SECTION B
Q - What is Secondary Metabolites ?
A - Secondary metabolites are organic compounds produced by plants, bacteria, fungi, and animals that are not directly involved in the normal growth, development, or reproduction of the organism. Unlike primary metabolites (such as amino acids, nucleotides, and carbohydrates) that are essential for the basic functions and structure of the organism, secondary metabolites often serve ecological purposes such as defense mechanisms, signaling, and interactions with other organisms.
Q - Discuss entomopathogenic pathogens with examples.
A - Entomopathogenic pathogens are microorganisms that cause disease in insects. They are used as biological control agents in agriculture to manage insect pest populations. These pathogens include bacteria, fungi, viruses, and nematodes. Here are brief descriptions and examples of each type:
1. **Bacteria**:
- **Example**: *Bacillus thuringiensis* (Bt)
- **Description**: Bt produces toxins that are harmful to certain insect larvae. It is widely used in bioinsecticides to control pests like caterpillars, beetles, and mosquitoes.
2. **Fungi**:
- **Example**: *Beauveria bassiana*
- **Description**: This fungus infects a wide range of insects by penetrating their cuticle and growing inside the host, eventually killing it. It is used against pests like whiteflies, aphids, and thrips.
3. **Viruses**:
- **Example**: Nuclear Polyhedrosis Virus (NPV)
- **Description**: NPV infects caterpillars of various moth species, causing them to liquefy and die. It is used in managing pests like the gypsy moth and the armyworm.
4. **Nematodes**:
- **Example**: *Steinernema carpocapsae*
- **Description**: These parasitic nematodes infect and kill insects by releasing symbiotic bacteria inside the host. They are used to control soil-dwelling pests like grubs and larvae of beetles.
Q - Explain virulence and pathogenicity ?
A - **Virulence** and **pathogenicity** are related concepts in the study of infectious diseases, but they refer to different aspects of a pathogen's ability to cause disease.
1. **Pathogenicity**:
- **Definition**: The ability of a microorganism to cause disease in a host.
- **Description**: It refers to whether or not an organism can produce disease. If a microorganism is pathogenic, it means it has the potential to cause disease in a host organism.
2. **Virulence**:
- **Definition**: The degree or severity of pathogenicity.
- **Description**: It indicates how severe the disease caused by the pathogen can be. Virulence is often measured by the extent of damage caused to the host, the speed of disease onset, and the number of organisms needed to cause infection.
Q - Factors effect the efficiency of Biofertilizers ?
A - The efficiency of biofertilizers, which are natural fertilizers containing living microorganisms, can be influenced by various factors. Here are ten key factors:
1. **Microbial Strain**:
- The specific strain of microorganisms used in the biofertilizer impacts its effectiveness. Some strains are more efficient at nitrogen fixation, phosphate solubilization, or promoting plant growth than others.
2. **Soil Conditions**:
- Soil pH, texture, and organic matter content can influence the activity and survival of biofertilizer microorganisms. Optimal soil conditions are necessary for maximum efficiency.
3. **Moisture Levels**:
- Adequate soil moisture is crucial for the survival and activity of biofertilizer microbes. Both drought and waterlogging can negatively impact their effectiveness.
4. **Temperature**:
- Microbial activity is temperature-dependent. Extreme temperatures, either too high or too low, can reduce the efficiency of biofertilizers.
5. **Nutrient Availability**:
- The presence of essential nutrients in the soil affects the growth and activity of biofertilizer microorganisms. Deficiencies or imbalances can limit their effectiveness.
6. **Host Plant**:
- The type of crop or plant species can influence the efficiency of biofertilizers. Some plants have better symbiotic relationships with specific microbial strains.
7. **Application Method**:
- The method of biofertilizer application (e.g., seed treatment, soil application, foliar spray) affects the distribution and colonization of microbes, impacting their efficiency.
8. **Competition with Native Microbes**:
- Native soil microorganisms can compete with introduced biofertilizer microbes for resources, which can affect the establishment and activity of the biofertilizer strains.
9. **Chemical Inputs**:
- The use of chemical fertilizers, pesticides, and herbicides can negatively impact the viability and effectiveness of biofertilizer microorganisms.
