Monday, April 30, 2012

3. Strategies for enhancement in food production

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I. ANIMAL HUSBANDRY
-    It is the agricultural practice of breeding and raising livestock by applying scientific principles.
-    It deals with
o The care & breeding of livestock (buffaloes, cows, pigs, horses, cattle, sheep, camels, goats, bees, silkworms etc).
o Poultry farming and fisheries.
-    More than 70% of the world livestock population is in India & China. However, the contribution to the world farm produce is only 25%, i.e., the productivity per unit is very low. Hence new technologies have to be applied to achieve improvement in quality and productivity.
Management of Farms and Farm Animals
1. Dairy Farm Management (Dairying)
-    It is the management of animals for increasing yield and quality of milk and its products.
-    Milk yield depends on the quality of breeds in the farm.
-    Selection of good breeds having high yielding potential and resistance to diseases is important.
-    For the yield potential:
o The cattle have to be well looked after – they have to be housed well, should have adequate water and be maintained disease free.
o The feeding of cattle should be carried out in a scientific manner – with special emphasis on the quality and quantity of fodder.
o Stringent cleanliness and hygiene (of cattle & handlers) while milking, storage and transport of the milk.
-    Nowadays, these processes have mechanized. It reduces chance of direct contact of the produce with the handler.
-    To ensure these stringent measures there should be
o Regular inspections, with proper record keeping. It also helps to identify and rectify the problems.
o Regular visits by a veterinary doctor.
2. Poultry Farm Management
-    Poultry is the domesticated birds used for food or eggs. E.g. chicken, ducks, turkey and geese.
-    Components of poultry farm management:
o Selection of disease free and suitable breeds.
o Proper and safe farm conditions.
o Proper feed and water.
o Hygiene and health care.
Animal Breeding
-    A breed is a group of animals related by descent and similar general appearance, features, size etc.
-    Breeding is the modification of genotype of an organism to make that organism more useful to humans.
-    Animal breeding aims at increasing the yield of animals and improving the desirable qualities of the produce.
-    Breeding is 2 types: Inbreeding and out-breeding.
a. Inbreeding
It is the mating of more closely related individuals within the same breed for 4-6 generations. This strategy is as follows:
o Superior males and superior females of the same breed are identified and mated in pairs.
o The progeny obtained are evaluated and superior males and females among them are identified for further mating.
In cattle, a superior female produces more milk per lactation. A superior male (bull) gives rise to superior progeny.
Advantages of Inbreeding:
o It increases homozygosity to evolve a pure line animal.
o It exposes harmful recessive genes that are eliminated by selection.
o It helps in accumulation of superior genes and elimination of less desirable genes. This approach increases the productivity of inbred population.
Continued inbreeding, especially close inbreeding, may reduce fertility and productivity. This is called inbreeding depression. To solve this problem, selected animals should be mated with unrelated superior animals of the same breed.
b. Out-breeding
It is the breeding of the unrelated animals. It includes out-crossing, cross-breeding and inter-specific hybridization.
i)  Out-crossing:
-    This is mating of animals within the same breed, but having no common ancestors on either side of their pedigree up to 4-6 generations.
-    The offspring of such a mating is known as out-cross.
-    It is the best method for animals having low productivity in milk production, growth rate in beef cattle, etc.
-    It helps to overcome inbreeding depression.
ii)  Cross-breeding:
-    In this method, superior males of one breed are mated with superior females of another breed.
-    The desirable qualities of 2 different breeds are combined.
-    The progeny hybrid animals may be used for commercial production or may be subjected to inbreeding and selection to develop new stable superior breeds.
-    E.g. Hisardale (sheep) developed in Punjab by crossing Bikaneri ewes and Marino rams.
iii)  Interspecific hybridization:
-    It is the mating of male and female of two different species.
-    In some cases, the progeny may combine desirable features of both the parents, and may be of considerable economic value. E.g. Mule (male ass X female horse).
Controlled breeding experiments
-    These are carried out using artificial insemination.
