2nd PUC Biology Notes Chapter 9 Strategies for Enhancement in Food Production

Karnataka 2nd PUC Biology Notes Chapter 9 Strategies for Enhancement in Food Production

Animal Husbandry:

→ Animal husbandry is the agricultural practise which deals with the care and breeding of livestock, [buffaloes, cows, pigs, sheep, goats etc] that are useful to human beings.

→ It is estimated that more than 70% of the world’s livestock population is in India and China, but its contribution to the world farm produce is only 25%.

→ Hence, in addition to conventional practices of animal husbandry, new technologies must also be applied to achieve improvement in quality and productivity.

Dairy Farm Management:

→ Milk yield is dependent primarily on the quality of breeds.

→ Thus selection of good breeds (having high yielding potential, combined with resistance to diseases) is very important.

→ The following are necessary for realising the yield potential:

• The animal has to be provided with proper shelter.
• Sufficient quantity of water should be given.
• Feeding of the cattle should be done in a scientific manner, considering the quantity and quality of fodder.
• The animal must be maintained disease-free.
• Stringent cleanliness and hygiene-of both the cattle and the handler are very important.

Poultry Farm Management:

→ Poultry is rearing of domesticated birds (fowl) for meat and eggs.

→ Poultry typically includes chicken and ducks and sometimes turkey and geese.

→ The important components of poultry farm management include :

• Selection of disease-free and suitable breeds.
• Proper feed and water for the birds.
• Proper and safe farm conditions.
• Hygiene and health care of the birds.

Animal Breeding:

Animal breeding aims at:
(i) Increasing the quantity of yield and improving the quality of the produce.

Note: Breed: A group of animals related by descent and similar in most characters like general appearence, features, size, configuration etc is known as a breed.
Rearing of breeds on scientific lines is called Breeding.

Breeding is of the following types:
(a) Inbreeding :
→ The breeding strategy includes the identification of superior males and females of the same breed and mating them in pairs.

→ The progeny of such matings are evaluated and superior males and females are identified for further mating.

→ Inbreeding increases homozygosity and thus inbreeding is necessary for evolving pure line in any animal.

→ Inbreeding exposes the harmful recessive alleles, which become eliminated by selection.

→ Inbreeding also helps in the accumulation of superior genes and elimination of less desirable genes.

→ But, continued inbreeding causes inbreeding depression-that reduces vigour, fertility and even productivity.

→ Under such a situation, the selected animals of the breeding population are mated with unrelated superior animals of the same breed to restore fertility and yield.

(b) Outbreeding:
→ Outbreeding refers to the breeding of unrelated animals either of the same breed having no common ancestors for 4-6 generations (out crossing) or of different breeds (cross – breeding) or even different species (inter – specific).

→ Outbreeding is of the following types :
(i) Outcrossing:

• Outcrossing is the practice of mating of animals of the same breed, but that have no common ancestors on either side of their pedigree upto 4-6 generations.
• The offspring of outcrossing, is called an outcross.
• A single outcross helps to overcome inbreeding depression.
• It is the best breeding method for animals that are below average in productivity and growth rate.

(ii) Cross-breeding:
→ It is a method of outbreeding in which superior males of one breed are mated with the superior females of another breed of the same species.

→ This helps in combining the desirable qualities of the two different breeds into the hybrid progeny.

→ The hybrid progeny may be directly used for commercial production or they may be subjected to some form of inbreeding and selection, to develop new stable breeds. One example of cross-breeding is Hisardale, a new breed of sheep developed by crossing Bikaneri ewes and Marino rams.

(iii) Interspecific hybridisation:
It is a method of outbreeding in which male and female animals of two different species are crossed to combine the desirable features of both the parents into one, e.g. Mule is produced by a cross between a male donkey and a female horse.

Bee-keeping or Apiculture:

Maintenance of hives of honeybees for the production of honey and beewax is called apiculture.
→ Honey is used as:

• Food of high nutritive value and
• Medicine in Ayurveda.

→ Beewax is used in industry for the preparation of cosmetics and polishes.

→ The most common species of honeybee is Apis indica .

→ Bee-keeping can be practised in any area where there are sufficient bee pastures (some wild shrubs, cultivated crops, fruit-orchards, etc.)

→ Beehives can be kept in any place like courtyard, verandah or on the roof of the house.

