breeding :

Mutation : It is a sudden heritable change in the genotype, caused naturally.

Mutations can be induced by using various mutagens.

  • Natural (physical) mutagens : High temperature, high concentration of CO2, X-rays, UV rays. Natural mutations occur at a very slow rate.
  • Chemical mutagens : Nitrous acid, EMS [Ethyl - Methyl — Sulphonate), Mustard gas, Colchicine, etc.

Effects of mutagens :

  • Mutagens cause gene mutations and chromosomal aberrations.
  • Seedlings or seeds are irradiated by Cobalt 60 or they are exposed to UV bulbs,
  • X-ray machines, etc. The treated seedlings are then screened for resistance to diseases/pests, high yield, etc.

Some Mutant varieties : :

Mutant varieties :

  • Rice : Jagannath
  • Wheat : NP 836 (rust resistant)
  • Cotton : Indore-2 (resistant to bollworm)
  • Cabbage : Regina-II (resistant to bacterial rot), etc.


Plant Breeding for Developing a Resistance to Insect Pest :

Insects being herbivores, incur heavy loss in the quantity and quality of crops. Resistance in crops can be developed by following ways :

Resistance due to morphological characters :

  • Hairy leaves in cotton : Vector resistance from jassids.
  • Hairy leaves in wheat : Vector resistance from cereal leaf beetle.
  • Solid stem in wheat : Resistance to stem borers.

Resistance due to biochemical characters :

Biochemical characters provide resistance to insects and pests.

  • The high aspartic acid and low nitrogen and sugar content in maize: Resistance against stem borers.
  • The nectar-less cotton having smooth leaves Resistance against bollworms.

Some pest resistant varieties : :

Some pest resistant varieties :

Crop Variety Insect pest
Brassica Pusa Gaurav Aphids
Flat bean Pusa sem 2

Pusa sem 3

Jassids, aphids and fruit borer
Okra Pusa Sawani,

Pusa A-4

Shoot and fruit borer


Tissue culture :

It is a collection of different techniques. It is emerged as a technique of plant biotechnology.

Tissue culture: It is growing isolated cells, tissues, organs ‘in vitro‘ on a solid or liquid nutrient medium, under aseptic, controlled conditions of light, humidity and temperature, for achieving different objectives.

  • Explant : The part of plant used in tissue culture.
  • Totipotency : An inherent ability of living plant cell to grow, divide, redivide and give rise to a whole plant.
  • Haberlandt (1902) : He gave concept of in vitro cell culture (plant morphogenesis).
  • The plant tissue culture medium : It consists of all essential minerals, sources for carbohydrates, proteins and fats, water, growth hormones, vitamins and agar (for callus culture).
  • The most preferred medium for tissue culture : MS (Murashige and Skoog) medium.

Types of tissue culture :

  • Based on the nature of explant : There are three types- cell culture, organ culture and embryo culture.
  • Based on the type of in vitro growth : There are two types- Callus culture (solid medium) and Suspension culture (liquid medium).

Requirements of tissue culture : :

Requirements of tissue culture :

(i) Maintenance of aseptic conditions :

  • Sterilization of glassware : It is carried out using detergents, hot air oven.
  • Sterilization of nutrient medium : It is done by using autoclave.
  • Sterilization of explant : It is carried out by treatment of 20% ethyl alcohol and 0.1% HgCl2.
  • Sterilization of inoculation chamber (Laminar air flow) : It is carried out by using UV ray tube for 1 hour before performing actual inoculation of explant on the sterilized nutrient medium,

(ii) Temperature : 18 °C to 20 °C

(iii) pH of nutrient medium : 5 to 5.8

(iv) Aeration (particularly for suspension culture)



Steps for tissue culture technique.

  •  Cleaning of glass ware, sterilization of glass ware and instruments in an oven/ autoclave
  • Selection and preparation of nutrient medium- MS medium with known concentrations and proportions of different components.
  • Sterilization of medium in an autoclave for continuous 20 minutes under constant pressure of 15/ lb/ inch2.
  • Preparation of plant material (explant) includes isolation of explant followed by surface terilization and rinsing with water. Explant is obtained from the growing stock plant.
  • Inoculation of the explant in the culture flask containing sterilized nutrient medium.
  • Inoculation is done in the laminar air flow cabinet unit.
  • Incubation of the inoculated explant. Here cells of explant grow, proliferate to form callus, within 2-3 weeks.
  • Sub culturing of the callus (if callus is to be maintained for longer period, callus is divided into 3-4 segments and then transferred to fresh culture medium).
  • Organogenesis - Initiation of rooting and shooting, that eventually leads to plantlet formation.
  •  Hardening - Plantlets are transferred to polythene bags containing sterilized soil and kept at low light and high humid conditions for suitable period of time.
  • Hardened plantlets are transferred to field.

 Sub culturing : Both the Callus and suspension cultures die in clue course of time,

Therefore, sub culturing is necessary for continuation of the technique. In this a part of callus or suspension culture is transferred to fresh medium.

Callus culture : :

Callus culture :

  • In callus culture, nutrient medium is solidified using agar-agar is used.
  • Shaker or agitator is not required.
  • Sterilized explant is placed on solid nutritive medium.
  • The cells of explants absorb nutrients and start multiplying.
  • This results in the formation of callus.
  • Callus is a mass of undifferentiated cells, formed by division of the cells of explants.
  • Growth hormones, auxins and cytokinins are provided to callus in specific proportion to induce formation of organs.
  • If auxins are in more quantity, roots are formed (rhizogenesis) and if the cvtokinins are in more quantity, shoot formation takes place (caulogenesis).
  • Thus new plantlets are formed.
  • Callus culture required subculturing to ensure its continuous growth.


