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Plant Pathology > Viral Plant Diseases > Flashcards

Viral Plant Diseases Flashcards

1
Q

How are viruses proven to exist?

A

Sap from infected plant forced through bacterial proof filter… filtered sap used to recreate disease

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2
Q

Virus names

A

First host on which it was found (not all hosts are infected)

Symptom
- ex Cucumber mosaic virus, tomato spotted wilt virus, etc…

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3
Q

Isolate

A

Collected from a particular place

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4
Q

Strain

A

Isolate with some kind of difference from previous others

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5
Q

Shapes of viruses

A
  • Rod
  • Bacilliform (bullet-like)
  • Flexous rod
  • Polyhedral (crystal-like)
  • Bipartite … gemini = 2 pieces
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6
Q

Viruses are ‘obligate parasites’ because…

A
  • Need host materials
  • Can’t reproduce on their own
  • Not considered living… more like infectious chemicals
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7
Q

Three steps of infection

A
  1. Initial infection
  2. Cell to cell until particles move to phloem
  3. Moves through plant
  • depends on non-lethal wound sites or vector transmission *
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8
Q

Movement through plants

A

Source to sink with photosynthesis

Results in systemic infection

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9
Q

General symptoms

A
  • Stunting
  • Lesions … necrotic spots, local
  • Mosaics … blotches
  • Yellowing … associated with stunting
  • Distortion … curling of parts / leaves … “shoestringing”
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10
Q

Physiological effects

A
  • decreased photosynthesis
  • increased respiration
  • N2 decreases
  • translocation decreases
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11
Q

Survival of viruses

A

Some are ‘stable’ and can stay viable for days.

Most are unstable and cannot survive outside of a host… vectors are very important

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12
Q

Spread of viruses

A
  • Seed … infected cells.
  • Grafts … color streaking, variegation (desirable)
  • Dodder … parasitic plant on plants
  • Nematodes
  • Pollen … with systemic infection
  • Mechanical … people
  • Insects ***
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13
Q

Important insect vectors

A
  • Aphids
  • Leafhoppers
  • Sharpshooters
  • Whiteflies
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14
Q

Two types of insect transmission

A

Non-persistent = most common by plants

Persistent = mostly by leaf hoppers

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15
Q

Non-persistent transmission

A
  • Most common by plants
  • Tend to cause mosaics
  • Fast transmission
  • Short retention time < 6 hours
  • No latent period
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16
Q

Persistent transmission

A

Most common by leafhoppers

Circulative - virus survives in hemolymph, does not replicate

Propagative - virus multiplies in insect, associated with all stages of life. Retention time measured in weeks… latent period - virus circulates through insect

17
Q

Virus ID

A
  • Host range
  • means of transmission
  • Temperature of inactivation
  • Indexing - grafting of affected plant onto indicator plant
  • Serology - ELISA, PCR
18
Q

Virus Management

A
  • Resistance… little or no input by grower. Fully susceptible plants that can yield well despite infection
  • Resistance to VECTOR … undesirable traits
  • Cultural practices … Delay infection! Time of planting, avoid insect migration. Mulches = reflective, insects don’t recognize site. Certified seed
  • Chemical … none for virus themselves
  • Biocontrol … Predator of vector, activate plant defenses
  • Transgenic Resistance … GMO
19
Q

Plant Viruses in AL

A
  • Cucumber Mosaic Virus
  • Tomato Spotted Wilt Virus
  • Papaya ringspot
  • Watermelon Mosaic Virus
  • Zucchini Yellow Mosaic
  • Potato Leaf Roll
20
Q

Plant Viruses of AL field crops

A

Wheat

  • Barley yellow dwarf (aphid)
  • Cereal yellow dwarf (aphid)

Peanut

  • TSW
  • Peanut stunt
21
Q

Cucumber Mosaic Virus geo

A

worldwide

22
Q

Cucumber Mosaic Virus hosts

A

very wide range, more than any other plant virus

- ex. tomato, beans, beets, petunias, lilies

23
Q

Cucumber Mosaic Virus symptoms

A

Young leaves become mosaic and mottled… possibly distorted and wrinkled.

Subsequent growth reduced, shortened internodes… fewer flowers / fruits

24
Q

Cucumber Mosaic Virus signs

A

NONE

25
Q

Cucumber Mosaic Virus disease cycle

A
  • OW in perennials
  • aphids - non-persistent
  • few plants initially
  • man can transmit this further
  • systemic in plants
  • OW
26
Q

Cucumber Mosaic Virus managament

A
  • Resistance
  • Eliminate weed hosts and manage insect vectors… promote beneficials
  • Certified seed
  • Prevent insects from reaching crop (netting)
  • Remove / burn diseased plants
27
Q

Tomato Spotted Wilt Virus host

A

wide range -> tomato, peanut, annual crops

28
Q

Tomato Spotted Wilt Virus geo

A

limited, (present where tested)

29
Q

Tomato Spotted Wilt Virus symptoms

A
  • Chlorotic, concentric rings
  • Mottling of leaves
  • Bud necrosis
  • Stunting in early plants
  • Less severe in older plants
30
Q

Tomato Spotted Wilt Virus signs

A

NONE!

31
Q

Tomato Spotted Wilt Virus disease cycle

A
  • thrips vector … larvae can acquire virus and transmit it for lifetime
  • no seed transmission
32
Q

Tomato Spotted Wilt Virus losses

A

reduced production, smaller plants

33
Q

Tomato Spotted Wilt Virus management

A
  • resistance
  • delayed planting
  • higher populations help minimize yield reduction
  • alternate insecticides
  • conventional tillage helps
34
Q

Prunus Necrotic Ringspot host

A

fairly limited to Prunus = stonefruits.

  • cherry, plum, peach, nectarine, almonds
  • some ornamantals … rose
35
Q

Prunus Necrotic Ringspot geo

A

worldwide, wherever hosts are grown

36
Q

Prunus Necrotic Ringspot symptoms

A
  • delayed foliation in spring, may be localized or systemic
  • later, foliage with light and dark green ringspot… spots are necrotic, fall off leaving shothole damage
  • blossoms can be distorted, limited fruit set
  • overall reduction in plant growth and vigor
37
Q

Prunus Necrotic Ringspot signs

A

NONE!

38
Q

Prunus Necrotic Ringspot disease cycle

A
  • OW in infected trees
  • spread by pollen (more rapid in older orchards)
  • virus infects through flower
39
Q

Prunus Necrotic Ringspot management

A
  • virus free stock
  • rogue (remove affected plants)
  • remove affected wild hosts
  • avoid planting too close

Plant Pathology (10 decks)

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