Samacheer Class 12 Bio Botany - Plant Breeding

Primary introduction
Secondary introduction
1. The introduced Variety is well adapted to the new environment.
2. There is no alternation to the original genotype
1. The introduced Variety is subjected to selection
2. The introduced Variety is subjected to selection
3. That variety is hybridized with a local variety to transfer one or a few characters to them.
–
Example:
Tea varieties collected from china and North East India initially grown in Botanical garden of kolkate from which appropriate clones have selected and introduced to different parts of India.

Biofertilizers or microbial innoculants are defined as preparations containing living cells or latent cells of efficient strains of microorganisms that help crop plants uptake of nutrients by their interactions in the rhizosphere when applied through seed or soil.
They are efficient in fixing nitrogen, solubilising phosphate and decomposing cellulose. They are designed to improve the soil fertility, plant growth, and also the number and biological activity of beneficial microorganisms in the soil. They are ecofriendly organic agro inputs and are more efficient and cost effective than chemical fertilizers.

Types of hybridization:
(i) Intravarietal hybridization:
The cross between the plants of same variety. such crosses are useful only in the self. pollinated crops.
(ii) Intervarietal hybridization:
The cross between the plants belonging to two different varieties of the same species and is also known as intraspecific hybridization.
(iii) Interspecific hybridization:
The cross between the plants belonging to different species belonging to the same genus is also called intragenic hybridization.
Example:
Gossypium hirsutum
Gossypium arboreum
(v) Intergeneric hybridization:
* The crosses are made between the plants belonging to two different genera.
* The disadvantages are hybrid sterility time consuming and expensive procedure.
Example: Raphanobrassica x Triticale

Mutation breeding represents a new method of conventional breeding procedures as they have the advantage of improving the defect without losing an agronomic and quality character in agriculture and crop improvement. Mutation means the sudden heritable changes in the genotype or phenotype of an organism. Gene mutations are of considerable importance in plant breeding as they provide essential inputs for evolution as well as for recombination and selection. It is the only method for improving seedless crops.

* The superiority of the FI hybrid in performance over its parents is called heterosis or hybird vigour.
* G.H. Shull was the first scientist to use the term heterosis in 1912.
* Heterosis are of the following types.
* Euheterosis, Mutational Euheterosis, Balanced Euheterosis and Pseudoheterosis
(i) Euheterosis:
This is the true heterrosis which is inherited and is further classified as.
(a) Mutational Euheteosis:
Simplest type of euheterosis and results from the sheltering or eliminating of the deleterious unfavourable often lethal, recessive, mutant genes by their adaptively superior dominant alleles in cross pollinated crops.
(b) Balanced Euheterosis:
well balanced gene combinations which is more adaptive to environmental conditions and agricultural usefulness.
(ii) Psuedohetrosis:
Also termed as luxuriance progeny possess superiority over parents in vegetative growth but not in yield and adaptation usually sterile or poorly fertile.

New Breeding Techniques (NBT) are a collection of methods that could increase and accelerate the development of new traits in plant breeding. These techniques often involve genome editing, to modify DNA at specific locations within the plants to produce new traits in crop plants. The various methods of achieving these changes in traits include the following.
* Cutting and modifying the genome during the repair process by tools like CRISPR /Cas.
* Genome editing to introduce changes in a few base pairs using a technique called Oligonucleotide-directed mutagenesis (ODM).
* Transferring a gene from an identical or closely related species (cisgenesis).
* Organizing processes that alter gene activity without altering the DNA itself (epigenetic methods)
12th Bio Botany Guide Plant Breeding Additional Important Questions and Answers
I. Match the Following

