What are Kochs postulates (4) 1. ) same pathogen 2. ) isolate 3. ) induce 4. ) re-isolate

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

Lecture 1 Flashcards by Amiel Encomienda

Define pathogen

an agent that can cause disease

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Define disease

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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Define symptoms

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

true

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What are the microorganisms that cause disease

nematode
fungi 
bacteria
mollicutes
viruses
viroids

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What is the disease triangle

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

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What are Kochs postulates (4)

) same pathogen
) isolate
) induce
) re-isolate

) A specific organism must always be associated with disease
) The organism must be isolated in pure culture
) When inoculated into healthy host, under favorable conditions, the organism must produce the characteristic symptoms of the disease in that host
) 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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What does the disease triangle indicate

proof of pathogenicities

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What does phytophora mean in latin

plant destroyer

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What are causal disease agents

species of phytophora

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

true

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

because phytophora have cellulose but no chitin

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true or false; phytophora require water to complete life cycle

true

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Which oomycete caused the late potato blight in Ireland

P.infestans

Phytophthoora infestans

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what causes the symptoms, when a person ingests Phytophthora infestans

asexual “zoospore” stage of the life cycle causes epidemics

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What conditions do Phytophthora infestans favor

cool and wet; favors zoospore production

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how many Irish died because of this epidemic

1-1.5 million died of hunger and disease

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What are the symptoms of Kauri Die back

) defoliation
) yellowing
) thinning
) dead branches
) stag heads
) large bleeding lesions = gummosis
) kauri collar rot

trees of all ages and sizes can be infected

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scientific name of kauri

Agathis Australis

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How is kauri dieback spread

soil
soil water movement
plant to plant transmission through root to root contact
human and animal vectors

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What is the other name of Kauri dieback

PTA

phytophthora taxon agathis

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Where did PTA originate

tropical origin

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

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When was Kauri Die back first reported and where

2006

Waitakere Ranges

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Where were other places that Kauri Die back was spotted

Great Barrier island
Waipoua Forest
Northland
Rodney District
North shore city

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

- Maori involvement (iconic species) - impacts on ecosystem - NZ recreational opportunities - research - land owners

What are the diseases caused by fungi

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

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

Chromista

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

Disease triangle

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

Hemileia vastatrix (a basidiomycete fungus)

What does hemileia vastatrix attack

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

What causes the yellow orange powdery spots on coffee leaves

- the production on the underside of the leaves of asexual urdeospores - by Hemileia vastatrix

Why is coffee leaf rust harmful to the coffee growing industry

- crop losses result from reduced photosynthetic capacity of infected leaves and premature defoliation ( affects berry production )

what is the abbreviation for coffee leaf rust

- CLR

Where was coffee leaf rust first reported

Kenya; East Africa | 1861

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

coffee

When did CLR arrive in Sri Lanka

1869

What is Claviceps purpurea (fungi)

- causes ergot of cereals and grasses

What types of plants is Claviceps purpurea common in

pearl millet | rye

What is ergotism

toxic alkaloids that are psychoactive (humans)

What are the symptoms after ingesting Claviceps purpurea

- gangrene - nervous patterns - psychosis

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

true

What are the benefits of Claviceps purpurea

Ergotamine: eases migraines and labour

What is Botrytis cinerea

- ascomycete fungus

What does Botrytis cinerea infect

a wide range of fruit and vegetable crops - grapes - strawberries - raspberries

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

Botrytis cinerea

How is Botrytis cinerea controlled

chemicals- however problems with resistance and residues

How is Botrytis cinerea spread

airborne conidia (asexual spores)

What are the conditions that Botrytis cinerea develops in

warm temperature | high humidity

What are effects of Botrytis cinerea to grapes

- moist rot on the grapes - and other fleshy parts of the vines - producing masses of grey conidia

How does Noble rot occur

- 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)

what is the color of botrytised wine

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

What is DED

Dutch Elm Disease

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

true

What causes DED

Ascomycete fungus | - Ophiostoma novo-ulmi

how is DED spread

- by bark beetles (Scolytus spp.)

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

- they carry the fungal conidia (asexual spores) from tree to tree

Where did DED spread from

Asia to Europe (1910) and America (1928)

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

from imported timber | - devastated susceptible native elm populations

What are the symptoms of DED

- leaves starting to wither | - leaves before the normal autumn; senescence

What does Ophiostoma novo-ulmi do

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

When was DED found in Auckland

1989

How did NZealanders tried to prevent DED

Pheromone trapping | - failed

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

potato late blight (Phytophthora infestans) | kauri die back (Phytophthora taxon agathis)

What are the fungal diseases discussed today (4)

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

How is Claviceps purpurea spread

conidia, ascospores

What kingdom do Oomycetes belong to

Stramenopila

true or false; phytophthora are a a type of Oomycete

true

What are the general effects of fungi on crops

- causes serious crop losses in the field - storage rots - make food inedible due to production of toxins

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

true

where are the alkaloids produced; Claviceps purpurea

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

where did DED originate

Asia

Lecture 1 Flashcards

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