What is germplasm?
A - Germplasm refers to the genetic material that is used for plant and animal breeding, conservation, and research. It encompasses a wide range of genetic resources including seeds, tissues, cells, or DNA that carry the hereditary information of an organism. Germplasm is crucial for preserving genetic diversity, improving crop varieties, and ensuring food security.
It is the sum total of heridatory material in the crop species and its wild relatives.
Define genetic Erosion
A - **Genetic erosion** refers to the gradual loss of genetic diversity within a species, particularly in agricultural crops and livestock, due to factors such as modern farming practices, habitat destruction, climate change, and the replacement of local varieties with high-yielding but genetically uniform commercial varieties. This reduction in genetic variation can decrease the resilience of species to diseases, pests, and environmental changes, and it can lead to the extinction of unique genetic traits.
Define Genetic variability
A - **Genetic variability** refers to the diversity in gene frequencies within a species or a population. This variability arises from differences in the genetic makeup of individuals, which can be due to mutations, gene flow, sexual reproduction, and genetic recombination. Genetic variability is crucial for the adaptability and evolution of species, as it provides the raw material for natural selection to act upon, enabling populations to survive and thrive in changing environments.
SECTION-B
Briefly explain the land Races, obsolete cultivars and advanced breeding lines.
A - Sure, let's dive into each of these terms:
### Land Races:
- **Definition**: Land races refer to traditional or indigenous varieties of crops that have evolved through adaptation to local environmental conditions and farming practices over many generations. These varieties are often genetically diverse and well-adapted to specific climates, soils, and pest pressures.
- **Characteristics**:
- High genetic variability within the population.
- Generally low-input requirements, as they are adapted to local conditions.
- Often have unique traits such as drought tolerance, pest resistance, or specific culinary qualities.
- **Importance**: Land races are valuable genetic resources for crop improvement programs as they provide genetic diversity that can be used to develop new cultivars with desirable traits.
### Obsolete Cultivars:
- **Definition**: Obsolete cultivars are older varieties of crops that were once widely grown but have been replaced by newer, improved cultivars. These older cultivars may have become obsolete due to factors such as lower yields, susceptibility to diseases or pests, or changes in market demand.
- **Characteristics**:
- Often lack traits that are important in modern agriculture, such as disease resistance or high yield potential.
- May still possess valuable genetic traits that are not present in newer cultivars.
- **Importance**: While no longer widely grown, obsolete cultivars can be important sources of genetic material for breeding programs, especially if they carry unique traits that are beneficial for modern agricultural needs.
### Advanced Breeding Lines:
- **Definition**: Advanced breeding lines are populations of plants that have been developed through controlled breeding programs with the goal of incorporating desirable traits from different parental lines. These lines are typically several generations into the breeding process and are closer to being released as new cultivars.
- **Characteristics**:
- Often exhibit improved traits such as higher yield, disease resistance, improved quality, or better adaptation to specific environmental conditions.
- Can be genetically diverse if multiple breeding approaches (e.g., hybridization, selection, backcrossing) were used.
- **Importance**: Advanced breeding lines serve as the bridge between initial breeding efforts and the release of new cultivars. They undergo rigorous testing and selection to ensure they meet the criteria for commercial release, contributing to the continuous improvement of crop varieties.
Define the gene pool and briefly explain its types
A- The gene pool refers to the total collection of genes and alleles present in a population or species. It encompasses all the genetic variability found within a population, including variations in traits, genetic mutations, and different versions of genes (alleles). The gene pool is dynamic and can change over time due to factors such as mutation, gene flow, genetic drift, and natural selection.
Based on degree of relationship, the gene pool of crops can be divided into three groups
(Harland and Dewet, 1971)
1. Primary gene pool
2. Secondary Gene pool
3. Tertiary gene pool
These are briefly discussed below:
1. Primary gene pool (GP1) : This is also known as gene pool one (GP1). The gene
pool in which intermating is easy and leads to production of fertile hybrids is known
as primary gene pool. It includes plants of the same species or of closely related
species which produce completely fertile offspring on intermating. In such gene pool,
genes can be exchanged between lines simply by making normal crosses. This is the
material of prime breeding importance.
2. Secondary gene pool (GP2) : This type of gene pool is also known as gene pool two
(GP2). The genetic material that leads to partial fertility on crossing with GP1 is
referred to as secondary gene pool. It includes plants that belong to related species.
Such material can be crossed with primary gene pool, but usually the hybrids are
sterile and some of the progeny to some extent are fertile. Transfer of gene from such
material to primary gene pool is possible but difficult.
3. Tertiary gene pool (GP3) : The genetic material which leads to production of sterile
hybrids on crossing with primary gene pool is termed as tertiary gene pool or gene
pool three (GP3). It includes material which can be crossed with GP1, but the hybrids
are sterile. Transfer of genes from such material to primary gene pool is possible with
the help of special techniques.
Define adaptability and the factors that affect adaptability.
A - Adaptability:
Ability to genotype to exhibit relatively stable performance in different environment or
capacity of a genotype or population for genetic change in adaptation.