10. **Storage and Handling**:
- Proper storage and handling of biofertilizers are essential to maintain microbial viability. Exposure to unfavorable conditions such as high temperatures, humidity, or UV light can reduce their effectiveness.
Q - Discuss Nitrogen - fixing Bio-fertilizers ?
A - Nitrogen-fixing biofertilizers are natural fertilizers that contain microorganisms capable of converting atmospheric nitrogen into a form that plants can absorb and utilize. This process, known as biological nitrogen fixation, is crucial for plant growth and soil fertility. Here are some key points about nitrogen-fixing biofertilizers:
1. **Types of Nitrogen-Fixing Microorganisms**:
- **Symbiotic Nitrogen Fixers**: These bacteria form symbiotic relationships with specific plants. The most well-known example is the rhizobia bacteria that form nodules on the roots of leguminous plants (e.g., beans, peas, clover). The bacteria fix atmospheric nitrogen into ammonia, which the plant can use for growth.
- **Non-Symbiotic (Free-Living) Nitrogen Fixers**: These bacteria fix nitrogen independently without a host plant. Examples include *Azotobacter* and *Clostridium*. They live freely in the soil and can fix nitrogen under certain conditions.
- **Associative Symbiotic Fixers**: These bacteria live in close association with plant roots but do not form specialized structures like nodules. Examples include *Azospirillum*, which is associated with grasses and cereals.
2. **Examples of Nitrogen-Fixing Biofertilizers**:
- **Rhizobium**: Used for leguminous crops. It forms root nodules where nitrogen fixation occurs.
- **Azotobacter**: Used for a variety of crops, including cereals, vegetables, and fruits. It fixes nitrogen in aerobic conditions.
- **Azospirillum**: Beneficial for grasses, maize, and other cereals. It enhances root growth and nitrogen uptake.
- **Blue-Green Algae (Cyanobacteria)**: Used in paddy fields. *Anabaena* and *Nostoc* are examples that fix nitrogen in aquatic environments.
- **Frankia**: Forms symbiotic relationships with non-leguminous plants like alder trees.
Q - Discuss FCO specifications for biopesticides ?
A - The FCO (Fertilizer (Control) Order) specifications for biopesticides are part of the regulatory framework established by the Government of India to ensure the quality and effectiveness of biopesticides. These specifications are intended to standardize biopesticides, ensuring they are safe for use and environmentally friendly. Here is a detailed discussion on the key aspects of FCO specifications for biopesticides:
### Key Components of FCO Specifications for Biopesticides
1. **Active Ingredient Content**:
- The FCO specifies the minimum content of the active ingredient(s) in biopesticides. This ensures that the product contains a sufficient concentration of the biological agents (like bacteria, fungi, viruses, or other microorganisms) that are responsible for the pest control activity.
2. **Microbial Content and Purity**:
- The microbial content must be identified and quantified. The purity of the biopesticide in terms of the absence of contaminants (other than the intended microorganisms) is crucial. This includes ensuring no harmful microorganisms are present.
3. **Formulation and Carrier Material**:
- Specifications include the types of carriers and adjuvants used in the formulation. The choice of carrier can impact the stability and effectiveness of the biopesticide. Common carriers might include organic materials like talc or clay.
4. **Viability and Shelf Life**:
- The FCO provides guidelines for the viability of the microorganisms over time, which translates to the product’s shelf life. This ensures that the biopesticide remains effective during its stated shelf life under specified storage conditions.
5. **Efficacy**:
- The product must demonstrate efficacy against specific pests as claimed by the manufacturer. This is usually verified through field trials and laboratory tests.
6. **Safety and Environmental Impact**:
- Specifications address the safety of the biopesticide for humans, non-target organisms, and the environment. This includes toxicity studies and environmental impact assessments.
7. **Labeling Requirements**:
- Proper labeling with detailed instructions for use, safety precautions, shelf life, and storage conditions are mandated. This helps users apply the biopesticides correctly and safely.
8. **Registration and Compliance**:
- Biopesticides must be registered with the appropriate regulatory authorities, and manufacturers must comply with quality control and assurance protocols. The FCO includes procedures for registration, inspection, and certification of biopesticides.
