Exam 3 Flashcards
What is an abnormal physical state, physiological malfunctioning, disordered or incorrectly functioning, or a deviation from the normal functioning?
Disease
What physiological function’s purpose is sugar production?
Photosynthesis
What physiological function’s purposes are movement, storage, etc?
Sugar allocation
What physiological function’s purposes are uptake, movement, allocation, and retention?
Water balance
What physiological function’s purposes are respiration, transcription/translation, membrane integrity?
Cell functions
What physiological function’s purposes are cells, tissues, fertilization, etc?
Growth and reproduction
How does TMV affect photosynthesis?
Attacks chloroplasts
How does HLB affect photosynthesis?
Blocks phloem, no energy for photosynthesis
How do foliar nematodes affect photosynthesis?
Destruction of leaf cells
How is sugar allocation affected by rust, root rots, or nematodes?
Nutrient deficiency
What pathogens affect water balance?
Pythium, wilts, fire blight, nematodes
What pathogens affect cell functions?
Rots, crown gall, nematodes, rhizoctonia, viruses
What pathogens affect growth and reproduction?
Crown gall, HLB
Fire blight: Necrotroph or Biotroph?
Necrotroph
Which polysacharide factors are affected by fire blight? How?
Amylovoran, levan: clog xylem
Which protein factor is affected by fire blight? How?
DspA/E: disrupts photosynthesis
Amylovoran requisite for…
biofilm formation
Levan contributes to…
biofilm
What is the 3-step process of DspE/A?
- Interacts with/binds to a precursor-ferredoxin.
- Pre-Fd imported into chloroplasts, converted to Fd (Fd serves as an electron carrier in PS1)
- Bound Pre-Fd unavailable for use (ETC impaired due to lack of Fd)
Which plant disease is a soilborne fungus (ascomycete), infects through roots, produces macro- and microconidia, and moves upwards in xylem?
Fusarium Wilt
Which plant disease has symptoms of older leaves first, “yellow flag” and red-brown vascular discoloration?
Fusarium Wilt
Which host compound impairs water movement using the protoplast of the adjacent cell?
Tyloses
Which host compound uses plant polysaccharide to impair water movement?
Callose
Which host compound uses plant protein and binds to carbohydrates to impair water movement?
Lectin
Which plant disease affects water movement because there is no increased transpiration, no reduced root uptake and the xylem is blocked?
Fusarium wilt
Nutrients are reliant upon…
water movement
Which plant disease is fastidious, phloem-limited and vectored by psyllids? It is also called “yellow dragon” and its yellowing starts on one limb.
HLB (Citrus Greening)
HLB affects callose and lectin (HR response), disrupts carbohydrate transfer, and causes sugar to back up. What does these three things cause?
Phloem plugging and necrosis
HLB causes accumulation of starch in chloroplasts and disrupts the plasma membrane causing ____ ____.
Starch packing.
What effects on reproduction does HLB have? (4)
Reduced flower set, reduced fruit number and size, malformed and bitter fruit, aborted seeds
TMV translation can reach ___% of total protein production in infected cells.
50
The viral proteins and genomes of TMV are ~__% of the leaf’s fresh weight.
1
The virus RNA of TMV contains _____ ______.
Enhancer structures
How does TMV affect photosynthesis? (3)
Reduction in chlorophyll and carotenoid, reduced ETC activity in isolated chloroplasts, reduced activity of PS II
What are the 3 steps of the central dogma of genetics?
- DNA carries code (genes)
- Code is transcribed into mRNA
- mRNA is translated into protein
What is the term for when genes are turned on or off?
Gene expression
2 types of gene expression
constitutive and induced
What are the 4 regulatory regions of DNA?
Promoters, enhancers, terminators, silencers
What is the ultimate source of variability in DNA?
Mutation
What are 4 possibilities of mutation that causes changes in DNA?
Base addition, base deletion, base substitution, transposable elements
What occurs when mutations are passed around?
Recombination
What are 4 ways recombination can occur?
Sex, Heterokaryosis, Parasexualism, Horizontal Gene Transfer, Co-infection by multiple viruses
Which 3 organisms participate in sex for means of recombination?
Fungi, Oomycetes, Nematodes
Which 2 organisms are heterokaryotes (recombination)?
Fungi, Oomycetes
Which 2 organisms are parasexual?
