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118 Cards in this Set
- Front
- Back
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% of all food that is lost to disease?
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10
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What is the significance of disease and why should we stop it?
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Exotic plant pathogens can cause great loss...
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how much does disease cost each year?
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billions
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What is a disease? WRITE OUT THE DEFInitioN
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Disease is the injurious alteration of one or more physiological processes in a living system caused by the CONTINUOUS IRRITATION of a primary causal factor.
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What is the disease triangle
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The three ingredients of disease, Host, environment, and a pathogen.
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What is a symptom? 3 examples
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Terms that describe the disease, Necrosis, Gall, scab, canker
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What is a sign? 3 examples
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The observed pathogen structure, Spores, fruiting bodies, Streaming bacteria, cysts
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2 Causal agents of disease?
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Abiotic and biotic
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8 steps to disease diagnosis
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Know whats normal
Know whats possible Collect background info Check for signs or symptoms Observe patterns Ask Questions Laboratory testing Final diagnosis |
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3 pattern styles?
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Random
Aggregated Patchy |
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Primary symptoms vs secondary
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Primary is at the sight of infection, secondary is away
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Sexual and asexual spores in oomycetes?
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Sexual- Oospore
Asexual- Sporangia and zoospores |
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Difference between oomycetes and ascomycetes
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Cell walls are cellulose instead of chitin and they have nonseptate hyphae
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4 important diseases caused by oomycetes?
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Pythium damping off
phytopthora root rot late blight of potato or tomato Sudden oak death |
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how do oospores develop and what are they considered in oomycetes
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the atheridium and oogonium, survival spores
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What information is hard to find on a disease cycle diagram?
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A sense of time and significance
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infectious propagule, usually from an overwintering source, that initiates/ perpetuates the primary disease cycle, as opposed to infectious propagules spread disease during the season.
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Primary inoculum
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Typically, the primary inoculum in oomycetes and ascomycetes is the _______ spores. Name them
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Sexual spores,
Ascomycetes- ascocarps Oomycetes- oospore |
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infectious propagules that were produced by infections that took place during the same growing season
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Secondary inoculum
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Soilborne diseases are commonly
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monocyclic
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Define a monocyclic disease?
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A disease where the infection is caused by the primary inoculum only
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Define a polycyclic disease?
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A disease where one to many cycles of infection are initiated by secondary inoculums
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Define incubation period? what regulates it?
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The time between infection and symptom expression, typically regulated by temp
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Define latent period?
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From infection to new infectious propagules
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Define Quiescent infection?
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Post-infection pathogen dormancy.
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What are the 'conventions' of the diagrams? 7
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Deposition
Infection Incubation Disease development Reproduction Survival Dissemination |
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What is a primary cycle? does it involve sexual or asexual?
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its infection with the primary inoculum, usually involves sexual but sometimes asexual
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What is a secondary cycle?
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The secondary inoculums, involves asexual reproduction
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Sexual and asexual in Ascomycetes
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Ascospore and conidia
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2 characteristics about ascomycetes
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Septate hyphae and chitin cell walls
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3 kinds of ascocarps? APC
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Apothecium, perithecium, and chasmothecium
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3 diseases caused by ascomycetes
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powdery mildew, apple scab, eastern filbert blight
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EFB is mono or poly
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mono
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Powdery mildew- poly or mono
Obligate or facultive Bio or sapro |
Poly, Obligate biotroph
Primary is either sexual or asexual, secondary is conidia |
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Apple scab- poly or mono
Obligate or facultive Bio or sapro |
Poly, Facultative saprophyte
Primary is sexual and second is conidia |
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What is an obligate parasite? What is a biotroph?
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Organisms that can grow only as a parasite in association with a living host., An organism that obtains nutrients from a living host only
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Define parasitism
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A parasite is a living organism that lives inside another living organism and obtains nutrients from it
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What is a facultative saprophyte?
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Normally parasitic but are capable of being saprophytic
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What is a facultative parasite?
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normally saprophytic but are capable of being parasitic
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What is a necrotroph?
