Structural and biochemical defense mechanisms help plants defend against pathogens. Structural defenses include pre-existing structures like cuticular wax, thick cuticles, and tough cell walls, as well as structures that develop after infection, such as cell wall thickening, callose deposition, and formation of layers and cork. Biochemical defenses include pre-existing inhibitors that prevent pathogen germination and growth, as well as responses after infection like phytoalexin production, oxidative burst, and hypersensitive response cell death. These multifaceted defense strategies help plants resist invading pathogens.
1. The document discusses the defense mechanisms of plants against plant pathogens, including structural and biochemical defenses.
2. Structural defenses include pre-existing structures like wax, thick cuticles, and thick-walled cells, as well as induced structures like cork layers and tyloses formation in response to infection.
3. Biochemical defenses include pre-existing inhibitors and phenolic compounds, as well as induced responses like phytoalexin production, hypersensitive response, and pathogenesis-related protein synthesis post-infection.
4. Both structural and biochemical defenses work together and are influenced by factors like the plant's age, organ infected, and environmental conditions.
1. The document discusses various defense mechanisms in plants, including preexisting structural defenses like cuticular wax, cuticle thickness, and epidermal cell wall structures.
2. It also describes defense structures that develop after a pathogen attack, such as cytoplasmic reactions, cell wall thickening, gum deposition, and formation of layers.
3. Biochemical defenses are also summarized, including the release of inhibitory compounds and production of phenolic compounds and phytoalexins after infection.
Mechanism of disease control by endophytesPooja Bhatt
The document discusses alternative methods for pest management to address problems with chemical pesticides such as development of resistance and environmental contamination. It suggests that biological control using endophytic microorganisms is a promising alternative as endophytes have antagonistic properties against plant pathogens. Endophytes can inhibit pathogens through direct mechanisms such as hyperparasitism, competition, antibiosis, and lytic enzyme production or indirect induction of host plant resistance. Case studies provide examples of endophytes inhibiting fungal plant pathogens through siderophore production, parasitic growth, and antibiotic compounds.
In a computer simulation of an epidemic, the computer is given data describing the various sub components of the epidemic and control practices at specific points in time (such as at weekly intervals).Computer simulation of epidemics is extremely useful as an educational exercise for students of plant pathology and also for farmers so that they can better understand and appreciate the effect of each epidemic sub component on the final size of their crop loss.Simulators serve as tools that can evaluate the importance of the size of each epidemic sub component at a particular point in time of the epidemic by projecting its effect on the final crop loss.Computer simulation are expert systems,that try to equal and suppress the logic and ability of an expert professional in solving problems.Systems are used in plant pathology frequently for diagnosis of plant diseases.Systems can advice growers in making decisions on disease management in respect of kind, amount and time of application of pesticides etc.Simulators can decompose disease progress so they are used now to develop forecaster.
EFFECT OF PATHOGEN ON HOST PLANT PHYSIOLOGYfarheen khan
Plant pathogens can interfere with key plant physiological functions such as photosynthesis, respiration, transpiration, nutrient transport, and cellular processes. This document discusses how pathogens disrupt these functions through tissue damage, toxin production, and cellular changes. Specifically, it notes that pathogens reduce photosynthesis by destroying chlorophyll or inhibiting related enzymes. They also increase plant respiration and interfere with nutrient transport through the xylem and phloem.
Chemical composition and physical properties of plant virusesN.H. Shankar Reddy
This document discusses the chemical composition and physical properties of plant viruses. It notes that plant viruses contain nucleic acids (RNA or DNA) and protein coats. The nucleic acid content ranges from 5-40% and determines infectivity, while the protein coat protects the nucleic acid and facilitates entry into host cells. It also discusses various physical properties of viruses like their thermal inactivation temperature, dilution endpoint, longevity in crude sap extractions, and use of local lesion assays to quantify infectivity.
My this document is very comprehensive attempt to describe the very important disease of shisham tree. I have included almost all the major aspects of the disease with the appropriate references. I hope you will get a better chance to gain the knowledge from it.
This document discusses seed borne diseases and their management. It notes that seed borne pathogens can cause significant losses through reduced germination, seedling mortality, and yield losses. Some key seed borne diseases mentioned include late blight of potato, brown spot of rice, and downy mildew of pearl millet. The document then outlines methods for detecting seed borne pathogens, including visual examination, growing tests, and molecular methods. It discusses management approaches like seed selection, quarantine, hot water treatment, chemical seed treatments, and biological seed treatments using microbes like Trichoderma and Pseudomonas.
1. The document discusses the defense mechanisms of plants against plant pathogens, including structural and biochemical defenses.
2. Structural defenses include pre-existing structures like wax, thick cuticles, and thick-walled cells, as well as induced structures like cork layers and tyloses formation in response to infection.
3. Biochemical defenses include pre-existing inhibitors and phenolic compounds, as well as induced responses like phytoalexin production, hypersensitive response, and pathogenesis-related protein synthesis post-infection.
4. Both structural and biochemical defenses work together and are influenced by factors like the plant's age, organ infected, and environmental conditions.
1. The document discusses various defense mechanisms in plants, including preexisting structural defenses like cuticular wax, cuticle thickness, and epidermal cell wall structures.
2. It also describes defense structures that develop after a pathogen attack, such as cytoplasmic reactions, cell wall thickening, gum deposition, and formation of layers.
3. Biochemical defenses are also summarized, including the release of inhibitory compounds and production of phenolic compounds and phytoalexins after infection.
Mechanism of disease control by endophytesPooja Bhatt
The document discusses alternative methods for pest management to address problems with chemical pesticides such as development of resistance and environmental contamination. It suggests that biological control using endophytic microorganisms is a promising alternative as endophytes have antagonistic properties against plant pathogens. Endophytes can inhibit pathogens through direct mechanisms such as hyperparasitism, competition, antibiosis, and lytic enzyme production or indirect induction of host plant resistance. Case studies provide examples of endophytes inhibiting fungal plant pathogens through siderophore production, parasitic growth, and antibiotic compounds.
