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Bacterial Plant Diseases Flashcards

(58 cards)

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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

Study These Flashcards
A

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

25
Crown Gall signs
NONE
26
Crown Gall disease cycle
Monocyclic. - OW in galls - Enter root or stem, usually through wound - Galls
27
Crown Gall favorable conditions
Moisture, temperatures suboptimal for plant growth
28
Crown Gall management
- inspect, reject infected shipments - quarantine - in soil, avoid susceptible hosts... grasses in rotation can help - biocontrol ... Agrobacterium radiobacter (no plasmid)
29
Bacterial spots and blights
Spots are most common, necrotic areas fall from leaf - leaves "shothole" damage. Veins of foliage stop bacterial progress (angular appearance)
30
Angular leaf spot of cotton pathogen
Xanthamonas campestris pv. malvacearum can also affect cereals, beans, stonefruits, and vegetables
31
Angular leaf spot of cotton geo
wherever cotton is grown
32
Angular leaf spot of cotton symptoms
- 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
Angular leaf spot of cotton signs
difficult to find
34
Angular leaf spot of cotton disease cycle
- OW in (colonization) / on seed (surface with biofilm) - New seedlings are infected - Symptoms - Boll / seed development - OW
35
Angular leaf spot of cotton favorable conditions
high temperatures, 85 - 95° F
36
Angular leaf spot of cotton losses
- death of plant - reduced vigor fewer bolls, less yield - soil infestation
37
Angular leaf spot of cotton management
- Resistance! so much available, disease hardly a problem - Rotation (avoid cotton every year) - Seed certification
38
Southern Bacterial Wilt pathogen
Ralstonia solanacearum races one is considered a 'bioterror threat'
39
Southern Bacterial Wilt hosts
Tomatoes, peppers, etc...
40
Southern Bacterial Wilt geo
tropics and warmer parts of the world
41
Southern Bacterial Wilt symptoms
- 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
Southern Bacterial Wilt disease cycle
- In soil / water - Infects through wounds in roots - Colonizes plant, blocks vascular system - Plant dies - Repeat
43
Fire Blight pathogen
Erwinia amylovora
44
Fire Blight symptoms
- Twigs turn brownish black - Hooked - Leaves turn black - Flowers are water-soaked, then shrivel... fall or hang on tree
45
Fire Blight geo
worldwide
46
Fire Blight host
Pome fruits: apple, pear, quince
47
Fire Blight management
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
Fastidious prokaryotes
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
RLO
Rickettsia-Like-Organism
50
Xylella fastidiosa
Xylem limited, insect vectored. Rod shaped, wide host range
51
Xylella fastidiosa host range
- Grape (Pierce's Disease) - Citurs (Citrus Variegated Chlorosis, CVC) - Blueberry (Bacterial Leaf Scorch) - Almond, peach, coffee, olive, pecan, plum...
52
Liberibacter spp.
Transport of organic compounds... associated with Citrus Greening Disease (aka Huanglongbing or yellow dragon disease)
53
Liberibacter spp. symptoms
- Leaf chlorosis - Yellowing of tree in quadrants - Immature fruits (greening) - Small, lopsided fruit - Bitter taste
54
Liberibacter spp. management
- No cure... control insect vectors! - Scout for affected trees, remove (4x/year) - Use pathogen free material
55
Candidatus Liberibacter asiaticus
LAS, suspected causal agent of HLB... non-culturable
56
Mollicutes
No cell wall Two genera: - Phytoplasma - Spiroplasma
57
Phytoplasma sp.
- MLO (Mycoplasma-Like-Organism) - Cell wall absent, "unit membrane" - non spore forming
58
Spiroplasma citri
- No cell wall, helical shape - Only known to parasitize plants - May parasitize insects and grow saprophytically

Plant Pathology (10 decks)

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