Exam 2 Flashcards
what are bacteria
-prokaryotes
-round, rod shaped, or spiral shaped
-reproduce by fission
-exchange genetic material through conjugation
-have flagella (at end or all over)
-secrete EPS
-contain plasmids that replicate independently of chromosomal DNA
bacterial pathogens
most are…
-facultative parasites
-aerobic
-gram -
gram +
peptidoglycan on outer layer
-stains purple
gram -
outer layer above peptidoglycan
-stains pink
gram stain method
crystal violet
iodine
alcohol
safranin
fire blight pathogen
erwinia amylovora
fire blight hosts
apple and pear
fire blight symptoms
-leaves look burnt, then blighted
-black water soaked bark
-shepherds crook on tip of shoot
how is fire blight spread
-relies on insects and rain to spread
-insects are attracted to ooze from infected flowers
fire blight disease cycle
-overwinters in margin of cankers
-bacteria live epiphytical on flowers
-spread through insects and rain splash
-infects inside of flowers
-ooze spreading due to insects is a secondary infection
fire blight management
-trim infected parts off
-eliminate cankers by removing trees
-antibiotics
-remove infected plants and plant debris
bacterial spot pathogen
Xanthomonas sp.
bacterial spot host
pepper and tomato
bacterial spot symptoms
-yellow-green, small lesions on leaves
-twisted, deformed leaves
-water soaked lesions on upper and lower surfaces of leaves
-fruit spots
fire blight biology of pathogen
-flagellated on all sides
-gram -
-rod shaped
bacterial spot bio of pathogen
gram -
-several species cause disease
-wide host range
how does bacterial spot spread
rain splash
bacterial spot management
-use disease free seeds
-crop rotation
-use resistant cultivars
-bacteriophages
bacterial leaf scorch pathogen
xyella fastidiosa
bacterial leaf scorch host
shade trees
bacterial leaf scorch bio of pathogen
-gram -
-aerobic
-lacks flagella
-difficult to grow in culture
how is bacterial leaf scorch spread
-rain splash and vectors (sharpshooters and spittlebugs feed on xylem which clogs it)
bacterial leaf scorch symptoms
-leaf scorch
-looks like abiotic factors
-grows slowly
IC-PCR
fishing for antigen with small amount of bacteria, then completing pcr
-good to catch disease at beginning
-most sensitive
ELISA
-wells contain antibody
-color change signals presence of antigen
-second antibody binds to first antibody and substrate will bind to second antibody (causes color change)
-very few false positives, cheap, relatively fast
PCR
-need: primers, DNA, bases, buffer, DNA polymerase
-denaturation: heat to 98 degrees
-annealing: primers will stick to DNA at lower temp
-elongation: adding base pairs (DNA polymerase does this)
-do this 35 times
bacterial leaf scorch management
-maintain plant vigor
-sanitation: remove dead branches or severely diseased trees
-use tolerant plants
-antibiotics: inject in trunk or roots
crown gall pathogen
agrobacterium tumefaciens
crown gall host
members of 93 families of plants
crown gall symptoms
-overgrowths on roots or at base of crown
-stunted growth
-lack of vigor and reduction in foliage
crown gall bio of pathogen
-gram -
-ti plasmid produces auxins, opines, and cytokinins that result in cell enlargement and uncontrolled growth
-opines used as nitrogen and carbon source for nutrition
crown gall disease cycle
-overwinters on detached galls in soil
-enters through wounds in stem or root
-tdna enters and multiples, divides, and enlarges, leading to gall formation
-primary inoculum in galls in soil
galltrol
-a. radiobacter is a non-pathogenic strain
-agocin 84 mimics opines produced by plant cells during infection with a. tumefaciens and is taken up by it
-inhibits dna replication and cellular growth
crown gall management
-screen planting stock for presence of galls
-remove infected trees and plants
-crop rotation
-copper based solutions
-genetic engineering
what are viruses
-noncellular
-only reproduce inside infected cells
-virus particles composed of: genome (ss+RNA, ss-RNA, dsDNA) and protein protective shell (capsid)
viral symptoms
-mosaic: chlorophyll is degrading, but not all at once
-chlorosis: yellowing of leaf
-flower break: anthocyanin degraded
-leaf roll: whole leaf no longer exposed to sun
-ringspot: degrades chlorophyll
-fruit deformation
virus signs
-viruses are found in phloem
-can’t be seen with naked eye
-inclusion bodies (crystalline clusters of viruses)
how do viruses survive?
-no survival structures
-some viruses survive for short periods on their own until finding.a living host (makes them stable)
-unstable viruses survive within plant structures or In vectors
how do viruses spread?