In a computer simulation of an epidemic, the computer is given data describing the various sub components of the epidemic and control practices at specific points in time (such as at weekly intervals).Computer simulation of epidemics is extremely useful as an educational exercise for students of plant pathology and also for farmers so that they can better understand and appreciate the effect of each epidemic sub component on the final size of their crop loss.Simulators serve as tools that can evaluate the importance of the size of each epidemic sub component at a particular point in time of the epidemic by projecting its effect on the final crop loss.Computer simulation are expert systems,that try to equal and suppress the logic and ability of an expert professional in solving problems.Systems are used in plant pathology frequently for diagnosis of plant diseases.Systems can advice growers in making decisions on disease management in respect of kind, amount and time of application of pesticides etc.Simulators can decompose disease progress so they are used now to develop forecaster.
EFFECT OF PATHOGEN ON HOST PLANT PHYSIOLOGYfarheen khan
Plant pathogens can interfere with key plant physiological functions such as photosynthesis, respiration, transpiration, nutrient transport, and cellular processes. This document discusses how pathogens disrupt these functions through tissue damage, toxin production, and cellular changes. Specifically, it notes that pathogens reduce photosynthesis by destroying chlorophyll or inhibiting related enzymes. They also increase plant respiration and interfere with nutrient transport through the xylem and phloem.
Chemical composition and physical properties of plant virusesN.H. Shankar Reddy
This document discusses the chemical composition and physical properties of plant viruses. It notes that plant viruses contain nucleic acids (RNA or DNA) and protein coats. The nucleic acid content ranges from 5-40% and determines infectivity, while the protein coat protects the nucleic acid and facilitates entry into host cells. It also discusses various physical properties of viruses like their thermal inactivation temperature, dilution endpoint, longevity in crude sap extractions, and use of local lesion assays to quantify infectivity.
My this document is very comprehensive attempt to describe the very important disease of shisham tree. I have included almost all the major aspects of the disease with the appropriate references. I hope you will get a better chance to gain the knowledge from it.
This document discusses seed borne diseases and their management. It notes that seed borne pathogens can cause significant losses through reduced germination, seedling mortality, and yield losses. Some key seed borne diseases mentioned include late blight of potato, brown spot of rice, and downy mildew of pearl millet. The document then outlines methods for detecting seed borne pathogens, including visual examination, growing tests, and molecular methods. It discusses management approaches like seed selection, quarantine, hot water treatment, chemical seed treatments, and biological seed treatments using microbes like Trichoderma and Pseudomonas.
This document summarizes the key principles of plant infection:
1) Penetration is the entry of the pathogen into the host, which can occur directly through the plant surface, through wounds, or through natural openings like stomata, hydathodes, or lenticels.
2) Infection is the establishment of the pathogen within the host plant by procuring nutrients from host cells or tissues.
3) Invasion is the spread of the pathogen within the host, which can be intercellular or intracellular depending on the type of pathogen.
4) Dissemination refers to the spread of the pathogen from one plant to another, which can occur autonomously through soil, seeds, or plant parts,
This document provides an overview of bacterial plant pathogens. It begins with an introduction to bacteria and their role in nature, both beneficial and pathogenic. It then discusses the classification of phytopathogenic bacteria according to their shape, cellular structure, staining properties, and taxonomy. The document outlines common symptoms of bacterial diseases including leaf spots, blights, wilts, cankers, and galls. It provides examples of genera of bacteria that cause specific symptoms and diseases.
The document discusses plant disease forecasting. It provides information on:
1. The principles of disease forecasting are based on the nature of the pathogen, environmental effects on pathogen development, host response to infection, and grower activities.
2. Models for disease prediction include empirical, simulation, and general circulation models, but these models have limitations due to uncertainty and non-linear relationships.
3. Disease forecasts are used for strategic decision making like crop selection and tactical decisions around disease management measures. Successful forecasting requires reliability, simplicity, importance of the disease, and usefulness.
Fastidious vascular bacteria (FVB), also known as Rickettsia-like bacteria or Rickettsia-like organisms, are small, non-motile bacteria that inhabit the vascular system of plants and reproduce by binary fission. They are transmitted by insect vectors and cause diseases in various crop plants such as citrus greening, Pierce's disease of grapevines, and clover club leaf. FVB that inhabit the xylem cause symptoms like leaf necrosis, stunting, and yield reduction, while those limited to the phloem cause stunting, yellowing, and premature death. Examples include Leifsonia xyli subsp. xyli in sugarcane and Xylella fastid
This presentation summarizes several diseases that affect the sissoo tree species (Dalbergia sissoo), including leaf spot caused by various fungi which produce yellowish or grayish lesions on leaves, leaf blight caused by Rhizoctonia solani which causes stomata-infected blotches on leaves, powdery mildew caused by Phyllactinia dalbergiae which produces a dense white mycelium on leaves, and rust disease caused by Maravalia achroa which infects seedlings. It also discusses wilt symptoms of flagging leaves and die-back symptoms of thinning foliage and drying branches. Control methods include fungicide applications and sanitation practices.
The document discusses factors that affect plant disease epidemics. It describes the disease triangle of host, pathogen, and environment interacting to cause disease. It further expands the triangle to the disease tetrahedron with the addition of time and human factors. Key factors discussed for each element include the susceptibility and genetics of host plants, the virulence and life cycle of pathogens, and the role of temperature, humidity and other environmental conditions in supporting pathogen survival and spread. The concepts of epidemiology, plant disease forecasting, and remote sensing in detecting and monitoring diseases are also summarized.
Nematode management in protected cultivation describes about existing practices of farmers and scientific integrated nematode management techniques along with IIHR package of practices.
Late blight of potato is caused by the oomycete Phytophthora infestans. It was first described in the 1840s and caused the Irish potato famine. The disease affects potato and tomato leaves, stems, and tubers, causing lesions and rot. Favorable conditions for the disease include temperatures of 16-22°C and wet weather. Management strategies include using disease-free seed tubers, fungicide sprays, crop rotation, and resistant varieties.
