Plant Pathology Basics
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Questions and Answers

What is meant by the term 'plant disease'?

  • A genetic disorder in plants
  • A condition caused by pathogens affecting plants (correct)
  • A term used to describe healthy plants
  • A condition caused by non-living factors

    • Koch's Postulates are used to determine the relationship between a pathogen and the disease it causes.

    True (A)

    What are the main components of the disease triangle?

    Pathogen, Host, Environment

    The _____ triangle helps explain the factors necessary for plant disease occurrence.

    <p>disease</p> Signup and view all the answers

    Match the following aspects of plant pathology with their descriptions:

    <p>Pathogen = Organisms that cause diseases in plants Disease sign = Physical evidence of a disease Disease symptom = Plant's response to a disease Koch's Postulates = Criteria for identifying pathogens causing disease</p> Signup and view all the answers

    Which pathogen is responsible for causing brown rot of peach?

    <p>Monilinia fructicola (A)</p> Signup and view all the answers

    Powdery mildew is caused by Podosphaera leucotricha.

    <p>True (A)</p> Signup and view all the answers

    What type of plant disease is caused by Agrobacterium tumefaciens?

    <p>Crown gall</p> Signup and view all the answers

    Stem rust on barley is caused by the pathogen known as __________.

    <p>Puccinia graminis</p> Signup and view all the answers

    Match the following diseases with their corresponding pathogens:

    <p>Brown rot of lettuce = Botrytis cinerea Canker on apple = Nectria galligena Verticillium wilt of cucumber = Verticillium dahliae Herbicide injury of beans = Herbicide chemical</p> Signup and view all the answers

    What is the primary purpose of epidemiology?

    <p>Study of factors influencing the initiation, development, and spread of infectious disease (A)</p> Signup and view all the answers

    Abiotic factors include living organisms such as animals and plants.

    <p>False (B)</p> Signup and view all the answers

    Who first published the concept of the disease triangle?

    <p>Stevens</p> Signup and view all the answers

    ____________ influence each and every step in the disease development process.

    <p>Environmental conditions</p> Signup and view all the answers

    Which of the following is NOT considered an abiotic factor?

    <p>Plants (B)</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Etiology = Determining the cause of disease Epidemiology = Study of infectious disease factors Disease Triangle = Concept for disease management Abiotic factors = Non-living environmental components</p> Signup and view all the answers

    Symptoms and signs of disease can appear quickly, usually within minutes to hours.

    <p>False (B)</p> Signup and view all the answers

    What crucial aspect of disease severity is considered in epidemiology?

    <p>Time</p> Signup and view all the answers

    Which virus is known to have a typical diameter of approximately 30 nm?

    <p>African cassava mosaic virus (ACMV) (A)</p> Signup and view all the answers

    A biotroph organism can survive only on a living host.

    <p>True (A)</p> Signup and view all the answers

    What does the term 'pathogenicity' refer to in plant pathology?

    <p>The ability of a pathogen to cause disease.</p> Signup and view all the answers

    The organism that incites the disease process in a plant is called a ______.

    <p>pathogen</p> Signup and view all the answers

    What type of virus is associated with a multipartite genome?

    <p>Brome mosaic virus (BMV) (D)</p> Signup and view all the answers

    A disease is defined as an abnormal biochemical process that does not change the physiological state of the host.

    <p>False (B)</p> Signup and view all the answers

    What is the disease triangle in plant pathology?

    <p>A concept that illustrates the interaction between the host, pathogen, and environment.</p> Signup and view all the answers

    Which pathogen is primarily associated with the Irish Potato Famine?

    <p>Phytophthora (C)</p> Signup and view all the answers

    Viruses are classified under microbial phytopathogens.

    <p>False (B)</p> Signup and view all the answers

    Name two examples of fungal phytopathogens.

    <p>Colletotrichum, Fusarium</p> Signup and view all the answers

    The pathogen that severely affected potatoes during the Irish Potato Famine is _____ .

    <p>Phytophthora</p> Signup and view all the answers

    Match the following pathogens with their type:

    <p>Xanthomonas = Bacterial phytopathogen Colletotrichum = Fungal phytopathogen Tobacco mosaic virus = Viral pathogen Ralstonia = Bacterial phytopathogen</p> Signup and view all the answers

    Which of the following is NOT a type of fungal phytopathogen?

