-
What is the difference between a symptom and a sign?
- Symptom- the hosts reaction to a pathogen; Sign- Observing
- the pathogen itself
-
What are the three factors represented in the disease
triangle? Why are they required?
- HOST that is susceptible PATHOGEN that is capable of causing disease
- ENVIRONMENT that is favorable for disease to develop….required for the disease
- to develop…if any of the 3 are lacking: no disease occurs
-
Provide characteristics that are commonly true for
biotrophs.
- Keep host alive,
- host will remain green but may be stunted, have
- narrow host ranges, cannot be cultured on media, attack healthy host tissue
- at any stage, kill host cells slowly, penetrate
- directly or via natural openings, includes all viruses most nematodes
- parasitic plants and some fungi
-
Provide characteristics that are commonly true for
necrotrophs.
- May kill host,
- causes lots of necrosis, have wider host
- ranges, can be cultured on media, attack
- young weak or senescent tissues, kills host rapidly with toxins or enzymes,
- penetrates through wounds or natural
- openings, include most bacteria many fungi and oomycetes
-
Name the 5 types of symptoms and some examples
- Necrotic (dead
- cells) – leaf spot, blotch, blight, scorch, canker, rot, and damping off. Secretion
- of Liquids— bleeding, gummosis, and resinosis. Changes
- in Coloration—mosaic, mottle, streak, stripe, yellowing (chlorosis). Changes
- in Form—stunting, rugosity, leaf roll, galls, witches’ broom. Wilt—rot.
-
What is an infection court?
- The place on a plant that is susceptible to infection
- (stoma, natural openings, wounds)
-
What is colonization?
- The time after infection that a pathogen reproduces
- and multiplies
-
What is the incubation period?
- The time from penetration to when symptoms of infection
- appeared.
-
What is the secondary inoculum?
- Inoculum produced by infections that took place
- during the same growing season. The part of a pathogen that results in new
- disease with the same season
-
What is Koch’s postulate?
- The name of the procedure used to prove that a specific
- organism is the cause of a disease.
-
What are the 4 disease management strategies?
- AVOIDANCE—grow
- the plant where or when the pathogen is not present or active. EXCLUSION—legal restrictions
- (quarantines, pathogen free seed, or propagation parts). ERADICATION—removal of pathogens from infested soils and tools,
- infected seed or propagation parts. PROTECTION—protect
- plant from pathogen (spray fungicides or plant resistant cultivars)
-
What are the sexual and asexual spores of
Basidiomycetes, Ascomycetes, Zygomycetes, and Oomycetes?
- Basidiomycetes:
- sexual-basidiospores, asexual- usually not present. Ascomycetes: sexual- ascospores, asexual- conidiaspores. Zygomycetes: sexual-zygospores,
- asexual- sporangiospores. Oomycetes:
- sexual- oospores, asexual- zoospores.
-
What fungal group do most plant pathogens belong to?
Ascomycetes
-
What is the difference between a heteroecous rust and
an autoeceous rust? Provide an example
of each.
- ) Heteroecous—needs two unrelated host plants
- (cedar-apple rust); Autoeceous—only needs one host (peanut rust)
-
Cell walls of oomycete hyphae are primarily composed
of what?
Cellulose
-
Cell walls of fungal hyphae are primarily composed of
what?
Chitin
-
The ploidy level of oomycete in its dominant phase is
what?
Diploid
-
The ploidy level of fungal hyphae in its dominant phase if
it is a zygomycete or ascomycete is what?
) Haploid
-
The ploidy level of fungal hyphae in its dominant phase if
it is a basidiomycete is what?
Dikaryotic
-
What is one similarity between a chlamydospore and a
condium?
Both are asexual
-
Most plant pathogens are..
Facultative parasites
-
Name 2 mollicutes. What are mollicutes?
Phytoplasmas and Spiroplasmas. Mollicutes are bacteria that lack a cell wall.
-
Are most plant pathogenic bacteria gram negative or gram positive?
Gram negative
-
The prescence of slime in a KOH test indicates what?
gram negative bacteria
-
Analysis of DNA sequence on 16S ribosomal gene is useful to..