c) Clostridium
IX. Fill in the blanks.
1. De candolle in his ……………. studied 247 caltivated plants.
Origen of cultivated plants
2. Bamboo eas demesticated by ……………….
China
3. He was an eminet Sorghum breeder,devoloped World’s first hybrid of Sorghum CSH-1.
N.G.P.Rao.
4. ……………… is used as a biofertilizer for wetland rice cultivation
Azolla.
5. Vavilov in the year ………………. converted 8 main geographic centres of origin to 12
1935
6. Harlan says that the centre of crop plants means the places of ……………… origin of the crop plants.
Agricultural
7. The ……………… was domesticate only in the Chiloe centre
Potato
8. ………………. could be also called as Bioinoculants
Biofertilizers
9. C.T.Patel devoloped World’s first …………….. hybrid
Cotton
10. Choudhary ram dhan made …………….. as punjab granary of India.
Wheat
11. Azdla is used as biofertiliser for wetland rice cultivation and is known to contribute ……………./ha/crop.
40-60 kg
12. …………….. is Associated with Phycomycetous fungi and angiosperm roots.
Arbuscular Mycorhizzoe
13. ……………… contains Auxin,Cytokinin and Gibberellins
Seaweed liquid fertiliser
14. ……………… species are free living fungi that are common in soil and root ecosystem
Trichoderma
15. Damping of tomato is caused by ……………..
Rhizoctonia Solani
16. It is one of the most important green manure crops
Tephrosia Purpurea
17. The double helix structure of DNA was identified by ……………. and …………….
James Watson,Francis Crick
18. By 2050 we will …………….. need more food to feed the rapid growing population.
50%
19. Crop domestication started early during ……………….
10,000 Bc
20. ………………. Corn was developed using targetted breeding.
Waxy
21. Rice variety of ……………. introduced from Philippines
IR8
22. NBPGR is located in Chennai at …………………..
Meenembakkan
23. Introduced plants get adapted to the new environment is called as ……………….
Acclimatization
24. Tea varieties collected from China and North East India initially grown in Botanical garden of ……………….
Kolkatta
Selection
25. ______ is the oldest and basic method of plant breeding
Preliminary
26. In clonal selection …………… yield trial takes place during 3rd year.
Intrageneric
27. Interspecific hybridization is also called as _____
hybridization
28. Green revolution scheme began in ……………. in 1940’s.
Mexico
29. In 2005 …………….. organized a first ever traditional paddy seed festival in his farm as an individual.
Nel jayaraman
30. …………… is a cleaving protein.
Cas9
X. Two Marks

* Archeological evidence for earliest record of agriculture is found in the fertile crescent region in and around Tigris and Euphrates river valleys, approximate about 12,000 years
ago

• Initially he proposed eight main geographic centres of origin.
• Later by dividing few centres into two or three centres and added a new centre USA.
• Thus making the 8 centres of Origin into 12.

• All the introduced Crop must be free from presence of weeds, insects and disease causing Organisms.
• It has to be carefully examined by the process called quarantine.
• A strict isolation imposed to prevent the spread of disease.

• This is a rule in the nature.
• It results in evolution reflected in the Darwinian’s principle survival of the fittest.
• It takes longer time to bring about desired Variation.

• It is a form of mutation breeding.
• The Radioactive sources are cobalt – 60 and Caesium -137
• The first Gamma Garden in India is Bose Research institute at Calcutta.

Crop
Variety
Insect pests
Brasica (rapeseed mustard)
Flat been
Okra (Bhindi)
Pusa Gaurav
Pusa Sem 2, Pusa Sem 3
Pusa Sawani, Pusa A
Aphids
Jassids, aphids and fruit borer
Shoot and Fruit borer

Tissue culture is the modern artifical reproductive technique.
Reasons:
* large scale production of clones (genitically uniform population) from the callus tissue – developed from the chosen explant cells (invitro)
* Both crop and tree species useful in forestry can be produced with desirable characters in large numbers with in a short span of time.

• Azolla is a free floating water fern that fixes atmospheric nitrogen in association with nitrogen fixing blue green algae. Anabaena azolla.
• It is used as a bio-fertilizer for wetland rice cultivation and is known to contribute 40-60 kh/hal/crop.

Biofertilizers
Green Manure
It is defined aspreparations containing living or latent cells of efficient strains of micro organisms
It is defined as the growing of green manure crops and use of these crops directly in the field by ploughing
It helps the crops uptake of nutrients, when they are applied through seed or soil.
It helps in increasing the content of nitrogen in the soil.
In improve soil fertility and ecofriendly
It helps in improving the structure and physical properties of the soil.

Pureline Selection
Clonal Selection
It is a collection of plant obtained as a result of repeated self pollination from a single homozygous individual.
It is asexually propagated and the clonal selection is employed to select improved variety from a mixed population.
The progeny shows more. homozygosity with respect to all genes.
The progeny resemble in genetic constitution with the parent plant as they are mitotically divided

Mutation Breeding
Polyploid Breeding
Mutation means the sudden heritable changes in the genotype or phenotype
The plants which possess more than two sets of chromosomes are called polyploids.
It is of considerable importance in plant breeding as they provide essential inputs for evolution as well as for recombination and selection.
Poly ploidy often exhibit increased hybrid vigour and increased heterozygosity.

Intervarietal Hybridization
Interspecific Hybridization
The cross between the plants of two different varieties of the same species.
The cross between the plants of two different species.
This technique has been the basis of improving self pollinated as well as cross pollinated crops.
It is commonly used for transferring the beneficial genes from one species to another.
XII. Three marks

• It is as alternative agricultural system.
• It is due to rapidly changing farming practices.
• It is a production system that sustains the health of the soils, ecosystems and people.
• It is based on ecological processes biodiversity and cycles adapted to local conditions

• It is an entomo-pathogenic fungi
• It acts as a parasite on various arthropod that causes white muscardine disease.
• It also controls datnping off of tomato caused by Rhizoctonia Solani.