→ Bee-keeping is relatively easy and requires the following considerations:

• Knowledge of the nature and habits of bee.
• Selection of suitable location of keeping beehives.
• Catching and hiving of swamis.
• Management of beehives during different seasons.
• Handling and .collection of honey and beewax.

→ Bees are the pollinators of many crop plants (apple, pear, sunflower, Brassica, etc.) and hence keeping beehives in crop fields during flowering seasons increases pollination efficiency and thereby improves the yield.

Fisheries:

→ Fisheries refer to catching, processing or selling of fish or other aquatic animals

→ Fisheries is classified into Fin Fisheries and Shell Fisheries. Rearing of fishes is Fin Fisheries and rearing of molluscanS, crustaceans etc are included under Shell Fisheries.

→ It is an important industry for the following reasons :

• A large number of people depend of fish and fish products as food.
• It provides income and employment to millions of fishermen ill the coastal states.
• Products like fish-liver oil are of medicinal value.

→ Some common fresh water fishes are Catla, Rohu, common carp, etc.

→ Some common marine fishes are Hilsa, Sardines, Mackerel and Pomfrets.

→ Blue Revolution is the movement launched to increase the production of fish and fish products; it is being implemented in the same lines as Green Revolution.

Artificial insemination :
→ It is the process in which the semen collected from a superior male is injected into the reproductive tract of the selected female by the breeder.

→ The advantages of this practice are :

• Semen can be used immediately or stored/frozen and used at a later date when the female is in the right reproductive phase.
• Semen can be transported in the frozen form to a distant place where the selected female animals are present.
• Semen from one selected male animal can be used on a number of female animals.

→ The disadvantage is that the success rate is fairly low.

Multiple Ovulation Embryo Transfer (MOET).

→ It is a method to improve the herds,

→ The steps in the method are as follows :

• A cow is administered hormones (like FSI-I) to induce follicular maturation and super ovulation, i.e., production of 6-8 ova in one cycle.
• The cow is mated with the selected bull or artificially inseminated.
• The fertilised eggs at 8-32-celled stages are recovered and transferred to surrogate mothers.

→ This technology has been used for cattle, rabbits, mares, etc.

→ High milk-yielding breeds of females and high quality meat-yielding bulls have been bred successfully to increase the herd size in a short time.

Plant Breeding:

Plant breeding is the manipulation of plant species in order to create desired plant types that are better suited for cultivation, give better yields and are disease resistant. The various methods are selection, hybridization, polyploidy, mutation breeding and genetic engineering.

→ The list of traits that breeders have tried to incorporate into crop plants are as follows.

• High yield.
• Better quality of the produce.
• Increased tolerance to environmental stresses.
• Resistance to pathogens (diseases).
• Increased tolerance to insects and pests.

→ The main steps in breeding a new genetic variety of a crop are :

1. Collection of variability or germplasm collection.
2. Evaluation and selection of parents.
3. Cross-breeding or hybridisation of the selected parents.
4. Selection and testing of superior recombinants.
5. Testing, release and commercialization of new cultivars.

1. Collection of variability:
Collection and preservation of all the different wild varieties, species and related plants of the cultivated species is a pre-requisite for effective exploitation of natural genes available in the populations. This collection constitutes the germplasm.

2. Evaluation and selection of parents:

• The germplasm so collected is evaluated to identify plants with desirable characters.
• The selected plants are multiplied and used in the process of hybridisation.
• Pure lines are created (by repeated self-pollination) wherever possible and desirable.

3. Cross hybridisation of the selected parents:

• It involves crossing of two plants which differ in one or more desirable characters to produce a hybrid having the characters of both the parents. This is a very time-consuming and tedious process.
• Also, it is not necessary that the hybrids will combine the desirable characters.

4. Selection and testing of superior recombinants:

• First the individuals with the desired combination of characters have to be selected from among the progeny of hybrids.
• Such hybrids are superior to both of the parents (hybrid vigour/heterosis).
• They are self-pollinated for several generations till they reach a state of homozygosity so that there will be no segregation of characters in the progeny.

5. Testing, release and commercialisation of new cultiva’rs:
(a) Evaluation:

• The selected lines are evaluated for their yield and other agronomic traits, disease resistance, etc.
• Evaluation is done by growing these plants in the research fields and recording their performance under ideal conditions of irrigation, application of fertilisers and other crop management practices.

