Pollination: It refers to the transfer of pollen grains from anthers to stigmas. The pollination is divided into three groups.
A). Self-Pollination: It is transfer of pollens from and to the stigma within the same flower, is always found in bisexual flower.
I) Bisexuality: Male and female sexual organs present in the same flower e.g. Wheat, rice, groundnut, etc.
II) Homogamy: Male and female sexual organs mature at the same time e.g. wheat, groundnut, etc.
III) Cleistogamy: In this condition flowers does not open at all and ensure complete self-pollination e.g Oat, Barley, Wheat, Grasses, etc.
IV) Chasmogamy: In some species, flower open but only after pollination has taken place. e.g Barley, Wheat, Oat, and many cereals.
V) Position of anthers: I) In crop like Tomato and Brinjal stigma are closely surrounded by anthers, hence pollination occurs after opening of flower but the position of anther in relation to stigma ensure self – pollination.
V) Position of anthers: I) In crop like Tomato and Brinjal stigma are closely surrounded by anthers, hence pollination occurs after opening of flower but the position of anther in relation to stigma ensure self – pollination.
B). Cross Pollination: The transfer of pollen from a flower to the stigma of the other flower of different flower plant.
I) Dicliny (Unisexuality):
It is a condition in which flower is either staminate or pistilate.
It is a condition in which flower is either staminate or pistilate.
a)Monoecy: Staminate and pistilate flowers occur in the same plant either in the same inflorescence. e.g. Mango, banana, coconut or in the separate inflorescence. e.g. Maize, Cucurbit, Strawberry, etc.
b) Dioecy: The male and female flowers are present on different plants i.e. the in such species are male or female i.e. sec is governed by a single gene. E.g. Papaya, hemp, date, palm, etc.
ii) Dichogamy: Anther and stigma of hermaphrodite flower mature at different time, facilitating cross pollination.
ii) Dichogamy: Anther and stigma of hermaphrodite flower mature at different time, facilitating cross pollination.
a) Protogyny: Gynoecium matures earlier than the androecium e.g. Bajara.
b) Protandry: Androecium matures earlier than gynoecium. e.g. marigold, maize, cotton, etc.
iii) Heterostyly: Different length of style and filaments e.g. Linseed.
iv) Self – Incompatibility: It refers to the failure of pollen from a flower to fertilize the same flower or other flowers on some plants. It may be saprophytic or gametophytic e.g. mustard, tobacco, sunflowers, reddish.
V) Male Sterility: It refers to the absence of functional pollen grains in hermaphrodite flower.
V) Male Sterility: It refers to the absence of functional pollen grains in hermaphrodite flower.
C) Often cross pollination: In many crop plants cross-pollination often exceeds 5 % and may reach 30 per cent. e.g., Jowar, Cotton, arhar, safflower etc. The genetic architecture of such crops is intermediate between self-pollinated and cross-pollinated species.
Q2. Define Ediotype. Describe main features of idiotype breeding:
Ideotype Breeding: Ideotype breeding can be defined as a method of crop improvement which is use to enhance genetic yield potential through genetic manipulation of individual plant character.
Main features of ideotype breeding are:
1. Emphasis on individual trait: In ideotype breeding, emphasis is given on individual morphological and physiological trait which enhances the yield.
2. Includes yield enhancing traits: Various plant characters to be included in the ideotype are identified through correlations analysis. Only those characters which exhibit positive association with yield are included in the model.
3. Exploits physiological variation Genetic differences exist for vario us physiological characters such as photosynthetic efficiency, photo respiration, nutrient uptake, etc.
4. Slow progress: Ideotype breeding is a slow method of cultivar development, because incorporation of various desirable characters from different sources into a single genotype takes long time.
5. Selection: In ideotype breeding selection is focused on individual plant character which enhance the yield
6. Designing of model: In ideotype breeding, the phenotype of new variety to be developed is specified in terms of morphological and physiological traits in advance.
7. Interdisciplinary approach: Ideotype breeding is in true sense an interdisciplinary approach, it involves scientist from the disciplines of genetics, breeding, physiology, pathology, entomology etc.
8. A continuous process: Ideotype breeding is a continuous process, because new ideotypes have to be developed to meet changing and increasing demands.
Q3. State objectives of plant breeding in: Rice , Gram, Cotton, Mango:
A) Rice:
1. Enhancing Yield
2.Stability and Adaptability
3.Disease and Pest Resistance
4. Quality
5. Market quality.
6. Milling quality
7. Cooking and processing quality
8. Nutritional quality.
9. Aromatic rices.
10. Enhancing Yield: Rice yields ranged from as little as 1 t/ha in many countries of Africa to more than 6 t/ha in China, Japan and South Korea
11. Quality: Rice grain quality is a combination of many characteristics that affect its market value and utilization as food. Breeding objectives for quality in rice may be grouped into four classes: Market quality, Milling quality, Cooking and processing quality, and Nutritional quality. lination a in China, Japan and South Korea.
B).Gram:
1.Breeding for vegetable type.
