The first natural hybridization was done by Cotton Mather in maize.

(a) Okra: Pusa Sawani and Pusa A-4 varieties of Okra are resistant to shoot and fruit borers.
(b) Rapeseed mustard: Pusa Gaurav variety of rapeseed mustard shown resistance against Aphids.

Breeding crops with high vitamin, mineral, protein and fat.

Triticale (Triticum durum x Secale cereale).
Raphanobrassica (Brassica oleraceae x Raphanus sativus).

Advantage: Polyploidy often exhibit hybrid vigour and increased tolerance to biotic and abiotic stresses.
Disadvantage: Polyploidy results in reduced fertility due to meiotic error resulting in seedless varieties.

Atomic Garden: Is a form of mutation breeding where plants are exposed to radioactive sources typically cobalt-60 or caesium-137 in order to generate desirable mutation in crop plants

UV short waves, X-rays - Physical mutagens.
Nitromethyl, Urea - Chemical mutagens.

The superiority of the F1 hybrid in performance over its parents is called heterosis or hybrid vigour.

Emasculation: It is a process of removal of anthers to prevent self-pollination before anthesis (period of opening of a flower).
Bagging: The stigma of the flower is protected against any undesirable pollen grains, by covering it with a bag.

Johannsen in 1903 coined the word pureline. It is a collection of plants obtained as a result of repeated self-pollination from a single homozygous individual.

The newly introduced plant has to adapt itself to the new environment. This adjustment or adaptation of the introduced plant in the changed environment is called acclimatization.

Plant breeding is the science of improvement of crop varieties with higher yield, better quality, resistance to diseases and shorter durations which are suitable to particular environment.

Bio-pesticides are biologically based agents used for the control of plant pests. They are in high use due to their non-toxic, cheaper and eco-friendly characteristics as compared to chemical or synthetic pesticides.

Azotobacter and Clostridium

Micro organisms are efficient in fixing nitrogen, solubilizing phosphate and decomposing cellulose. They improve soil fertility, plant growth. They are ecofriendly and cost-effective than chemical fertilizers. Example. Azospirillum.

Steps involved in hybridization are as follows:
1. Selection of Parents: Male and female plants of the desired characters are selected. It should be tested for their homozygosity.
2. Emasculation: It is a process of removal of anthers to prevent self pollination before anthesis (period of opening of a flower).
3. Bagging: The stigma of the flower is protected against any undesirable pollen grains, by covering it with a bag.
4. Crossing: Transfer of pollen grains from selected male flower to the stigma of the female emasculated flower.
5. Harvesting seeds and raising plants: The pollination leads to fertilization and finally seed formation takes place. The seeds are grown into new generation which are called a hybrid.

Seaweed liquid fertilizer (SLF) contains cytokinin, gibberellins, and auxin apart from macro and micro nutrients. Most seaweed-based fertilizers are made from kelp (brown algae) which grows to length of 150 metres. Liquid seaweed fertilizer is not only organic but also eco-friendly. The alginates in the seaweed that reacts with metals in the soil and form long, crosslinked polymers in the soil. These polymers improve the crumbing in the soil, swell up when they get wet and retain moisture for a long time. They are especially useful in organic gardening which provides carbohydrates for plants. Seaweed has more than 70 minerals, vitamins and enzymes. It promotes vigorous growth. Improves resistance of plants to frost and disease. Seeds soaked in seaweed extract germinate much rapidly and develop a better root system.

i. Intravarietal hybridization
The cross between the plants of same variety.
ii. Intervarietal hybridization 
The cross between the plants belonging to two different varieties of the same species 
iii. Interspecific hybridization
The cross between the plants belonging to different species belonging to the same genus
Example: Gossypium hirsutum x Gossypium arboretum - Deviraj.
IV. Intergeneric hybridization
The crosses between the plants belonging to two different genera.
Example: Raphanobrassica and Triticale.

(i) Heterosis or Hybrid vigour
(ii) Vegetative propagation is the best-suited measure to maintain the vigorousity of hybrid.

(i) Dr. Norman E. Borlaug.
(ii) Dr. M.S. Swaminathan.

(i) The process is referred as bagging in plant hybridization.
(ii) It is done after emasculation to protect the contact of the stigma of the flower against any other pollen grain.

When chromosome number is doubled by itself in the same plant, is called Autopolyploidy. Example: A triploid condition in sugar beets, apples and pear has resulted in the increase in vigour and fruit size, large root size, large leaves, flower, more seeds and sugar content in them. It also resulted in seedless tomato, apple, watermelon and orange

In asexually propagated crop, progenies derived from a plant resemble in genetic constitution with the parent plant as they are mitotically divided. Based on their phenotypic appearance, clonal selection is employed to select improved variety from a mixed population (clones). The selected plants are multiplied through vegetative propagation to give rise to a clone. The genotype of a clone remains unchanged for a long period of time.

i) To increase yield, vigour, and fertility of the crop.
ii) To increase tolerance to environmental condition, salinity, temperature, and drought.
iii) To prevent the premature falling of buds and fruits, etc.
iv) To improve synchronous maturity.
v) To develop resistance to pathogens and pests.
vi) To develop photosensitive and thermos-sensitive varieties.

Green manuring is defined as the growing of green manure crops and use of these crops directly in the field by ploughing. One of the main objectives of the green manuring is to increase the content of nitrogen in the soil. Also, it helps in improving the structure and physical properties of the soil. The most important green manure crops are Crotalaria juncea, Tephrosia purpurea, and Indigofera tinctoria.

Trichoderma species are free-living fungi that are common in soil and root ecosystem. They have been recognized as bio-control agent for
(1) the control of plant disease
(2) ability to enhance root growth development
(3) crop productivity
(4) resistance to abiotic stress and
(5) uptake and use of nutrients.

i) Arbuscular mycorrhizae have the ability to dissolve the phosphate found in soil.
ii) Provides resistance against diseases, germs, and unfavorable weather conditions.
iii) It assures water availability.

Azolla is a free-floating water fern that fixes the atmospheric nitrogen in association with nitrogen fixing blue green alga Anabaena azolla. It is used as a bio-fertilizer for wetland rice cultivation and is known to contribute 40 - 60 kg/ha/crop. The agronomic potential of azolla is quite significant particularly for increasing the yield of rice crop, as it quickly decompose in soil.

Bio-fertilizers containing rhizobium bacteria are called rhizobium bio-fertilizer culture. Symbiotic bacteria that reside inside the root nodules convert the atmospheric nitrogen into a bio available form to the plants. This nitrogen-fixing bacterium when applied to the soil undergoes multiplication in billions and fixes the atmospheric nitrogen in the soil. Rhizobium is best suited for the paddy fields which increase the yield by 15 - 40%.

(a) Dr. M.S. Swaminathan
(b) C.T. Patel
(c) Dr. B.P. Pal

Euheterosis: True heterosis
(i) Mutational Euheterosis: Simplest type Often lethal, recessive mutant genes from cross pollinated genes.
(ii) Balanced Euheterosis: Well balanced gene combinations, more adaptive to environmental conditions and agricultural.
Pseudo heterosis: Also called luxuriance, has superiority over parents in vegetative growth but not in yield and adaptation, usually sterile or poorly fertile.