(b) Testing:

• The plants selected after evaluation are tested in the farmers’ fields for at least three growing seasons, at several locations in the country, representing different agroclimatic zones, where the crop is normally grown.
• The material is evaluated in comparison to the best available local cultivar as a reference material.

(c) Release:
→The material thus selected is certified and released as a variety.

→ There are three important plant breeding techniques, they are
(a) Hybridization
(b) Mutation breeding
(c) Polyploid breeding.

(a) Hybridization: It involves crossing of two plants which differ in one or more desirable characters , to produce a hybrid having the characters of both the parents. It includes three main types such as

1. Intraspecific;
2. Interspecific;
3. Intergeneric

e.g. Jaya, padma rice, NP-165 Wheat. Triticale [Ma] produced by crossing wheat and rye] Rabage [Radish with Cabbage]. Bromato

Note : Heterosis (= Hybrid vigour): It is the phenotypic superiority of the hybrid over either of its parents in one or more traits.

(b) Mutation breeding: Improvement of crops by changing the genotype of plants through induced mutations is called mutation breeding. Mutations can be induced by radiations or by chemicals and the agents used to induce mutations are called mutagens, e.g. Indole -2 = Cotton, Jaga’nnath rice, primax white mustard, Sharbathi sonara, a wheat variety [Produced through radiations by Dr. Swaminathan-Father of Green revolution in India].

(c) Polyploid breeding: Crop plants can also be improved by artificial induction of poly ploidy [increasing the number of sets of chromosomes] in plants, e.g. Triticum aestivum [wheat], Seedless water melon, Oryza sativa [paddy] etc.

Green Revolution:

→ It is the movement launched in 1960’s that has increased the food production not only to meet the national requirement, but also for export.

→ It was dependent to a large extent on plant breeding techniques to raise high-yielding and disease resistant varieties in wheat, rice, maize, etc.

→ Agriculture accounts for 33% of India’sdOP and employs 62% of the population.
(a) Wheat:

• Wheat production has increased from million tonnes in 1960 to 75 million tonnes in 2000; this is due to development of semi dwarf varieties.
• Norman E. Borlaug developed semi-dwarf varieties of wheat at the International Centre for Wheat and Maize Improvement in Mexico.
• Varieties of wheat like Sonalika and Kalyan Sona selected from these semi-dwarf varieties were introduced in India; they are high-yielding and disease-resistant.

(b) Rice:

• Rice production has increased from 35 million tonnes in 1960 to 89.5 million tonnes in 2000.
• Semi-dwarf rice varieties were derived from IR-8 and Taichung Native-I.
• The derivatives were introduced in India in 1966.
• Better yielding semi-dwarf varieties like Jaya and Ratna were developed in India.

(c) Sugar cane:

• Saccharum barberi, originally grown in North India, had poor sugar content.
• Saccharum officinarum, grown in South India, has thicker stems and higher sugar content.
• A cross has been made between these species and the hybrid variety, combining the desirable qualities like thick stem, high sugar content and higher yield, is being grown in North India.

(d) Millets:

• Several hybrid varieties of maize, bajra and jowar have been developed in India.
• These breeding programmes have resulted in the development of high-yielding varieties that are resistant to water stress.

Plant Breeding for Disease Resistance:

→ Plant breeding for disease resistance has two advantages :

1. Enhanced food production by reducing losses due to diseases.
2. Reduced dependence or use of fungicides and bactericides.

→ Resistance of a plant to a disease is genetically determined and it is the ability of the host plant to prevent the pathogen from causing the disease.

→ Diseases in crop plants are caused by viruses, bacteria and fungi.

→ Some examples are as follows :

• Viral Diseases – Tobacco mpsaic, Turnip mosaic.
• Bacterial Diseases – Black rot of crucifers, Citrus canker, Blight of rice.
• Fungal Diseases – Rust of wheat, Red rot of Sugar cane, Late blight of potato.

→ The conventional method of breeding for resistance includes the following steps:

• Screening the germplasm for resistant sources.
• Hybridisation of selected parents.
• Selection and evaluation of the hybrids.
• Testing and release of new varieties.

→ The resistance-gene may be present in the wild relatives, which are low yielding; hence the gene for resistance has to be incorporated into the better-yielding variety by hybridisation, e.g., the gene for resistance to yellow mosaic virus found in a wild species of bhindi has been transferred to raise a new variety of Abelmoschus esculentus, called Parbhani kranti.

