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Plant Pathology > Bacterial Plant Diseases > Flashcards

Bacterial Plant Diseases Flashcards

1
Q

Why are bacteria important?

A

Degrade organic matter, used in food production

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2
Q

Characteristics of bacteria

A
  • single-celled
  • prokaryotic
  • various shapes
  • Gram stain for ID
  • many have flagella
  • reproduce by binary fission
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3
Q

Gram +

A
  • thick cell walls
  • peptidoglycan retains stain
  • stains purple
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4
Q

Gram -

A
  • thin cell walls
  • viscous
  • stains red
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5
Q

Variation - transformation

A

cells picks up loose DNA

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6
Q

Variation - transduction

A

insertion of viral DNA

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7
Q

Variation - conjugation

A

transfer of plasmid

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8
Q

plasmid

A

unnecessary DNA

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9
Q

Three kinds of bacterial ecology

A
  • host
  • debris
  • saprophytic in soil
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10
Q

Spread of bacteria

A

Long distance: die with prolonged exposure

  • aerosols, rain, irrigation
  • vectors: insects, birds, animals, man

Short distance: inches

  • splattering
  • swimming (wet areas)
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11
Q

Survival of bacteria

A

Living / dead plant tissue … 50% survive in / on seed.

Reduced metabolic state - do not produce endospores

Epiphytic - on host surface without causing infection

In soil, ooze, and vectors.

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12
Q

Entry of bacteria

A

Strictly passive! Through wounds, natural openings (stomata)

Colonize apoplast in xylem

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13
Q

Effects of bacteria

A
  • Reduction of photosynthesis (necrosis)
  • Increase phenol content -> plant compounds self-destruct
  • Increase hormone production
  • Produce toxins (to host and animals)
  • Produce enzymes that break down plant compounds
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14
Q

Streptomyces

A

Not rod-shaped

Branched mycelium, pseudofilamentous, curled chain of conidia

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15
Q

Size, shape, and structure of bacterial colony changes with…

A
  • age of culture
  • composition media
  • pH
  • temperature
  • staining method
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16
Q

Classification of bacteria

A

Difficult, variable, “controversial”

Based on morphological, physiological, and molecular traits

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17
Q

Genus

A

Taxonomic group above species

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18
Q

Species

A

Basic taxonomic unit

Group of strains that cluster due to shared traits

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19
Q

Pathovar

A

Strain of bacteria, or set of strains, with similar characteristics

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20
Q

Bacterial galls

A

Swollen areas in woody tissue, disorganized overgrowth

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21
Q

Olive knot disease

A

Pseudomonas syringae pv. savatanoi

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22
Q

Crown Gall causal organism

A

Agrobacterium tumefaciens

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23
Q

Crown Gall host

A

large range, especially on ornamentals

also popular crops like carrots

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24
Q

Crown Gall symptoms

A

Galls - small overgrowths at soil line on roots and stems… initially soft, but eventually enlarge, harden, and darken

25
Q

Crown Gall signs

A

NONE

26
Q

Crown Gall disease cycle

A

Monocyclic.

  • OW in galls
  • Enter root or stem, usually through wound
  • Galls
27
Q

Crown Gall favorable conditions

A

Moisture, temperatures suboptimal for plant growth

28
Q

Crown Gall management

A
  • inspect, reject infected shipments
  • quarantine
  • in soil, avoid susceptible hosts… grasses in rotation can help
  • biocontrol … Agrobacterium radiobacter (no plasmid)
29
Q

Bacterial spots and blights

A

Spots are most common, necrotic areas fall from leaf - leaves “shothole” damage.

