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Plant Pathology > introduction > Flashcards

introduction Flashcards

1
Q

Plants are the primary producers of biomass on earth. Photosynthese?

A

6 CO2+ 6 H2O –>
C6H12O6+ 6 O2
plants are energy souce, nutrient acquisition

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2
Q

Plants compete, cooperate and are consumed. Which interactions?

A
  • Competition with other plants
  • Consumption by herbivores and pathogens
  • Cooperation with symbiotic microbes
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3
Q

Types of interaction?

A
  • Mutualistic and symbiotic interactions
  • Defense against pathogens and pests
  • Competitive and cooperative interaction with plants
  • Plants and humans: Food, Resource and anthropogenic climate change
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4
Q

Symbiotic Interactions

Biological nitrogenfixation

A

Biological nitrogen fixation: symbiosis of Rhizobia with members of the Fabaceae (legumes), formation of root nodules
plant: takes light, CO2, gives Kohlenhydrate
Bacteria takes: N2 —> NH4+Glutamine

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5
Q

Symbiotic Interactions: Mycorrhiza:

A

Evolutionarily very old symbiosis between plant(roots) and certain soilborne fungi(applies to 80-90% o fall landplants)
•The plant provides carbohydrates to fungi and receives mineral nutrients(phosphorus)
•Mycorrhization can also benefitially affect plant stress resistance (biotic and abiotic stresses

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6
Q

Parasitic interactions: pathogens

Visible symptoms= pathogens

A

Potato late blight (Phytophtora infestans; oomycete), Wheat stem rust (Puccinia graminis; fungus), Onion leaf blight (Xanthomonas axonopodis pv. alii; gram negative bacterium)

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7
Q

Commonalities between: Symbiosis and Parasitism

A

Commonalities between both types of interaction:

  • specificity (only certain microorganisms can interact with certain hosts)
  • Communication (exchange of signals) between microbe and potential host
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8
Q

most plants are resistant towards most pathogens, disease is the exception and not the rule.
which organisms can cause plant diseases? how much losses of yield can disease cause?

A

Diverse organisms can cause plant diseases:
•Viruses
•Fungi
•Oomycetes (water moulds)
•Nematodes
•Bacteria
Plant diseases cause yield losses of about 30% annually

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9
Q

Why study plant pathology?

A
  • Understanding plant –pathogen interactions can help to develop durable control strategies in agriculture
  • Enables insight into general stress resistance mechanisms in plants
  • Shows how organisms from different branches of the tree of life can communicate with each other
  • Shows how different organisms can coexist with each other without causing disease
  • Enables insight in to evolutionary mechanisms
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10
Q

Disease is the exception–plants possess an effective immune system, two layers of immunity

A

•non-host resistance, PTI
•host (race) –specific resistance
(R-gene-based resistance, ETI)

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11
Q

Non-Host Resistance

A
  • all genotypesofa plant are resistant towards all genotypes(races) of a given pathogen
  • is part of the plant‘s survival strategy and evolutionary very old
  • acts on several levels:
  • preformed: mechanical and chemical barriers
  • induced, basal defense(InnateImmunity, PTI): activated upon recognition of certain microbial structures (PAMPs)
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12
Q

Host Resistance

A

•A particular pathogen can generally infect certain genotypes of the host plant
•individual host genotypes can be resistant towards certain genotypes of the pathogen
•evolutionarily later developed(after breakdown of non-host resistance)
•controlled by a single or few polymorphic host genes (proteins):
Resistance (R) –proteins recognize a particular microbial . protein(effector) and trigger a hypersensitive response(HR; cell death)

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13
Q

Pflanze –Pathogen Interactions

A

Compatible interaction: Plant is susceptible
Pathogen is virulent

Incompatible interaction:
Non-host plant
Host plant
Plant is resistant
Pathogen is a virulent
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14
Q

Plant defense acts on different levels

A

I.Preformed defense:
•mechanical and chemical barriers present on the surface of the plant regardless of th any contact with the pathogen (e.g. metabolites, morphology of barrier tissues, wax layers)

II. Induced defense:
•basal immunity (unspecific=similar response regardless of the type of pathogen)
•specific defense(gene for gene)

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15
Q

Wind, water, insects and chemotaxis

A

… help pathogens reach their hosts

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16
Q

Preformed structural barriers

A

Cuticle, Cell wall, Leaf hairs, Stomata

17
Q

Pathogens must be able to penetrate or circumvent physical barriers

A

cell wall - apressorium: Melanized appressoria build up high pressure to puncture the cell wall.
Some pathogens produce non-melanized but effective appressoria

Stomata:
Some pathogens enter through stomata and grow extracellularly

18
Q

Infection cycle of a foliar bacterial pathogen

A

Natural openings(wounds; stomata)

19
Q

Preformed chemical barriers

A 
Phytoanticipins
(released from constitutively
stored precurors):
-Saponins
-Glucosinolates

Defensins

20
Q

Saponins

A
  • Glycosides of triterpenes, steroids, and steroid alkaloids
  • Widely present in higher plants
  • effective agains fungi
  • act on membrane permeability, complex with cholesterols

Oat Avenacin A1

tomato: alpha tomatin
sorghum: 3 Deoxyanthocyanidin

21
Q

Saponins: Avenacin A-1

A

effective against
Gauemannomyces graminis var. tritici
causative agent of the „take all disease“ on cereals

Saponine: The proposed model for the pore formation by avenacin A-1.

22
Q

Glycosinolate

A

• Glycosides, aglycon is connected to glucose via a sulfur
atom (thioglycoside)
• mustard oil glycosides
• confined to the Brassicaceae
• act against herbivores and fungi
• become active only after tissue obstruction
Importance Agric Culture:
highly toxic, kill fungi and insects, attscts insects that are adapted to brassicas, attat predators

23
Q

Glucosinolates are stored within the vacuole

A

and released upon cell damage

24
Q

Defensins

A
  • small, stablepeptides(ca. 45 AA)
  • possess three intramolecular disulfide bridges
  • present in animals and higher plants
  • effective against microbial invaders
  • fall into four families: mammal, plant, insect, mollusc
25
Q

Defensins cause

A

membrane permeabilization

hydrophobic and Positively charaged
AA

26
Q

Pathogens are

A

biotrophs, necrotrophs or hemibiotrophs

27
Q

Necrotrophs

A

kill cells and then consume the contents

28
Q

Biotrophs

A

live within host tissue without causing death

29
Q

Hemibiotrophs

A

can switch from biotroph to necrotroph

30
Q

Non-host resistance: induced defense

Pathogen-induced responses:It’s a race!!!!

A

“As soon as a plant has recognized an attacking pathogen, the race is on. The plant attempts to prevent infection and to minimize potential damage, the pathogen attempts to gain access to nutrients for growth and reproduction.”

31
Q

Infection cycle of a foliar pathogen

A

epiphytic phase, tissue entry, endophytic phase

Plant Pathology (4 decks)

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