This document discusses structural defense mechanisms in plants against pathogens. It describes both constitutive and induced defenses, which can be morphological (structural) or biochemical. Structural defenses include pre-existing barriers like waxy coatings, hairs, lignin and cuticles, as well as post-infection structures like tyloses, cork layers and abscission zones that limit pathogen spread. These physical barriers block pathogen entry and movement.
This document discusses several fungal, bacterial, viral, viroid, and phytoplasma diseases that affect apples. It provides details on the symptoms, disease cycle and management of important diseases like apple scab caused by Venturia inaequalis, fire blight caused by Erwinia amylovora, and apple proliferation caused by phytoplasma mali. India is the 5th largest producer of apples globally, with Jammu and Kashmir and Himachal Pradesh being the major apple growing regions.
This document discusses red rust, an algal disease affecting horticultural crops like mango, guava, and tea. It is caused by the algae Cephaleuros virescens, C. mycoides, or C. parasiticus. Symptoms include green to orange spots on leaves and stems that can cause dieback. The disease spreads through airborne spores and favors humid conditions in stressed or poorly drained plants. Management strategies include sanitation, pruning to improve air circulation, controlling weeds and plant stress, selecting resistant varieties, and applying fungicides according to label directions.
DEFENCE MECHANISM IN PLANTS AGAINST PATHOGENS (STRUCTURAL & BIOCHEMICAL) ansarishahid786
Plants have both structural and biochemical defense mechanisms against pathogens. Structural defenses include pre-existing traits like thick cuticles and presence of thick-walled cells, as well as induced responses like formation of cork layers and tyloses after infection. Biochemical defenses include pre-existing inhibitory compounds and enzymes, as well as induced responses like phytoalexins, hypersensitive response, and transgenic production of plantibodies after pathogen detection. Together these defenses provide multiple layers of protection against the wide variety of fungi, bacteria, viruses and other pathogens that plants encounter.
Epidemiology, etiology and management of fusarium wilt of muskmelonNageshb11
This document summarizes research on Fusarium wilt of muskmelon caused by the fungus Fusarium oxysporum f. sp. melonis. It provides background on the epidemiology, etiology, and management of the disease. It also presents 4 case studies that examined the influence of environmental factors on disease development, evaluated biological control agents for managing the disease, and assessed integrated management approaches. The case studies found that temperature, soil moisture, and texture influence disease incidence and that the bacteria Streptomyces olivaceus and fungi Trichoderma viride and Aspergillus niger show potential for biological control of the pathogen.
Juvenility is a developmental stage in seedling plants where they are unable to induce flowers. The length of the juvenile period varies between plant species, from as short as 20-30 days in roses to 4-8 years in apples. During juvenility, seedling plants exhibit characteristics like vigorous leaf growth, whip-like shoot growth, and the presence of thorns in some species. Environmental factors like temperature, photoperiod, light intensity and quality, and nutrient and moisture availability can influence the transition out of juvenility and induce flowering.
Cultural Disease Management Strategies.pptxOm Prakash
Cultural practices are important for eco-friendly disease management in agriculture. This includes manipulating planting times and locations, crop rotations, and sanitation to reduce pathogen inoculum levels and disrupt disease cycles. Specifically, selecting dry areas, rotating fields, using disease-resistant varieties, rouging infected plants, and destroying crop debris can help manage many fungal and bacterial diseases. Proper nutrient management and irrigation practices also impact disease development and severity.
The document discusses diseases that affect several fruit crops including mango, banana, and citrus. For mango, it describes the symptoms and management of powdery mildew, anthracnose, and red rust. For banana, it covers yellow and black sigatoka, Panama wilt, Erwinia rhizome rot, banana bunchy top virus, and anthracnose. Finally, for citrus it discusses gummosis and citrus canker, outlining the causal organisms, symptoms, and recommended control measures for each disease.
The document summarizes plant defense mechanisms against pathogens. It discusses both structural and biochemical defenses. For structural defenses, it describes preexisting structures like cuticular wax, thick cuticles, and lignified cell walls that physically block pathogens. It also discusses defense structures that develop after infection, like cell wall thickening, callose deposition, and tissue necrosis. For biochemical defenses, it outlines preexisting inhibitors and lack of nutrients for pathogens. It also describes phytoalexins and other compounds produced after infection, such as phenolic compounds and substances that deactivate pathogen enzymes and toxins. The document provides several examples to illustrate different defense strategies in plants.
This document summarizes the key principles of plant infection:
1) Penetration is the entry of the pathogen into the host, which can occur directly through the plant surface, through wounds, or through natural openings like stomata, hydathodes, or lenticels.
2) Infection is the establishment of the pathogen within the host plant by procuring nutrients from host cells or tissues.
3) Invasion is the spread of the pathogen within the host, which can be intercellular or intracellular depending on the type of pathogen.
4) Dissemination refers to the spread of the pathogen from one plant to another, which can occur autonomously through soil, seeds, or plant parts,
This document provides an overview of bacterial plant pathogens. It begins with an introduction to bacteria and their role in nature, both beneficial and pathogenic. It then discusses the classification of phytopathogenic bacteria according to their shape, cellular structure, staining properties, and taxonomy. The document outlines common symptoms of bacterial diseases including leaf spots, blights, wilts, cankers, and galls. It provides examples of genera of bacteria that cause specific symptoms and diseases.
The document discusses plant disease forecasting. It provides information on:
1. The principles of disease forecasting are based on the nature of the pathogen, environmental effects on pathogen development, host response to infection, and grower activities.
2. Models for disease prediction include empirical, simulation, and general circulation models, but these models have limitations due to uncertainty and non-linear relationships.
3. Disease forecasts are used for strategic decision making like crop selection and tactical decisions around disease management measures. Successful forecasting requires reliability, simplicity, importance of the disease, and usefulness.