-immobile: depend on other organisms to be moved around
-require wounds to access plant tissue
passive transmission
-mechanically (rare in nature)
-vegetative propagation
-seed
active transmission
-requires vector (plant feeding insects and nematodes)
mechanical transmission
-deliberate (rub inoculation)
-field (ex. farm tools)
-greenhouse (cutting tools, plant handling)
transmission by vectors
-mostly insects with sucking mouthparts
(aphids most important, then leafhoppers)
-some insects with biting mouthparts (ex. ants)
-some by nematodes
-some by soilborne fungi
-a given virus species typically has a single type of vector
non-persistant transmission
-virus sticks to mouth part of insect and doesn’t multiply inside insect
-virus acquired during exploratory probes
-virus is…
acquired quickly
retained for short period
transmitted quickly
persistant transmission
-virus ingested by insect
-virus is…
acquired slowly
retained for long period
transmitted slowly
circulative transmission
-virus circulates in insect without replication
-transmission for days or months
propagative transmission
-transmitted during all the insects life
-virus replicates inside insect
virus hosts
-can infect all species of cultivated and wild plants
-host range varies form broad to narrow
-resistance of plant to virus is determined by genome
-for the most part, they spread through whole plant
-sometimes viruses can cause local lesions at site of infection
pathogenicity assay
-uses indicator plants such as Nicotiona to diagnose virus
transmissibility-vector transmission assays
identify vector that transmits virus
how to use electron microscopy to diagnose virus
-architecture of virus particles
-presence of virus specific structures in infected cells
how to use Elisa to diagnose virus
properties of protein coat (relies on id of virus through its reaction with an antibody)
how to use per to diagnose virus
-properties of viral nucleic acid
tobacco mosaic virus host
tobacco, tomato
tobacco mosaic symptoms
-mosaic, necrosis, leaf curling, stunting, yellowing of plant tissue
-fruit: poor yield, distorted fruit, delayed fruit ripening
tobacco mosaic biology
-belongs to tobamovirus species
-rna with 6400 nucleotides
-rna encodes 4 genes (2 replicases, mp, and coat protein)
tobacco mosaic disease cycle
-no overwintering structures
-overwinters in infected tobacco stalks and leaves in soil or contaminated seeds
-transmitted by human handling, contaminated tools (no vector)
-very stable
how does tobacco mosaic spread
-uses mp and host proteins to enter cll through plasmodesmata (enlarged when virus enters)
-rna release mp and host proteins to start new round of infction
tobacco mosaic management
-wash tools
-discard tmv contaminated soils, leaves, and plants
-cross protection by inoculating young plants with mild tmv strain
-resistant cultivars
-seed treatment (10% trisodium phosphate 2-4 days before planting)
soil borne wheat mosaic pathogen
soil borne mosaic virus
soil borne mosaic host
wheat, barley, rye
soil borne mosaic symptoms
-irregular chlorotic patches in field
-stunted plants
-leaves with chlorotic mosaic, irregular mottling and streaking
-yield loss
soil borne mosaic biology
-2 rna molecules with different lengths
-rna2 encodes a suppressor of gene silencing
soil borne mosaic disease cycle
-transmitted through slime mold
-p. graminis produces resting spores that transmit virus
-resting spores can remain dormant in soil up to 30 years
-found in xylem
p. graminis transmission
-high humidity in soil produces and germinates zoospores
-zoospores produce satchel that penetrates host cell wall once it reaches roots
-virus is emptied into host cells with satchel
soil borne mosaic management
-sanitize equipment or tools that touches soil
-crop rotation
-use varieties that are resistant to vector and/or virus
-soil fumigants
potato spindle tuber pathogen
potato spindle viroid (PTSVd)
PTSVd hosts
potato and tomato
PTSVd symtoms in tomato
-growth reduction
-smaller leaves that turn yellow
-flower and fruit inititiation stopped
PTSVd symptoms in potato
-reduced growth
-small, elongated, cracked tubers
PTSVd pathogen biology
-viroid
-341-364 nucleotides
PTSVd transmission
-vegetative propagation: by tubers and cutting (no visible symptoms)
-mechanical: by cultivation activities
-aphid: requires both PLVR and PTSVd in source plant
viroid
small circular rna genome that doesn’t code for proteins or particles
PTSVd management
-viroid free planting material
-sanitation of equipment and use of gloves and specific clothing
-control aphid population and planting PLVR are potato seeds
-incineration of PTSVd infects plants and materials in contact with infected plants or eqiup.
-clean infected equip. and greenhouses (acid treatment)
-crop rotation
