NEET Biology Notes Biology and Human Welfare Plant Breeding
It is the purposeful manipulation of plant, species in order to create desired plant types tliat are better suited for cultivation, give better yield,and are disease resistant.
The first and foremost aim; ifr.plant breeding is to create useful variation in the crop plant.
This can be achieved by:
- Bringing wild food crops for cultivation as, e.g. wheat, oats and many cereal crops were once wild plants, which had now been domesticated.
- Obtaining genes from desirable plants or related species, e.g. as seeds from various parts of the world.
- Introduction of plants from nearby regions or even from other countries for improvement of the crop, e.g. cauliflower, tpmato, potato and soybean.
- By employing certain plant breeding techniques, new varieties are developed, e.g. maize, Sorghum, cotton and sunflower.
- Auto and allopolyploid breeding.
- By inducing mutations using physical and chemical mutagens.
- Production of haploids by the application on plant tissue culture of anther and ovary.
- Improvement of nutritional quality, by genetic engineering, e.g. fortified rice, iron rich rice and carotene rich rice.
- Development of disease, drought and environmental stress resistant varieties.
Selection in Plant Breeding
It is the oldest method of plant breeding, in which individual plant or group of plants are sorted out from mixed population, thus eliminating undesirable ones. The selection methods include mass selection, pure line selection and clonal selection.
Mass Selection Method
In mass selection method, plants are selected based on their desirable morphological characters (phenotype).
Some crop varieties developed by mass selection are as follows:
Pure Line Method
A pure line is a collection of plants obtained as a result of repeated self-pollination from a single homozygous individual. Hence, a variety formed by this method shows more homozygosity with respect to all genes.
Some crop varieties developed by pure line selection are
Clonal Selection Method
It is used for crops like sugarcane, potato, tea, banana and certain species of grasses which are asexually propagated and produce very poor seeds.Some crop varieties developed by clonal selection are
It is an offspring of a cross between two genetically unlike individuals.
It is the method of producing new crop varieties, in which . two or more plants of unlike genotype (genetically dissimilar) are crossed.
The first natural hybridisation was reported in corn (maize) by Mather, whereas first artificial hybrid was obtained by Thomas Fairchild, who is known as Fairchild Mule.
Hybridisation can be ifttravarietal (i.e. cross between two plants of the same variety having different genotypes), intervarietal (i.e. cross between the plants of different varieties of the same species), interspecific or intrageneric (i.e. cross between two different species of the same genus) and intergeneric hybridisation (i.e. cross between the plants belonging to different genera of the same family).
Some crop varieties developed by hybridisation are
It involves the fusion of protoplasts of two different species, which resulted into hybrid formation. The fusion of protoplasts from two different varieties can be enhanced by treating them with the chemical called Polyethylene Glycol (PEG) in the presence of high voltage electric current on a suitable medium. This method in plant breeding is called protoplasmic fusion.
Emasculation is the removal of anthers or male reproductive part from flowers of female parents before maturity or before anthesis (i.e. first opening of flower) or before\bursting of anthers. Emasculation is a step in hybridisation
It is the mating between individuals related by descent or ancestry. The main effect of inbreeding is an increase in homozygosity in the progeny.Inbreeding depression is the reduction or loss in vigour and fertility as a result of inbreeding. A wheat variety Sharbati Sonora was produced from Sonora-64, by mutation breeding using gamma rays, NP-386 (wheat), Jagannath (rice), Arana (castor), MU-7 and Indore-2 (cotton), Pusa Lai Meerati (tomato) and Primex (white mustard) are some new varieties, which are developed by mutation breeding.
It is the mating between individuals related by descent or ancestry. The main effect of inbreeding is an increase in homozygosity in the progeny.
Inbreeding depression is the reduction or loss in vigour and fertility as a result of inbreeding.
A wheat variety Sharbati Sonora was produced from Sonora-64, by mutation breeding using gamma rays, NP-386 (wheat), Jagannath (rice), Arana (castor), MU-7 and Indore-2 (cotton), Pusa Lai Meerati (tomato) and Primex (white mustard) are some new varieties, which are developed by mutation breeding.