Crop	Variety	Resistance to diseases
Wheat	Himgiri	Leaf and stripe rust, hill bunt
Brassica	Rusa swarnim (Karan rai)	White rust
Cauliflower	Pusa Shubhra, Pusa Snowball k-l	Black rot and curl blight black rot
Cowpea	Pusa Komal	Bacterial blight
Chilli	Pusa Sadababhar	Chilly mosaic virus Tobacco mosaic virus and Leaf curl

→ Currently mutation breeding is being’ carried out for disease-resistance, as there is limited availability of disease-resistance genes in the crop plants and their wild relatives.

→ By mutation, disease-resistance gene(s) is/are created.

→ Mutation breeding involves the following steps:

• Inducing mutation(s) through various methods/mutagens.
• Screening-the plant materials for disease-resistance.
• Multiplication ion of these selected plants for direct use dr for use in breeding.
• Hybridisation of the selected plant materials.
• Selection for disease-resistance, testing and release as a variety.

→ Through mutation breeding, varieties of mung bean have been developed that are resistant to yellow mosaic virus and powdery mildew.

Plant Breeding for Resistance to Insect Pests:

→ Resistance to insect pests is also genetically controlled and manifested, in the form of morphologcal physiological or biochemical characteristics.

Name of the crop	Characteristics	Resistance to pest (s)
wheat	Hairy leaves solid stem	Cereal leaf beetle
Cotton	Hairy leaves smooth leaves and nectraless condition	Boll worm
Maize	High aspartic acid and low, Nitrogen and sugar contents.	stem borer

→ Breeding for pest-resistance involves the same steps as breeding for disease-resistance.

→ The first step is to locate the source of resistance in the germplasm collect on.

→ The following are good sources of resistance :

• Cultivated varieties
• Wild relative species
• Germplasm collection.

Crop	Variety	Insect Pests
Brassica	Pusa Gaurav	Aphids
Flat bean	Pusa sem 2, Pusa sem    3	Jassids, aphids and fruit borer
Okra (Bhindi)	Pusa sawant Pusa A –  4	Shoot and Fruit borer

Plant Breeding for Improved Food Quality:

→ Consumption of food lacking iii essential micronutrients like vitamin A, iron, iodine and zinc can lead to diseases, reduced life span and reduced mental abilities .

→ Biofortification : breeding crops with higher levels of vitamins and minerals, or higher protein and healthier fats – is the most parctical means to improve public health.

→ Breeding for improved nutritional quality is undertaken with the objectives of improving.

• Protein content and quality.
• Oil/fat content and quality.
• Vitamin content.
• Mineral nutrients.

→ Some examples of crop varieties, with increased nutritional qualities, that have been developed ‘ and released in India, are given below :

• Lysine and tryptophan-rich varieties of maize.
• High protein variety of wheat.
• Iron – fortified variety of rice.
• Vitamin C-enriched variety of bitter gourd, tomato, mustard, bathua.
• Iron and Calcium – enriched variety of spinach and bathua.
• Protein – enriched variety of beans like, French beans, Lablab beans, broad bean and ^ garden peas.
• Vitamin A – enriched variety of carrots, spinach and pumpkin.

Single Cell Protein (SCP):

→ Single cell protein is one of the alternative sources of proteins for nutrition of humans and animals.

→ Microbes are being grown on an industrial scale as source of good protein.

→ Microbes can be grown easily on materials like waste water from potato processing plants (containing starch), straw, molasses, animal manure and even sewage, to produce large quantities and can serve as food, rich in protein, minerals, fats, carbohydrate and vitamins.

Note It has been calculated that a 250 kg cow produces 200 g of protein per day whereas 250 g of Methylophilns methylotrophus produces 25 tonnes of protein.

→ The advantages are that:

• SCPs are rich in proteins, minerals, vitamins and carbohydrates and low in fats.
• They can be easily grown with cheaper materials like wastewater from potato-processing plants, animal manure, molasses, etc.
• The use of waste materials (as culture medium) reduces pollution.
• They reduce the pressure on agriculture (for supply of pesticides, fertilizers, etc.) e.g., 250 g of Methylophilus methylotrophus bacterium has been used to produce 25 tonnesof proteins.