-    The semen collected from male parent is injected into the reproductive tract of selected female by the breeder.
-    The semen may be used immediately or can be frozen and used later. It can also be transported in a frozen form to where the female is housed.
-    Success rate of crossing mature male & female animals is low even though artificial insemination is carried out.
Multiple Ovulation Embryo Transfer
Technology (MOET)
-    It is a programme for herd improvement.
-    In this, a cow is administered hormones, with FSH-like activity, to induce follicular maturation and super ovulation (production of 6-8 eggs per cycle instead of one egg).
-    The animal is either mated with an elite bull or artificially inseminated. Fertilised eggs at 8–32 cells stages are recovered and transferred to surrogate mothers.
-    This technology has been demonstrated for cattle, sheep, rabbits, buffaloes, mares, etc.
-    High milk yielding breeds of females and high quality (lean meat with less lipid) meat-yielding bulls have been bred successfully to increase herd size in a short time.
Bee-keeping (apiculture)
-    It is the maintenance of hives of honeybees for the production of honey and beeswax.
-    Honey is a food of high nutritive and medicinal value.
-    Beeswax is used for preparation of cosmetics, polishes etc.
-    Bee-keeping can be practiced in any area where there are sufficient bee pastures of some wild shrubs, fruit orchards and cultivated crops.
-    Most common species that can be reared is Apis indica.
-    Important points for successful bee-keeping:
(i)     Knowledge of the nature and habits of bees.
(ii)   Selection of suitable location for keeping beehives.
(iii) Catching and hiving of swarms (group of bees).
(iv)  Management of beehives during different seasons
(v)    Handling and collection of honey and of beeswax.
-    Bees are the pollinators of many of our crop species such as sunflower, Brassica, apple and pear.
-    Keeping beehives in crop fields during flowering period increases pollination. It improves crop and honey yield.
Fisheries
-    Fishery is an industry of catching, processing or selling of fish, shellfish or other aquatic animals (prawn, crab, lobster, edible oyster etc).
-    Freshwater fishes: Catla, Rohu, common carp etc. Marine fishes: Hilsa, Sardines, Mackerel, Pomfrets etc.
-    Fisheries provide income and employment to millions of fishermen and farmers.
-    Aquaculture and pisciculture are the techniques to increase the production of aquatic plants and animals.
-    Blue Revolution: The development and flourishing of the fishery industry.
II. PLANT BREEDING
-    It 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.
-    Green Revolution: The development and flourishing of the agriculture. It was dependent on plant breeding.
-    Classical plant breeding involves hybridization of pure lines and artificial selection to produce desirable traits.
-    Now plant breeding is carried out by using molecular genetic tools.
-    Desirable traits that breeders have tried to incorporate:
o Increased crop yield.
o Improved quality.
o Increased tolerance to environmental stresses (salinity, extreme temperatures & drought), resistance to pathogens.  
o Increased tolerance to insect pests.
Steps of breeding
(i) Collection of genetic variability
-    In many crops pre-existing genetic variability is available from wild relatives of the crop.
-    Collection and preservation of all the different wild varieties, species and relatives of the cultivated species is a pre-requisite for effective exploitation of natural genes.
-    The entire collection of plants/seeds having all the alleles for all genes in a given crop is called germplasm collection.
(ii) Evaluation and selection of parents
-    The germplasm is evaluated so as to identify plants with desirable combination of characters.
-    Selected plants are multiplied and used for hybridisation.
-    Pure lines are created wherever desirable and possible.
(iii) Cross hybridisation among the selected parents
-    The desired characters have to be combined from two different plants (parents). E.g. high protein quality of one parent is combined with disease resistance from another parent. This is possible by cross hybridizing the two parents to produce hybrids that genetically combine the desired characters in one plant.
-    Limitations:
o This is a very time-consuming and tedious process.
o The hybrids may not combine the desirable characters. Usually only one in few hundred to a thousand crosses shows the desirable combination.
