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102 Microorganisms as plant pathogens > Lecture 1 > Flashcards

Lecture 1 Flashcards

To understand the causes and nature of plant disease To understand the impact and importance of oomycete and fungal pathogens

1
Q

Define pathogen

A

an agent that can cause disease

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2
Q

Define disease

A

A series of harmful physiological processes caused by continuous irritation of the plant by primary agent and which results in the expression of the characteristic pathalogical responses called symptoms

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3
Q

Define symptoms

A

Visible changes in a plant resulting from the physiological reactions of the host to the pathogen or the direct effects of the pathogen on the host tissue

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4
Q

true or false; all major groups of microorganisms (bacteria, fungi & viruses) are capable of causing plant disease

A

true

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5
Q

What are the microorganisms that cause disease

A 
nematode
fungi 
bacteria
mollicutes
viruses
viroids
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6
Q

What is the disease triangle

A
  • shows how disease results from an interaction between host, pathogen, environment
    (top: pathogen, left: host, right: environment)
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7
Q

What are Kochs postulates (4)

  1. ) same pathogen
  2. ) isolate
  3. ) induce
  4. ) re-isolate
A
  1. ) A specific organism must always be associated with disease
  2. ) The organism must be isolated in pure culture
  3. ) When inoculated into healthy host, under favorable conditions, the organism must produce the characteristic symptoms of the disease in that host
  4. ) The organism must be re-isolated from the artificially inoculated host, obtained in pure culture and identified as that first inoculated
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8
Q

What does the disease triangle indicate

A

proof of pathogenicities

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9
Q

What does phytophora mean in latin

A

plant destroyer

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10
Q

What are causal disease agents

A

species of phytophora

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11
Q

true or false; phytophora are similar to true fungi but are NOT related

A

true

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12
Q

Why are fungi more closely related to humans than phytophora and oomycetes

A

because phytophora have cellulose but no chitin

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13
Q

true or false; phytophora require water to complete life cycle

A

true

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14
Q

Which oomycete caused the late potato blight in Ireland

A

P.infestans

Phytophthoora infestans

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15
Q

what causes the symptoms, when a person ingests Phytophthora infestans

A

asexual “zoospore” stage of the life cycle causes epidemics

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16
Q

What conditions do Phytophthora infestans favor

A

cool and wet; favors zoospore production

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17
Q

how many Irish died because of this epidemic

A

1-1.5 million died of hunger and disease

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18
Q

What are the symptoms of Kauri Die back

A
  1. ) defoliation
  2. ) yellowing
  3. ) thinning
  4. ) dead branches
  5. ) stag heads
  6. ) large bleeding lesions = gummosis
  7. ) kauri collar rot
  • trees of all ages and sizes can be infected
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19
Q

scientific name of kauri

A

Agathis Australis

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20
Q

How is kauri dieback spread

A
  • soil
  • soil water movement
  • plant to plant transmission through root to root contact
  • human and animal vectors
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21
Q

What is the other name of Kauri dieback

A

PTA

phytophthora taxon agathis

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22
Q

Where did PTA originate

A

tropical origin

- closest relative is chestnut pathogen from Korea (Phytophthora katsurae)

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23
Q

When was Kauri Die back first reported and where

A

2006

Waitakere Ranges

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24
Q

Where were other places that Kauri Die back was spotted

A 
Great Barrier island
Waipoua Forest
Northland
Rodney District
North shore city
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25
Q

What is the long term management of the Kauri Die Back; how does it affect the New Zealanders

A
  • Maori involvement (iconic species)
  • impacts on ecosystem
  • NZ recreational opportunities
  • research
  • land owners
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26
Q

What are the diseases caused by fungi

A
  1. ) Coffee leaf rust
  2. ) Ergot
  3. ) Botrytis grey mould
  4. ) DED (dutch elm disease)
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27
Q

What are Oomycetes grouped with now; what kingdom are they placed in

A

Chromista

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28
Q

Disease results from an interaction between host, pathogen and environment in time and space. This is called the ____

A

Disease triangle

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29
Q

What is the scientific name for coffee leaf rust (fungi)

A

Hemileia vastatrix (a basidiomycete fungus)

30
Q

What does hemileia vastatrix attack

A

leaves
producing yellow orange powdery spots; on the underside of the leaves
- caused by the production of asexual uredospores

31
Q

What causes the yellow orange powdery spots on coffee leaves

A
  • the production on the underside of the leaves of asexual urdeospores
  • by Hemileia vastatrix
32
Q

