Agriculture accounts for 33% of India’s Gross Domestic Product and employs nearly 62% of the population. Producing enough food for the growing population is the main challenge faced by the country today. The growing human population is imposing growing demand on food production. But the cultivable land is not increasing according to the increased need for food production. In fact the agricultural land is decreasing due to urbanization and construction of buildings and houses for domestic and agricultural needs. Further increase in consumption of non-vegetarian food adds additional burden on crop production. As production of 1 kg of meat requires at least 3-10 kgs of grain, non-vegetarian diet adds to crop production demand. By all means there is every need to increase food production both in terms of quantity and quality. Despite the fact that the purchasing power of middle and upper classes has increased the poor are still suffering from malnutrition and hidden hunger. Both the government and the scientific community need to boost up food production according to the growing demands of human population.

          We have gone through eating plants, animals and their products and now landed in eating fungi like mushrooms. Nearly 2/3 of world’s population living in coastal areas relies on sea foods. Not able to meet the supply of food, scientists are continuously searching for more and more range of organisms to be used as food. The answer to this came in the form of “Single Cell Proteins”. Today we have started using microorganisms for food production. Hope there will be a day that no living organism is spared in need of human food demand. Intensive agriculture is practiced in many parts of the world to increase crop yields. 
          In this chapter we will discuss about some strategies which enhance food production.
Key concepts:
 The 20th century world population witnessed a great scientist “Norman Borlaug” who initiated the green revolution to solve the problem of hunger in many countries.
 Norman Borlaug is known for developing semi dwarf wheat varieties at the International Centre for Wheat and Maize improvement in Mexico.
 He is known as the father of green revolution.
 The same revolution entered India in the form of “Technology Mission” initiated by the efforts of Dr. M.S.Swaminathan.

 M.S. Swaminathan is the chief pioneer of green revolution in India which led to increase production of food crops using chemical fertilizers and pesticides, better irrigation practices and better land use patterns.
 However some of the ills of green revolution are felt today and they are being reformed by the father of green revolution in India Dr. Swaminathan himself.
Some of the advantages of green revolution are:
 Increase in biomass yield as food for humans and animals.
 Meeting the national requirements in food production and also exports.
 Developing high yielding and disease resistant varieties of wheat, rice and maize by using plant breeding techniques.
Some of the achievements of green revolution in our country are:
 Wheat production increased from 11 million tonnes to 75 million tonnes during the period 1960-2000 due to introduction of semi dwarf wheat variety.
 Rice production increased from 35 million tonnes to 889.5 million tonnes due to introduction of semi dwarf rice varieties.
 In 1963 Sonalika and Kalyan Sona varieties of high yielding and disease resistant wheat were introduce in India.

 The derivatives from IR-8 and Taichung Native-1 rice varieties were introduced in India.
 Better yielding semi-dwarf varieties Jaya and Ratna were developed in India.
 High yielding varieties of sugarcane with high sugar and thick stems were produced by crossing Saccharum barberi with Saccharum officinarum.
 Hybrid maize, jowar and bajra have been successfully developed in India.
Plant breeding:
Definition: Plant breeding is the purposeful manipulation of plant species in order to create desired plant types that are better suited for cultivation, give better yields and are disease resistant.
 Plant breeding began some 9000-11,000 years ago.
 Plant breeding involves domestication, introduction, selection, hybridization, mutation breeding and ploidy breeding.
 Plant breeding is carried out using the advancement in genetics, molecular biology and tissue culture.
Plant breeding aims at:
          High and healthy yields.
          Increase in resistance to temperature, drought etc.
          Tolerance to environmental stresses like salinity etc.
          Qualitative and quantitative yield.
          Resistance to pests and diseases (caused by fungi, bacteria and viruses).

The main steps in breeding a new variety of crop involve:
         Collection of variability
         Evaluation and selection of parents
         Cross hybridization among the selected parents
         Selection and testing of superior recombinants
         Testing, release and commercialization of new cultivars
Collection of variability:
       Preexisting genetic variability is available from wild relatives of crop plants. Hence the wild varieties are collected and preserved for further breeding. The entire collection of plants or seeds having all the diverse alleles for all genes in a given crop is called germplasm collection.
Evaluation and selection of parents
       The germplasm is evaluated to identify plants with desirable combination of characters. The selected plants are multiplied and used for hybridization.
Cross hybridization among the selected parents:
       Cross hybridization between two parents produces hybrids that possess desired characters of both plants. The pollen grains of desirable plant chosen as male parent are collected and placed on the stigma of the flowers selected as female parent.

