CHAPTER AT A GLANCE
- The strategies for enhancement in food production aim at
- increasing the amount of food obtained from animals.
- increasing the yield of agricultural crops.
- For the above purposes, several methods have been developed which can be broadly grouped as – animal breeding and plant breeding.
ANIMALHUSBANDRY
- Animal husbandry deals with the care, breeding & management of domesticated animals (called livestock) that are useful to humans.
- These livestock are important in human welfare in the following ways:
- They are responsible for the production of milk through cattle breeding.
- Increased production of eggs through poultry farming.
- Improvement of quality of meat through fish farming.
- This livestock helps in the proper utilization of animal wastes, e.g. production of biogas and manure from the dung.
- Through beekeeping or apiculture, they produce more honey and bee wax.
- Animals used in animal husbandry are cattle, pigs, sheep, poultry, fish, and honeybees.
- Animal husbandry consists of several practices, including dairy farming, poultry farming, fisheries, and apiculture (beekeeping).
- In dairy farming, those animals are housed from which we obtain milk and milk products. Milk yield is primarily dependent on the quality of breeds on the farm.
- Poultry is the rearing of domesticated fowls (chickens), ducks, geese, turkeys, guinea fowls and pigeons. These birds and their eggs are used as food.
- Poultry birds exclusively grown for meat are called broilers, layers are for egg production, cockerel is for young male fowls and roosters are for mature male fowls. Poultry were the last major group of food animals to be domesticated.
- The fishery is an industry devoted to the rearing, breeding, catching, and marketing of fish. Besides fishes, other aquatic animals like prawns, crab, etc. are also included.
- Pisciculture is the rearing, breeding, and catching of fish.
- Aquaculture is the rearing and management of useful aquatic plants and animals like fishes, oysters, mussels and prawns etc.
- Fishes are reared and caught for food which is rich in proteins, vitamins A and D. Marine animals are also richer in iodine. Shark liver oil and cod liver oil are very good source of vitamins A and D.
- Apiculture is the rearing and breeding of honey bees for the production of honey.
- The commonest species of honeybee is Apis indica.
- Honeybees have three social castes, each with a specific role or set of roles. These are queen, worker bee and drones.
- Hives produce 5 distinct substances: honey, beeswax, propolis, pollen, and royal jelly.
Animal Breeding
- Animal breeding is the production of new breeds of domesticated animals with improved traits.
- Improvement in genetic material is brought about by selective mating.
- Reduction in fertility after 4 – 6 matings is called inbreeding depression. This is overcome by breeding the superior animal with the animal of an unrelated breed.
- Out-breeding is the mating between the animals which are not closely related. Cross-breeding is the mating between the superior animals of different breeds of the same species.
- Cross breeding permits the desirable qualities of two different breeds to be combined. Hisardale is a new breed of sheep developed in Punjab by crossing Bikaneri ewes and Marino rams.
- Interspecific hybridisation is the mating between the animals of two different species. Mule is produced bymating between male ass and female horse (mare).
- Hybrid vigour is the superiority of hybrid in traits over either of its parents. It is also known as heterosis.
- Artificial insemination is a reproductive technology in which semen of a selected male artificially deposited into the vagina of a selected female.
- MOET (Multiple Ovulation Embryo Transfer) technique is a programme which improves the chances of successful production of hybrids.
PLANT BREEDING
- Plant breeding refers to the modification and improvement of genetic material of plants resulting in the development of crops which are more beneficial to human beings.
- It involves the production of a new variety with the desired characteristics such as resistance to diseases, climatic adaptability, and better productivity.
- There are different methods to produce desired variety of plants. The most common method of plant breeding is hybridisation
- Hybridisation is defined as the process of mixing of genome of two organisms to produce organism with new trait. Such plants with modified genome are known as transgenic plants.
- India is mainly an agricultural country. Agriculture accounts for approximately 33 per cent of lndia’s GDP and employs nearly 62 per cent of the population.
- Steps involved in plant breeding are as follows:
- Collection of genetic variability.
- Evaluation of germplasm and selection of parents.
- Cross-hybridisation or breeding between selected parents. Selection of superior hybrids.
- Testing, release, and commercialization of new cultivars.
- Disease resistance is the ability of plants to withstand, oppose, lessen or overcome the attack of pathogen.