Fungi, Oomycetes
Which organism is capable of Horizontal Gene Transfer?
Bacteria
How does parasexualism contribute to recombination?
The nuclei are fused in a heterokaryon and reverts to 1N by discarding chromosomes in mitosis.
Which type of reproduction increases diversity?
Sexual
In the gene flow of ____ _____, the next generation has SOME new genes, new combinations may be advantageous, and a new feature may be diluted or lost.
Sexual
In the genotype flow of ____ ____, the entire genotype moves in a boom or bust fashion.
Asexual
A large population indicates which two things regarding mutations?
Larger number of mutants, larger likelihood of mutants reproducing
What is the changes in allele frequency due to random events?
Genetic drift
What is the capability of a pathogen to cause disease?
Pathogenicity
What are factors essential to disease development?
Pathogenicity factors
Pathogenicity factors are encoded by one or more ____ _____.
Pathogenicity genes
What is the degree of pathogenicity?
Virulence
What factors are not essential to disease development and are encoded by virulence genes?
Virulence factors
What is the ability of a pathogen to survive and reproduce?
Pathogen fitness
4 factors affecting pathogen fitness:
- Growth/multiplication rate
- Reproductive rate
- Infection efficiency
- Aggressiveness (amount of disease caused)
What are 4 ways a pathogen can be defined beyond species?
- Variation by host species
- Variation by host cultivar/variety
- Localized population (by field)
- Clonal population (by individual)
What 3 ways can host species variation be broken down for fungi, bacteria, and viruses?
Variety or forma specialis (Fungi), variety of pathovar (Bacteria), Type (virus)
When pathogen variation defined by host cultivar/variety, Fungi/Bacteria are defined by ____ and Viruses by _____.
Race, Strain
In the localized population, which are defined as “isolate?”
Fungi, bacteria
In the clonal population, Fungi are classified as ____, Bacteria by _____, and Viruses by ____ ____ ____ _____.
Biotype, strain, single local lesion isolate
Pathogen or host?
Has pathogenicity genes, infects at least one host, maybe hundreds
Pathogen
Pathogen or host?
Combination of genes makes it susceptible to some pathogens, non-host to most pathogens
Host
Which type of resistance is outside the host range of the pathogen?
Non-host
Which type of resistance has genes specific to recognizing and defeating the pathogen?
Resistance genes
Which type of resistance has two subsets: escape and tolerance?
Apparent resistance
Which subset of apparent resistance is when the host is not infected due to avoidance of disease interaction (disease triangle)?
Escape
Which subset of apparent resistance is when the host is infected, but not highly damaged?
Tolerance
How is horizontal “true” resistance defined? (4)
- Not specific to one pathogen
- Controlled by multiple genes (usually)
- Genes control various steps/aspects of plant defense systems
- Doesn’t prevent infection, but slows subsequent steps of disease cycle
How is vertical true resistance defined? (3)
Clear difference in resistance to certain pathogen races (race-specific), resistance conferred by ONE or a few gene(s), R genes control pathogen recognition
What are the 3 reactions of vertical true resistance?
Apparent immunity, hypersensitive response, inhibition of pathogen reproduction
Which type of vertical true resistance reaction shows no infection?
Apparent immunity
Which type of vertical true resistance reaction shows no colonization?
Hypersensitive response
Which type of resistance stability has complete resistance under most conditions and is defeated by one or a few pathogen mutations?
Race specific (R gene)
Which type of resistance stability has variable resistance, affected by conditions, and is more difficult to defeat because it requires many mutations?
Partial (Quantitative)
What resistance stability combination is when multiple R genes are stacked?
Pyramid
Each ____ ____ in a plant (R) has a corresponding ____ ____ (A) in the pathogen.
Resistance gene; virulence gene
Host resistance gene can only be identified by its _____ in the pathogen.
Counterpart
Which gene set (pathogen or host plant) has virulence usually recessive, gene codes for a pathogenicity or virulence factor, and the factor is termed the “elicitor” in the interaction?
Pathogen
Which gene set (pathogen or host plant) is the resistance usually dominant, the gene codes for a receptor which recognizes the elicitor, and if the elicitor is recognized - defenses are triggered?
Host plant
Gene for gene interactions:
a r
No elicitor molecules
No receptor on host
Will host recognize pathogen?
Will interaction result in disease?