ID species
-
How do the flollowing differ:
Xanthomonas axonopodis pv. citri and Xanthomonas axonopodis pv. vesicatoria
- different pathovars; indicates host differences
-
How does a fungal leaf spot differ from a baterial leaf spot?
Fungal- uasually round; Bacterial- follows veins, could be vertical or triangular
-
Provide 2 signs that are unique to bacterial pathogens.
bacterial streaming and oozing
-
Characteristics of Basidiomycetes
septate hyphae, clamp connections, basidium
-
Characteristics of Ascomycetes
septate hyphae, ascus
-
Characteristics of Zygomycetes
coenocytic hyphae, sporangia
-
Characteristics of Oomycetes
coenocytic hyphae, sporangia
-
one way that facultative parasitic bacteria survive when they are not parasitic to a host
as a saprophyte in the soil
-
Difference between direct and indirect penetration
Direct- enter host through an opening the pathogen created; Indirect- enter through natural opening or wound
-
What type of penetration do facultative parasitic bacteria use?
INDIRECT
-
Name the host and disease of Xylella fastidiosa subsp: multiplex
Disease- bacterial leaf scorch; Host- wodded plants (oak and elm)
-
Host and disease of Septoria tritici
Disease- leaf blotch of wheat; Host- wheat
-
Host and disease of Blumeria graminous
Disease- powdery mildew; Host- wheat
-
Host and disease of Claviceps purpurea
Disease- Ergot; Host- wheat
-
Is septoria tritici monocyclic or polycyclic
polycyclic
-
What is the initial inoculum of Xylella fastidiosa? How is inoculum dispersed?
The bacteria itself. Dispersed through insect vectors
-
In Claviceps purpurea: what is initial inoculum? Secondary inoculum? How is secondary inoculum dispersed?
Ascospores. Conidia. Conidia dispersed by wind
-
Is Blumeria graminous necrotroph or biotroph?
Biotroph
-
What type of spore is produced in corn smut?
Teliospores
-
What is the function of clamp connections?
To prolong the dikaryotic phase
-
Which fungus is believed to be the largest organism on earth?
Armillaria Root Rot
-
Are plant parasitic nematodes obligate or facultative parasites
obligate
-
Migratory ectoparasite
feeds on plant surface, only stylet enters plant, moves from cell to cell and sometimes plant to plant
-
Sedentary endoparasite
feed from inside plant tissue, does not move, stays in one feeding site and dies there
-
What type of reproduction does bacteria use? By what process?
Asexual reproduction. Binary fission
-
What can be concluded about a nematode with a stylet
It may be parasitic however not all parasites with stylets are parasitic
-
Provide info for Trichodorus
Stubby root nematode, migratory ectoparasite, affects root, unique symptom of stubby root
-
Provide info for Heterodera
Cyst nematode, sedentary endoparasit, affects root, unique symptom is cyst on root
-
Provide info on Pratylenchus
Lesion nematode, migratory endoparasite, affects underground plant part (root), unique symptoms are lesions on underground plant parts
-
Provide info on Aphelenchoides
Foliar nematode, migratory endoparasite, affects leaf, unique symptoms are lesions on leaf
-
Provide info on Meloidogyne
Root knot nematode, sedentary endoparasite, affects root, unique symptoms is the root knot (change in form)
-
Common name for 2 nematodes that can transmit viruses
Dagger and Needle nematodes
-
In what stage do plant parasitic nematodes hatch
J2
-
What are the two nematodes that can only initiate infection at the J2 stage? What do they have in common?
Root knot and cyst nematodes. Both are sedentary endoparasites so they stay at one feeding site inside plant tissue until they die
-
Soybean cyst nematode has a *** host range. It establishes feeding sites called ***** by secreting **** from their *****.
narrow, syncytia, polysacharrides and protein, stylets
-
Soybean Cyst nematodes overwinter in ******* and it can be dispersed over long distances by *****..
leathery cuticle of female's dead body, wind blown soils and birds (ingestion)
-
What is one limitation of crop rotation
It could be hard to trade out crops and cost more money
-
One limitation of fumigant nematicide
It can be harmful to the growth of plants and harmful to humans
-
Are plant parasitic viruses obligate or facultative parasites
obligate
-
What is the function of a movement protein?
