Q - What is a wild species?
A - Wild species refers to organisms that live and reproduce in their natural, undomesticated state, without direct influence or management by humans. These species are found in their native habitats and ecosystems, where they have evolved naturally over time through processes of natural selection and adaptation.
Define in situ conservation
A - In situ conservation of germplasm refers to the preservation of genetic resources in their natural habitats and ecosystems. This method involves protecting and maintaining species within the environments where they have naturally evolved, allowing them to continue interacting with their surroundings, undergo natural selection, and adapt to changing conditions.
Q - Define qualitative characters
A - **Qualitative characters** are traits of an organism that can be distinctly categorized and are typically controlled by one or a few major genes. Here are five key points defining qualitative characters:
1. **Discrete Variation**:
- Qualitative characters exhibit distinct, easily recognizable categories or classes, such as flower color (e.g., red, white), seed shape (e.g., round, wrinkled), or leaf shape (e.g., lobed, entire).
2. **Monogenic or Oligogenic Control**:
- These traits are usually controlled by one (monogenic) or a few (oligogenic) genes, each having a significant effect on the trait. For example, the flower color in peas (Pisum sativum) is controlled by a single gene.
3. **Non-Continuous Expression**:
- Unlike quantitative traits, qualitative traits do not show a continuous range of variation but rather distinct categories. There are no intermediate forms between the categories.
4. **Less Environmental Influence**:
- The expression of qualitative traits is generally less influenced by environmental factors compared to quantitative traits. For instance, the presence or absence of a particular disease resistance gene will determine the resistance status regardless of minor environmental variations.
5. **Mendelian Inheritance**:
- Qualitative characters often follow simple Mendelian inheritance patterns, such as dominant and recessive traits, where the genetic basis and ratios of inheritance can be predicted using Mendel's laws. For example, the presence of a dominant allele can mask the effect of a recessive allele, as seen in the classic Mendelian pea plant experiments.
SECTION-B
Q -. Briefly explain the land Races, obsolete cultivars and advanced breeding lines
A - Sure! Here’s a brief explanation of land races, obsolete cultivars, and advanced breeding lines:
### Land Races:
- **Definition**: Land races are traditional, locally adapted plant varieties that have evolved naturally over time through farmer selection and adaptation to local environmental conditions.
- **Characteristics**:
- High genetic diversity within the population.
- Well-adapted to specific local conditions, including climate, soil, and pests.
- Typically maintained by small-scale farmers through traditional farming practices.
- **Importance**:
- Serve as valuable genetic resources for breeding programs due to their adaptability and resilience.
- Provide a wide range of genetic traits that can be used to improve modern cultivars.
### Obsolete Cultivars:
- **Definition**: Obsolete cultivars are older plant varieties that were once popular but have been replaced by newer, more improved varieties.
- **Characteristics**:
- Generally have lower yields or lack resistance to modern pests and diseases compared to newer varieties.
- May still possess unique traits that are valuable for breeding purposes.
- **Importance**:
- Can be sources of valuable genetic traits not present in current cultivars.
- Important for maintaining genetic diversity and historical crop heritage.
### Advanced Breeding Lines:
- **Definition**: Advanced breeding lines are plant populations that have been developed through controlled breeding programs and are in the final stages of selection before being released as new cultivars.
- **Characteristics**:
- Possess specific desirable traits such as high yield, disease resistance, or improved quality.
- Result from multiple generations of selection and breeding.
- Undergo rigorous testing to ensure they meet the required standards for release.
- **Importance**:
- Serve as the basis for developing new, improved cultivars.
- Help address specific agricultural challenges and improve crop performance and productivity.
Q - Differentiate between pure-line selection and mass selection.
A -
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.
Q - Delineate the stability analysis and enfist 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
3A Give the botanical description and explain the different varieties of desi gram and kabuli
Write the floral biology of families based on these floral formulas (Br%P2 A3 61. and 1% K (5) C1+2+(2) A (9)+1 GI
A Define genetic resistance Describe briefly vertical and horizontal resistance with suitable examples
A - ### Genetic Resistance:
**Genetic resistance** refers to the inherent ability of a plant or animal to withstand or minimize damage caused by pests, pathogens, or environmental stressors, due to its genetic makeup. This resistance is encoded in the organism's DNA and can be passed from one generation to the next.
### Types of Genetic Resistance:
1. **Vertical Resistance**:
- **Definition**: Vertical resistance, also known as specific or monogenic resistance, is controlled by one or a few major genes and is effective against specific strains or races of a pathogen.
- **Characteristics**:
- **Gene-for-Gene Interaction**: Each resistance gene in the plant corresponds to a specific avirulence gene in the pathogen. When the pathogen with the avirulence gene attacks the plant, the plant's resistance gene triggers a defense response.