### Examples of Specific Biopesticides under FCO
- **Trichoderma spp.**: A fungal biopesticide used against soil-borne diseases. Specifications include spore count per gram, viability, and absence of contaminants.
- **Bacillus thuringiensis (Bt)**: A bacterial biopesticide used against various insect pests. Specifications include the potency in terms of International Toxic Units (ITU), purity, and formulation standards.
SECTION C
Q - Explain mode of Action of BT Toxin ?
A - The mode of action of Bacillus thuringiensis (Bt) toxin, a commonly used biopesticide, involves a series of steps that ultimately lead to the death of target insect larvae. Bt toxins are a group of proteins, commonly referred to as Cry and Cyt proteins, which are toxic to specific insects when ingested. Here's a detailed explanation of how Bt toxin works:
Steps in the Mode of Action of Bt Toxin
Ingestion by Target Insect:
The insect larvae must ingest the Bt toxin, which is present in the form of crystalline inclusions (Cry proteins) within the Bt spores, for it to be effective.
Solubilization in the Gut:
Once inside the larval gut, the alkaline pH (typically around 9.5 to 10) solubilizes the crystalline protein, releasing the active toxin.
Activation by Proteolytic Cleavage:
The solubilized protoxin is then activated by proteolytic enzymes present in the insect gut. These enzymes cleave the protoxin into smaller, active toxin fragments.
Binding to Midgut Receptors:
The activated toxin fragments bind to specific receptors on the epithelial cells of the midgut lining. These receptors are typically cadherin-like proteins, aminopeptidases, and alkaline phosphatases.
Formation of Pores in Gut Cells:
Binding of the toxin to the receptors induces a conformational change, leading to the insertion of the toxin into the cell membrane and the formation of pores or channels.
Cell Lysis and Gut Paralysis:
The formation of pores disrupts the osmotic balance within the epithelial cells, causing cell lysis and leakage of gut contents. This damage impairs the gut function, leading to paralysis of the digestive tract.
Systemic Infection and Death:
The damaged gut lining allows Bt spores and normal gut bacteria to invade the body cavity (hemocoel) of the larvae. The combination of gut paralysis, septicemia, and overall physiological disruption results in the death of the insect.
Q - Difference between Botanical pesticide and synthetic pesticides. ?
A - Botanical pesticides and synthetic pesticides are two distinct types of pest control products used in agriculture and pest management. Here are the key differences between them:
### Botanical Pesticides:
1. **Source**:
- Botanical pesticides are derived from natural plant sources. They are often extracted from plants or plant parts known for their insecticidal or pesticidal properties. Examples include neem oil, pyrethrins (from chrysanthemum flowers), and rotenone (from the roots of certain plants).
2. **Chemical Composition**:
- The active ingredients in botanical pesticides are complex mixtures of compounds, including secondary metabolites produced by plants. These compounds can have diverse chemical structures and modes of action.
3. **Mode of Action**:
- Botanical pesticides typically have multiple modes of action. They may disrupt insect physiology, interfere with feeding or reproduction, or act as repellents or growth regulators. This diversity can make them effective against a wide range of pests.
4. **Environmental Impact**:
- Botanical pesticides are generally considered more environmentally friendly compared to synthetic pesticides. They often degrade more rapidly in the environment and have lower persistence, reducing the risk of residual effects on non-target organisms.
5. **Target Specificity**:
- Botanical pesticides can exhibit varying degrees of target specificity. While some may target specific insect pests, others may have broader effects, impacting a range of pests as well as beneficial organisms.
6. **Regulatory Status**:
- Regulatory requirements for botanical pesticides may differ from those for synthetic pesticides. They may undergo testing for efficacy, safety, and environmental impact, but the criteria and standards can vary based on regional regulations.
### Synthetic Pesticides:
1. **Source**:
- Synthetic pesticides are chemically synthesized compounds designed specifically for pest control purposes. They are not derived from natural sources like plants or microorganisms.
2. **Chemical Composition**:
- Synthetic pesticides have defined chemical structures and are often formulated to contain a single active ingredient or a few active ingredients. These chemicals are designed to target specific aspects of pest biology.
