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Plant Pathology > Exam notes > Flashcards

Exam notes Flashcards

1
Q

Plant Defense (structural)

A

pre existing structures

formed in response to pathogen invasion

cellular structures

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2
Q

cork layers

A

stop phy advance fungi,bac,virus,nematodes

stop nutrients going pathogen

stop toxin movement from pathogen

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3
Q

Abscission layers

A

middle lamella dissolves and dead area fall out

caused by fungi,bac,vir

shot hole sys

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4
Q

Tyloses

A

overgrowths of the protoplasts of adj living parenchymatous cells protrude into xylem vessels through pits

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5
Q

biochemical defense

A

pre existing bioch def

lack of essential factors
induced by attack pathogen

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6
Q

biochem induced by attacking pathogen

A

hypersensitive response

production of chem

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7
Q

induced antimicrobial chem

A

*phytoalexins

*fungitoxic phenolics

*phenol-oxidizing compounds
(peroxidase)

*enzymes (PR proteins,chitinase)

*inactivation of path enzyme

*release of fungitoic cyanides

*detoxification path toxins

*systemic acquired resistance

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8
Q

Phytoalexins

A

very specific chem R induced by elicitor produced by host

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9
Q

tulipalin against Fusarium

A

fungitoxic phenolics

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10
Q

polyphenoloxidase
peroxidase

A

phenol-oxidizing compounds

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11
Q

PR proteins
chitinase

A

enzymes

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12
Q

polygalacturonase inhibitor in orange rind

A

inactivation of pathogen enzymes

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13
Q

amygdalin in stone fruit

A

release of fungitoxic cyanides

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14
Q

Chitinase

A

breaks down cell wall

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15
Q

System acquired resistance

A
  1. induced chem or microorganisms
    1. signal transport through plant
    1. systemic activated resistance
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16
Q

host defense
resistance varieties are best means of crontrol

A
  1. least expensive
  2. most effective
  3. environmentally safe
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17
Q

Pathogens have genes encoding virulence factors

A

often specific for infection of a few plants

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18
Q

pathogenicity factors

A

necessary for a pathogen to cause disease on a certain species of host plant

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19
Q

virulence factors

A

necessary for or enhancing the ability of a pathogen to cause disease on a certain cultivar, variety, or ecotype of the host plant

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20
Q

avirulence factors

A

pathogen components used by the host plant to recognize the pathogen through resistance genes

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21
Q

Risistance genes confer resistance to a ________ of a pathogen

A

specific race

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21
Q

Virulent races of pathogens occur in response to plant resistance:

A

*genes already present in small number

*mutation

*recombination genetic material

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22
Q

most common non host plant resistance

A

immunity

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23
Q

True resistance

A

controlled genetically
(function differently)

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24
Q

Horizontal plant resistance

A

nonspecific
quantitative
field
durable
multigene

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25
Q

Vertical plant resistance

A

specific
qualitative
single gene

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26
Q

Susceptible plants do not become infected from apparent resistance due to

A

the disease escapes
tolerance to disease

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27
Q

gene that confers resistance in the host and pathogen confers virulence
(gene for gene concept)

A

*operates in many disease

*plant resistance is dominant

*pathogen virulence is recessive

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28
Q

Pathogen produced enzymes

A

*cutinases
*pectinases
*cellulases
*hemicellulases
*ligninases
*proteinases,lipases

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29
Q

a non ezymatic metabolite of one organism which is injurious to another

A

toxin

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30
Q

toxins work by

A

-increasing the permeability of the cell membrane
-inactivating or inhibiting enzyme activity
-inducing a deficiency of an essential growth factor

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31
Q

Non host specific toxins

A

-effect a wide range of plants

-non essential for pathogen to cause disease

-must be present for disease to occur

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32
Q

T-toxin

A

-disrupts mitochondria

-susceptibility to fungus and toxin are inherited maternally in cytoplasmic genes

-virulence and t toxin controlled by same fungal genes

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33
Q

Victorin (HV toxin)

A

-causes leaky plasma membrane
-toxin production controlled by single fungal gene
-toxin responsible for all disease symptoms

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34
Q

Types of growth regulators in plant disease

A

-auxins
-gibberellins
-cytokinins
-ethylene

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35
Q

characteristics of growth regulators in plant disease

A

-work at low concentration
-usually synthesized away from site of action
-promote synthesis of messenger RNA molecules

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36
Q

The effects auxins (indole acetic acid -IAA)

A

-cell elongation and differentiation
-cell membrane permeability
-general increase in respirationn and promote protein synthesis

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37
Q

Auxins (IAA) is produced by

A

-plant alone or induced by pathogen stress
-pathogen
-degradation of IAA oxidase

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38
Q

Gibberellins

A

-speed elongation of dwarf varieties
-promote flowering
-cause stem and root elongation
-help fruit growth
-induce IAA formation

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39
Q

Cytokinins

A

-necessary for cell growth and differentiation
-too much inhibit senescence
-zeatin

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40
Q

excess cause of ethylene

A

-chlorosis
-leaf epinasty and abscission
-simulation of adventitious roots
-fruit ripening
-increased permeability of membranes
-induction of plant resistance mech.

