Table of Contents
Strategies for Enhancement in Food Production Notes Class 12 Biology Chapter 9
→ The agricultural practice of breeding and raising livestock is termed animal husbandry. It mainly deals with the care and breeding of commercially important livestock like cows, buffaloes, pigs, cattle, horses, sheep, camels, goats, and poultry farming, and fisheries. Bees, silk-worm, prawns, crabs, birds are also used for their products like honey, milk, and meat, etc.
→ The dairy food industry deals with the management of animals for milk production and its products for the consumption of human beings. Milk yield depends on the quality of breeds with high yielding potential and disease-resistant features.
Those processes and systems are practiced which would increase the yield and improve the quality of milk. The cattle should be well housed, given adequate water, and maintained disease-free. Feeding is done with special emphasis on the quality and quantity of fodder in a scientific manner. Cleanliness and hygiene are of paramount importance while milking, storage, and transport of milk and milk products.
→ Poultry includes all those birds which can be raised under domestication for economic purpose. Poultry farming is highly advantageous. It yields quick returns, requires less space, and easy to manage. Birds like chickens, ducks, geese, turkey, etc. are raised for their eggs and meat.
→ Poultry farm management includes the selection of disease-free and suitable breeds, proper and safe farm conditions, proper feeding and water, hygienic and healthy care.
→ To increase the yield and get desirable qualities in animals, breeding of animals is done. A group of animals that are similar in most characters such as general appearance, features, size, configuration, etc. is said to belong to a breed.
→ When breeding is done between the animals of the same breed, it is called inbreeding. When breeding is done between animals of different breeds it is called cross-breeding or out-breeding.
→ Inbreeding is done by carrying out mating between closely related individuals within the same breed for 4 to 6 generations. Superior males and females are identified and mated in pairs. The progeny is evaluated and superior males and females are selected for further mating. This is repeated for some generations, it leads to the development of pure lines. It increases homozygosity. In cattle, a superior female is one that produces more milk and a superior male is one that gives rise to superior progeny.
→ Inbreeding depression occurs because of continued, close inbreeding, which reduces fertility and productivity. This can be solved by outbreeding.
→ The breeding of unrelated animals is called outbreeding. It may be between some breeds with no ancestral link or between different breeds called cross-breeding. It may happen in different species, called interspecific hybridization.
→ Out-crossing is done within the same breed. It helps to overcome inbreeding depression and the best breeding method to increase productivity.
→ Crossbreeding allows the desirable qualities of two different breeds to combine together. The hybrids are either used commercially or allowed to inbreed so as to select a new stable breed that is superior to the existing breeds.
→ Interspecific hybridization allows the mating of male and female, of two different species. The progeny will have the combined features of both the parents, e.g. mule.
→ Controlled breeding is done with artificial insemination. The semen is collected from males and injected into the reproductive tract of females. This helps in desirable mating and ensures good quality progeny. The semen obtained from a single bull can inseminate a few thousand cows at far-off places.
→ Superovulation and embryo transplantation are new techniques employed for cattle improvement. For this, the cow is administered hormones to induce follicle maturation and superovulation. Due to which several eggs are produced per cycle. These are artificially inseminated, the fertilized eggs are surgically removed at an 8 – 32 celled stage and transferred to the surrogate mother.
→ Apiculture is the maintenance of hives of honey bees for honey production. A. dorasata, Apis, florea, A. indica species are reared for honey. It is an age-old cottage industry. Beehives can be kept in courtyards, or bee pastures of some wild shrubs, fruit orchards, and cultivated crops.
It is not labor intensive but it requires some specialized knowledge and training. Before starting apiculture practice, knowledge of the nature and habits of honey bees, selection of suitable location for keeping the beehives, catching and hiving of a group of bees, management of hives during different seasons, handling and collection of honey and beeswax, is very important.
→ Along with honey, honey bees also produce beeswax, which is used for cosmetics, polished, and various other industries. Honey is aromatic, viscid, and sweet material. Its constituents are :
(a) Levulose – 41.80%,
(b) Glucose and fructose (grape sugar) – 35.40%,
(c) Water – 15.43%,
(d) Sucrose – 5.39%,
(e) Bee wax and pollen grains – 1.68%.