Types of Adaptability –
1. Specific genotype adaptation 1. Specific population adaptation
2. General genotypic adaptation 2. General population adaptation
1. Specific genotype adaptation – It is the close adaptation of genotype to a limited
environment.
2. General genotypic adaptation – It is refers to the capacity of a genotype to produce a
wide range of phenotypes compatible with a wide range of environmental conditions.
3. Specific Population adaptation – It refers to the capacity of heterogeneous population to
adapt to specific environment.
4. General population adaptation – It is the capacity of heterogeneous population to adapt
to the variety of environment.
FACTOR AFFECTING ADAPTABILITY-
1. Heterogeneity – The heterogeneous population have broad genetic base, Such
population have greater capacity to stabilize production over a wide range of changing
environment.
2. Heterozygosity – It has been observed that heterozygous individual such as F1
hybrids are more stable than their homozygous parents to environmental variation.
3. Genetic polymorphism – The regular occurrence of several phenotypes in a genetic
population is known as genetic polymorphism.
Population Adaptation
It is related with the heterozygous
population in a specified environment
Genotypic Adaptation
It is associated with the individual
genotype whether homozygous (inbred)
or heterozygous (hybrid) in as specific
environment
Adaptation
4. Mode of Pollination – The cross pollination species have better buffering capacity
that self pollination species because of more heterozygosity.
Delineate the stability analysis and enlist the models for stability analysis.
A - STABILITY ANALYSIS
It refers to the suitability of variety for general cultivation over wide range of
environments.
Stability refers to the performance with respective changing environmental factors
overtime within given location.
Selection for stability is not possible until a biometrical model with suitable parameters is
available to provide criteria necessary to rank varieties / breeds for stability.
Low magnitude of G.E interaction involves the consistent performance of a population
over variable environments.
It consists of following steps: Location / environment wise analysis of variance. pooled
analysis of variance for all the locations/ environments.
If G.E interaction is found significant ,stability analysis can be carried out using one of
the four methods:
1.Finlay and Wilkinson model (1963)
2.Eberhat and Russell model(1966)
3.Perkins and Jinks model(1968)
4.Freeman and Perkins model (1971)
SECTION-C (
A Explain the germplasm activities.
A- Germplasm activities
There are six important activities related to plant genetic resources
1. Exploration and collection
2. Conservation
3. Evaluation
4. Documentation
5. Multiplication and Distribution
6. Utilization
Certainly! Here's a brief explanation of each of the six important activities related to plant genetic resources:
1. **Exploration and Collection**:
- This involves systematically exploring different regions and habitats to identify and collect plant genetic resources (PGRs) that possess valuable traits, such as resistance to pests, diseases, drought, or salinity.
- Collecting diverse PGRs ensures the conservation of genetic variability and potential sources of beneficial traits for crop improvement.
2. **Conservation**:
- Conservation activities focus on preserving collected PGRs to maintain their genetic integrity and ensure their availability for future use.
- Conservation methods include storing seeds in seed banks under controlled conditions (ex situ conservation) and conserving plants in their natural habitats (in situ conservation).
3. **Evaluation**:
- Evaluation involves assessing the characteristics, traits, and potential uses of PGRs through systematic evaluation trials and studies.
- Evaluating PGRs helps identify valuable traits, genetic variability, and their suitability for specific breeding objectives or agricultural purposes.
4. **Documentation**:
- Documentation involves recording and cataloging detailed information about collected PGRs, including their origin, characteristics, genetic profiles, and conservation status.
- Proper documentation ensures the traceability, accessibility, and management of genetic resources for research, breeding, and conservation purposes.
5. **Multiplication and Distribution**:
- Multiplication refers to increasing the quantity of conserved PGRs through propagation methods such as seed germination, tissue culture, or vegetative propagation.
- Distribution involves sharing conserved and evaluated PGRs with researchers, breeders, farmers, and other stakeholders for use in breeding programs, research projects, or agricultural activities.
6. **Utilization**:
- Utilization refers to the practical application of conserved PGRs for crop improvement, genetic studies, trait discovery, and developing new plant varieties.
- Utilizing genetic resources helps enhance crop resilience, productivity, nutritional quality, and adaptation to changing environmental conditions, contributing to sustainable agriculture and food security.
Define germplasm conservation and briefly discuss the different methods of conservation.
A - 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. or
Germplasm conservation refers to maintain the collected germplasm in such a state that there
is minimum risk for its loss and that either it can be planted directly in the field or it can be
prepare for planting with relative ease when ever necessary. There are two important
methods of germplasm conservation or preservation viz.,1. In situ conservation 2. Ex situ
conservation
i. 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. A gene sanctuary is best located within the
centre of origin of crop species concerned, preferably covering the microcenter with in the
centre of origin. NBPGR, New Delhi is making attempts to establish gene sanctuaries in
Meghalaya for Citrus and in the North-Eastern region for Musa, Citrus, Oryza, Saccharum
and Megifera.