Why is coffee leaf rust harmful to the coffee growing industry

A
  • crop losses result from reduced photosynthetic capacity of infected leaves and premature defoliation ( affects berry production )
33
Q

what is the abbreviation for coffee leaf rust

A
  • CLR
34
Q

Where was coffee leaf rust first reported

A

Kenya; East Africa

1861

35
Q

What was the first major Agricultural export of Ceylon (Sri lanka) prior 1869

A

coffee

36
Q

When did CLR arrive in Sri Lanka

A

1869

37
Q

What is Claviceps purpurea (fungi)

A
  • causes ergot of cereals and grasses
38
Q

What types of plants is Claviceps purpurea common in

A

pearl millet

rye

39
Q

What is ergotism

A

toxic alkaloids that are psychoactive (humans)

40
Q

What are the symptoms after ingesting Claviceps purpurea

A
  • gangrene
  • nervous patterns
  • psychosis
41
Q

true or false; Claviceps Purpurea is what caused St. Anthony’s fire in 994 AD which killed 40 000 people

A

true

42
Q

What are the benefits of Claviceps purpurea

A

Ergotamine: eases migraines and labour

43
Q

What is Botrytis cinerea

A
  • ascomycete fungus
44
Q

What does Botrytis cinerea infect

A

a wide range of fruit and vegetable crops

  • grapes
  • strawberries
  • raspberries
45
Q

What is the most important fungal disease for the New Zealand wine industry

A

Botrytis cinerea

46
Q

How is Botrytis cinerea controlled

A

chemicals- however problems with resistance and residues

47
Q

How is Botrytis cinerea spread

A

airborne conidia (asexual spores)

48
Q

What are the conditions that Botrytis cinerea develops in

A

warm temperature

high humidity

49
Q

What are effects of Botrytis cinerea to grapes

A
  • moist rot on the grapes
  • and other fleshy parts of the vines
  • producing masses of grey conidia
50
Q

How does Noble rot occur

A
  • When Botrytis cinerea slowly rots grapes while they are ripening
  • causes them to shrivel and dehydrate
  • which concentrates both the flavor and the sugars
  • botrytised wine (result)
51
Q

what is the color of botrytised wine

A

honey color
sweet taste
typically served as a dessert wine
or with sharply flavored ripe cheese

52
Q

What is DED

A

Dutch Elm Disease

53
Q

true or false; DED is a destructive and fast spreading disease of elms

A

true

54
Q

What causes DED

A

Ascomycete fungus

- Ophiostoma novo-ulmi

55
Q

how is DED spread

A
  • by bark beetles (Scolytus spp.)
56
Q

How do the bark beetles (Scolytus spp.) spread the DED

A
  • they carry the fungal conidia (asexual spores) from tree to tree
57
Q

Where did DED spread from

A

Asia to Europe (1910) and America (1928)

58
Q

How was DED spread from Asia to Europe (1910) and America (1928)

A

from imported timber

- devastated susceptible native elm populations

59
Q

What are the symptoms of DED

A
  • leaves starting to wither

- leaves before the normal autumn; senescence

60
Q

What does Ophiostoma novo-ulmi do

A

fungus clogs the xylem vessels causing infected trees to wilt and then die

  • disease is nearly always fatal and can kill trees in just a few months
  • 1960s USA spent 1.2 * 10^ 10 dollars on removal of infected and dead elms alone
61
Q

When was DED found in Auckland

A

1989

62
Q

How did NZealanders tried to prevent DED

A

Pheromone trapping

- failed

63
Q

What are the oomycetes discussed in todays’ lecture (2)

A

potato late blight (Phytophthora infestans)

kauri die back (Phytophthora taxon agathis)

64
Q

What are the fungal diseases discussed today (4)

A
  • Coffee leaf rust (Hemileia vastatrix)
  • (wine) Botrytis cinerea
  • Claviceps purpurea (ergotism; cereals; pearl millet, rye grass)
  • DED (Dutch Elm disease; Ophiostoma novo-ulmi)
65
Q

How is Claviceps purpurea spread

A

conidia, ascospores

66
Q

What kingdom do Oomycetes belong to

A

Stramenopila

67
Q

true or false; phytophthora are a a type of Oomycete

A

true

68
Q

What are the general effects of fungi on crops

A
  • causes serious crop losses in the field
  • storage rots
  • make food inedible due to production of toxins
69
Q

true or false; Claviceps purpurea do not have major effects on plant growth or grain yield, but can cause serious problems because it produces alkaloid poisons that contaminate the grain and cause a disease known as ergotism

A

true

70
Q

where are the alkaloids produced; Claviceps purpurea

A

red-purple sclerotia, which the fungus produces in the developing grain

71
Q

where did DED originate

A

Asia

102 Microorganisms as plant pathogens (4 decks)

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