The Green revolution or thrid Agricultural Revolution is the intensive plan of 1960’s to increase crop yield in developing countries by introducing the high yielding, resistant varieties, increased irrigation facilities, fertilizer application and better agricultural management.

• It is responsible for introduction and maintence of germplasm of various agricultural and horticultural station in our country.
• It is also responsible for maintenance of plant materials of botanical and medicinal interest.
• It is located at Rangpuri/New Delhi with four regional station at Amristar, Kolkata, Mumbai and Chennai.

• Hybridization is the method of producing new crop verities by crossing of plants that are genetically different.
• It offers improvement in crop by combining the desirable character of two or more varities.
• The first natural hybridization was observed by Cotton Mather in maize.

Crop
Variety
Resistance to diseases
Wheat
Himgiri
Leaf and Stripe rust, hill bunt
Brassica
Pusa swarnim (Kara 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.

* Saccharum bareri was originally grown in north India.
* It is poor sugar content and yield.
* Tropical canes grown in south India saccharurn officinarum had thicker stems and higher sugar content.
* It did not grow well in North India
* These two species were successfully crossed to get sugar cane varieties combining the desirable qualities of high yield thick stems high sugar and ability to grows in the sugar cane areas of North India.
XIII. Five Marks

• Adaption to the environmental alteration.
• Adaption to wider geographical range.
• Uniformity in flowering and fruiting.
• Increased size of fruits and seeds.
• Change in breeding system.
• Increase in yield.
• Increased resistance for disease and pest.
• Developing seedless parthenocarpic fruit.
• Enhancing the taste and nutritional composition.

* 1807 – Alexander Yon Humboldt considered that original & source of most and their origin is an importable secret.
* 1868 – Darwin’s theory proposed that natural selection and hybridization led to the origin of cultivate plants.
* 1883 – De Candolle studied 247 cultivated plants species and was able to find the ancestral form, region of domestication and history.
* 1887-1943 – Vavilov studied about the diverse forms of plants based on various criteria like morphology,cytology etc., He proposed 8 geographic centres and later developed it to 12 centres.
* 1968 – Zhukovsky put forward the concept of mega gene and divided the whole world into 12 mega gene centres.
* 1971 – Harlen believed that agriculture originated independently in three different areas.
– There were non centres are the area were the crop has been shifted.

Vavilov’s centres of crop origin and crops domesticated.
Vavilov’s centre of crop origin
Crops domesticated
1. China
Foxtail millet, soybean, bamboo, onion,.crucifers
2. India
Rice, Sugarcane, mango, orange, eggplant, sesame
2a. South East Asia
Rice, banana, coconut, clove, hemp.
3. Central East
Wheat, pea, hemp, cotton, etc.,
4. The Near East
Wheat, rye, many subtropical and tropical fruits
5. Mediterranean
Olive, vegetables, oil, yielding plants, wheats
6. Ethiopia (Abyssinian)
Wheat, barley, sesame, castor, coffee
7. Mesomerica (South Mexican & central American centre)
Maize, bean, sweet potato, papaya, guava,
tobacco
8. South America
Tomato, pine-apple
8a. South America
Potato
8b. The Brazilian-Paraguayan centre
Groundnut, cashew nut, pine apple, peppers, rubber.

* Dr.M.S.Swaminathan- He is pioneer in mutation breeder.
* Sir.T.S.Venkatraman- An eminent sugarcane breeder.
* Dr.B.P.Pal-Developed superior disease resistant varieties of wheat
* Dr.K.Ramiah- Eminent Rice Breeder.
N.G.P.Rao-An eminent sorghum breeder, developed world’s first hybrid of sorghum (CSH-1).
* C.T.Patel-Developed world’s first cotton hybrid.
* Choudhary Ram Dhan – wheat breeder,developed C-591 wheat which made Punjab as wheat granary of india.

* Bio-fertilizers could also be called as microbial cultures or bacteria) fertilizers.
* They are efficient in fixing nitrogen improve soil fertility, eco-friendly and cost effective.
Rhizobium:
* It resides in the root nodules of leguminous plants.
* It fixes the atmospheric Nitrogen.
* It increases yield of paddy by 15-40%
Azolla:
* Free floating water fern, with blue green algae fixes the Nitrogrn.
* It increases the yield of rice.
* It decomposes quickly.
Arbuscular Mycorrhizae:
* They can dissolve the phosphates found in the soil.
* It provides strength to resist disease, germ and unfavourable weather.
Seaweed Liquid Fertilizer:
* It contains cytokinin, gibberellins and Auxin
* Most of it are made from kelp ( Brown Algae).
* The alginates in it react with metals in soil and retain moisture for a long time.
* They have more than 70 minerals vitamin and enzymes.
* Seeds soaked in seaweed germinate rapidly.