2. Breeding for resistance to pests.
3.Breeding for disease resistance.
4.Breeding for high protein content and quality.
5.Breeding high yielding perennial redgram suitable for bund cropping.
C) Cotton:
• High yield (more bolls, bigger bolls and highlint percentage).
• Early maturity.
• Superior fibre quality.
• Better plant type.
• Resistance to diseases like fusarium wilt, rots etc.,
•Resistance to insects like boll worms, Jassids, Thrips etc.,
• Resistance to abiotic stresses.
Q4. State Sources used for drought Resistance. Explain its Mechanisms: DROUGHT
RESISTANCE:- DEF: The ability of crop plants to grow, develop and reproduce normally under moisture deficit conditions is referred to as drought resistance.
Mechanisms of Drought Resistance:
1. Drought Escape: The simplest way of survival under drought conditions is to escape drought. Generally, drought occurs either in the mid or late-crop season. For Example, yields of early varieties of wheat, sorghum, maize, and rice are less affected by severe drought than late maturing ones.
2. Drought Avoidance: Drought avoidance refers to ability of the plant to maintain a favourable internal water balance under moisture stress. In other words, plants which avoid drought retain high water contents in their tissues.
3. Drought Tolerance: The ability of crop plants to withstand low tissue water content is referred to as drought tolerance. Drought tolerance is more desirable because the crop can produce more yield at lower water potential.
4. Drought Resistance: Drought resistance is the sum of drought avoidance and drought tolerance. In other words, drought resistance refers to the ability of crop plants to give good yield under moisture deficit conditions.
Source of Drought Resistance in Plant Breeding:
1) Cultivated varieties,
2) Germplasm collections, and.
3) Wild relatives and wild species. Transfer of drought resistance is easy from cultivated variety and germplasm of cultivated species, because such material can be easily used in the breeding programmes. Moreover, there is no problem of cross incompatibility.
Morphological Characters:
1. Earliness: Earliness is a desirable character which leads to drought escape in many crops.
2. Stomatal Features: Sunken, small size and a smaller number of stomata are associated with drought resistance
Control of stomatal aperture is important in drought resistance
3. Leaf Characters
4.Rooting Patterns
5. Growth Habit
6. Awns
Q5.Method of Gene transfer.
A. Indirect Gene transfer method:
1. Transformation(Agrobacterium spp).
Q5.Method of Gene transfer.
A. Indirect Gene transfer method:
1. Transformation(Agrobacterium spp).
B. Direct
Gene transfer method.
Gene transfer method.
i. Transfer via Electroporation.
ii. Transfer via Polyethylene Glycol (PEG):
iii. Transfer viaBiolistic:( Particle bombardment method)
iv.Transfer via Microinjection:
v. Liposome Mediated Gene Transfer:Transfer via Agrobacterium: The transformation of a plant can be carried out directly by using Agrobacterium spp. which is a common bacterium causing crown gall tumour in legumes. This bacterium carries a plasmid with T-DNA which is capable of being integrated into the host chromosome.
v. Liposome Mediated Gene Transfer:Transfer via Agrobacterium: The transformation of a plant can be carried out directly by using Agrobacterium spp. which is a common bacterium causing crown gall tumour in legumes. This bacterium carries a plasmid with T-DNA which is capable of being integrated into the host chromosome.
2. Direct Method: i. Transfer via Electroporation: Electric field membrane permeabilization is based on the fact that the electric pulses can open the cell membrane and allow penetration of alien DNA. Heat shock, in combination with electroporation has been used resulting in a higher efficiency of the transformation.
Q6. Define PGR Explain in brief kinds of germplasm and activities related with germplasm conservation.
PGR: The sum total of genes in a crop species is referred to as genetic resources.
Kinds of Germplasm:
1. Land races: These are nothing but primitive cultivars which were selected and cultivated by the farmers for many generations without systematic plant breeding efforts.
2. Obsolete Cultivars: These are the varieties developed by systematic breeding effort which were popular earlier and now have been replaced by new varieties.
3. Modern cultivars: The currently cultivated high yielding varieties are referred to as modern cultivars. They are also known as improved cultivars or advanced cultivars.
4. Advanced breeding lines: These are pre -released plants which have been developed by plant breeders in modern scientific breeding programmes. These are known as advanced lines, cultures and stocks.
4. Advanced breeding lines: These are pre -released plants which have been developed by plant breeders in modern scientific breeding programmes. These are known as advanced lines, cultures and stocks.
5. Wild forms of cultivated species: Wild forms of cultivated species are available in many crop plants. Such plants have generally high degree of resistance to biotic and abiotic stresses and are utilized in breeding programmes.
6. Wild Relatives: Those naturally occurring plant species which have common ancestry with crops and can cross with crop species are referred to as wild relatives or wild species.
7. Mutants: Mutation breeding is used when the desired character is not found in the genetic stocks of cultivated species and their wild relatives.
Germplasm activities: There are six important activities related to plant genetic resources.