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A parasite that typically kills and obtains energy from dead host cells
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What is a saprophyte?
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a necrotroph
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How does fungal infection take place?
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The appressorium (infection cushion) is formed, then the penetration peg goes into the organism and then a haustorium is created inside.
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2kinds of toxins that necrotrophic fungi can attack with?
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Non-specific and specific
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5 infection events?
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Germination
Germ tube search appressorium formation penetration peg haustorium |
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Define constitutive biochemical defense? 2
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Having the right chemicals to defend themselves... Wax cuticle thickness and preformed phenolics.
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Define induced biochemical defense? and 4 examples
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Plants respond immediately to a pathogens attempt to get inside. Papillae formation, cork and lignin layears, systemic acqured resistance SAR, and phytoalexins.
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What do cork layers do?
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Control the size of the infection, making it smaller
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define phytoalexins
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antimicrobial compounds made after the pathogen attacks
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Problem with phytoalexins/
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The pathogens can counter attack with a enzyme that degrades the phytoalexin
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Define System aquired resistance SAR
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The activation of defense in distant, non-infected plant parts
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3 steps to SAR
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Plant is primed to produce a pathogen stopper, The cell walls begin the thicken, and Accumulation of PR-proteins begins
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Difference between teleomorphic and anamorphic names?
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Teleomorphic is sexual, ana is asexual
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3 steps to conidial lifecycle? GPS
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Germination penetration sporulation
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2 fruiting bodies of asexual ascomycetes?
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Acervulus and pycnidia
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1 constiutive structural and one biochemical
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Wax thickness
Phenolics |
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2 induced structural and 2 biochemical
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Cork and lignin layers and papillae formation, SAR and Phytoalexins
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What is hypersensitivity response and programmed cell death?
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A localized death of host cells at the sight of infection. hypersensitive response is an example of programmed cell death
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4 kinds of basidiomycetes?
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Root rot, Heart rot, smut, rust
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smuts have how many kinds of spores?
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2 basidiospore and teliospore
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macrocyclic vs. microcyclic vs. asexual
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MAcro has 5 spore types, micro is only basido and telio, and asexual is only urediniospores
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Rusts that complete their lifecycle on one host
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Autoecious
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Rusts that complete their lifecycle on more than one host
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heteroecious
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What is a disease progress curve?
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The amount of disease, plotted as a function of time
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3 phases of the disease progress curve?
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Exponential, logistic, and terminal
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How does sanitation and host resistance influence disease progress?
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The more sanitized it is the slower the start time, they delay the beginning
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what is r in progress curves?
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Disease "infection rate"
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2 methods for measuring disease?
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Incidence- Portion of crop, a number
Severity- % of material affected |
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How many propagules are required to give a certain amount of disease, what are the labels of this graph and what shape?
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Disease severity and amount of inoculum, Upsidedown J
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What does the graph look like and labels for the speed of infection?
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S curve Severity and time
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What does the graph look like on how far, what are the labels?
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Disease gradient diagram, backwords J, Disease severity and distance
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What is germ plasm
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Collection of a perticular gene for that plant
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2 major types of host resistance
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Race specific and non race specific
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How do we breed and select for resistance?
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Backcross breeding or Biotechnology
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Difference between major and minor genes?
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Major- Genes whose effects are large enough to be discerned individually
Minor- genes whose effects are so small that they cannot be observed individually |
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Difference between host resistance and nonhost resistance
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Host resistance- the host is resistant to one specific pathogen,
Nonhost- the host is resistant to numerous pathogens |
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What is the Gene for Gene Hypothesis?
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A single gene in the host specifically recognizes the product of a pathogen gene, when this happens it will resist
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Who produces the R-gene, AVR gene, and r gene
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Host, path, host
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Downside to major gene resistance?
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It breaks down quickly
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Why are Asexual pathogens beter candidates for suppression of R-Genes?
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They don't recombine their genomes
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What are bacteria?
