Term
| Four definitions of disease |
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Definition
abnormal physical state
physiological malfunctioning
disordered or incorrectly functioning
deviation from normal functioning |
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Term
| Basic physiological functions |
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Definition
Photosynthesis
Water & nutrient uptake
Cell functions
Growth
Reproduction |
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Term
| What is autotrophy and clorophyll? |
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Definition
autotrophy: using sunlight energy
chlorophyll: a pigment that absorbs light energy (photon) and transfers energy |
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Term
| What can inhibit photosynthesis? |
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Definition
Inhibition of photosynthesis via toxins.
Degradation of chloroplasts via membrane disruption.
Destruction of leaf tissue via spots & blights.
Reduction of leaf area via stunting.
Loss of leaves via defoliation. |
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Term
| What is DsPE/A and how does it impair photosynthesis? |
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Definition
| DsPE/A = a protein produced by Erwinia amylovora that binds to precursor-ferredoxin and makes it unavailable. |
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Term
| How is precursor-ferredoxin used in photosynthesis? |
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Definition
| Precursor-ferredoxin is imported into the chloroplasts and converted to ferredoxin. Ferredoxin serves as an electron carrier in PS 1. |
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Term
| How can water uptake be impaired? |
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Definition
Disruption of root integrity.
Decreased production of feeder roots and root hairs.
Altered root permeability.
Loss of roots. |
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Term
| What can impair water movement? |
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Definition
Collapse of xylem tissue (toxins & enzymes, physical pressure).
Blockage of vessels (pathogen biomass, pathogen exudates, host defenses).
Host compounds (tyloses, calloses, lectins).
Increased transpiration (disrupts cuticle or epidermis and causes stomata dysfunction). |
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Term
| What are the three host defense compounds that can impair water movement? |
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Definition
Tyloses: the protoplast of an adjacent cell
Callose: plant polysaccharide
Lectin: plant protein that binds to carbohydrates |
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Term
| Describe the sugar movement and carbon allocation in a diseased host. |
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Definition
Increased carbon sink.
Reduced movement from leaf cells to phloem (damage phloem or enzyme impairment).
No movement within phloem due to blockages or destroyed phloem cells. |
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Term
| How can transcription and translation be affected in diseased cells? |
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Definition
| There would be an increased use of energy for the production and movement of defenses. |
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Term
| How can disease affect reproduction? |
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Definition
Indirect: effects on resources and growth.
Direct: infected reproductive parts and/or fewer flower production. |
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Term
| Fusarium Wilt: Fusarium oxysporum f. sp. lycopersici |
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Definition
Soil-borne fungus (Ascomycete).
Infects through the roots and moves upward through xylem.
Produces macro- & microconidia.
Causes yellow flag and red/brown vascular discoloration. Wilting through xylem blockage. |
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Term
| What is Huanglongbing in citrus? |
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Definition
Canditatus liberibacter asiaticus
Fastidious, vector-limited (psyllid)
Causes host to produce callose & lectin which plugs phloem and causes 'yellow dragon'. Carbohydrate transfer is disrupted and sugar backs up.
Starch accumulates in chloroplasts and thylakoid membranes are disrupted.
Causes reduced flower set/#/size, malformations, bitterness, and seed abortion. |
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Term
| How does TMV affect Tobacco? |
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Definition
It hijacks the host's metabolism to protein viral proteins. TMV can reach 50% of a host-cell's total protein production through preferential translation (vs. host mRNA).
Chlorophyll and carotenoids are broken down by ROS which reduces electron transport chain activity and in turn reduces PS II activity. |
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Term
| What are the sources of genetic variability? |
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Definition
Mutation: ultimate source. occurs through base addition/deletion/substitution.
Recombination: passes mutations around. |
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Term
| What are the different methods of genetic recombination? |
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Definition
Sex (fungi, oomycetes, nematodes).
Heterokaryosis (fungi, oomycetes): 2 or more genetically different nuclei.