The breeding of crops with the higher levels of vitamins and minerals or higher proteins and healthier fats is called biofortification.
Examples of biofortified plant foods are enriched carrots, spinach, pumpkin, vitamin-C, enriched bitter gourd, bathua, mustard, protein enriched beans broad, lab-lab, French and garden peas.
Single Cell Proteins (SCP)
Single cell protein is protein rich biomass produced by unicellular and multicellular organisms like bacteria, fungi, yeast, algae, etc. These organisms are processed and used as human food.
Tissue culture technique is based on the totipotency (i.e. ability of a cell to give rise to whole plant) of plant cell. The concept of totipotency was given by Haberlandt (1902) and detailed practical applications of totipotency was shown by Steward (1932), who developed a complete carrot plant from a root cell.
NE Borlaug, a famous Mexican plant breeder, was awarded by a Nobel Peace Prize (1970) for developing high yielding dwarf varieties such as Sonora-64 and Lerma Rojo-64. He is also known as Father of Green Revolution. NE Borlaug developed semi-dwarf wheat varieties by using Norin-10 gene (dwarfing gene) from a Japanese variety and semi-dwarf rice varieties.
Dr. MS Swaminathan is the pioneer in mutation breeding. He is also known as founder of radiation genetics and Father of Green Revolution in India.
India received semi-dwarf wheat material from Mexico and introduced Lerma Rojo and Sonora-64 varieties.
IR-36 is a rice variety, developed by a team of IRRI (Philippines) scientists led by Dr. Gurudev S Khush. It is the most widely planted variety in history.
Types of pesticide and their examples are as follows:
The science of rearing, caring, feeding, breeding, improvement and utilisation of domesticated animals is called animal husbandry.
The domesticated animals kept for use or profit are collectively called live stock. The live stock of India can be categorised into milk yielding animals meat and egg yielding animals utilised as motive power and wool yielding animals.
Dairy Farm Management
Dairying is the management of animals for milk and its products for human consumption. Milk yield is dependent primarily on the quality of breeds.
The following are requirements for good dairy management:
- Sufficient and nutrient-rich fodder; clean water and proper shelter.
- Disease-free conditions and hygiene should be maintained.
The rearing and breeding of fishes in ponds, artificial water reservoirs is known as pisciculture.
Some freshwater fishes found in India are as follows:
The production of raw silk from the silk worm by rearing practices on commercial scale is called sericulture.
Silk is obtained from six species of silk worm,
i. e. mulberry silkworm (Bombyx mon), tasar silk worm [Antheraea paphia), muga silk worm (Antheraea assama), eri silk worm [Attacus ricinni), oak silk worm [Antherae pemyi) and giant silk worm (Attacus alias).
It is the rearing of honey bees on commercial scale, four species of honey bees are reported in different parts of India, i.e. Apis florea (little bee), Apis indica (Indian bee), Apis dorsata (rock bee) and Apis mellifera (European bee). European bee is the best species for commercial point of view.
Bees communicate with one another by dance language. Round dance indicates the closeness of food source from hive, while tail wagging dance indicates distance and direction of food source. Prof K von Fritsch succeded in recording of honeybee dance and honoured by Nobel Prize.
Nosema disease caused by protozoan Nosema apis.
The term ‘poultry’ means rearing of fowls, ducks, geese, turkeys and some varieties of pigeons but more often is used for fowl rearing. Fowls are reared for food or for their eggs. Poultry birds are reared for meat are called broilers. Layers are female fowls being raised for egg production. Cockerel is a young male fowl. Rooster is the mature male fowl. The hens normally starts egg laying from February and continue till August with some intervals. The average production of an Indian breed is about 60 eggs per annum.
Poultry Farm Management
The rearing of fowls, ducks, turkeys and some varieties of pigeons is called poultry.
The important points of poultry management are
- Selection of disease-free and suitable breeds.
- Proper feed and water.
- Safe and hygenic shelter.
The most common disease amongst fowls is Ranikhet disease or new castle disease, which is caused by a virus. In this disease, bird opens the beak, becomes thirsty and suffers from fever and yellowish white diarrhoea occurs.