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41
Q

fungi causes diseases by

A

-penetration structures
-enzymes
-growth regulators

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42
Q

how does bacteria cause disease

A

-enzymes
-tissue degradation
-change membrane permeability
-obstruct water movement

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43
Q

bacteria disease of growth regulators cause

A

hypertrophic growth

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44
Q

nematodes cause disease by

A

-enzymes that
altered cell walls (pectinases)
-growth regulators due to IAA production, auxin movement

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45
Q

Viruses use ____ to reproduce and cause disease

A

host

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46
Q

Phytoplasmas cause disease by using _____

A

growth regulators

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47
Q

fungal pathogenicity factors

A

necessary for a pathogen to cause disease on certain species of host plant

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48
Q

fungal virulence factors

A

necessary for or enhancing the ability of a pathogen to cause disease on a certain cultivar, variety, or ecotype of the host plant

49
Q

fungal avirulence factors

A

pathogen components used by the host plant to recognize the pathogen through resistance genes

50
Q

inoculum

A

the pathogen or pathogen parts that come in contact with the host, potentially causing disease

51
Q

propagule

A

a unit of inoculum, a colony forming unit

52
Q

fungi inoculum

A

spores, sclerotia,mycelium

53
Q

inoculum of nematodes

A

adults, larvae, eggs

54
Q

individuals that can be inoculated

A

-bacteria
-viruses
-viroids
-phytoplasmas

55
Q

sources of inoculum

A

-plant debris
-soil
-seed
-transplants (tubers,propagative material)
-weeds (or alternate hosts

56
Q

how do pathogens (fungi,bacteria,parasitic plants,nematodes) produce inoculum on the plant surface or can reach the plant surface after __________.

A

tissue break down

57
Q

viruses, phytoplasmas, and viroids produce inoculum within plants to __________.

A

help to get out of the plant

58
Q

inoculum: most inoculum does not reach susceptible hosts and inefficient

A

wind

59
Q

inoculum: more efficient way

A

water

60
Q

inoculum: insects

A

efficient form of inoculum

61
Q

how does direct placement of pathogen into a host

A

insect vectors

62
Q

fungi, bacteria, parasitic higher plants must become _____

A

attached

63
Q

pathogen to host have ________ and ________

A

-polysaccharides
-glycoproteins

64
Q

attachment of pathogen to host by muscilaginous substances associated with ____________

A

germ tubes

65
Q

penetration sites for fungi

A

-moisture
-soil texture
-topography of leaf

66
Q

penetration sites for bacteria

A

-moisture
-topography of leaf

67
Q

penetration sites for nematodes

A

-tempurature
-soil texture
-plant exudates
-co2
-amino acids

68
Q

penetration sites for zoospores

A

plant exudates

69
Q

the way for invasions in plants

A

-subcuticular
-surface with haustoria in epidermis
-intracellular or intercellular
-xylem tissue
-intracellular
-intercellular

70
Q

bacterial invasions start with _____ and then __________

A

intercellular,
intracellular

71
Q

definition of infection

A

process by which pathogens establish contact with susceptible cells or tissues of the host and procure nutrients from them

72
Q

pathogens grow and/or multiply within the ________ and invade and colonize the plant during infection

A

plant tissues

73
Q

symptoms result from infection, usually within _________

A

a few weeks

74
Q

delayed symptoms, usually due to poor environmental conditions or wrong host maturity level

A

latent infection

75
Q

reproduction:
phytoplasmas move slow and move through _________ and _________ respectively

A

xylem, phloem

76
Q

viroids and viruses reproduce in individual cells to high levels and are moved with ____________

A

phloem

77
Q

dissemination : spread of pathogen inoculum by ________ or ____ spread

A

active ; passive

78
Q

_____,_____, and _____ can be moved in or on seed

A

fungi, viruses, bacteria

79
Q

seeds are a _________ form of dissemination

A

very efficient

80
Q

the level of infection determines the ability of _________ to transmit the pathogen

A

the seed

81
Q

bacteria, nematodes, fungal inoculum in soil can be spread by ————– or ———.