No
Yes
Gene for gene interactions:
a R
No elicitor molecules
Receptor on host
No
Yes
Gene for gene interactions:
A r
Elicitor molecules
No receptor on host
No
Yes
Gene for gene interactions:
A R
Elicitor molecules
Receptor on host
Yes
No
AR
Resistant or susceptible?
Resistant (-)
Ar
Resistant or susceptible?
Susceptible (+)
aR
Resistant or susceptible?
Susceptible (+)
ar
Resistant or susceptible?
Susceptible (+)
One pathogen can produce many elicitors and a host can have many resistance genes. In this case, will disease occur?
No, it only needs to recognize one elicitor to intiate defenses.
An ___ combination for ANY gene will result in recognition and resistance.
AR
A plant variety with no ____ ____ is susceptible to all pathogen races.
resistance genes
A pathogen that produces no _____ _____ can cause disease on host varieites.
recognizable elicitors
What are two reasons pathogens produce elicitors?
Pathogenicity factors: vital to critical steps in the disease cycle
Virulence factors: advantageous in causing disease , enabling disease on particular host varieties
What component is required for appressorium wall reinforcement?
Melanin
What is the required step for pathogenicity (quorum sensing to swarm)?
Type IV Pili for aggregation
Bacterial Secretion System #
Most plant pathogenic bacteria, toxin secretion
Type I
Bacterial Secretion System #
Gram (-), export of proteins, toxins, virulence factors
Type II
Bacterial Secretion System #
Gram (-), Transport of effector proteins into plant cell
Type III
Bacterial Secretion System #
Transport of macromolecules to host cell
Type IV
Bacterial Secretion System #
Surface-associated adhesins
Type V
Which type of bacterial secretion system is a gram (-) bacteria that can interact with a host, uses an injectisome as a delivery apparatus, and has a Hrp system?
Type III SS
What is a cluster of pathogenicity related genes regulated together and sometimes found on plasmids?
Pathogenicity island
What are proteins required for the production of T3SS?
hrp
What are proteins required to assemble the injectisome?
hrc
What are virulence genes that determine the host range?
avr
What are hrp-dependent outer proteins (effector proteins)?
hop
R Genes have which 3 things?
Receptors, signal transduction, 6 structural classes
Which common, but not ubiquitous mechanism causes localized cell death?
HR response
Which induced defense mechanism of the entire plant has a signal generated 4-6 hours after inoculation?
Systemic acquired resistance
3 Steps of Staging an Invasion
- Enter Plant
- Avert Defenses
- Reap the Rewards
What is produced via pathogenicity genes and essential for one or more steps in the disease progress on a host?
Pathogenicity factor
3 types of mechanical entry
Fungi, Nematodes, Parasitic plants
4 types of chemical entry
enzymes, toxins, growth regulators, polysaccharides
What mechanical apparatus of fungi adheres, builds pressure, and concentrates pressure to penetrate?
Appressorium
What are proteins that catalyze chemical reactions?
Enzymes
What is an enzyme that is always produced?
Constitutive
What is an enzyme whose production is turned on as needed?
Induced
4 examples of cell wall degrading enzymes
Cutinases (and esterases)
Pectinases
Cellulases
Ligninases
4 examples of cell content degrading enzymes
Proteases
Amylases
Lipases
Phospholipases
What causes direct injury to host cells by permeability of membranes and inhibition/inactivation of enzymes?
Toxins
What type of toxin affects only the host plant?
Host-specific
What type of toxin affects a wide range of plants?
Nonhost-specific
Tabtoxin (Pseudomonas syringae) is a host-specific/nonhost-specific toxin.
Nonhost-specific
Which nonhost-specific toxin inactivates glutamine synthetase?
Tabtoxin (Pseudomonas syringae)
Cercosporin is a host-specific/nonhost-specific toxin.
Nonhost-specific
Which nonhost-specific toxin generates active oxygen and is light-activated?
Cercosporin
T Toxin (Cochliobolus heterostrophus) is a host-specific/nonhost-specific toxin.
Host-specific
What disease does T Toxin cause?
Southern Corn Leaf Blight
What years had isolated incidences of Southern Corn Leaf Blight?
1968-1969
In 1970, ___% of corn was TMS.
85
Alternaria alternata toxin is a host-specific/nonhost-specific toxin.