Fastidious vascular bacteria (FVB), also known as Rickettsia-like bacteria or Rickettsia-like organisms, are small, non-motile bacteria that inhabit the vascular system of plants and reproduce by binary fission. They are transmitted by insect vectors and cause diseases in various crop plants such as citrus greening, Pierce's disease of grapevines, and clover club leaf. FVB that inhabit the xylem cause symptoms like leaf necrosis, stunting, and yield reduction, while those limited to the phloem cause stunting, yellowing, and premature death. Examples include Leifsonia xyli subsp. xyli in sugarcane and Xylella fastid
This presentation summarizes several diseases that affect the sissoo tree species (Dalbergia sissoo), including leaf spot caused by various fungi which produce yellowish or grayish lesions on leaves, leaf blight caused by Rhizoctonia solani which causes stomata-infected blotches on leaves, powdery mildew caused by Phyllactinia dalbergiae which produces a dense white mycelium on leaves, and rust disease caused by Maravalia achroa which infects seedlings. It also discusses wilt symptoms of flagging leaves and die-back symptoms of thinning foliage and drying branches. Control methods include fungicide applications and sanitation practices.
The document discusses factors that affect plant disease epidemics. It describes the disease triangle of host, pathogen, and environment interacting to cause disease. It further expands the triangle to the disease tetrahedron with the addition of time and human factors. Key factors discussed for each element include the susceptibility and genetics of host plants, the virulence and life cycle of pathogens, and the role of temperature, humidity and other environmental conditions in supporting pathogen survival and spread. The concepts of epidemiology, plant disease forecasting, and remote sensing in detecting and monitoring diseases are also summarized.
Nematode management in protected cultivation describes about existing practices of farmers and scientific integrated nematode management techniques along with IIHR package of practices.
Late blight of potato is caused by the oomycete Phytophthora infestans. It was first described in the 1840s and caused the Irish potato famine. The disease affects potato and tomato leaves, stems, and tubers, causing lesions and rot. Favorable conditions for the disease include temperatures of 16-22°C and wet weather. Management strategies include using disease-free seed tubers, fungicide sprays, crop rotation, and resistant varieties.
This document discusses structural defense mechanisms in plants against pathogens. It describes both constitutive and induced defenses, which can be morphological (structural) or biochemical. Structural defenses include pre-existing barriers like waxy coatings, hairs, lignin and cuticles, as well as post-infection structures like tyloses, cork layers and abscission zones that limit pathogen spread. These physical barriers block pathogen entry and movement.
This document discusses several fungal, bacterial, viral, viroid, and phytoplasma diseases that affect apples. It provides details on the symptoms, disease cycle and management of important diseases like apple scab caused by Venturia inaequalis, fire blight caused by Erwinia amylovora, and apple proliferation caused by phytoplasma mali. India is the 5th largest producer of apples globally, with Jammu and Kashmir and Himachal Pradesh being the major apple growing regions.
This document discusses red rust, an algal disease affecting horticultural crops like mango, guava, and tea. It is caused by the algae Cephaleuros virescens, C. mycoides, or C. parasiticus. Symptoms include green to orange spots on leaves and stems that can cause dieback. The disease spreads through airborne spores and favors humid conditions in stressed or poorly drained plants. Management strategies include sanitation, pruning to improve air circulation, controlling weeds and plant stress, selecting resistant varieties, and applying fungicides according to label directions.
DEFENCE MECHANISM IN PLANTS AGAINST PATHOGENS (STRUCTURAL & BIOCHEMICAL) ansarishahid786
Plants have both structural and biochemical defense mechanisms against pathogens. Structural defenses include pre-existing traits like thick cuticles and presence of thick-walled cells, as well as induced responses like formation of cork layers and tyloses after infection. Biochemical defenses include pre-existing inhibitory compounds and enzymes, as well as induced responses like phytoalexins, hypersensitive response, and transgenic production of plantibodies after pathogen detection. Together these defenses provide multiple layers of protection against the wide variety of fungi, bacteria, viruses and other pathogens that plants encounter.
Epidemiology, etiology and management of fusarium wilt of muskmelonNageshb11
This document summarizes research on Fusarium wilt of muskmelon caused by the fungus Fusarium oxysporum f. sp. melonis. It provides background on the epidemiology, etiology, and management of the disease. It also presents 4 case studies that examined the influence of environmental factors on disease development, evaluated biological control agents for managing the disease, and assessed integrated management approaches. The case studies found that temperature, soil moisture, and texture influence disease incidence and that the bacteria Streptomyces olivaceus and fungi Trichoderma viride and Aspergillus niger show potential for biological control of the pathogen.
Juvenility is a developmental stage in seedling plants where they are unable to induce flowers. The length of the juvenile period varies between plant species, from as short as 20-30 days in roses to 4-8 years in apples. During juvenility, seedling plants exhibit characteristics like vigorous leaf growth, whip-like shoot growth, and the presence of thorns in some species. Environmental factors like temperature, photoperiod, light intensity and quality, and nutrient and moisture availability can influence the transition out of juvenility and induce flowering.
Cultural Disease Management Strategies.pptxOm Prakash
Cultural practices are important for eco-friendly disease management in agriculture. This includes manipulating planting times and locations, crop rotations, and sanitation to reduce pathogen inoculum levels and disrupt disease cycles. Specifically, selecting dry areas, rotating fields, using disease-resistant varieties, rouging infected plants, and destroying crop debris can help manage many fungal and bacterial diseases. Proper nutrient management and irrigation practices also impact disease development and severity.
The document discusses diseases that affect several fruit crops including mango, banana, and citrus. For mango, it describes the symptoms and management of powdery mildew, anthracnose, and red rust. For banana, it covers yellow and black sigatoka, Panama wilt, Erwinia rhizome rot, banana bunchy top virus, and anthracnose. Finally, for citrus it discusses gummosis and citrus canker, outlining the causal organisms, symptoms, and recommended control measures for each disease.
The document summarizes plant defense mechanisms against pathogens. It discusses both structural and biochemical defenses. For structural defenses, it describes preexisting structures like cuticular wax, thick cuticles, and lignified cell walls that physically block pathogens. It also discusses defense structures that develop after infection, like cell wall thickening, callose deposition, and tissue necrosis. For biochemical defenses, it outlines preexisting inhibitors and lack of nutrients for pathogens. It also describes phytoalexins and other compounds produced after infection, such as phenolic compounds and substances that deactivate pathogen enzymes and toxins. The document provides several examples to illustrate different defense strategies in plants.