Microbes in Human Welfare
Microbes are microscopic organisms, i.e. can be seen only under a microscope. The diverse microbes are viruses, viroids, bacteria, fungi, protozoans and certain algae. These like bacteria and fungi can be cultured on nutritive media to form colonies in the laboratory. Microbes can be useful as well as also harmful.
The useful aspects of microbes are given below:
Microbes in Household Food Processing
Curd is produced by Lactobacillus and other Lactic Acid Bacteria (LAB), which grow in milk and convert it into curd.
Dough is fermented product by bacteria. The puffed up. appearance is due to the C02 produced during fermentation. Toddy is produced by fermenting coconut water and sap from planes.
Cheese differs in texture, flavour, taste, depending on the microbe used for fermentation,
e.g. Swiss cheese
Bioactive molecules like cyclosporin (Immuno Suppressive Agent) statins (lowers blood cholesterol levels) are prepared using a fungus Trichoderma polysporum and a type of yeast Monascus purpureus, respectively.
Organic acids are made by using different microbes, e.g. citric acid (Aspergillus niger- fungus),acetic acid [Acetobacter
aceti-bacterium), lactic acid (Lactobacillus delbrueckii – bacterium), etc.
Some of the important acids, their sources and applications are listed below:
Microbes in Industrial Products
In industries, microbes are employed to produce beverages, antibiotics, organic acids, enzymes, bioactive molecules, etc.
Beverages like whisky, rum and brandy, wine and beer and made by using different types of raw materials using yeast, Saccharomyces cerevisiae.
Antibiotics like penicillin is obtained from the fungus Pénicillium notatum.
Enzymes are produced with the help of microbes are lipases, proteases and pectinases.
Microbes in Sewage Treatment
Sewage contains a large amount of organic matter and microbes. This cannot be discharged into natural water bodies like rivers directly. Treatment of sewage is done by the heterotrophic microbes naturally present in sewage. This treatment is carried in two stages as primary treatment and secondary treatment.
This treatment step basically involves physical removal of particles, i.e. large and small, from the sewage through filtration and sedimentation.
Secondary Treatment or Biological Treatment
The primary effluent is passed into large aeration tanks, where it is constantly agitated mechanically and air is pumped into it. This allows vigorous growth of useful aerobic microbes into floes (masses of bacteria associated with fungal filaments to form mesh-like structures). While growing, these microes consume the major part of the organic matter in the effjuqnt. This significantly reduces the Biochemical Oxygen Demand (BOD) of the effluent.
Microbes in Energy Generation
Biogas in a mixture of gases (mainly methane) produced by the microbial activity and which as used as fuel.
Methanogen like Methanobacterium produce large quantities of methane along with carbon dioxide and hydrogen by acting on cellulosic compound. Cattle dung is used for the production of biogas as it contains cellulosic material as well as methanogens.
Microbes as Bicontrol Agents
- Biocontrol refers to the use of biological methods for controlling plant diseases and pests.
- Bacillus thuringiensis is the most widely applied species of bacteria used for biological cqptpol with at least three sub-species used to control Lepidopteran (moth, butterfly), Coleopteran (beetle) and Dipteran (true flies) insect pests.
- Doom is another bacterial pesticide, which is a mixture of Bacillus papillae and Bacillus leniimorbus, which has been commercially used for controlling Japanese beetle Popilliae. Bacillus sphaericus is toxic to larvae of Anopheles mosquito.
- The first bioherbicide was a mycoherbicide, which was based on a fungus Phytophthora palmivora in 1981 to control the growth of milk weed in Citrus orchards.
- Fungi that causes diseases in insects are known as entomopathogeniq fungi, including at least fourteen species of entomophthoraceous fungi which attack aphids.
- Beauveria bassiana is used to manage different types of pests such as white flies, thrips, aphids and weevils.
Microbes as Biofertilisers
The two groups of organisms used as biofertilisers are bacteria and cyanobacteria.
Bacteria These fix atmospheric nitrogen and enrich soil nutrients. Rhizobium is symbiotic and others are Azospirillum and Azotobacter.
Cyanobacteria Function as biofertilisers by fixing atmospheric nitrogen and increase organic matter of the soil through the photosynthetic activity, e.g. Anabaena, Nostoc, Oscillatoria, etc.