Parasexualism (fungi, oomycetes): fusion of nuclei in heterokaryon but reverts to 1N by discarding chromosomes in mitosis.
Horizontal gene transfer (bacteria): conjugation, transduction, transformation
Recombination (viruses): co-infection by multiple viruses |
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Term
| How to genes move among populations? |
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Definition
Sexual reproduction: increases diversity and allows gene combinations.
Asexual reproduction: entire genotype moves |
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Term
| What are pathogenicity and pathogenicity factors? |
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Definition
Pathogenicity: capability of a pathogen to cause disease.
Pathogenicity factors: factors encoded by pathogenicity genes that are essential for disease development. |
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Term
| What are virulence and virulence factors? |
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Definition
Virulence: the degree of pathogenicity
Virulence factors: encoded by virulence genes but not essential for disease development. |
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Term
| What is pathogen fitness? |
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Definition
Pathogen fitness is the ability of a pathogen to survive and reproduce.
Reproduction, growth, infection efficiencies, aggressiveness |
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Term
| How are pathogens defined by host species? |
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Definition
Fungi: variety or forma specialis/ f. sp.
Bacteria: variety or pathovar/pv.
Virus: type |
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Term
| How are pathogens defined by host cultivar/variety? |
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Definition
Fungi & Bacteria: race
Virus: strain |
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Term
| How are pathogens defined by localized population? |
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Definition
| Fungi & Bacteria: isolate |
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Term
| How are pathogens defined by their clonal population? |
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Definition
Fungi: biotype
Bacteria: strain
Virus: single local lesion isolate |
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Term
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Definition
Non-host: outside the host range of the pathogen
Resistance genes: genes specific to recognizing and defeating the pathogen
Apparent resistance: escape (disease triangle) and tolerance |
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Term
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Definition
Partial: quantitative, horizontal, polygenic
R-gene: race-specific/monogenic, vertical, qualitative |
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Term
| Partial/quantitative/horizontal/polygenic resistance |
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Definition
Not specific to one pathogen.
Controlled by multiple genes.
Genes control various steps of defense systems.
Doesn't prevent infection but slows disease cycle steps. |
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Term
| R-gene/qualitative/vertical/monogenic resistance and possible reactions |
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Definition
Race specific.
Resistance conferred by one or a few genes.
R-genes control pathogen recognition.
Apparent immunity: no reaction
HR: hypersensitive response, no colonization
Inhibition of pathogen reproduction. |
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Term
| Stability of true resistance types |
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Definition
R-gene: complete resistance
Partial: variable resistance |
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Term
| What is gene-for-gene resistance? |
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Definition
Each resistance gene (R) has a corresponding virulence gene (A) in the pathogen.
Host resistance can be identified by its counterpart in the pathogen.
virulence is recessive (a).
Elicitor is the pathogenicity or virulence factor.
Host resistance is usually dominant (R).
Gene codes for a receptor which recognizes pathogenic elicitor. If elicitor is recognized, defenses are triggered. |
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Term
| Gene-for-gene interactions |
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Definition
(-) indicates an incompatible interaction.
(+) indicates a compatible interaction.
A=avirulent, a=virulent, R=resistant, r=susceptible
AR (-), Ar (+), aR (+), ar (+) |
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Term
| How do genes-for-genes interactions work? |
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Definition
One pathogen may produce many elicitors and one host may have many resistance genes.
An AR combination for any gene will result in resistance. A plant variety with no resistance genes is susceptible to all pathogen races. A pathogen that produces no recognizable elicitors can cause disease on all host varieties. |
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Term
| What are some pathogenicity genes? Virulence genes? |
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Definition
Pathogenicity genes: host recognition, attachment, penetration, colonization.
Virulence genes: secretion systems, enzymes, motility |
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Term
| What are the 5 types of bacterial secretion systems? |
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Definition
I: most plant pathogenic bacteria, toxin production.
II: gram (-). export of proteins, toxins, virulence factors.
III: gram (-). transport of effector proteins into the cell
IV: transport of macromolecules into cell
V: surface-associate adhesins |
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