Plants have two types of defense mechanisms against pathogens: structural barriers and biochemical reactions. Structural barriers include pre-existing features like thick cell walls and wax coatings, as well as post-infection responses like cork layers, tyloses, and necrotic tissue that isolate the pathogen. Biochemical defenses include pre-existing inhibitors exuded by the plant and induced responses like the hypersensitive response where infected cells undergo rapid cell death to prevent pathogen spread. Together these mechanisms inhibit pathogens from entering plants, limit their growth and movement within plants, and produce toxic compounds to kill pathogens.
Plants have both pre-existing and induced defense mechanisms against pathogens. Pre-existing defenses include structural barriers like the cuticle, cell walls, and natural openings. Biochemical pre-existing defenses include a lack of recognition factors for pathogens and an absence of receptors for pathogen toxins. When a plant is challenged by a pathogen, it induces additional structural defenses like cork layers and gum deposition. Induced biochemical defenses include the hypersensitive response, which causes cell death around the infection site, production of antimicrobial compounds, and detoxification of pathogen toxins. Both pre-existing and induced defenses help plants resist pathogen infection and disease development.
1. Plants have various structural defence mechanisms to prevent pathogen infection, including waxes, cuticles, thickened cell walls, and natural openings that limit pathogen entry.
2. After infection occurs, plants form additional defensive structures like cork layers, tyloses, gum deposits, and abscission layers that isolate the pathogen from healthy tissue.
3. Structures like tyloses and sheath formations around hyphae can physically block pathogen spread within the plant. Together, pre-existing and infection-induced structures help plants resist pathogens.
This document discusses the defense mechanisms of plants against plant pathogens. It describes two main types of defense mechanisms: structural (morphological) defenses and biochemical defenses. Structural defenses include pre-existing barriers like wax layers and thick cell walls, as well as induced defenses created after infection like cork layers and tyloses formation. Biochemical defenses include both pre-existing compounds like phenolics and induced responses like phytoalexin and PR protein production. The document provides examples of specific defense mechanisms employed by plants in response to various pathogens.
Morphological Resistance of Plants against plant pathogens.pptxmanohargowdabp
This document discusses morphological resistance mechanisms in plants against pathogens. It describes that plants defend themselves through structural characteristics and biochemical reactions. Structural defenses include pre-existing features like wax, cuticles, thick cell walls, and stomata shape. Post-infection structural defenses are induced, like cork layer formation, abscission layers, tyloses, and gum deposition that contain or isolate the pathogen. Cell wall defenses also morph to trap pathogens through swelling, thickening, or papillae formation. Overall, plants employ a variety of physical and induced structural changes to resist pathogen penetration and growth.
This document discusses the structural and biochemical defense mechanisms in plants against pathogens. It begins by introducing that plants lack an immune system like animals but have developed defenses to detect and prevent extensive damage from invading organisms. It then describes structural defenses like waxes, thick cuticles and cell walls that act as pre-existing barriers, as well as post-infection responses like cork layer formation. Biochemical defenses include pre-existing inhibitors and phenolic compounds, as well as induced responses like phytoalexins - toxic antimicrobial substances produced after infection. Overall, the document provides an overview of the key physical and chemical defenses plants have evolved to protect against various fungi, bacteria, viruses and other pathogens.
Defence mechanism in plants: Preformed substances and structures.DR. AMIR KHAN
This document discusses various types of plant disease resistance. It begins by defining resistance and describing non-host resistance and gene for resistance. It then discusses true resistance, which is genetically controlled, and divides it into horizontal and vertical resistance. Horizontal resistance is polygenic while vertical is monogenic. Apparent resistance is also discussed, relating to disease escape or tolerance. The document then examines preexisting and induced structural and chemical defenses in plants, providing examples for mechanisms like waxes, cell wall thickening, and pathogenesis-related proteins.
Avs defense responses of plants to pathogenAMOL SHITOLE
This document provides information on the defense mechanisms used by plants against pathogens like fungi, bacteria, and viruses. It discusses both pre-existing and induced defense structures and biochemical defenses. Pre-existing structural defenses include waxy cuticles, thick cell walls, and natural openings that block pathogen entry. Induced structural defenses are formed in response to infection, such as cork layers, tyloses, and gum deposits that inhibit pathogen spread. Biochemical defenses include inhibitors released by plants, as well as induced responses like the hypersensitive response and production of antimicrobial compounds like phytoalexins and phenolics. The document outlines the process of pathogen recognition, signal transduction, and activation of these various defense responses in plants.
Structural defence mechanism in plantsraichur agri
This document discusses structural and post-infection defense mechanisms in plants. Pre-existing structural defenses include waxes, cuticles, epidermal and sclerenchyma cells that form physical barriers against pathogens. Post-infection defenses are produced after infection, including histological barriers like cork layers and abscission layers that isolate the infection, and cellular defenses where invading hyphae are enveloped by the plant cell. Together these defenses provide plants with multilayered protection against fungal, bacterial and viral pathogens.
Plants have developed structural, chemical, and protein-based defenses against pathogens. Structural defenses include waxy coatings, thick cell walls, and pores designed to limit pathogen entry. Chemical defenses include pre-existing compounds like phenolics and induced responses like phytoalexins and hypersensitive response that are activated post-infection. Together, a plant's layered defenses work to detect, stop, and limit damage from invading pathogens.
structuralbarriers for defence-191001065252.pdfdawitg2
This document discusses structural defense mechanisms in plants against pathogens. It describes both constitutive and induced defenses, which can be morphological (structural) or biochemical. Structural defenses include pre-existing barriers like waxy coatings, hairs, lignin and cuticles, as well as sub-surface barriers like epidermal cells, stomata and lenticels. Post-infection defenses form after pathogen attack, such as tyloses that block vascular systems, cork layers that limit lesion size, and hypersensitive response that causes rapid cell death around the infection site. These structural defenses help protect plants by physically blocking pathogens or limiting their spread and access to nutrients.