Movement of virus (help with cell to cell movement through plasmodesmata)
-
Function of replicase (RNA-dependent RNA polymerase)
replicate virus within host
-
Provide 2 specific change in color symptoms caused by viruses
mosaic and mottle
-
The only viral sign that can be observed with a compound light microscope
inclusion bodies- crystalline clusters
-
If a healthy lower leaf of a resistant plant in inoculated with a virus what type of symptom would you see and where would you see it?
Hypertension response, on the lower leaf that was innoculated
-
Persistent insect vector transmission
virus located within salivary glands, not immediately transmissible, vector can transmit virus from hours to days
-
Nonpersistent insect vector transmission
virus located within stylet, immediately transmissible, vector can transmit virus for a few hours
-
Persistent propagative insect vector transmission
virus reproduces within vector (salivary glands), not immediately transmissible (latent period), can transmit virus for the entire life of the insect vector
-
Example of vertical transmission
transmission from mother to seed
-
Viral genome can move from cell to cell through ***** and from *******through ******
plasmodesmata, source to sink, phloem
-
Full name of TMV
Tobacco Mosaic Virus
-
Full name of CMV
Cucumber Mosaic Virus
-
Full name of TSWV
Tomato Spotted Wilt Virus
-
What viruses are multiparticulate
TSWV, CMV
-
The virions of which virus are encapsulated by a membrane of host origin
TSWV
-
Common name of the insect vector of TSWV
Thrips
-
2 viruses that have genes that code for proteins that interfere with RNA silencing by the host
TSMV and CMV
-
Hemiparasite
Root- to get water and minerals from xylem, capable of photosynthesis
-
Holoparasite
All of plant--food, water, and minerals through phloem and xylem, not capable of photosynthesis
-
Examples of holoparasite
Dodder, Broomrape, and Dwarf Mistletoe
-
Examples of hemiparasite
leafy mistletoe, witchesweed
-
What parasitic plant grows as a yellow vine
Dodder
-
What parasitic plants includes species in Phoradendron genus
leafy mistletoe
-
1 crop that belongs to Solanaceae
tomato
-
Why is removing the leafy portion of leafy mistletoe not enough to eradicate the pathogen?
Because the haustoria (which is taking plant nutrients) extends deeper into the plant
-
Your neighbor has leafy mistletoe hanging on their front porch, you have a tree that is susceptible. What do you do?
Ask the neighbor to take it down because birds are attracted to the fruit and can spread the disease to your tree by ingesting from the mistletoe and pooping on your tree. (avoidance)
-
Sunscald is caused by
excess sunlight
-
The abiotic factor that causes the most damage to plants around the world is
insufficient moisture (drought)
-
Info about carbon
macronutrient, enters plant through air (stomata)
-
Info on Nitrogen
Macronutrient, enters plant through roots (enters phloem)
-
Info on Iron
Micronutrient, enters plant through roots (enters phloem)
-
Info on Copper
Micronutrient, enters plant through roots (phloem)
-
Info on Potassium
Macronutrient, enters plant through roots (phloem)
-
Info on Calcium
Macronutrient, enters plant through roots (phloem)
-
If an element is mobile through what tissue will it move and in what part of the plant would the symptoms first appear?
phloem, in bottom leaves first
-
Two nutrient elements that are mobile
nitrogen, potassium
-
Two nutrient elements that are immobile
calcium, iron
-
What are some clues that suggest a disease symptom is caused by an abiotic factor
symptoms appear suddenly, symptoms are uniform throughout entire plant, there is a distinct line between symptoms of affected part of the plant and unaffected parts of plant
-
What are saprophytic plant pathogens? explain
soil invaders--they are less competitive than soil inhabitants and their populations drop quickly without a host but also recover quickly when host is introduced
-
Where do epiphytes of the rhizosphere survive and what do they feed on?
on top of root surface, feed on exudates on surface
-
Phenological synchrony
host and pathogen synchronize, pathogen produces inoculum when host is susceptible
-
Chemotaxis
used to direct movement of nematodes toward roots
-
Fungistasis
keep spores from germinating too soon
-
A pathogen that produces lignase is capable of degrading ***. What plant would be a suitable host for a pathogen that produces this enzyme? why?