   
Emasculation is done at bud condition. It is the removal of stamens in bud condition to prevent undesirable self-pollination. Bagging the cross pollinated flowers with a polythene cover is done to prevent undesirable cross pollination.

Selection and testing of superior recombinants:
        Hybridization does not ensure combination of desirable characters every time.
Only one in hundred or thousand crosses may produce the desirable combination of characters. Such plants which combine both the desirable characters and are superior to both the parents are selected and self-pollinated to reach a homozygous condition.
Testing, release and commercialization of new cultivars:
        The newly selected lines are tested in the farmer’s field under ideal fertilizer application irrigation and other crop management practices. The testing process is carried out for at least three years at different locations. The material is evaluated in comparison to the best available local crop cultivar.

Uses and achievements of plant breeding:
Disease resistance:
 Using conventional and mutation breeding disease resistance have been introduced in plants.
e.g.: Himgiri variety of wheat resistant to leaf and stripe rust and hill burnt. 
         Pusa Sadabahar variety of Chillie resistant to chillie mosaic virus TMV and leaf curl.
 Using mutation breeding resistance to yellow mosaic virus and powdery mildews was induced in mung bean.
 Parbhani Kranti variety of Bhendi (Abelmoschus esculentus) was made resistant to yellow mosaic virus.
Resistance to insect pests:
      Some morphological, biochemical or physiological characters are characteristic of resistance to insect pests.
Morphological:
 Hairy leaves on plant parts show resistance to insect pests.
e.g.:1 Resistance to Jassids in cotton and cereal leaf beetle in wheat.
e.g.:2 Solid stems in wheat are not preferred by stem sawfly.
e.g.:3 Smooth leaves of cotton do not attract boll worms.

Biochemical or Physiological:
 Nectar less cotton does not attract boll worm.
 High aspartic acid, low nitrogen and sugar content in maize leads to resistance to maize stem borers.
    Pusa Gaurau variety of mustard is made resistant to Aphids.
    Pusa Sem 2 and Pusa Sem 3 varieties of Flat bean are made resistant to Jassids, aphids and fruit borers.
Hidden hunger:
       The world is facing a new challenge in the form of inequality of availability of food. As the rich are becoming richer and the poor poorer, the affordability for food is incomparable. More than 25% of human population is suffering from hunger and malnutrition. The rich are suffering from overweight and obesity due to over consumption of high calorie diets and the poor suffering from nutrient deficiencies due to nonavailability of minimum food requirement or availability of low nutrient food. The suffering caused due to deficiencies of micro nutrients, proteins or vitamins due to non-affordability to buy fruits, vegetables, legumes, fish, meat etc. is called “Hidden Hunger”. The “Hidden Hunger” problem is seen in more than three billion people all over the world.

Bio-fortification:
       Producing crops with higher levels of vitamins, minerals or higher protein and healthy fats is called Bio-fortification. The main aims of Bio fortification are:
 Crops with high protein quality and quantity
e.g.: Hybrid maize with doubled amount of amino acids lysine and tryptophan
       Atlas 66 Wheat with high protein content.
       Protein enriched broad beans, lablab beans, French beans and garden Peas
 High oil quality and quantity
 Adequate vitamin content
    Vitamin A enriched carrot, spinach, pumpkin.
    Vitamin C enriched bitter gourd, bathua, mustard tomato etc.
 Adequate and balanced micronutrients and mineral content
e.g.: Iron fortified rice with 5 times more iron
       Golden rice with high β carotene content
       Calcium and iron enriched spinach and bathua

Single Cell Protein (SCP)
       Search for right protein food to feed astronauts in space led to the discovery of protein food from microorganisms. Later it was found to be supplemental to some patients who are allergic to certain vegetable and animal proteins. As the conventional production of pulses and animal products is unable to meet the protein demand Single Cell Protein emerged as an alternate source of proteins for animal and human nutrition. Mushrooms can be considered as the first Single Cell Proteins obtained in nature from fungi. 
       Single Cell Protein is the protein obtained from microorganisms like algae, fungi and bacteria fit for human and animal consumption. They are produced and purified on industrial scale by growing microorganisms on different kinds of media like straw wastes, molasses, animal manures, sewage etc.
The advantages of Single Cell Proteins are:
 Production of SCP reduces environmental pollution caused by such wastes.
 Very less biomass of microorganisms can produce huge quantities of proteins in a short time.
 They can be used as alternative source of proteins to people who are allergic to pulses or animal proteins.