1.Exploration and collection.
2. Conservation
3. Evaluation.
3. Evaluation.
4. Documentation.
5. Multiplication and Distribution.
6. Utilization
2. Germplasm conservation: Conservation refers to protection of genetic diversity of crop plants from genetic erosion. There are two important methods of germplasm conservation or preservation. In situ conservation: Conservation of germplasm under natural habitat is referred to as in situ conservation. This is achieved by protecting this area from human interference: such an area is often called as natural park, biosphere reserve or gene sanctuary.
2. Germplasm conservation: Conservation refers to protection of genetic diversity of crop plants from genetic erosion. There are two important methods of germplasm conservation or preservation. In situ conservation: Conservation of germplasm under natural habitat is referred to as in situ conservation. This is achieved by protecting this area from human interference: such an area is often called as natural park, biosphere reserve or gene sanctuary.
2. Ex situ conservation: Conservation of germplasm away from its natural habitat is called ex situ germplasm conservation. This method has following three advantages. It is possible to preserve entire genetic diversity of a crop species at one place.
Q7. Define somatic hybridization. Describe in brief applications of Somatic Hybridization:
Q7. Define somatic hybridization. Describe in brief applications of Somatic Hybridization:
Def: It is fusion between isolated somatic protoplasts under in vitro conditions and subsequent development of their product to a hybrid plant is known as somatic hybridization.
Applications of Somatic Hybridization:
Somatic hybridization has opened new possibilities for the in vitro genetic manipulation of plants to improve the crops.
1. Disease resistance: Several interspecific and inter-generic hybrids with disease resistance have been created. For example, resistance has been introduced in tomato against diseases such as TMV, spotted wilt virus and insect pests.
1. Disease resistance: Several interspecific and inter-generic hybrids with disease resistance have been created. For example, resistance has been introduced in tomato against diseases such as TMV, spotted wilt virus and insect pests.
2. Environmental tolerance: The genes responsible for the tolerance of cold, frost and salt could be successfully introduced through somatic hybridization, e.g., introduction of cold tolerance gene in tomato.
3. Quality characters: Somatic hybrids for the production of high nicotine content, and low erucic acid have been developed. A modification of hybridization in the form of cybridization has made it possible to transfer cytoplasmic male sterility.
4.Somatic hybridization has helped to study the cytoplasmic genes and their functions.
5.Protoplast fusion will help in the combination of mitochondria and chloroplasts to result in a unique nuclear-cytoplasmic genetic combination.
6.Somatic hybridization can be done in plants that are still in juvenile phase.
7.Protoplast transformation (with traits like nitrogen fixation by incorporating exogenous DNA) followed by somatic hybridization will yield innovative plants.
Q.8) Define emasculation and methods of emasculation:
Q.8) Define emasculation and methods of emasculation:
Def: Removal of stamens or anthers or killing the pollen of a flower without the female reproductive organ is known as emasculation. Methods of Emasculation
1. Hand Emasculation: In species with large flowers, removal of anthers is possible with the help of forceps. It is done before anther dehiscence. It is generally done between 4 and 6 PM one day before anthers dehisce. It is always desirable to remove other young flowers.
2. Suction Method: It is useful in species with small flowers. Emasculation is done in the morning immediately after the flowers open. A thin rubber or a glass tube attached to a suction hose is used to suck the anthers from the flowers.
3. Hot Water Treatment: Pollen grains are more sensitive than female reproductive organs to both genetic and environmental factors. In case of hot water emasculation, temperature of water and duration of treatment vary from crop to crop.
2. Suction Method: It is useful in species with small flowers. Emasculation is done in the morning immediately after the flowers open. A thin rubber or a glass tube attached to a suction hose is used to suck the anthers from the flowers.
3. Hot Water Treatment: Pollen grains are more sensitive than female reproductive organs to both genetic and environmental factors. In case of hot water emasculation, temperature of water and duration of treatment vary from crop to crop.
4. Alcohol Treatment: It is not commonly used. The method consists of immersing the inflorescence in alcohol of suitable concentration for a brief period followed by rinsing with water.
5. Cold Treatment: Cold treatment like hot water treatment kills the pollen grains without damaging gynoecium.
6.Genetic Emasculation: Genetic/ cyoplasmic male sterility may be used to eliminate the process of emasculation.
7. Use of Gametocide: Also known as chemical hybridizing agents (CHA) chemicals which selectively kills the male gamete without affecting the female gamete.
Q.9) Difference between Qualitative and Quantitative characters:
Q10. Stress: Constraining influence, force, pressure or adverse conditions for crop growth caused by biological or environmental factors.
Biotic (living): Adverse effects due to pests and diseases abiotic stresses.
Abiotic (nonliving): Adverse effects on host due to environmental factors eg: Drought, water logging, heat, cold, salinity, alkalinity and air pollution etc. Host: Plant effected by a disease or which can accommodate pathogen.
Pathogen: An organism that produces the disease Disease: an abnormal condition in the plant caused by an organism(pathogen)