wood, oak tree because lignase is complex and is best at wood decaying
-
Are nonspecific toxins pathogenicity factors or virulence factors
virulence factors
-
What ype of toxin is the T toxin produced by Bipolaris maydis
host-specific toxin
-
Fuction of Gibberellins
stimulates stem elongation
-
Function of Cytokinins
promotes cytokinesis
-
Function of Auxin
promotes mitosis and cell expansion
-
Function of Ethylene
promotes tissue maturity
-
Function of Salicylic Acid
activates genes that aid in defense
-
What hormone imbalance causes a gall
overproduction of auxins and cyokinins by host
-
What hormone imbalance causes premature defolitiation
ethylene production by pathogen
-
What hormone imbalance causes witches broom
multiple hormone imbalance in host
-
What hormone imbalance causes Etiolation
gibberellins produced by pathogen
-
What hormone imbalance causes stunting
down regulation of gibberellins in host
-
Induced chemical Defense
Induced defense mechanism that is biochemical (produced before symptoms occur
-
Constitutive Chemical Defense. Example.
Active defense mechanisms that are biochemical. secondary metabolites (already produced, not induced)
-
Induced Structural Defense. Example
Induced defense mechanisms that are structural (produced before symptoms occur). Changes in cell wall form
-
Constitutive Structural Defense. Example.
Active defense mechanisms that are structural (already present, not induced). Waxy cuticle
-
What does SAR stand for
Systemic Acquired Resistance
-
What does ISR stand for
Induced Systemic Resistance
-
What is the gene for gene hypothesis. what type of resistance does it explain
For every gene a plant has for resistance a pathogen has one for virulence and vise versa...it explains complete resistance
-
AVR gene + R gene = ?
Hypersensitivity Response
-
AVR gene initiates disease on a host that does not have R gene what would occur?
There would not be complete resistance so disease would occur
-
What is the function of avr genes for pathogens on hosts that do not have R genes?
Virulence or pathogenicity factors
-
Function of avr genes for pathogens on hosts with R genes
Signal (elicitor)
-
An alternative name for complete resistance
specific
-
Alternative name for partial resistance
non specific
-
Complete resistance more durable with monocyclic or polycyclic pathogen
monocyclic--there are less cycle happening therefore less of a chance to cause mutations
-
Complete resistance more durable with airborne or soilborne pathogen
soilborne-- because airborn pathogens spread more easily than soilborne leaving more chance for infection
-
Complete resistance more durable with plant population with 2 compatible mating types or populations with only 1 mating type
only 1 mating type because there is a smaller chance for genetic mutation
-
What is one ecological concern about the use of GMO crops
genes that were inserted into the GMO crops could spread to wild crops
-
Cryphonectria parasitica
fungus, disease- chestnut blight, host- chestnut tree
-
Magnaporthe oryzae
Ascomycete, disease- rice blast, host- rice
-
Hemileia vastatrix
Fungus, disease-coffee rust, host- coffee
-
Erwinia Amylovera
Bacteria, disease- fire blight of apple and pear, host- apple and pear
-
Plasmopara viticola
Oomycete, disease-downy mildew of grape, host- grape
-
Phytophthora infestans
Oomycete, disease- late blight of potato, host- potato
-
Common name of a disease that causes stem canker
sudden oak death
-
Pathogens that cause stem cankers infect wi=hich tissues of stem
phloem
-
What is Antone DeBary famous for?
recognizing there are plant pathogens rather than spontaneous disease
-
What is Pierre Marie Alexis Millardet famous for?
using fungicides on downy mildew of grape
-
What is the main difference between a blotch and a blight
Blotch- large location of dead cells; Blight- covers more area of dead cells (can appear burned)
-
What disease is a concern because of the production of mycotoxins
Fusarium head blight
-
What does AUDPC stand for
Area Under Disease Progress Curve
-
Name 2 ways a pathogen can travel long distances (in citrus canker)
tools that havent been cleaned, vectors (such as humans moving them)
-
Reason that recent eradication of citrus canker was unsuccessful
The hurricanes blew the disease around and spread it even further
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