The disadvantages of SCP are:
 It requires skill and scientific knowledge to produce them.
 As they contain high amount of nucleic acids they may cause accumulation of uric acid in humans and animals.
Some of the important microorganisms used as single cell proteins are:
 Algae
    Spirulina maxima
    Chlorella pyrenoidosa
    Scenedesmus acutus
 Fungi
    Candida utilis (Torula yeast)
    Saccharomyces cervisiae (Baker’s yeast)
    Chaetomium cellulolyticum
 Bacteria
    Brevibacterium ketoglutamicum
    Methylophilus methylotropus

Tissue Culture: 
      Tissue culture is one of the most efficient technologies for crop improvement. Tissue culture is the method of culturing cells or tissues on special nutrient media under sterile conditions to produce whole plants or plant organs.     
       Tissue culture is dependent on the totipotency of plant cell. Totipotency is the capacity of a plant cell to generate a whole plant. The plant part used in tissue culture is called an Explant.
      The tissue culture aims at production of millions of plants in a short time by growing explants on artificial nutrient medium in the laboratory. It is also called in vitro culture as it is carried out in a laboratory. Tissue culture may be defined as in vitro production of plants and plantlets by growing explants on artificial nutrient medium. The tissue culture technique involves the following steps:
            1) Preparation of nutrient medium
            2) Sterilization of the medium
            3) Preparation of explant
            4) Inoculation of explant into the nutrient medium
            5) Incubation for growth
            6) Acclimatization

Preparation of nutrient medium:
      The nutrient medium should contain a carbon source sucrose, inorganic salts, vitamins, amino acids and growth regulators like auxins and cytokinins. Agar agar is used to make it a semi solid.
Sterilization of the medium:
      As the nutrient medium is rich in nutrients it attracts microorganisms hence it must be sterilized. The culture medium is autoclaved for 15 minutes at 121º C and 15 pounds pressure.

Preparation of the explant:
      The cells, tissues or any part of the plant used for tissue culture may be called an explant. The plant part is carefully collected, thoroughly washed with water and detergents and surface sterilized to be used as an explant.
Inoculation:
      The transfer of explants onto the sterilized nutrient culture medium is called inoculation and is carried out in a laminar air flow chamber under aseptic conditions.

Incubation for growth:
      The cultures are incubated for 3 to 4 weeks in tissue culture lab providing adequate temperature and light during which the explants utilize nutrients and undergo cell division. They produce an undifferentiated mass of cells called “Callus”. Organogenesis from callus is promoted by balancing the auxin and cytokinins ratio. 

       A higher auxin concentration induces root production called rhizogenesis and higher cytokinins concentration induces shoot production from the callus called caulogenesis. Sometimes somatic embryos may be formed from callus which is preserved for further use as synthetic seeds.
Acclimatization:
      The plantlets formed are replanted in small pots with sterilized soil and manure. They are first raised under shade and gradually exposed to sunlight for further acclimatization.
Advantages of Tissue culture:
      Large numbers of plants are produced in very short time in limited space. Genetically identical soma clones are produces.
      Economically important plants like tomato, banana, apple eucalyptus etc., are produced on commercial scale.

      Virus free plants are produced by using meristem cells in banana, sugarcane and potato.
      Somatic hybrids are produced by protoplasmic fusion techniques e.g.: Pomato.
Somatic hybridization:
      The process of isolating protoplasts from two different varieties of plants with desirable characters, fusing them and culturing them to produce hybrids is called somatic hybridization. The hybrids formed by somatic hybridization are called somatic hybrids. The plants which show physical and chemical incompatibility under normal sexual crossing can be made to produce somatic hybrids. For example the protoplasmic fusion between potato and tomato has produced Pomato. But this plant did not have desirable combination of characters.