Tissue culture:

A branch of biotechnology jvhere isolated cells or tissues of plants or animals are grown on artificial medium to produce an entire organism or an organ is called tissue culture. This was first developed by Haberlandt [1902] The main basis for tissue culture is totipotency of the cells. The ability of a plant cell to give rise to an entire plant on the medium is called totipotency. This was first observed by F.C.Steward and the term was coined by Morgon.

Requirements for tissue culture:
The basic requirements for tissue culture are as follows.
1. Media preparation room.

2. Incubation chamber: It is provided with laminar air flow bench which helps for sterilizing and to cut the explant is into smaller parts.

3. Culture rooms: Aseptic rooms where temperature, light and humidity are maintained.

4. Source of material: Any part of desirable and disease free plant can be selected as a source. The material isolated for culture is called explant and the plant from which explant is isolated is called stock plant.

5. Medium: It is one of the basic needs for tissue culture. It is a liquid or semisolid chemical substance having organic and inorganic nutrients. Solid medium is used to culture tissues and organs whereas liquid medium is used to culture the cells and protoplasts, e.g. M.S.medium, Nitsch’s medium, White’s medium etc.

Types of tissue culture:
There are different types in tissue culture. Some of the important types are as follows.

• Protoplast culture
• Cell culture
• Embryo culture
• Meristem culture
• Root culture
• Stem culture,
• Leaf culture.
• Anther culture etc.

Steps of stem culture:
The process of stem culture involves the following steps.

1. Selection and collection of explant: A small part or piece of the plant is collected from the 1 desired and disease free plant. These plant parts taken for culture are called explant.

2. Sterilization: These, explants are then washed in sterilants [Such as chlorine water or 0.1
mercuric chloride] and then washed in distilled water. These sterilized explants are transferred to laminar air flow bench to cut them into smaller explants.

3. Inoculation: It means transferring the explants on to the medium. These stem explants are placed horizontally on the medium in culture tubes by using sterile forceps. This should be carried out in a laminar air flow cabinet. Then the mouth of culture tubes are plugged with cotton plugs and incubated at 25 to 28° C for about 7 to 10 days.

4. Callogenesis: The explants in the culture tubes divide and redivide producing undifferentiated mass of cells called callus. This process is called callogenesis. The callus may turn green and develop into microshoots or test tube plants without roots.

5. Organogenesis [Morphogenesis]: The process of producing the organs like stem, root etc from the callus is called Organogenesis, It is controlled by specific rate of auxins-cytokinins and sucrose. The shoots are made to develop from callus by keeping it in a cytokinins rich medium. The callus develops into stem and leaves without roots. The roots are produced by transferring the plants of 2-3 cm long into the medium, rich with auxins. The process of production of roots in the medium from callus or from a rootless, plant, is called rhizogenesis.

6. Hardening of acclimatization: These test tube plants are gradually exposed to environmental factors in the green houses, to develop cuticle and this process is called Hardening. These hardened plants are then transferred to pots or garden soil.

Applications of tissue culture:
The important applications of tissue culture are as follows.

1. Micropropagation: The method of rapid vegetative propagation of desired plants is called micropropagation. Large number of medicinal, ornamental and forest plants can be produced through this technique.

2. Production of virus free plants: Virus free or disease free plants can be produced through meristem culture, as the apical meristems are devoid of virus.

3. Androgenic haploid plants: Haploid plants can be produced through anther or pollen culture. Diploid homozygous plants can be produced from the haploid plants by doubling the chromosome numbers.

4. Induction and selection of mutants: Mutations are induced in the cell cultures and the mutants are then, subjected to herbicides, toxins etc. The mutant cells that show resistance are selected and grown by tissue culture to raise the resistant varieties.

5. Germplasm preservation: It refers to the storage of breeding material. The tissues of vegetatively propagated plants having desirable characters can be stored.

6. Production of transgenic plants: Genetically modified crop plants that show resistance to pests and diseases and plants producing provitamins and other hormones can be produced by tissue culture technique, e.g. Golden rice.

7. Somatic hybridization: The process of physical fusion of two different protoplasts of somatic cells of plants is called somatic hybridization. New plant varieties can be produced through this technique, e.g; pomato [by fusing the protoplast of potato and protoplast of tomato.

8. The plants in which the seed propagation can alter the desirable characters can be retained by the tissue culture method.

9. Tissue culture can be carried out in those plants where seed propagation and vegetative propagation are difficult.

2nd PUC Biology Notes