Biofilm is a complex aggregate of microorganisms that attach to each other and to surfaces. Bacteria predominantly exist in biofilms, embedded in a self-produced matrix. Biofilm formation involves three phases - attachment, maturation, and dispersion. During attachment, bacteria attach reversibly and then irreversibly to surfaces. In maturation, bacteria activate genes to recruit other cells and build a matrix. Mature biofilms are resistant to antibiotics and host defenses. Dispersion spreads biofilms to new surfaces. Biofilms pose threats as the leading cause of healthcare-associated infections and are resistant to treatment.
Plants have two main ways to defend themselves against pathogens: structural characteristics and biochemical characteristics. Structural defenses include waxy cuticles, thick cell walls, stomata shape and distribution, trichomes, lenticels, hydathodes, cork layers, abscission layers, and tyloses. Biochemical defenses include the hypersensitive response where infected cells are killed to contain the pathogen, and inducible chemical defenses where pathogens are recognized by molecular patterns which triggers immune responses. Together these structural and biochemical defenses help plants survive attacks from hundreds of potential pathogens.
How plants defend themselves against pathogensMohamed Barakat
Plants have two main ways to defend themselves against pathogens: structural characteristics and biochemical characteristics. Structural defenses include waxy cuticles, thick cell walls, stomata shape and distribution, trichomes, lenticels, hydathodes, cork layers, abscission layers, and tyloses. Biochemical defenses include the hypersensitive response where infected cells are killed to contain the pathogen, and inducible chemical defenses where pathogens are recognized by molecular patterns which triggers immune responses. Together these structural and biochemical defenses help plants survive attacks from hundreds of potential pathogens.
Defense Mechanism & Pollination pattern in plants pptSUNILKUMARSAHOO16
This document provides an overview of defense mechanisms in plants and patterns of pollination. It discusses structural, chemical, and protein-based defenses plants use against pathogens like fungi, bacteria, and viruses. It also outlines different pollination types including abiotic (wind, water), biotic (insects, birds, bats), and artificial pollination used in hybridization. The document contains detailed information on specific defense structures, chemicals, and the characteristics of different pollination methods. It aims to explain the complex interactions between plants and pathogens or pollinators.
This document provides information on fundamental principles of microbiology. It discusses that microbiology is the study of microscopic organisms and medical microbiology focuses on pathogens that infect humans. The main types of microorganisms covered are bacteria, fungi, viruses, protozoa, and more. It provides details on the classification, structure, growth and diseases caused by different bacteria and fungi.
a detailed description of structural and biochemical mechanisms and importance of phytoalexins in plants and different types of phytoalexins produced the plants and its functions and importance in plant defense mechanism
The document discusses periderm, the protective layer of bark that forms in plants. It is composed of three layers: the phellogen or cork cambium, the phellem or cork layer, and the phelloderm. The document describes where the phellogen layer originates in different plant species, either just under the epidermis or deeper in the stem tissue. It also discusses lenticels, which allow gas exchange, and rhytidome, the layers of old periderm. Commercial cork is harvested from cork oak trees.
Secondary growth occurs in woody stems and roots through the activity of vascular cambium, which adds secondary xylem inward and secondary phloem outward. This increases the girth of the plant. In temperate regions, tree rings form from differences between early and late secondary xylem, and can be used to estimate a tree's age and study past climate. Cork cambium also forms a protective periderm layer over the stem. Together, secondary growth and protective layers allow woody plants to grow larger.
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Three new species of the genus Agaricus were discovered in Punjab, India between 2008-2012: A. stellatus-cuticus, A. punjabensis, and A. patialensis. A. stellatus-cuticus is characterized by a stellate splitting cap surface and abundant cheilocystidia. A. punjabensis is campestroid with an annulate stipe lacking brown scales and a pileus cuticle that does not change in KOH. A. patialensis has small, golden brown carpophores with a distinctly bulbous stipe. These new discoveries were identified through detailed examination of macroscopic and microscopic characteristics.
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Defence mechanism in plants
1. Defense Mechanism in Plants (With Diagram)
Structural and biochemical defense mechanisms in plants
I. Structural Defense:
In plants some structures are already present to defend the attack while in others, the structures to
defend the host develops after the infection. In this way, structural defense can be characterised as (A)
Preexisting defense structures and (B) Defense structures developed after the attack of the pathogen.
(A) Pre-existing Defense Structures:
(i) Cuticular Wax:
Wax-mixtures of long chain aliphatic compounds get deposited on the cuticular surface of some plants.
Deposition of wax on the cuticular surface is thought to play a defensive role by forming a hydrophobic
surface where water is repelled.
As a result, the pathogen does not get sufficient water to germinate or multiply. In addition, a negative
charge usually develops on the leaf surface due to the presence of fatty acids – the main component of
cuticle. The negative charge prevents/reduces the chance of infection by many pathogens.
(ii) Cuticle Thickness:
The thickness of cuticle is most important for those which try to enter the host through the leaf surface.
The cuticle thickness obstructs the path of pathogen. In addition, a thick cuticle checks the exit of the
pathogen from inside the host, thus reducing the secondary infection.
(iii) Structure of Epidermal Cell Walls:
Tough and thick outer walls of epidermal cells may directly prevent the entry of the pathogen
completely or make the entry difficult. The presence or absence of lignin and silicic acid in the cell
walls may show variation in resistance to penetration of the pathogen.
Most outer walls of epidermal cells of rice plants are lignified and are seldom penetrated by blast
disease of rice pathogen. In resistant varieties of potato tubers (resistant to Pythium debaryanum) the
epidermal cells contain higher fibre content than the susceptible ones.
(iv) Structure of Natural openings:
Structure of natural openings like stomata lenticels etc. also decide the fate of the entry of the pathogen.
In Szincum variety of citrus, the stomata are small and possess very narrow openings surrounded by
broad lipped raised structures which prevent entry of water drops containing citrus canker bacterium.
In the same way, the size and internal structures of lenticels may play a defensive role against the
pathogens. Varieties having small lenticels in the apple fruits prevent the entry of the pathogen while
those having large openings easily allow the pathogen to enter.