* They are biologically based agents used for the control of plant pests.
* They are ecofriendly, Non – toxic and cheaper the chemical pesticide.
Trichoderma:
* They are free living fungi in the soil.
* They control plant disease.
* It has the ability to enhance root growth development.
* Increases the crop productivity.
* It helps in resisting Abiotic stress.
* It increases the uptake and use of nutrients.
Beauveria:
* It is an entomo – pathogenic fungus
* It parasitse arthropods that cause white muscardine and controls damping off of tomato

• To increase yield, Vigour and fertility of the crop.
• To increase tolerance to environmental condition, Salinity, Temperature and drought.
• To prevent premature falling of buds fruits etc.,
• To improve the maturation of both the male and female gametes at the same time.
• To develop resistance to pathogens and pests.
• To develop photosensitive and thermos – Sensitive Varieties.

* Selection is the oldest and basic method of plant breeding.
* There are two main types of selection – Natural and Artificial.
Natural Selection:
* It occurs naturally.
* It takes longer time in bringing about desired variation.
* It reflected the Darwinian principle.
Artificial Selection:
* It is a human involved process.
* Producing better crop from a mixed population.
a) Mass Selection:
* Large number of plants of similar phenotype are selected and crossed to get a new variety.
* After repeated selection for five to six years it is distributed to the farmers.
b) Pureline Selection:
* Plants obtained as a result of self pollination from a single homozygous individual.
* The progeny shows homozy gosity with respect to all genes.
* New Genotypes are never created,
c) Clonal Seection:
* The progenies that are asexually propagated resembles the parent genetically.
* The progeny is multiplied to form clone.
* The genotype of a clone remains unchanged for a long period of time.

a) Selection of Parents:
* Male and female plants of desired characters are selected.
* It should be tested for their homozygosity
b) Emasculation:
* It is removal of anther before blooming.
* It avoids self pollination
c) Bagging:
The stigma is protected against any undesirable pollen grains, by covering with a bag.
d) Crossing:
Transfer of pollen grains from selected male flower to the stigma of the emasculated female flower.
e) Harvesting Seeds and Raising Plants:
* Due to fertilization seeds form.
* These seeds are grown into a new generation.

a) Euheterosis:
* It is the true heterosis.
* It is inherited
b) Mutational Euheterosis:
* It is the simplest form.
* Removal of harmful, recessive, mutant genes by superior dominant allele in cross pollinated crops.
c) Balanced Euheterosis:
* Well balanced gene combination.
* More adaptive to environment and agricultural usefulness.
d) Psuedo heterosis:
* Also known as luxuriance.
* Progeny possess superiority over parents in regetative Growth.
* But not in yield & adaptation.
* Usually sterile or poorly fertile.

• The plants which posses more than two sets of chromosomes are called Polyploids.
• It is the major force in the evolution of both wild and cultivated plants.
• Polyploid of exhibit hybrid vigour.
• Increases tolerance to biotic and abiotic stresses.
• Polyploidy results in reduced fertility and producing seedless varieties.
• If chromosomes is doubled by itself it is autopolyploidy.
• Triploid condition in Sugarbeets result in Vigour.
• Colchicine used to double the chromosomes. Eg. Triticale and Raphanobrassica

Breeding of improved nutritional quality like
– Protein content and quality.
– Oil content and quality
– Vitamin Content
– Micro & Macro nutrient content.
* In 2000 – Maize hybrid had twice the nutrient value than the parents.
* Wheat – Atlass 66 having high protein content.
* Iron fortified rice can be developed.
* Vitamin A enriched vegetable.
* Vitamin C enriched vegetables and iron and calcium crops also developed.

• It is a collection of methods that could increase the development of new traits in plant breeding.
• It often involve genome editing.
• Cutting and modifying the genome during the repair process by tools like CRISPR.
• Genome editing to introduce changes in few base pairs using a technique called ODM.
• Transferring a gene from an identical or closely related species (Cisgenesis)
• Organising process that alter gene activity without altering the DNA itself.

(i) Somu will get the new variety. Because he had selected the mixed population method.
(ii) Advantages of self fertilization method:
The repeated self pollination from a single homozygous individual produces a variety that shows more homozygosity with respect to all genes.
(iii) Dis advantages:
* The major disadvantage of this type is that it never creates new genotypes.
* The plants produced are also less adaptible and less stable to the environmental fluctuations.
Advantages of Mixed population method
In this method, a large number of plants of similar phenotype (or) morphological characters are selected and their seeds are mixed together to constitute a newer variety’.
Disadvantages:
The disadvantage of mixed population method is that it is difficult to distinguish the hereditary variation from environmental variation.

• Prevents spread of plant disease
• Protects seed from seedling blights
• Improves germination
• Improves germination
• provides protection from storage insects
• controls soil insects.