Veins of foliage stop bacterial progress (angular appearance)

30
Q

Angular leaf spot of cotton pathogen

A

Xanthamonas campestris pv. malvacearum

can also affect cereals, beans, stonefruits, and vegetables

31
Q

Angular leaf spot of cotton geo

A

wherever cotton is grown

32
Q

Angular leaf spot of cotton symptoms

A
  • Small water-soaked spots on undersides, appear early in season
  • Angular spots on leaves / bolls … necrosis stopped by veins
  • Elongated black lesions on stems girdle and kill
33
Q

Angular leaf spot of cotton signs

A

difficult to find

34
Q

Angular leaf spot of cotton disease cycle

A
  • OW in (colonization) / on seed (surface with biofilm)
  • New seedlings are infected
  • Symptoms
  • Boll / seed development
  • OW
35
Q

Angular leaf spot of cotton favorable conditions

A

high temperatures, 85 - 95° F

36
Q

Angular leaf spot of cotton losses

A
  • death of plant
  • reduced vigor
    fewer bolls, less yield
  • soil infestation
37
Q

Angular leaf spot of cotton management

A
  • Resistance! so much available, disease hardly a problem
  • Rotation (avoid cotton every year)
  • Seed certification
38
Q

Southern Bacterial Wilt pathogen

A

Ralstonia solanacearum races

one is considered a ‘bioterror threat’

39
Q

Southern Bacterial Wilt hosts

A

Tomatoes, peppers, etc…

40
Q

Southern Bacterial Wilt geo

A

tropics and warmer parts of the world

41
Q

Southern Bacterial Wilt symptoms

A
  • Wilting
  • Early stage… during day with recovery at night
  • Whole mature plants… wilt, quick death, leaves remain green
  • any age can be infected
  • infection apparent during fruit expansion
42
Q

Southern Bacterial Wilt disease cycle

A
  • In soil / water
  • Infects through wounds in roots
  • Colonizes plant, blocks vascular system
  • Plant dies
  • Repeat
43
Q

Fire Blight pathogen

A

Erwinia amylovora

44
Q

Fire Blight symptoms

A
  • Twigs turn brownish black
  • Hooked
  • Leaves turn black
  • Flowers are water-soaked, then shrivel… fall or hang on tree
45
Q

Fire Blight geo

A

worldwide

46
Q

Fire Blight host

A

Pome fruits: apple, pear, quince

47
Q

Fire Blight management

A

Winter - cut twigs, branches, cankers, whole trees at least 10 cm below visible infection

Summer - cut blighted shoots (~30cm below)

  • Disinfect tools
  • Insect control
  • Resistance
  • Chemical (Bordeaux mixture)
48
Q

Fastidious prokaryotes

A

Cause diseases similar to viruses, difficult to culture. Vectored.

“obligate parasites” - no saprophytic phases

Restricted to vascular system, classified by presence (Xylella) or absence (Mollicutes) of cell wall

49
Q

RLO

A

Rickettsia-Like-Organism

50
Q

Xylella fastidiosa

A

Xylem limited, insect vectored. Rod shaped, wide host range

51
Q

Xylella fastidiosa host range

A
  • Grape (Pierce’s Disease)
  • Citurs (Citrus Variegated Chlorosis, CVC)
  • Blueberry (Bacterial Leaf Scorch)
  • Almond, peach, coffee, olive, pecan, plum…
52
Q

Liberibacter spp.

A

Transport of organic compounds… associated with Citrus Greening Disease (aka Huanglongbing or yellow dragon disease)

53
Q

Liberibacter spp. symptoms

A
  • Leaf chlorosis
  • Yellowing of tree in quadrants
  • Immature fruits (greening)
  • Small, lopsided fruit
  • Bitter taste
54
Q

Liberibacter spp. management

A
  • No cure… control insect vectors!
  • Scout for affected trees, remove (4x/year)
  • Use pathogen free material
55
Q

Candidatus Liberibacter asiaticus

A

LAS, suspected causal agent of HLB… non-culturable

56
Q

Mollicutes

A

No cell wall

Two genera:

  • Phytoplasma
  • Spiroplasma
57
Q

Phytoplasma sp.

A
  • MLO (Mycoplasma-Like-Organism)
  • Cell wall absent, “unit membrane”
  • non spore forming
58
Q

Spiroplasma citri

A
  • No cell wall, helical shape
  • Only known to parasitize plants
  • May parasitize insects and grow saprophytically

Plant Pathology (10 decks)

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