2. Nectaries provide openings in the epidermis and may play a defensive role due to high osmotic
concentration of the nectar. In resistant varieties of apple, presence of abundant hairs in the nectaries
acts as a defense mechanism while susceptible varieties are devoid of abundant hairs.
Internal Defense Structures:
There are many preexisting internal defense structures inside the plant that prevent the entry of
pathogen beyond these structures. In some plants, cell walls of certain tissues become thick and tough
due to environmental conditions and this makes the advance of the pathogen quite difficult.
In case of stems of cereal crops, vascular bundles or extended areas of sclerenchyma cells checks the
progress of rust pathogen. Leaf veins effectively obstruct the spread of pathogen like the angular leaf
spot pathogen.
(B) Defense Structures Developedafter the Attack of the Pathogen:
After the pathogen has successfully managed to overcome the preexisting defense mechanisms of the
host, it invades the cells and tissues of the host.
In order to check the further invasion by the pathogen, the host plants develop some
structures/mechanisms which may be defense reactions in the cytoplasm, cell wall defense structures,
defense structures developed by the tissues and ultimately the death of the invaded cell i.e. necrosis.
These will be briefly discussed here.
(i) Defense Reactions in the Cytoplasm:
The cytoplasm of the invaded cell surrounds the hyphae of the pathogen and the nucleus of the host cell
gets stretched to break into two. In some host cells, the cytoplasm and the nucleus of the infected cells
enlarge.
The cytoplasm becomes granular and dense and develops granular particles. These result in the
disintegration of the pathogen mycelium and thus the invasion stops. Such cytoplasmic defence
mechanisms can be seen in weak pathogens like Annillaria and some mycorrhizal fungi.
(ii) Cell Wall Defense Structures:
Cell wall defense structures are of limited help to the host. These include morphological changes in the
cell wall of the host.
Three types of cell wall defense structures are generally observed:
(i) Cell walls thicken in response to the pathogen by producing a cellulose material, thus preventing the
entry of the pathogen
(ii) The outer layer of cell walls of the parenchyma cells in contact with invading bacterial cells
produce an amorphous fibrillar material that traps the bacteria thus preventing them to multiply and
(iii) Callose papillae get deposited on the inner layers of the cell walls due to invasion by fungal
pathogens.
3. In raw cases, the hyphal tips of the infecting fungal pathogen penetrating the cell wall and thereafter
growing into the cell lumen get enveloped by callose material that, later become infused with phenolics
forming a sheath around the hyphae.
(iii) Defense Structures Developedby the Tissues:
The following four developments take place in the tissues after penetration:
(a) Gum Deposition:
Plants produce a variety of gummy substances around lesions or spots as a result of infection. These
gummy substances inhibit the progress of the pathogen. The gummy substances are commonly
produced in stone fruits.
(b) Abcission Layers:
Abscission layers are usually formed to separate the ripe fruits and old leaves from the plant. But in
some stone fruit trees, these layers develop in their young leaves in response to infection by several
fungi, bacteria or viruses. An abscission layer is a gap formed between two circular layers of cells
surrounding the point of infection.
This gap is created by the dissolution of one or two layers of the middle lamella, one or two layers of
cells surrounding the infected loci resulting in the infected locus becoming unsupported, shrivels, dies
and falls down along with the pathogen. Abscission layer formation protects the healthy leaf tissue
from the attack of the pathogen.
(C) Tyloses:
Tyloses are out growths of protoplasts of adjacent live parenchyma cells protruding into xylem vessels
through pits under stress or in response to attack by the vascular pathogens. Their development blocks
the Xylem vessels, obstructing the flow of water and resulting in the development of wilt symptoms.
However, tyloses are formed in some resistant plants ahead of infection and the prevent the plant from
being attacked.
(D) Formation of Layers:
Some pathogens like certain bacteria, some fungi and even some viruses and nematodes stimulate the
host to form multilayered cork cells in response to infection, these develop as a result of stimulation of
host cells by substances secreted by thus, pathogen.
These layers inhibit the further invasion by the pathogen and also block the flow of toxic substances
secreted by the pathogen. Cork layers also stop the flow of nutrients of the host thus also depriving the
pathogen of the nutrients.
Examples of cork layer formation as a result of infection are: soft not of potato caused by Rhizopus sp.,
potato tuber disease caused by Rhizoctonia sp., Scab of potato caused by Streptomyces scabies and
necrotic lesions on tobacco caused by tobacco mosaic virus.
4. IV. Necrosis or Hypersensitive Type of Defense:
Necrosis or hypersensitive type of defense is another defense mechanism adopted by some pathogens
like Synchytrium endobioticum causing wart disease of potato, Phytophthora infestans causing late
blight disease of potato and Pyricularia oryzae causing blast of rice etc.
In such diseases, the host nucleus moves toward the pathogen when the latter comes in contact with the
protoplasm of the host. The nucleus soon disintegrates into brown granules which first accumulate
around the pathogen, later dispersing throughout the host cytoplasm.
Soon the cell membrane swells and finally the cell bursts and dies. These cause the pathogen nucleus to
disintegrate into a homogenous mass and its cytoplasm dense. As a result, the pathogen fails to grow
beyond the necrotic or dead cells and the further growth of the pathogen is stopped.
II. Biochemical Defense:
Although structural defense mechanisms do prevent the attack of the pathogen, the defense mechanism
also includes the chemical substances produced in the plant cells before or after the infection.
It has now been established that biochemical defense mechanisms play more important role than the
structural defense mechanisms. This has been supplemented by the fact that many pathogens entering
non host plants naturally or artificially inoculated fail to cause infections in absence of any structural
barriers.
This does suggest that chemical defense mechanisms rather than structural mechanisms are responsible
for resistance in plants against certain pathogens.
(A) Preexisting Biochemical Defense:
(i) Inhibitors Releasedin the Prepenetration Stage:
Plant generally exudes organic substance through above ground parts (phyllosphere) and roots
(rhizosphere). Some of the compounds released by some plants are known to have an inhibitory effect
on certain pathogens during the prepenetration stage.
For example fungistatic chemicals released by tomato and sugar beet prevent the germination of
Botrytis and Cercospora. Presence of phenolics like protocatechuic acid and catechol in scales of red
onion variety inhibit the germination of conidia of Colletotrichum circinans on the surface of red onion.