(iv) Selection and testing of superior recombinants
-    It is crucial to the success of the breeding objective and requires careful scientific evaluation of the progeny.
-    It yields plants that are superior to both of the parents.
-    These are self-pollinated for several generations till they reach a state of uniformity (homozygosity), so that the characters will not segregate in the progeny.
(v) Testing, release & commercialization
-    The newly selected lines are evaluated for their yield and other agronomic traits of quality, disease resistance, etc.
-    This is done by growing them in the research fields and recording their performance under ideal fertiliser application irrigation and other crop management practices.
-    The evaluation is followed by testing the materials in farmers’ fields, for at least 3 growing seasons at several locations in the country, representing all the agro climatic zones. The material is evaluated in comparison to the best available local crop cultivar (a check or reference cultivar).
Wheat and Rice:
-    The development of high yielding varieties of wheat and rice in the mid-1960s, through plant breeding techniques has increased food production in our country. This phase is known as the Green Revolution.
-    During the period 1960-2000, wheat production increased from 11 million tons to 75 million tons. The rice production went up from 35 million tons to 89.5 million tons.
-    Nobel laureate Norman E. Borlaug (International Centre for Wheat & Maize Improvement, Mexico) developed semi-dwarf wheat. In 1963, high yielding and disease resistant varieties such as Sonalika & Kalyan Sona were introduced all over the wheat-growing belt of India.
-    Semi-dwarf rice varieties were derived from IR-8, (developed at International Rice Research Institute (IRRI), Philippines) and Taichung Native-1 (from Taiwan). Later better-yielding semi dwarf varieties Jaya and Ratna were developed in India.
Sugar cane: Saccharum barberi (grown in north India, but poor sugar content & yield) was crossed with Saccharum officinarum (tropical canes in south India, thicker stems and higher sugar content but do not grow well in north India) and got a hybrid sugar cane having desirable qualities like high yield, thick stems, high sugar and ability to grow in north India.
Millets: Hybrid maize, jowar & bajra developed in India. It includes high yielding varieties resistant to water stress.
Plant Breeding for Disease Resistance
-    It enhances food production and helps to reduce the use of fungicides and bactericides.
-    Resistance of the host plant is the genetic ability to prevent the pathogens from disease.
-    Some plant diseases:
o Fungal: Rusts (E.g. brown rust of wheat, red rot of sugarcane and late blight of potato).
o Bacterial: Black rot of crucifers.
o Viral: Tobacco mosaic, turnip mosaic, etc.
Methods of breeding for disease resistance: Include conventional breeding techniques & mutation breeding.
1. Conventional method: The steps are:
o Screening germplasm for resistance sources.
o Hybridisation of selected parents.
o Selection and evaluation of the hybrids.  
o Testing and release of new varieties.
Some crop varieties bred by this methods:
Crop
Variety
Resistance to
Wheat
Himgiri
Leaf & stripe rust, hill bunt
Brassica
Pusa swarnim (Karan rai)
White rust
Cauliflower
Pusa Shubhra, Pusa Snowball K-1
Black rot and curl Blight black rot
Cowpea
Pusa Komal
Bacterial blight
Chilli
Pusa Sadabahar
Chilly mosaic virus, Tobacco mosaic virus, and leaf curl.
-    Conventional breeding is constrained by the availability of limited number of disease resistance genes.
2. Mutation breeding:
Mutation (creation of genetic variations) can create new desirable characters not found in the parental type.
Plants having these desirable characters can be multiplied directly or can be used in breeding.
Mutation breeding is the breeding by mutation through use of chemicals or radiations (like gamma radiations), and selecting and using the plants that have desirable character as a source in breeding.
E.g. In mung bean, resistance to yellow mosaic virus and powdery mildew were induced by mutations.
-    Resistant genes from wild species are introduced into the high-yielding cultivated varieties. E.g. Resistance to yellow mosaic virus in bhindi (Abelmoschus esculentus) was transferred from a wild species and resulted in a new variety called Parbhani kranti.
-    Transfer of resistance genes is achieved by sexual hybridisation between the target and the source plant.