Pure honey is dissolved in water, makes a thread through the depth of glass while impure honey gets dissolved in water.
→ Pisciculture is the rearing and breeding of fish. It includes catching, processing, or selling fishes, shellfish, or other aquatic animals such as prawns, crab, oysters, etc. The flesh of fish has 60 – 80% water, 13 – 20% protein, and some amount of fat. Fish is a very good source of protein and forms an excellent food as it has very little fat and more protein, has a good quantity of vitamin A and D, a rich source of iodine, and easily digested than other meals.
→ In addition to providing food, the fishing industry yields a number of by-products that are of commercial importance.
Some are:
(a) liver oil, which is extracted from fish liver. It’s a good source of vitamin A, C, D, and E,
(b) fish meal is prepared from the waste of fish oil or canning industry or whole fish. It is used as a major food for domestic animals. It is rich in proteins, calcium, and phosphorus,
(c) fish proteins are 80-90% proteins with no fats. These are used in icecreams, pharmaceuticals, paints, varnishes, textile, paper, and cosmetics. Fish protein concentrate (FPC) is also used as a diet supplement,
(d) fish flour is used in biscuits, bread, cakes sweets, and soup. It is easily digested by the infants,
(e) fish fertilizers are wastes of fish meal preparation. These are used as manures for tea, coffee, and tobacco plantation,
(f) fish rees are rich in thymine, lecithin, cholesterol, tyrosine, xanthine, hypoxanthine, and vitamin B, C, D, and E. These are valuable foods.
→ Agriculture is the science or the practice of farming or cultivation, reaping, and management of farm products. Horticulture is the branch of agriculture that deals with the art of growing vegetables, fruits, and ornamental plants.
→ 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 disease resistant. The main objective of plant breeding is to reproduce new superior crop varieties with respect to crop yield and quality, increased tolerance to environmental stress such as salinity, extreme temperature, and drought, resistance to pathogens like viruses, fungi, and bacteria, and increased tolerance to insect pests.
→ Plants which are both self and cross-pollinated can produce homozygous and heterozygous population and are most suitable of breeding experiments.
→ First of all collection and preservation of all different wild varieties, species, and relatives of cultivated species is done to properly use the natural available genes. The entire collection of plants or seeds with all the diverse alleles for all genes in a given crop is called germplasm collection.
→ The germplasm is evaluated to identify the plants with a desirable combination of characters. Selection is the oldest breeding method and is the basis of crop improvement.
It may be of two types:
(a) Natural selection and
(b) Artificial selection.
Natural selection is a continuous process that is operating in nature. Here the fittest survives and the remaining ones vanish away.
→ In artificial selection, various types of plants are selected from bulk by plant breeders. This is purposefully done to have a better crop from a mixed population, in a. short duration of time as compared to the natural selection process. This may be achieved by mass selection, pure line selection, and clonal selection.
→ Mass selection is based on phenotypes. The best plants from the population are selected at the time of harvesting, with desired traits. The seeds from all such plants are collected and mixed to form a bulk. This process may be repeated for some generations to get the desired improvement.
→ Pure line selection is also called single plant selection. In it, several single plants with desired traits are selected from a population. This is the best method to improve the variety in self-pollinated plants and the crop is of uniform appearance.
→ Clonal selection is used to ensure purity to race, e.g. mangoes, apples, etc., or due to lack of seed formation, e.g. banana. It is the best method for vegetatively propagated plants
→ The plants are selected by using a suitable selection method. These are then multiplied and used further for hybridization.
→ Hybridization is the crossing of two plants differing from each other genotypically in one or more traits.
The purposes of doing hybridization are:
(a) to exploit and utilize the hybrid vigor and
(b) to increase and generate the genetic variations through recombination.
→ In hybridization, greater success is obtained with healthy and vigorous parents. Selfing is done to reduce heterozygosity. The selected inbreeds are used for hybridization.
→ Hybridization involves emasculation and bagging (discussed in Chapter 2) techniques, which are removal of stamens and bagging male and female flowers to prevent foreign pollen contamination. After these crossing is done by collected pollen grains from the male parent and dusting them on stigma. The same desired characters for hybridization are high protein content from one parent and disease resistance from another parent. The hybrid plant is a genetic combination of the two parents.