Suspension culture : :

Suspension culture :

  • In suspension culture, small groups of cells or a single cell are transferred to liquid nutritive medium as explants.
  • The liquid medium is constantly agitated by using shakers (agitators).
  • The agitation serves the purpose of aeration, mixing of medium and prevents the aggregation of cells.
  • Generally the suspension culture shows a high proportion of single isolated cells and small clumps of cells.
  • Suspension culture grows much faster than callus culture.
  • Suspension culture is used for cell biomass production which can be utilized for biochemical isolation, regeneration of new plants etc.


Micropropagation (Clonal Propagation) :

Micropropagation is also known as clonal propagation. It is a type of tissue culture technique by which large number of plants are regenerated using organogenesis.

  • It is the only process adopted by Indian plant biotechnologists in different industries.

Applications of Micropropagation : :

Applications of micropropagatlon :

  • Micropropagation involves in rapid multiplication of genetically similar plants (clones).
  • A large number of plantlets are obtained within a short period and in a small space.
  • Plants are obtained throughout the year, under controlled conditions, independent of seasons.
  • As micropropagation results in the formation of clones, desirable characters (genotype and sex) of superior variety can be maintained for many generations.
  • The rare plant and endangered species are multiplied and conserved using this technique.
  • With the help of somatic hybrids (cybrids), new variety can be obtained in short time span.
  • Micropropagation is involved in commercial production of ornamental plants like orchids, Chrysanthemum, Eucalyptus, etc. and fruit plants like banana, grapes, Citrus, etc.


Applications of tissue culture : :

Applications of tissue culture are as follows :

  • Production of healthy plants from diseased plants using apical meristems as explants.
  • Production of stress resistant plants.
  • Production of haploid plantlets by pollen culture.
  • Production of secondary metabolites such as alkaloids, enzymes, hormones, etc.
  • Multiplication of rare and endangered plants.
  • Production of somaclonal variants.
  • Use of micropropagation techniques to produce large number of genetically identical plants.
  • Protoplast culture
  • Tissue culture has applications in forestry, agriculture, horticulture, genetic engineering and physiology.


Single cell protein (SCP) :

Human population in underdeveloped and even in the developing countries is suffering from protein malnutrition, resulting into variety of nutritional diseases. To fight with this, efforts are undertaken to increase the food yield by different methods of crop improvement.

  • Conventional methods : Use of biofertilizers, biopesticides, chemical fertilizers and high yielding varieties (green revolution).
  • Nonconventional method : Production of SCP- single cell proteins.

Single-cell protein : Single-cell protein is a crude or a refined edible protein, extracted from pure microbial cultures or from dead or dried cell biomass.

  • Microorganisms like algae, fungi, yeast and bacteria with high protein content in their biomass, are grown using waste and inexpensive substrates.
  • Substrates used for growing microbial biomass are wood shavings, sawdust, corn cobs, paraffin, N-alkanes, sugar cane molasses, even human and animal wastes.
  • SCP is rich in proteins, vitamins, vitamin B complex, minerals and fats.
  • It can be used as fodder for achieving fattening of calves, pigs, in breeding fish and even in poultiy and cattle farming.

The microorganisms used for the production of SCP are as follows :

  • Fungi : Aspergillus niger, Trichoderma viride
  • Yeast : Saccharomyces cerevisiae, Candida utilis
  • Algae : Spirulina spp, Chlorella pyrenoidosa
  • Bacteria : Methylophilus methylotrophus, Bacillus megasterium.

Advantages of Single-Cell Protein :

Advantages of Single-Cell Protein :

  • Microorganisms have a high rate of multiplication that means a large quantity of biomass can be produced in a comparatively short duration.
  • The microbes can be easily genetically modified to vary the amino acid composition. They have high protein contents- 43% to 85% (W/W basis).
  • A broad variety of raw materials, including waste materials, can be used as a substrate for SCP. This also helps in decreasing the number of pollutants.
  • SCP serves as a good source of vitamins, amino acids, minerals, crude fibres, etc.
  • SCPs can be used as fodder for achieving fattening of calves, pigs, in breeding fish poultry and cattle farming.


Biofortification :

Biofortification is a method of developing crops for having higher quantity and quality of vitamins, minerals and fats, to overcome problem of malnutrition.

Objectives of biofortification :

  • Improvement in protein content and quality
  • Improvement in oil content and quality
  • Improvement in vitamin content
  • Improvement in micronutrient content and quality

Methods of development of biofortified varieties :

  • Biofortification can be achieved through conventional selective- breeding practices and also through r-DNA technology.
  • It focusses on making plant food more nutritive as plants grow or develop

Some examples of biofortification :

Some examples of biofortification :

  • Fortified Maize having twice the amount of amino acids- lysine and tryptophan.
  • Wheat -Atlas 66 has a high protein content and Iron-fortified rice has 5 times more iron, are developed.
  • Vegetable crops like carrot and spinach have more vitamin A and minerals.
  • Vitamin C enriched bitter gourd, tomato have been developed by IARI.


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