Plant Breeding for Developing Resistance to Insect Pests
-    Insect resistance in host crop plants may be due to morphological, biochemical or physiological characteristics.
o Hairy leaves: e.g., resistance to jassids in cotton and cereal leaf beetle in wheat.
o Solid stems in wheat: lead to non-preference by the stem sawfly.
o Smooth leaved and Nectar-less cotton varieties do not attract bollworms.
o High aspartic acid, low nitrogen and sugar content in maize leads to resistance to maize stem borers.
-    Sources of resistance genes for breeding are cultivated varieties, germplasm collections of crop or wild relatives.
Some crop varieties bred for insect pest resistance:
Crop
Variety
Insect pests
Brassica (rapeseed mustard)
Pusa Gaurav
Aphids
Flat bean
Pusa Sem 2,
Pusa Sem 3
Jassids, aphids & fruit borer.
Okra (Bhindi)
Pusa Sawani,
Pusa A-4
Shoot and Fruit borer
Plant Breeding for Improved Food Quality
-    More than 840 million people in the world do not have adequate food.  3 billion people suffer from micronutrient, protein and vitamin deficiencies (‘hidden hunger’).
-    Biofortification (breeding crops with higher levels of nutrients) helps to improve public health.
-    Objectives of breeding for improved nutritional quality:
§  To improve Protein content and quality.
§  To improve Oil content and quality.
§  To improve Vitamin content.
§  To improve Micronutrient and mineral content.
-    Examples for hybrids with improved nutritional quality:
o Maize hybrids having twice the amount of amino acids, lysine & tryptophan compared to existing maize hybrids.
o Wheat variety, Atlas 66, having high protein content.
o Iron-fortified rice variety containing over five times as much iron as in common varieties.
o Vegetable crops rich in vitamins & minerals: released by Indian Agricultural Research Institute, New Delhi.
E.g. vitamin A enriched carrots, spinach, pumpkin; vitamin C enriched bitter gourd, bathua, mustard, tomato; iron & calcium enriched spinach & bathua; and protein enriched beans (broad, lablab, French & garden peas).
III. SINGLE CELL PROTEIN (SCP)
-    It is an alternate source of proteins for animal and human nutrition. E.g. microbes like Spirulina.
-    Spirulina is rich in protein, minerals, fats, carbohydrate & vitamins. It is grown on materials like waste water from potato processing plants, straw, molasses, animal manure & sewage. This also reduces environmental pollution.
-    A 250 Kg cow produces 200 g of protein/day. In the same period, 250g of a micro-organism like Methylophilus methylotrophus produce 25 tonnes of protein.
IV. TISSUE CULTURE
-    A technique of growing plant cells/tissues/organs in sterile culture medium under controlled aseptic conditions.
-    The ability to generate a whole plant from any cell/explant is called totipotency. An explant is any part of a plant that is grown in a test tube under sterile nutrient media.
-    The nutrient medium must provide a carbon source (such as sucrose), inorganic salts, vitamins, amino acids and growth regulators like auxins, cytokinins etc.
-    The method of producing thousands of plants in very short time through tissue culture is called micropropagation.
-    These plants will be genetically identical to original plant, from which they were grown, i.e., they are somaclones.
-    Tomato, banana, apple etc. are produced using this method.
-    Tissue culture is also used for recovering healthy plants from diseased plants. The meristem (it will be free of virus) from infected plant is removed and grown it in vitro to obtain virus-free plants. Scientists have cultured meristems of banana, sugarcane, potato, etc.
-    Somatic hybridization: Protoplasts from two different varieties of plants (with desirable characters) are fused to get hybrid protoplasts. It can be grown to form a new plant called somatic hybrids. This process is called somatic hybridization. Protoplasts can be isolated after digesting the cell walls of single cells of plants.
A protoplast of tomato has been fused with that of potato, to form new hybrid plants with the characteristics of tomato and potato. But it has no all desired characteristics for its commercial utilization.


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