    <p>Agrobacterium (D)</p> Signup and view all the answers

    All phytopathogenic bacteria have a cell wall composed of peptidoglycan.

    <p>True (A)</p> Signup and view all the answers

    Identify one viral pathogen that affects plants.

    <p>Potato virus Y</p> Signup and view all the answers

    What term describes the visible response of a plant to an aetiological agent?

    <p>Symptoms (C)</p> Signup and view all the answers

    Signs are less specific than symptoms in diagnosing plant diseases.

    <p>False (B)</p> Signup and view all the answers

    Name a common sign of plant disease that is characterized by visible structures on leaves.

    <p>Rust</p> Signup and view all the answers

    The _____ of a microorganism should be consistent with its known biological characteristics.

    <p>nature</p> Signup and view all the answers

    Match the symptoms with their descriptions:

    <p>Mosaic = A pattern of light and dark green areas on leaves Blight = Death or decay of leaves or stems Wilt = Drooping of leaves due to loss of turgor Rot = Decay of plant tissue usually due to fungal infection</p> Signup and view all the answers

    Which of the following is NOT a common sign of plant disease?

    <p>Wilting leaves (A)</p> Signup and view all the answers

    Exudates or ooze are synonymous with symptoms of plant disease.

    <p>False (B)</p> Signup and view all the answers

    What disease symptom may result in merging spots on a leaf?

    <p>Blight</p> Signup and view all the answers

    Study Notes

    Course Information

    • Course title: BIOL 3025: Molecular Plant Pathology
    • Lecture: 1 - Introduction
    • Instructor: Dr. ANGELA T. ALLEYNE

    Learning Outcomes

    • Define "plant disease"
    • Describe different types of pathogens
    • Explain the disease triangle
    • Explain Koch's Postulates
    • Differentiate between disease signs and symptoms
    • Describe common plant disease symptoms

    Plant Pathology

    • The Irish Potato Famine (1845-1851) marked a turning point in plant pathology, highlighting the importance of understanding plant diseases.
    • Widespread "stinking" rotten potato mass in Europe played a role, as well as the fact that the microbes responsible for the rot were found to be responsible for the destruction of potatoes.
    • This led to the acceptance of the germ theory of disease.

    Microbial Phytopathogens

    • Microbial phytopathogens include bacteria, fungi, viruses, nematodes, and phytoplasmas.
    • These pathogens enter the plant through various ways, such as natural openings, injuries, and direct penetration.
    • Specific examples of microbial phytopathogens:
    • Xanthomonas
    • Streptomyces
    • Ralstonia
    • Xylella
    • Agrobacterium
    • Pseudomonas
    • Clavibacter
    • Phytoplasmas

    Prokaryotic Cells

    • Prokaryotic cells, like bacteria, are characterized by their lack of a nucleus and membrane-bound organelles.
    • Key components: cell wall (peptidoglycan), capsule, fimbriae (pili), cytoplasm, ribosomes, flagellum, and DNA.

    Fungal Phytopathogens

    • Fungal phytopathogens are a diverse group impacting plants.
    • Specific examples: Colletotrichum, Cercospora, Ustilago, Puccinia, Phytophthora, Erysiphe, Claviceps, Fusarium

    Fungi Structure

    • Fungi are characterized by their hyphae, mycelia, conidiophores, and conidia (spores).
    • These structures facilitate the spread and infection of the fungus, playing a critical role in successful pathogenicity.

    Viruses

    • Viruses are a variety of plant pathogens.
    • Examples: Tobacco mosaic virus (TMV), Tomato spotted wilt virus (TSWV), Tomato yellow leaf curl virus (TYLCV), Cucumber mosaic virus (CMV), Potato virus Y (PVY), Cauliflower mosaic virus (CaMV), African cassava mosaic virus (ACMV), Plum pox virus (PPV), Brome mosaic virus (BMV), Potato virus X (PVX).
    • Structure: a nucleic acid (RNA or DNA) enclosed within a protein coat; some have a segmented genome, and some are spherical others are rod-shaped.