→ Hybridization is followed by a selection of hybrids that have desired characters. This step needs expertise and careful scientific evaluation. These plants are superior to both the parents. These are further self-pollinated for several generations to attain homozygosity and to ensure that the desired characters will not segregate in the progeny.
→ After successful experimentation, the crop is grown in the research field under ideal fertilizer application, irrigation, and crop management practices. This is followed by testing in farmer’s fields in different locations for three growing seasons. These are evaluated for their yield and quality, disease resistance qualities, etc.
→ Wheat, rice, and maize are the chief cereals of the world. These belong to the Gramineae family. Wheat flour is used for making chapatis, bread, cakes, biscuits, etc. Its straw is used as fodder and for stuffing. Sonalika and Kalyan Sona are two high-yielding and disease-resistant varieties of wheat.
→ Rice is a staple food for half of the world. It is a semi-aquatic crop. It’s used in various preparations like idli, dosa, kheer, etc. It’s straw issued for making hats. Rice flavor is used in the cosmetic industry. IR-8 and Taichung Native-1, Jaya, and Ratna are few varieties of rice.
→ Maize or corn is rich in carbohydrates, fats, and proteins. It lacks binding gluten so can’t be used for bread making. It can be boiled, roasted, or popped up.
→ Smaller grained cereals are called millets, e.g. ragi, Jowar, and Bajra.
→ Sugarcane is a hybrid obtained from crossing between Saccharum Barberi and Saccharum officinarum. It is the chief source of sugar. Baggage (leftover) is used in the fuel and paper industry. The molasses is used in alcohol anti vinegar preparation.
→ Resistance of the host plant is the ability to prevent the pathogen from causing disease. Some plants are disease resistant while some are susceptible, it is determined by the genetic constitution of the host plant. These pathogens Rhay be fungal, bacterial, or viral, e.g. brown rust of wheat (fungi), red rot of sugarcane, late blight of potato (fungi), black rot of crucifers (bacteria), tobacco mosaic, turnip mosaic (virus). Breeding helps to develop disease-resistant varieties and reduce the fungicides and bactericides treatment.
→ Breeding for disease resistance is achieved by the usual steps like screening for disease-resistant plants through germplasm, hybridization of selected parents, selection and evaluation of the hybrids, followed by testing and finally release of new varieties.
→ Due to a limited number of disease resistance genes in a species, conventional breeding has a limited scope. Other breeding methods such as induced mutations, selection among somaclonal variants, and genetic engineering have promising results in producing desirable characters. Initially, mutations are induced in plants, these are screened for disease resistance genes. Such plants are either directly multiplied or used inbreeding.
→ The mutation is a sudden, stable, and heritable change that alters the genotype of an organism. Mutations are induced artificially in plants which change base sequence in genes, creating genetic variation, this results in new traits in the progeny.
→ The application of induced mutations for crop improvement is called mutation breeding. Mutations can be induced chemically or by radiations, e.g. UV rays, X-rays, cosmic rays, gamma rays, 60cobalt, and 137caesium, nitrous acid, EMS, mustard gas, colchicine, etc.
→ Plant breeding experiments are used for developing pest and insect-resistant varieties. These are dependent on morphologica1, biochemical, and physiological characters of the host plant. For example, hairy leaves are associated with resistance to insect pests, solid stems of wheat are resistant to stem sawfly, sugar content in maize leads to resistance for maize stem borers. Breeding methods are the same as discussed earlier.
→ Plant breeding is also practiced for improved food quality, it is done for improving protein content and quality, oil content, and quality, for increasing vitamin content, for micronutrient and mineral content. For example, Atlas 66 wheat has high protein content, maize hybrids with more amino acids, lysine and tryptophan and rice with more iron content have been developed.
→ Single-cell proteins (SCPs) are an alternative source of proteins for animal and human nutrition.
→ Microbes like spirulina which can be grown on waste materials can serve as rice food for proteins, minerals, fats, carbohydrates, and vitamins and reduces environmental pollution too. Microbes are grown increasingly on large scale to serve as a good source of proteins.
