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Plant Pathology > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

what are bacteria

A

-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

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2
Q

bacterial pathogens

A

most are…
-facultative parasites
-aerobic
-gram -

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3
Q

gram +

A

peptidoglycan on outer layer
-stains purple

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4
Q

gram -

A

outer layer above peptidoglycan
-stains pink

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5
Q

gram stain method

A

crystal violet
iodine
alcohol
safranin

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6
Q

fire blight pathogen

A

erwinia amylovora

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7
Q

fire blight hosts

A

apple and pear

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8
Q

fire blight symptoms

A

-leaves look burnt, then blighted
-black water soaked bark
-shepherds crook on tip of shoot

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9
Q

how is fire blight spread

A

-relies on insects and rain to spread
-insects are attracted to ooze from infected flowers

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10
Q

fire blight disease cycle

A

-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

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11
Q

fire blight management

A

-trim infected parts off
-eliminate cankers by removing trees
-antibiotics
-remove infected plants and plant debris

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12
Q

bacterial spot pathogen

A

Xanthomonas sp.

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13
Q

bacterial spot host

A

pepper and tomato

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14
Q

bacterial spot symptoms

A

-yellow-green, small lesions on leaves
-twisted, deformed leaves
-water soaked lesions on upper and lower surfaces of leaves
-fruit spots

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15
Q

fire blight biology of pathogen

A

-flagellated on all sides
-gram -
-rod shaped

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16
Q

bacterial spot bio of pathogen

A

gram -
-several species cause disease
-wide host range

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17
Q

how does bacterial spot spread

A

rain splash

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18
Q

bacterial spot management

A

-use disease free seeds
-crop rotation
-use resistant cultivars
-bacteriophages

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19
Q

bacterial leaf scorch pathogen

A

xyella fastidiosa

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20
Q

bacterial leaf scorch host

A

shade trees

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21
Q

bacterial leaf scorch bio of pathogen

A

-gram -
-aerobic
-lacks flagella
-difficult to grow in culture

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22
Q

how is bacterial leaf scorch spread

A

-rain splash and vectors (sharpshooters and spittlebugs feed on xylem which clogs it)

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23
Q

bacterial leaf scorch symptoms

A

-leaf scorch
-looks like abiotic factors
-grows slowly

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24
Q

IC-PCR

A

fishing for antigen with small amount of bacteria, then completing pcr
-good to catch disease at beginning
-most sensitive

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25
Q

ELISA

A

-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

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26
Q

PCR

A

-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

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27
Q

bacterial leaf scorch management

A

-maintain plant vigor
-sanitation: remove dead branches or severely diseased trees
-use tolerant plants
-antibiotics: inject in trunk or roots

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28
Q

crown gall pathogen

A

agrobacterium tumefaciens

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29
Q

crown gall host

A

members of 93 families of plants

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30
Q

crown gall symptoms

A

-overgrowths on roots or at base of crown
-stunted growth
-lack of vigor and reduction in foliage

31
Q

crown gall bio of pathogen

A

-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

32
Q

crown gall disease cycle

A

-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

33
Q

galltrol

A

-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

34
Q

crown gall management

A

-screen planting stock for presence of galls
-remove infected trees and plants
-crop rotation
-copper based solutions
-genetic engineering

35
Q

what are viruses

A

-noncellular
-only reproduce inside infected cells
-virus particles composed of: genome (ss+RNA, ss-RNA, dsDNA) and protein protective shell (capsid)

36
Q

viral symptoms

A

-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

37
Q

virus signs

A

-viruses are found in phloem
-can’t be seen with naked eye
-inclusion bodies (crystalline clusters of viruses)

38
Q

how do viruses survive?

A

-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

39
Q

how do viruses spread?

A

-immobile: depend on other organisms to be moved around
-require wounds to access plant tissue

40
Q

passive transmission

A

-mechanically (rare in nature)
-vegetative propagation
-seed

41
Q

active transmission

A

-requires vector (plant feeding insects and nematodes)

42
Q

mechanical transmission

A

-deliberate (rub inoculation)
-field (ex. farm tools)
-greenhouse (cutting tools, plant handling)

43
Q

transmission by vectors

A

-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

44
Q

non-persistant transmission

A

-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

45
Q

persistant transmission

A

-virus ingested by insect
-virus is…
acquired slowly
retained for long period
transmitted slowly

46
Q

circulative transmission

A

-virus circulates in insect without replication
-transmission for days or months

47
Q

propagative transmission

A

-transmitted during all the insects life
-virus replicates inside insect

48
Q

virus hosts

A

-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

49
Q

pathogenicity assay

A

-uses indicator plants such as Nicotiona to diagnose virus

50
Q

transmissibility-vector transmission assays

A

identify vector that transmits virus

51
Q

how to use electron microscopy to diagnose virus

A

-architecture of virus particles
-presence of virus specific structures in infected cells

52
Q

how to use Elisa to diagnose virus

A

properties of protein coat (relies on id of virus through its reaction with an antibody)

53
Q

how to use per to diagnose virus

A

-properties of viral nucleic acid

54
Q

tobacco mosaic virus host

A

tobacco, tomato

55
Q

tobacco mosaic symptoms

A

-mosaic, necrosis, leaf curling, stunting, yellowing of plant tissue
-fruit: poor yield, distorted fruit, delayed fruit ripening

56
Q

tobacco mosaic biology

A

-belongs to tobamovirus species
-rna with 6400 nucleotides
-rna encodes 4 genes (2 replicases, mp, and coat protein)

57
Q

tobacco mosaic disease cycle

A

-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

58
Q

how does tobacco mosaic spread

A

-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

59
Q

tobacco mosaic management

A

-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)

60
Q

soil borne wheat mosaic pathogen

A

soil borne mosaic virus

61
Q

soil borne mosaic host

A

wheat, barley, rye

62
Q

soil borne mosaic symptoms

A

-irregular chlorotic patches in field
-stunted plants
-leaves with chlorotic mosaic, irregular mottling and streaking
-yield loss

63
Q

soil borne mosaic biology

A

-2 rna molecules with different lengths
-rna2 encodes a suppressor of gene silencing

64
Q

soil borne mosaic disease cycle

A

-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

65
Q

p. graminis transmission

A

-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

66
Q

soil borne mosaic management

A

-sanitize equipment or tools that touches soil
-crop rotation
-use varieties that are resistant to vector and/or virus
-soil fumigants

67
Q

potato spindle tuber pathogen

A

potato spindle viroid (PTSVd)

68
Q

PTSVd hosts

A

potato and tomato

69
Q

PTSVd symtoms in tomato

A

-growth reduction
-smaller leaves that turn yellow
-flower and fruit inititiation stopped

70
Q

PTSVd symptoms in potato

A

-reduced growth
-small, elongated, cracked tubers

71
Q

PTSVd pathogen biology

A

-viroid
-341-364 nucleotides

72
Q

PTSVd transmission

A

-vegetative propagation: by tubers and cutting (no visible symptoms)
-mechanical: by cultivation activities
-aphid: requires both PLVR and PTSVd in source plant

73
Q

viroid

A

small circular rna genome that doesn’t code for proteins or particles

74
Q

PTSVd management

A

-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

Plant Pathology (4 decks)

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