This method of preservation has following main disadvantages
Each protected area will cover only ve ry small portion of total diversity of a crop species,
hence several areas will have to be conserved for a single species.
The management of such areas also poses several problems.
This is a costly method of germplasm conservation
Merits : Gene sanctuaries offer the following two advantages.
A gene sanctuary not only conserves the existing genetic diversity present in the population,
it also allows evolution to continue. As a result, new alleles and new gene combinations
would appear with time.
The risks as sociated with ex situ conservation are not operative.
ii. 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.
Handling of germplasm is also easy
This is a cheap method of germplasm conservation.
A Define genetic resistance. Describe briefly vertical and horizontal resistance with suitable examples.
A - **Genetic resistance** refers to the inherent ability of an organism, typically a plant or animal, to withstand or reduce the severity of infections, diseases, or pests due to its genetic makeup. This resistance is encoded in the organism's genes and can be passed down to future generations. Genetic resistance plays a crucial role in agriculture by reducing the reliance on chemical pesticides and improving crop yield and quality.
### Vertical Resistance:
- **Definition**: Vertical resistance involves the presence of major genes or single gene loci that confer strong and specific resistance against a particular pathogen or pest strain.
- **Characteristics**:
- Typically involves a gene-for-gene interaction, where a specific gene in the host plant recognizes and triggers a defense response against a corresponding gene in the pathogen.
- Resistance is often effective against specific races or strains of pathogens but may be overcome by new pathogen variants.
- **Example**: The gene **R1** in soybean confers resistance to the soybean cyst nematode (SCN). When soybean plants carrying the **R1** gene encounter SCN carrying the corresponding avirulence gene, the plant activates a defense response, resulting in reduced nematode reproduction and damage.
### Horizontal Resistance:
- **Definition**: Horizontal resistance involves the presence of multiple genes or quantitative trait loci (QTLs) that collectively contribute to a broad-spectrum and durable resistance against a range of pathogens or pests.
- **Characteristics**:
- Involves a polygenic inheritance pattern, where multiple genes contribute to the overall resistance phenotype.
- Resistance is often more durable and stable over time compared to vertical resistance, as it targets multiple pathways or mechanisms in the pathogen.
- **Example**: The wheat cultivar **Marquis** exhibits horizontal resistance to stripe rust (caused by the fungus *Puccinia striiformis*). This resistance is controlled by multiple genes, and while individual genes may be overcome by specific pathogen variants, the combined effect of multiple resistance genes provides durable protection against various strains of stripe rust.
Q - describe briefly different mechanisms of insect resistance.
A - MECHANISMS OF INSECT RESISTANCE:
There are four mechanisms of insect resistance, viz 1) no preference, 2) antibiotics, 3)
tolerance, and 4) avoidance or escape.
Certainly! Here's a brief explanation of each of the four mechanisms of insect resistance:
1. **No Preference**:
- **Definition**: Plants with this type of resistance are not preferred or attractive to insects for feeding or egg-laying due to certain physical or chemical characteristics.
- **Characteristics**:
- Insects may avoid these plants due to their taste, odor, texture, or color, which are unappealing or deterrent to them.
- Examples include plants with strong odors, bitter taste, hairy or waxy surfaces, or physical barriers like thick cuticles that make them less attractive to insects.
- **Example**: Certain varieties of tomatoes produce compounds like acylsugars that repel insects, reducing pest damage.
2. **Antibiotics**:
- **Definition**: Plants with antibiotic resistance produce chemicals or secondary metabolites that have toxic or inhibitory effects on insects, pathogens, or pests.
- **Characteristics**:
- These chemicals can interfere with insect digestion, growth, development, or reproduction, leading to reduced insect populations or damage.
- Plants may produce toxins, alkaloids, terpenoids, phenolics, or other compounds with insecticidal properties.
- **Example**: Some plants in the Solanaceae family (e.g., potatoes, tomatoes) produce glycoalkaloids like solanine and tomatine, which are toxic to insects and pests.
3. **Tolerance**:
- **Definition**: Tolerance refers to the ability of plants to withstand or recover from insect feeding or damage without significant impact on growth, yield, or fitness.
- **Characteristics**:
- Tolerant plants can compensate for insect damage through rapid regrowth, increased photosynthesis, or redirected resource allocation.
- They may have mechanisms to repair damaged tissues, enhance nutrient uptake, or activate defense responses.
- **Example**: Some grasses and cereals like wheat and barley can tolerate grazing by herbivorous insects without significant yield loss due to their ability to regrow or tiller.
4. **Avoidance or Escape**:
- **Definition**: Plants with avoidance or escape mechanisms reduce insect damage by altering their growth, development, or phenology to avoid peak insect activity or exposure.
- **Characteristics**:
- Plants may change their growth habits, flowering time, or leaf production to avoid periods of high insect pressure or reduce attractiveness to egg-laying insects.
- They may also exhibit phenological synchrony with beneficial insects or predators that control pest populations.
- **Example**: Some plants may accelerate or delay flowering in response to insect cues to avoid peak herbivory or synchronize with natural enemies of pests for biocontrol.