- **High Efficacy but Narrow Spectrum**: This type of resistance can be highly effective but is often specific to certain pathogen strains. If the pathogen evolves and loses the avirulence gene, it can overcome the plant's resistance.
- **Example**:
- **Wheat Rust Resistance**: Wheat varieties with the **Lr34** gene exhibit resistance to leaf rust caused by the fungus *Puccinia triticina*. The resistance is highly effective against specific rust strains.
- **Rice Blast Resistance**: The **Pi-ta** gene in rice confers resistance to certain races of the rice blast fungus *Magnaporthe oryzae*.
2. **Horizontal Resistance**:
- **Definition**: Horizontal resistance, also known as general or polygenic resistance, is controlled by multiple genes, each contributing to a degree of resistance. This type of resistance is effective against a broad range of pathogen strains.
- **Characteristics**:
- **Polygenic Control**: Involves many genes, each providing partial resistance. The combined effect of these genes results in a more durable and broad-spectrum resistance.
- **Lower Efficacy but Wide Spectrum**: Horizontal resistance is generally less complete than vertical resistance but provides protection against a wider range of pathogen strains and is less likely to be overcome by pathogen evolution.
- **Example**:
- **Potato Late Blight Resistance**: Certain potato varieties show horizontal resistance to late blight caused by *Phytophthora infestans*. This resistance involves multiple genes, making it harder for the pathogen to overcome.
- **Maize Gray Leaf Spot Resistance**: Some maize varieties exhibit horizontal resistance to gray leaf spot, a fungal disease caused by *Cercospora zeae-maydis*. This resistance is controlled by several genes and provides broad protection.
### Summary:
- **Genetic Resistance**: The inherent ability to resist pests and diseases due to genetic factors.
- **Vertical Resistance**: Controlled by one or few major genes, highly effective but specific to certain pathogen strains. Example: **Lr34** gene in wheat for rust resistance.
- **Horizontal Resistance**: Controlled by multiple genes, broad-spectrum and durable. Example: Potato varieties with horizontal resistance to late blight.
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.
### Mechanisms of Insect Resistance:
1. **No Preference (Antixenosis)**:
- **Definition**: Plants with no preference mechanisms are less attractive or less suitable for insect pests for feeding, oviposition (egg laying), or shelter.
- **Characteristics**:
- Involves physical or chemical traits that deter insects from selecting the plant.
- Physical traits: Hairy leaves, thick cuticles, or surface waxes that discourage insect contact.
- Chemical traits: Unpleasant odors or tastes due to secondary metabolites.
- **Example**: Some varieties of cabbage have glossy leaves that deter aphids from feeding.
2. **Antibiotics**:
- **Definition**: Antibiotic resistance involves the production of substances by plants that adversely affect the biology of the insect pest, including growth, development, reproduction, or survival.
- **Characteristics**:
- Toxic or inhibitory compounds disrupt the normal physiological processes of insects.
- These substances can be secondary metabolites like alkaloids, phenolics, or terpenoids.
- **Example**: Wild potato species produce glycoalkaloids, which are toxic to many insect pests and reduce their survival rates.
3. **Tolerance**:
- **Definition**: Tolerance refers to the plant's ability to endure or recover from insect damage without significant loss of yield or fitness.
- **Characteristics**:
- Plants can compensate for damage by promoting growth, repairing tissues, or reallocating resources.
- Tolerant plants do not necessarily deter or kill insects but withstand their effects better than susceptible varieties.
- **Example**: Some varieties of wheat can tolerate aphid feeding by regrowing tissues and maintaining photosynthesis, resulting in minimal yield loss.
4. **Avoidance or Escape**:
- **Definition**: Avoidance or escape mechanisms involve strategies that allow plants to avoid periods of high insect pressure or to escape from pest attacks through growth patterns or phenological changes.
- **Characteristics**:
- Timing of growth stages, such as flowering or seed setting, to avoid peak insect activity.
- Rapid growth cycles or altered life cycles to minimize exposure to pests.
- **Example**: Some sorghum varieties flower earlier or later than the peak activity period of stem borers, reducing the chances of infestation.
### Summary:
- **No Preference (Antixenosis)**: Plants are less attractive to insects due to physical or chemical traits. Example: Glossy cabbage leaves deter aphids.
- **Antibiotics**: Plants produce substances that negatively affect insect biology. Example: Glycoalkaloids in wild potatoes.
- **Tolerance**: Plants endure or recover from insect damage with minimal impact on yield. Example: Tolerant wheat varieties regrow after aphid feeding.
- **Avoidance or Escape**: Plants avoid or escape insect pressure through timing or growth patterns. Example: Sorghum varieties avoid stem borers by flowering at different times.