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Single celled, Very small, with rigid cell walls
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What is an eiphytic phase
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growth along the plant, they live on the plant
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How do bacteria cause disease? 3 ways
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Secrete enzymes Type II secretion
Secrete virulence factors Type III secretion Secrete genetic material- Type IV secretion |
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How do we identify bacteria? 4
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Gram stain, Flagella arrangement, oxidation fermination test, Flourescents
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What is the significance of different types of secretion systems? BACTERIa
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They tell us what kind of bacteria we are dealing with and if it is even a plant pathogen.
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What are viruses
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Obligate , intracellular organisms, Very small, single dna strand
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Whats it mean to be monopartite, bipartite, or tripartite.
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Viruses are seperated this way, it is the number of particles that hold the viruses genome
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how do viruses move within the plant
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The enter go to the roots the up and then throughout
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how are viruses transfered? 4
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Seed, insects, mechanical, or grafting
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Typical virus genome has how many proteins
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4-7 very small
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2 types of insect vector transmission? describe them
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Nonpersistant- Uses a test probe and is quick
Persistant- uses a feeding tube and takes longer |
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5 methods for testing for viruses?
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Pathogenicity
Transmissibility Electron microscopy ELISA Characterization of viral nucleic acid |
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6 stages to a viruses lifecycle
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invasion
Genome uncoating Particle Assembly Cell to cell movement systemic transport Plant to plant movement |
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Describe RNA silencing
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It targets dsRNA(Double stranded)
siRNAs (silencing RNAs) Risc catches the red and contects with a good single stranded RNA and then destroys it… |
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How is RNA silencing involved in creating transgenic plants with high levels of resistance to viral diseases?
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by bicer defeatingthe double stranded DNA, it shreds the Virus, then RISC comes in and picks up the DNA and then leaves the shredded virus
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how do viruses replicate?
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They use a single cell to combine its RNA with the cells DNA to multiply within the cell
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What are the 6 principles to disease control and what part of the disease triangle is targeted?
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Pathogen: Exclusion, Eradication, Therapy
Host: Therapy, Host resistance, protection Environment: Protection and avoidance |
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2 disease control tactics for exclusion?
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Quarantine- Government steps in and regulates the spread of a disease SOD
Certification-Its the governments assurance of quality seed and root stocks |
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Define Disease avoidance?
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Avoiding disease by avoiding the pathogen or altering the environment
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How can we manage soil water content to avoid disease?
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By changing the soil water content, we can avoid disease by simply reducing the amount of water, alot of disease are spread through water and this will prevent that
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What is foliar leaf wetness duration and how is it limited?
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It is the duration of wetness required by foliar pathogens to achieve successful infection, Water in the morning, the afternoon will remove excess moisture.
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2 Examples of cultural practices that influence humidity levels within the crop canopy
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leaf removal and row spacing
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Can the methods used to handle plant and plant parts be involved with susceptibility to infection? How so?
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yes, If they are puntured, it could allow disease in easily
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How are fungicides applied?
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Ground boom, air blast, air plane, fertigation
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how long are contact fungicides effective?
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4-7 days
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What is the house paint analogy? why is it a good analogy
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A chemical barrier to protect plants from infection. This is what most fungicides are
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What is the difference between a contact and a locally-systemic herbicide?
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Contact protects where it hits, locally moves in apoplast
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how long a locally systemic herbicides effective?
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up to 96 hours
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What is kick-back activity in fungicides?
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a fungicide that after 96 hrs, it is transported systemically
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Which type of fungicide chemicals are most at risk of developing a resistance problem
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All of them
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How do we manage fungicide resistance?
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Mix fungicides
Rotate chemicals Limit usage |
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3 examples of eradication
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Fallow, heat, chemcial biocides
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What is fallow?
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The practice of allowing a field to remain uncropped
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What is targeted in heat eradication practices
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nearly all pathogens but not soil microbes
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What are targeted in hot water eradications
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Pathogens in seed
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How is solarization effective?
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It kills soil borne disease
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What are nematodes?
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Invertebrates Bilaterally symmetrical, No circulatory or respiratory system
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raised area along side the nematode?
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LAteral field
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4 major life strategies of soil borne nematodes
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Sedentary endo or ectoparasites
Migratory |