→ Plant tissue culture is a technique of growing cells, tissues, or organs in sterilized nutrient media under controlled aseptic conditions. The plant part which is used for culture preparation is called explant. Plant cells are totipotent i.e: they can form a complete plant under suitable conditions. In specific culture medium and sterile conditions, many plant cells and tissues divide and grow to form an unorganized mass of cells called callus.
→ The nutrient medium must provide a source for carbon and inorganic salts, vitamins, amino acids, and growth regulators like cytokinins and auxins, etc.
→ Micropropagation or cloning is a novel technique devised to produce vast quantities of strong and healthy plantlets by rapid vegetative multiplication under controlled conditions. Each of these plants is genetically identical to the parent plant and is called some clones.
→ Tissue culture is useful for
- Micropropagation,
- Production of disease-free plants,
- Androgenic haploids and their use in breeding,
- Embryo rescue for successful hybridization,
- Induction and selection of mutants,
- Somaclonal variations,
- Protoplast technology.
→ Culture of explant on an agar medium containing 2, 4-D results in the formation of callus. Suspension cultures are obtained by culturing pieces of callus in a liquid medium which is constantly agitated so that the larger masses are dissociated into smaller clumps and single cells.
→ The callus and suspension cultures are commonly used for achieving cell biomass production. Single cells can be isolated either from suspension culture or directly from explants by mechanical or enzymatic methods. They are cultured in liquid or semi-solid media by using filter paper raft-nurse tissue technique or by Bergmann’s plating technique. Plantlets can be regenerated from callus or suspension cultures either by shoot regeneration or by somatic embryo regeneration technique.
→ The regenerated plantlets can be transferred and established in the field. The term ‘micropropagation’ or ‘cloning’ is applied to a novel technique devised to produce vast quantities of strong and healthy plantlets by rapid vegetative multiplication under controlled conditions.
Haploid plants can be produced by another culture or by culturing microspores. These haploids can be converted to homozygous diploids by doubling their chromosomes using certain chemicals.
→ Young embryos can be cultured on artificial culture media containing specific nutrients. This technique is helpful in raising the plants from interspecific crosses as well as for ‘embryo rescue’. The multiple shootlet production techniques are useful in getting disease-free healthy plants.
→ Genetic vacations occur at all levels of the tissue culture process. They are termed somaclonal variations. These variations are useful for the improvement of crops if they are heritable and have agronomic traits.
→ Naked protoplasts of plant cells can be isolated by digesting their cell walls using certain hydrolytic enzymes. The isolated protoplasts can be cultured in a liquid or semi-solid medium. Naked protoplasts of two different plants can be allowed to fuse to form hybrids. This is called protoplast fusion and somatic hybridization.
The plant tissue culture technique is also used for the production of artificial seeds in those plants which either do not bear seeds or produce a small number of seeds.
→ Artificial seeds are used for direct field delivery of select elite genotypes, hand-pollinated hybrids, genetically engineered plants, sterile and fertile genotypes, etc.
→ Cultivation of plant cells in culture media promises great potential in large-scale production of secondary metabolites which are otherwise produced in minute amounts and their extraction from the plants is difficult and expensive.
→ Allotetraploid: AllotetraploidS are produced by the multiplication of chromosomç sets that are initially derived from two different species.
→ Apiculture: Rearing and management of beehives for obtaining honey and wax.
→ Aquaculture: Production of useful plants and animals.
→ Concentrates: They include cotton seeds, oil cakes, cereal grains, etc.
→ ElectrapOration: Genetic transformation by applying high electric potential for a few microseconds to change the porosity of protoplast to take up DNA.
→ EmasculatiOn: Removal of stamens from bisexual flowers before they burst and shed their pollen.
→ Hybrid vigor: The increased vigor often exhibited by hybrid progeny.
→ Livestock: The animals like cattle, sheep goat, camel, horse, pig, and poultry form livestock.
→ Pisciculture: The rearing of fishes for obtaining meat and oil.
→ Poultry: Rearing of fowls, ducks, turkeys for their eggs and meat.
→ Roughage: It includes straw of cereals such as wheat, rice, Jowar, and oat, etc.