Inhibitors present in high concentrations in the plant cells also play an important role in defense of
plants. Presence of several phenolics, tannins and some fatty acid like compounds such as dienes in
cells of young fruits, leaves or seeds afford them resistance to Botrytis.
The tubers of resistance vars of potato against potato scab disease contain higher concentrations of
chlorogenic acid around the lenticels and tubers than the susceptible vars. Several other compounds
like saponin tomatin in tomato and avinacin in oats have antifungal activity. Some enzymes like
glucanases and chitinases present in cells of some plants may break down the cell wall components of
pathogens.
5. (ii) Lack of nutrients essential for the pathogen is another preexisting biochemical defense mechanism.
Plant varieties or species which do not produce any of the chemicals essential for the growth of
pathogen may act as resistant variety.
For example, a substance present in seedling varieties susceptible to Rhizoctonia initiates hyphae
cushion formation from which the fungus sends penetration hyphae inside the host plants. When this
substance is not present, hyphal cushions are not formed and the infection does not occur.
(iii) Absence of Common Antigen in Host plant:
It is now clear that the presence of a common protein (antigen) in both the pathogen and host
determines diseases occurrence in the host. But if the antigen is present in the host and absent in the
host or vice-versa, it makes the host resistant to the pathogen.
For example, varieties of linseed which have an antigen common to their pathogen are susceptible to
the disease rust of linseed caused by Melampsora lini.
In contrast, the absence of antigen in linseed varieties but occurring in the pathogen are resistant to the
pathogen. Another example is leaf spot disease of cotton caused by Xanthomonas campestris pv.
malvacearum.
(B) Post-Infection-Biochemical Defense Mechanism:
In order to sight infections caused by pathogens or injuries caused by any other means, the plant cells
and tissues produce by synthesis many substances (chemicals) which inhibit the growth of causal
organism.
These substances are generally produced around the site of infection or injury with the main aim at
overcoming the problem.
Some such important chemicals are described below:
(i) Phenolic Compounds:
These are the most common compounds produced by plants in response to injury or infection. The
synthesis of phenolic compounds takes place either through “acetic acid pathway” or “Shikimic acid
pathway”.
Some common phenolic compounds toxic to pathogens are chlorgenic acid, caffeic acid and ferulic
acid. These phenolic compounds are produced at a much faster rate in resistant varieties than in
susceptible varieties.
Probably that the combined effect of all phenolics present is responsible for inhibiting the growth of the
infection.
(ii) Phytoalexins:
Phytoalexins are toxic antimicrobial substances synthesized ‘de novo’ in the plants in response to
injury, infectious agents or their products and physiological stimuli. The term phytoalexin was first
6. used by the two phytopathologists Muller and Borger (1940) for fungi static compounds produced by
plants in response to mechanical or chemical injury or infection.
All phytoalexins are lipophilic compounds and were first detected after a study of late blight of potato
caused by Phytophthora infestans. Phytoalexins are believed to be synthesized in living cells but
surprisingly necrosis follows very quickly.
According to Bill (1981), peak concentration of phytoalexins almost always coincides with necrosis.
Although the exact mechanism of production of phytoalexin has not been properly understood, it is
considered that a metabolite of the host plant interacts with specific receptor on the pathogen’s
membrane resulting in the secretion of “phytoalexin elicitor” which enters the host plant cells and
stimulates the phytoalexin synthesis.
Phytoalexins are considered to stop the growth of pathogens by altering the plasma membrane and
inhibiting the oxidative phosphorylation.
Phytoalexins have been identified in a wide variety of species of plants such as Soyabean, Potato, sweet
potato, barley, carrot, cotton etc. are being investigated. Some common phytoalexins are
Ipomeamarone, Orchinol, Pistatin, Phaseolin, Medicarpin, Rishitin, Isocoumarin, ‘Gossypol’ Cicerin,
Glyceolin, Capisidiol etc.
The following Table gives a list of phytoalexins, chemical nature the host and the pathogens in
response to which these are produced:
(iii) Substances Produced in Host to Resist Enzymes Produced by Pathogen:
Some hosts produce chemicals which neutralise the enzymes produced by pathogen, thus defending the
host. Therefore these substances help plants to defend themselves from the attack of the pathogen.
In bean plants, infection with Rhizoctonia solani causes necrosis. In resistant bean varieties, the entry
of pathogen causes the separation of methyl group from methylated pectic substances and forms
polyvalent cations of pectic salts which contain calcium.
The calcium ions accumulate in infected as well as neighbouring healthy tissues and because of the
calcium accumulation, the pathogen fails to disintegrate middle lamella by its polygalacturonase
enzymes. These are known to dissolve the middle lamella of healthy tissue in susceptible varieties.
(iv) Detoxification of Pathogen Toxins and Enzymes:
In some cases, the plants produce chemicals which deactivate the toxins produced by the pathogens.
For example, Pyricularia oryzae which causes blast disease of rice produces Picolinic acid and
pyricularin as toxins.
Although resistant varieties convert these toxins into N-methyl picolininic acid pyrecularin into other
compounds, the susceptible varieties do get affected by these toxins. Similarly in case of cotton and
tomato wilts, the toxin fusaric acid produced by the pathogen gets converted into non-toxic N-methyl-
fusaric acid amide in resistant varieties.
7. As in case of detoxification of toxins, the toxic enzymes produced by the pathogen is deactivated by
phenolic compounds or their oxidation products. Some varieties of cider apple are resistant to brown
not disease caused by Sclereotinia fructigena.
It may be because of the resistant varieties producing phenolic oxidation products which inactivate the
pectinolytic enzymes produced by the pathogen.
(v) Biochemical Alterations:
It has been observed that infection of the host by the pathogen brings about biochemical changes in the
host which may prove toxic to the pathogenic microorganisms and cause resistance to the pathogen.
Production of certain new enzymes and other compounds are synthesized and accumulated in higher
concentration. This may also add to the resistance of the plant by being toxic to pathogenic
microorganisms.