3. **Mode of Action**:
- Synthetic pesticides typically have well-defined modes of action targeting specific biochemical pathways or physiological processes in pests. Examples include nerve toxins (organophosphates, pyrethroids), growth regulators, and stomach poisons (chlorinated hydrocarbons).
4. **Environmental Impact**:
- Synthetic pesticides can have a higher environmental impact compared to botanical pesticides. Some synthetic pesticides may persist in the environment for extended periods, leading to concerns about residues, bioaccumulation, and effects on non-target organisms.
5. **Target Specificity**:
- Synthetic pesticides can vary in their target specificity. Some are highly specific to certain pests, while others may have broader effects and can affect beneficial organisms, leading to concerns about unintended consequences.
6. **Regulatory Status**:
- Synthetic pesticides are subject to stringent regulatory oversight and testing to assess their efficacy, safety for humans and the environment, and potential risks. Regulatory requirements may include registration, labeling, usage guidelines, and periodic reevaluation.
Q - Discuss about K solubalisation ?
A - K solubilization refers to the process of solubilizing potassium (K) in the soil, making it available for plant uptake. Potassium is an essential nutrient for plant growth, playing crucial roles in various physiological processes such as enzyme activation, osmoregulation, and stress tolerance. However, not all forms of potassium in the soil are readily available for plants. K solubilization helps convert insoluble forms of potassium into soluble forms that plants can absorb through their roots. Here's a detailed discussion about K solubilization:
### Forms of Potassium in Soil:
1. **Exchangeable Potassium (K<sup>+</sup>)**:
- This form of potassium is readily available to plants as it is loosely held on soil exchange sites and can be easily exchanged with other cations like calcium (Ca<sup>2+</sup>) and magnesium (Mg<sup>2+</sup>).
2. **Non-Exchangeable Potassium**:
- Non-exchangeable potassium includes potassium bound tightly to soil particles, organic matter, or within mineral structures. This form is not readily available for plant uptake.
3. **Fixed Potassium**:
- Fixed potassium is tightly bound within mineral structures and is not immediately accessible to plants.
### Mechanisms of K Solubilization:
1. **Acidification**:
- Soil microorganisms such as certain bacteria and fungi can produce organic acids (e.g., citric acid, oxalic acid) through metabolic processes. These organic acids can lower the pH of the soil solution, leading to the dissolution of potassium-bearing minerals (e.g., feldspars, micas) and release of soluble potassium ions.
2. **Chelation**:
- Some microorganisms produce chelating compounds (e.g., siderophores) that can bind to potassium ions and other nutrients, increasing their solubility in the soil solution and making them more available for plant uptake.
3. **Enzymatic Activities**:
- Certain enzymes produced by soil microorganisms can facilitate the breakdown of organic matter and mineral compounds, releasing potassium ions in the process. For example, phosphatases and proteases released by microbes can indirectly affect K solubilization by influencing soil nutrient dynamics.
4. **Root Exudates**:
- Plants themselves contribute to K solubilization through the release of root exudates such as organic acids, sugars, and enzymes. These exudates can interact with soil minerals and microbial populations, enhancing potassium availability in the rhizosphere.
### Factors Influencing K Solubilization:
1. **Microbial Activity**:
- The presence and activity of potassium-solubilizing microorganisms (KSMs) in the soil significantly influence K solubilization. Examples of KSMs include bacteria (e.g., Bacillus, Pseudomonas) and fungi (e.g., Aspergillus, Penicillium).
2. **Soil pH**:
- Acidic soils generally favor K solubilization due to increased activity of acid-producing microorganisms and the enhanced solubility of potassium-bearing minerals under lower pH conditions.
3. **Organic Matter**:
- Soils rich in organic matter can support higher microbial activity, including K solubilizers. Organic matter also serves as a source of carbon and energy for microbes involved in K solubilization.
4. **Soil Texture**:
- Soil texture influences the availability of potassium, with sandy soils often exhibiting lower potassium retention compared to clayey soils. K solubilization can be more effective in soils with good nutrient-holding capacity.
### Importance of K Solubilization:
- **Plant Nutrition**:
- Enhanced K solubilization improves the availability of potassium to plants, supporting healthy growth, nutrient uptake, and overall productivity.