Host-specific
Which host-specific toxin has multiple pathotypes where each produces a different form of toxin?
Alternaria alternata
Which toxin causes black spot on Japanese pear?
AK toxin
Which toxin causes stem canker on tomato?
AAL toxin
Which toxin causes issues on strawberries?
AF toxin
Which toxin causes issues on apples?
AM toxin
Which 3 alternaria toxins disrupt the plasma membrane?
ACT, AF, AK
Which alternaria toxin disrupts the plasma membrane and chloroplast?
AM
Which alternaria toxin causes the mitochondria to malfunction?
ACR
What are 4 plant growth hormones?
Auxins (IAA)
Gibberelins
Cytokinins
Ethylene
What other compounds function as growth regulators?
Growth inhibitors
What are the pathogenic effects of growth regulators?
Induce plant production and pathogen production
What polysaccharide functions in lubrication, protection, and disguise?
Mucilage, “slime”
What is pathogens are associated with mucilage?
Bacteria, fungi, nematodes
What are the major effects of mucilage?
Wilts
What are the 4 types of plant defenses?
Physical, Chemical, Induced, Preexisting
Which preexisting defense mechanism has structural components that physically block adhesion, entry, and movement of pathogens?
Physical
Which preexisting defense mechanism has inhibitors that prevent germination, growth, enzyme production/function of pathogens, and the absence of toxin molecules prevents pathogen recognition of the host, rendering pathogen toxins ineffective/
Chemical
Which induced plant defense is when structural components are altered or reinforced?
Physical
which induced plant defense is when the inhibitor production is initiated/increased and HR response prevents pathogen colonzation?
Chemical
Which plant surfaces are hydrophobic and reduces formation of water films?
Waxes and trichomes
Which plant surfaces provide a barrier to direct penetration?
Cuticle and epidermal cell walls
Which plant surface defenses cause reduced opportunity for entry?
Stomatal structure and timing
What are the 3 reinforced cells of plant interiors?
Xylem, bundle sheath, sclerenchyma
What is the primary function of reinforced cells?
Limit movement of pathogens within the plant
Chitinases and B-1,3,-glucanases break down ___ cell walls.
Fungal
Chemical defenses in plant interiors (4)
Phenolic compounds, tannins, saponins, enzyme inhibitors
All induced defenses require _____.
Recognition
What are 4 examples of nonspecific elicitors?
Toxins, carbohydrates, fatty acids, enzymes
What are 2 examples of specific elicitors?
avr gene products, hrp products
Success of defenses depends on which two things?
Speed of recognition and speed of reaction
What are 4 types of induced physical defenses?
Cell wall structures
Histological strucutres
Cytoplasmic reaction
Necrotic/hypersensitive reaction
Considering cell wall defense structures, what 3 changes occur in the cell wall?
Thickening, reinforcement, deposition of phenols
What 4 histological defense structures form ahead of the pathogen?
Cork layers, abscission layers, tyloses, gum deposition
HR reactoin is a common reaction to which 4 things?
Obligate fungal pathogens, viruses, bacteria, nematodes
Which effect of induced chemicals inhibits germination and lyses cell wall components? This directly inhibits the pathogen.
Direct effects
Which effect of induced chemicals affects host cell wall structures and is induced in the host or environment?
Indirect effects
What induced chemical causes a direct inhibition of the pathogen and its enzymes?
Phenolics
Which induced chemical is toxic to fungi and is induced by invasion or injury?
Phytoalexins
What are the 7 environmental factors?
Temperature, moisture, wind, light, soil characteristics, nutrient availability, human-made herbicides and pollutants
What is the optimum temperature range for the pathogen F. oxysporum?
22-28 C
What is the optimum temperature range for the onion host of F. oxysporum?
28-32 C
What is the optimum temperature for disease in onion for F. oxysporum?
17-23 C
What is the optimum temperature for the pathogen Thielaviopsis basicola on tobacco?
22-28 C
What is the optimum temperature for tobacco host in regards to T. basicola?
28-32 C
What is the optimum temperature for disease in tobacco for T. Basicola?
17-23 C
In _____, the higher the soil temperature, the higher prevalence of disease.
Pansy
In ____, the lower the soil temperature, the higher prevalence of disease.
Cotton
What are the 7 roles of moisture?
Dispersal, pathogen germination/growth, signal movement, penetration, host defenses, secondary dispersal, survival
Apple scab optimal growth is at what temperature?