A

rain; irrigation water

82
Q

bacteria and some spores are produced in ———- and need rain to wash them down or splash them

A

sticky matrix

83
Q

rain can wash ——- or ——- out of the air

A

spores; bacteria

84
Q

able to survive indefinitely as saprophytes and usually have many hosts

A

soil inhabitants

85
Q

specialized parasites that generally live in close association with their host but my survive in the soil for relatively short periods of time

A

soil transients

86
Q

how well fungi survives as a saprophyte in the soil depends on ——– and ——— practices that affect soiil and plant residue

A

climate ; agricultural

87
Q

Phytoplasma Identification

A

-symptoms
-graft transmission
-insect vector transmission
-electron microscopy
-sensitivity to specific antibiotics
-pcr

88
Q

Virus and Viroid identification

A

-symptoms
-transmission tests
-serological tests
-electron microscopy
-inclusion body examination
-electrophoresis
-hybridization
-pcr

89
Q

an organism that lives on or in another organism from which it obtains its nutrition

A

parasite

90
Q

the ability of the parasite to interfere with essential functions of the plant and is qualitative

A

Pathogenicity

91
Q

degree of pathogenicity of a pathogen and quantitative

A

virulence

92
Q

measure of the severity or speed of disease over time in a pathogen population (quantitative)

A

aggressiveness

93
Q

plants or plant parts that can be infected by a particular pathogen

A

host range

94
Q

organism that obtains its food from dead organic tissue (necrotroph)

A

Saprophyte

95
Q

organism that grows and reproduces only on living hosts (biotroph)

A

obligate parasite

96
Q

can utilize both living or dead hosts

A

non-obligate parasite

97
Q

parasites that usually live on a living host but can survive on dead organic matter

A

facultative saprophyte

98
Q

parasites that usually live on dead organic matter, but can attack living tissue

A

facultative parasite

99
Q

biotrophic fungi

A

-cant survive outside of living host
-usually wont grow in vitro
-doesnt usually kill host
-use haustoria to obtain nutrients from the host
-narrow host range

100
Q

Necrotrophic Fungi
(facultative parasits and facultative saprophytes)

A

-have wide host ranges
-usually produce toxins or enzymes
-kill plant cells (live saprophytically on dead tissue)
-can survive outside the host
-can often be manipulated genetically
-penetrate through natural openings or wounds

101
Q

1882 outlined set of procedures to determine the cuase of a disease

A

Robert Koch

102
Q

Koch postulates

A
  • The symptoms as well as the signs of the pathogen in the diseased
    host are carefully described.
  • The suspected pathogen is isolated from the diseased host, grown
    in pure culture, and described or identified.
  • A healthy host of the same variety and species is inoculated with the
    suspected pathogen. It is later observed for symptoms which must
    be identical to those initially described.
  • The pathogen in re-isolated from the inoculated host and must be
    identical to the organism previously isolated.
103
Q

How do pathogens cause disease?

A
  • -by diverting resources from plant
  • -blocking transport of food, minerals and water through plant
  • -killing plant
  • -direct withdrawal of cell contents
104
Q

Definition of plant disease

A

Agrios defines it as “the series of invisible and visible responses of
plant cells and tissues to a pathogenic microorganism or
environmental factor that results in adverse changes in the form,
function, or integrity of the plant and may lead to partial impairment
or death of the plant or its parts.
* Disease is an abnormal physiological process that harms the host.

105
Q

disease pyramid

A

(top) conductive environment
(left) susceptible host
(right) virulent pathogen

106
Q

process by which pathogens establish contact with susceptible host and obtain nutrient from host

A

infection

107
Q

the visible presence of the pathogen ex: white fuzz

A

signs

108
Q

cannot be cultured, requires a living host

A

biotrophic fungi

109
Q

the degree of pathogenicity of a pathogen

A

virulence

110
Q

kills host cells through toxins and enzymes and feeds on dead host tissue

A

necrotrophic fungi

111
Q

the expression of the pathogen (wilting and yellowing)

A

symptoms

112
Q

Enzymeit activities

A

-cutinase
-chitin deacetylase
-proteases
-acidic cellulases
-pectin methylesterases
-neutral cellulases
-polygalocturonate lyase
-amino acid permease

113
Q

susceptible plants do not become infected
(disease escape)
(tolerance to disease)

A

Apparent resistance

114
Q

For each gene that confers risistance in the host there is a corresponding gene in the pathogen that confers virulence to pathogen

A

Gene for gene concept

115
Q

operates in many diseases plant resistance is dominant
pathogen virulence is recessive

A

Gene for gene concept

116
Q

to know what is causing the problem before attempting control

A

Diagnosis

117
Q

Types of disease control

A

-plant resistance
-regulation (quarantine and inspection)
-cultural control
-biological control
-chemical control
-reduce initial inoculum
that starts the first disease of the season

118
Q

Pathogen introduction often causes

A

epidemics

119
Q

that starts the first disease of the season

A

reduce initial inoculation

120
Q

-pull out infected plants
-clean seed or stock
-eradicate wild or alternate hosts
-crop rotation
-sanitation
-change cropping conditions
-soil solarization

A

Cultural Control

Plant Pathology (3 decks)

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