- In 1963, several varieties such as Sonalika and Kalyan Sona, which were high yielding and disease resistant, were introduced all over the wheat-growing belt oflndia.
- Semi-dwarfrice varieties were derived from IR-8, and Taichung Native-Iwere introduced in 1966. Later better-yielding semi-dwarf varieties Jaya and Ratna were developed in India.
- Saccharum barberi and Saccharum officinarum were crossed to get the desirable qualities of high yield, thick stems, high sugar and ability to grow in the sugar cane areas of north India.
- Hybrid maize, jowar and bajra have been developed in India, which are high yielding and resistant to water stress.
- Conventional breeding is often constrained by the availability of limited number of disease resistance genes that are present and identified in various crop varieties or wild relatives. Inducing mutations in plants through diverse means and then screening the plant materials for resistance sometimes leads to desirable genes being identified.
- Mutational breeding is one of the methods of plant breeding that modifies base sequence/nucleotide sequence of a gene to obtain new traits other than those observed in parents. These mutations or changes are brought about either by chemicals or radiations such as X-rays. For example: Mung bean variety is obtained through mutation. This variety is resistant to “yellow mosaic virus”.
- The term mutation breeding was first coined by Freisleben and Lein in 1944 to refer the deliberate induction and development of mutant lines for crop improvement.
- Pusa Lerma and Sharbati Sonora are the two important varieties of wheat produced by gamma ray’s treatment of Lerma Roja 64 (Mexican dwarf wheat varieties) and Sonora 64.
- Dr Swarninathan is called the father of green revolution. He has produced Sharbati Sonora, a variety of wheat by mutation which is responsible for green revolution in India.
- Green revolution refers to increase in production of food grains (such as rice and wheat) due to the introduction of high-yielding varieties, use of pesticides, and better management techniques.
- Green revolution is achieved through introductions of high yielding variety, increased irrigation facilities, fertilisers applications, weed, pest and better agricultural managements.
- Biofortification is the improvement of nutritional quality of crops to improve public health.
- In plant breeding, biofortification aims at developing new crops with improved
- protein content and quality.
- lipid content and quality.
- vitamin and mineral content.
- It can be done either through selective breeding or genetic modification. This is employed to improve the content of proteins, oil, vitamins, minerals, and micro-nutrients in crops.
- There are several improved varieties of crop plants such as wheat, rice, maize, carrots, spinach etc. which have more nutritious value and more nutrients than the existing varieties.
- Bioremediation is a waste management technique that involves the use of organisms to remove or neutralize pollutants from a contaminated site.
- Single cell protein refers to the dried microbial cells or total protein extracted from pure microbial cell culture (algae, bacteria, yeasts and filamentous fungi) which can be used as food supplement to humans or animal.
- Pruteen was the first commercial single cell protein and was mainly used as animal feed supplement.
- Some common microbes used as SCP producers are as follows:
- Bacteria-Methylophillus, Methylotrophus, Brevibacterium
- Cyanobacteria-Spirulina
- Yeast-Saccharomyces cerevisiae, Candida utilize
- Filamentous fungi-Fusarium graminearum Algae-Chiarella
Advantages of SCP
- Microorganisms show rapid growth, so it can be grown in a large amount in a small period of time.
- We can grow on a wide range of raw materials and can be easily harvested.
- We have relatively higher protein content as compared to other healthy food items
- Somatic hybridization was first introduced by Carlson in Nicotiana glauca.
- Gottlieb Haberlandth started the technique of plant tissue culture in 1902.
- The term pure line was introduced by W. L. Johannsen in 1903. It is applicable to self-pollinated crops.
- The wheat variety HUW 468 is a good example of pure line.
- Plant tissue culture is defined as the maintenance and growth of plant cells, tissues and organs on a suitable culture medium in vitro.
- The part of the plant cultured is called explant.
- Explant may be excised root tips, shoot bud, leaf petiole, inflorescence, anther, ovule, ovary or embryo.
- Embryoids are embryo-like structures derived from vegetative cells.
- Plants thus produced are genetically identical to the original plant (somaclones).
- Transgenic plants are plants developed from the cells in which a particular gene has been transferred.
- Haploid production is the production of plants with cells having one genome. Culture of fused protoplasts produces somatic hybrid cells and the process of producing somatic hybrids are called somatic hybridisation.
- In embryo culture embryos taken out from seeds and grown on culture medium.
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