16-24 C
How does wind increase disease?
Pathogen dispersal and leaf injury
How does wind decrease disease?
Leaf drying
Shading (etiolation in high-light plants) causes what 4 things?
Increased opportunistic pathogens, decreased obligate pathogens, increased susceptibility to viruses, decreased severity of viral disease
Excessive light in shade-adapted plants can cause___ ____ in which plants for example?
More disease; coffee berry
Pathogen effects of light (3)
Light cues in pathogen physiology, light and pathogenicity factors, light damage
Apple scab ascospore release (3) things
Requires wetness, triggered by light, increases with temperature
2 host effects of soil texture and structure
Drainage, waterlogging
3 pathogen effects of soil texture and structure
reproduction, movement, survival
2 host effects of soil pH
host pH range, nutrient availability
2 pathogen effects of soil pH
pathogen pH range, enyzme activity
2 host effects of nutrients
growth rates, plant health and resistance
Nitrate increases which 3 pathogens
P. omnivora, G. graminis, S. scabies
Ammonium increases which 3 pathogens
Fusarium spp, P. brassicae, S. rolfsii
4 issues with herbicides or air pollution
damage to plants, pathogen effects, soil microbe effects, surrounding plant effects
Change in disease intensity within a host population over time and/or in space
epidemiology
Who created the first epidemiological forecasting system by creating tables showing duration of rain required at different temperatures for V. inaequalis infection (apple scab)?
Mills, 1944
Who published Plant Disease: Epidemics and Control, which showed mathematical models in epidemiology and monocyclic vs. polycyclic pathogens?
Van Der Plank, 1963
In the disease triangle, what do epidemiologists include as the 4th factor?
Time
What do epidemiologists include under environmental conditions?
Vectors
The disease progress curve shows the change in ______ variable over _____
Disease; time
On the disease progress curve, the percent of plants infected is called _____.
Incidence
On the disease progress curve, the disease rating is also called _____.
Severity
When measuring disease, which term is a binary measure (yes/no) and expressed as a percentage?
Incidence
When measuring disease, which term is a quantitative or semi-quantitative measure that has a variety of metrics?
Severity
When measuring severity, what are 3 variety of metrics used?
Percent leaf area, lesion size, symptom progression
How do you compare multiple disease progress curves?
Calculating the area under the disease progress curve
What is a unitless, quantitative summary that allows for comparison of disease progress curves?
AUDPC
In reference to quantity of inoculum, what is the number of propagules per unit weight or volume?
Inoculum density
What two factors indicate quality of inoculum?
Infectivity, inoculum potential
What is a measure of inoculum quantity and quality that shows the energy available for colonization of a host at the surface to be colonized?
Inoculum potential
What two components are required to measure and interpret inoculum potential?
Inoculum density, proportion of inoculum that can infect
What is required to measure and interpret inoculum potential?
Bioassay
What 3 things do modeling epidemics allow us to do?
Describe disease progress, compare progress under different conditions, and predict progress under different conditions
3 characteristics of monocyclic diseases
One infection cycle per growing season
No secondary inoculum within season
Typical of most soilborne pathogens
3 characteristics of polycyclic diseases
Multiple cycles per growing season
Secondary inoculum produced
Typical of most airborne pathogens
Monocyclic or Polycyclic?
Disease progress curve is typically a saturation curve.
Monocyclic
Monocyclic or Polycyclic?
Disease progress curve is typically a sigmoid curve.
Polycyclic
Spatial spread from an inoculum source
Pathogen dissemination
Disease forecasting is useful when: (1)
The disease is sporadic or occurs repeatedly at certain locations and control strategies are available.
Disease forecasting is NOT useful when: (2)
The disease is always severe
There is no control measure available
How is the disease triangle used in disease forecasting? (3)
Pathogen biology, environmental parameters, pattern of disease progress
What are 2 things that are the basis of forecasting?
amount of inoculum (primary and/or secondary) and weather conditions that favor the disease
What is the forecast system of BLITECAST? (4)
Assumes presence of inoculum.
Temperature and RH predict severity values
SV accumulate over time
First fungicide application when threshold is reached (18 SV)
What is the forecast system of tobacco blue mold? (2)
Outbreaks (sources) reported to forecaster.
NOAA database used to create trajectory model.