    Common Plant Pathology Terms

    • Biotroph: pathogen that survives by living on living tissues of the host plant
    • Necrotroph: pathogen that kills cells of the host plant and obtain nutrients
    • Hemibiotroph: pathogen that combines both biotrophic and necrotrophic growth mechanisms
    • Host: organism on or in which another organism lives
    • Pathogen: organism that causes disease
    • Host-defense: mechanisms by which a host plant resists or prevents the growth of pathogens.
    • Pathogenicity: ability of a pathogen to cause disease.
    • Virulence: relative capacity of a pathogen to cause disease, ranges from minimal damage to death of the plant.

    Pathogenesis

    • Disease is characterized by an abnormal change in the physiological or developmental processes of a host plant, often due to persistent biotic or abiotic factors.
    • The disease triangle includes factors like the pathogen, environment, and host plant interaction.

    Definition of Disease

    • Disease arises from a dynamic relation between an organism (pathogen) that interferes with the normal processes of a host (plant).
    • This interaction is detrimental, resulting in observable damage or symptoms.
    • Plant stresses or injuries are not considered diseases; they are not dynamic.

    Pathogen

    • Pathogens can be either animate or inanimate, including microbes, viruses, and viroids.
    • The definition of pathogen has evolved over time, reflecting advancements in our understanding of disease-causing agents.

    Koch's Postulates & Exceptions

    • These are steps used to prove that a certain microbe causes a specific disease.
    • Exceptions exist for microbes tough to culture in the lab. Molecular methods can often replace earlier steps.

    Signs and Symptoms

    • Symptoms: visible responses of the plant to the disease (e.g., discoloration, wilting, abnormal growth).
    • Signs: microscopic or macroscopic structures produced by the pathogen (e.g., fungal spores, bacterial ooze).

    Common signs of plant disease

    • Exudates or ooze; Wilt; Stem rust
    • Examples: Bacteria oozing from leaves (sign of infection), or mold growth on a plant (sign of infection)
    • Symptoms: change in appearance, necrosis, or death of parts of a plant, underdeveloped tissues, or organs, overdeveloped tissues or organs
    • Examples: Mosaic (discoloration in leaf), blight (rapid wilting and death of plant parts), rot (decay and softening of plant parts), cankers (lesions on stems or branches).

    Examples of Plant Diseases & Causative Agents

    • Various plant diseases and the organisms responsible were mentioned in the presented material.
    • Target spot lesion on tobacco caused by Rhizoctonia solani
    • Bacterial leaf spot on lettuce caused by Xanthomonas campestris pv. vitians.
    • Mosaic on squash leaves
    • Peanut leaf spots caused by Tomato spotted wilt virus.
    • Powdery mildew on apple blossoms caused by Podosphaera leucotricha
    • Stem rust on barley caused by Puccinia graminis
    • Herbicide injury on bean leaves;
    • Canker on an apple tree caused by Nectria galligena
    • Brown rot on peaches caused by Monilinia fructicola
    • Verticillium wilt of cucumber caused by Verticillium dahliae.
    • Crown gall on Euonymous caused by Agrobacterium tumefaciens.
    • Brown rot of lettuce caused by Botrytis cinerea

    Other Key Concepts

    • Time is a critical element in epidemiology, as disease initiation, development, and spread are all influenced by time.
    • Abiotic & Biotic factors influence plant disease, as do the interactions within the disease triangle.
    • Pathobiome: a new concept emphasizing the roles of native microbial community members that may contribute to disease. This includes aspects of the plant microbiome.
    • Disease Triangle: A model to visualize how factors like pathogen, host susceptibility, and environmental conditions contribute to disease.

    Etiology & Epidemiology

    • The study of disease cause and the factors influencing spread are crucial in plant pathology (etiology and epidemiology).

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    BIOL 3025 Molecular Plant Pathology Lecture 1-Introduction PDF

    Description

    Test your knowledge on fundamental concepts of plant diseases, including Koch's Postulates, the disease triangle, and key pathogens. This quiz covers the essential aspects and terminology in plant pathology. Perfect for students studying plant biology or agricultural sciences.

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