- **Soil Fertility**:
- K solubilization contributes to soil fertility by maintaining adequate potassium levels, which is essential for crop yield and quality.
- **Sustainable Agriculture**:
- Effective K solubilization reduces the need for external potassium fertilizers, promoting sustainable agricultural practices and minimizing environmental impacts associated with excessive fertilizer use.
Q - Discuss about Ectomycorrhiza and Endomycorrhiza ?
A - Ectomycorrhiza and endomycorrhiza are two types of mycorrhizal symbiotic associations between fungi and plant roots. These associations play crucial roles in nutrient uptake, plant growth, and ecosystem functioning. Here's a detailed discussion about ectomycorrhiza and endomycorrhiza:
### Ectomycorrhiza:
1. **Partners**:
- Ectomycorrhizal fungi form symbiotic relationships primarily with trees belonging to certain families like Pinaceae (pines), Fagaceae (oaks, beeches), and Betulaceae (birches). These fungi are found in temperate and boreal forest ecosystems.
2. **Colonization**:
- In ectomycorrhizal associations, the fungal hyphae form a dense network around the outer surface of the plant root, known as the root mantle, and between root cells without penetrating the cells themselves. This forms a sheath-like structure called the Hartig net.
3. **Benefits**:
- Ectomycorrhizal fungi enhance the plant's ability to acquire nutrients, especially nitrogen and phosphorus, from the soil. They also contribute to water uptake and protect the roots from pathogens and environmental stresses.
4. **Morphology**:
- Ectomycorrhizal fungi often produce characteristic fruiting bodies (e.g., mushrooms, truffles) aboveground, which are essential for their reproductive cycle. The fungal mycelium remains mostly external to the root tissues.
5. **Examples**:
- Examples of ectomycorrhizal fungi include species from genera like *Amanita*, *Boletus*, *Suillus*, *Laccaria*, and *Tricholoma*.
### Endomycorrhiza (Arbuscular Mycorrhiza):
1. **Partners**:
- Endomycorrhizal fungi, also known as arbuscular mycorrhizal fungi (AMF), form symbiotic associations with a wide range of plant species, including many agricultural crops, grasses, and wild plants. They are found in diverse ecosystems globally.
2. **Colonization**:
- In endomycorrhizal associations, fungal hyphae penetrate the root cells of the host plant, forming intricate structures called arbuscules and vesicles within the root cells. These structures facilitate nutrient exchange between the fungus and the plant.
3. **Benefits**:
- Endomycorrhizal fungi improve nutrient uptake, especially phosphorus, potassium, and micronutrients, for the host plant. They also enhance plant resistance to diseases, drought stress, and soil salinity.
4. **Morphology**:
- Endomycorrhizal fungi typically do not produce conspicuous aboveground structures like fruiting bodies. Their presence is mostly observed through microscopic examination of root tissues.
5. **Examples**:
- The most common endomycorrhizal fungi belong to the Glomeromycota phylum, including species from genera like *Glomus*, *Rhizophagus* (formerly *Glomus*), and *Acaulospora*.
### Key Differences:
1. **Colonization Pattern**:
- Ectomycorrhiza form a sheath-like structure around the root surface without penetrating the root cells, while endomycorrhiza penetrate the root cells to form arbuscules and vesicles inside the cells.
2. **Host Range**:
- Ectomycorrhizal associations are typically formed with specific tree species, while endomycorrhizal associations are more widespread and occur with a broader range of plants, including agricultural crops.
3. **Nutrient Uptake**:
- Ectomycorrhizal fungi are particularly effective at enhancing nitrogen and phosphorus uptake, whereas endomycorrhizal fungi excel in improving phosphorus and potassium uptake.
4. **Morphological Features**:
- Ectomycorrhizal fungi often produce visible fruiting bodies, while endomycorrhizal fungi are generally not visible without microscopic examination of root tissues.
5. **Ecosystem Distribution**:
- Ectomycorrhizal associations are common in temperate and boreal forest ecosystems, while endomycorrhizal associations are found in various terrestrial ecosystems globally, including grasslands, forests, and agricultural lands.
Q - Discuss Carrier material for Biofertilizers ?
A -
