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Stem rust of wheat
- Puccinia graminis f.sp. triticiOldest recorded plant disease
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Ergot of rye
- Claviceps purpureaSalem Witch Trials cause
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Brown spot of rice
Bipolaris oryzae
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Potato late blight
Phytophthora infestans
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Coffee rust
- Hemileia vastatrixCaused the Europeans to drink tea
- biggest factor in price of coffee
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Chestnut blight
- Cryphonectria parasiticaresulted in the Plant Quarantine Act of 1912
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Citrus canker
- Xanthomonas axonopodis pv. citri
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What is disease? (6 qualifiers)
- Caused by a pathogen: living biotic agent
- Infectious & transmissible/contagious
- Food relationship: all pathogens are parasites
- Disrupts physiological process causing harm/death
- Continual/progressive
- Plants respond by onset of histological or morphological symptoms
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6 types of organisms that cause plant diseases
- Bacteria
- Fungi
- Viruses
- Nematodes
- Phytoplasmas/Mycoplasmas
- Parasitic higher plants
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Biotic vs Abiotic causes of plant death
Biotic: Biotic agent, infectious, transmissible, parasitic
Abiotic: Nutrient deficiencies/toxcities, Physical injury or damage, Edaphic conditions
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8 Disease SYMPTOMS
- Leaf spots
- Blights
- Wilts
- Cankers
- Rots
- Galls
- Mosaics
- Tissue Discoloration
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6 Pathogen SIGNS
- Mycelium
- Fruiting bodies
- Spores
- Bacterial ooze
- Eggs
- Cysts
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Koch's Postulates (4)
- Pathogen must be consistently associated with the diseased plants
- Pathogen must be isolated in a pure culture
- Disease must be reproduced in a healthy plant with the isolated organism
- Same pathogen must be reisolated from the plant
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The Disease Triangle
ENVIRONMENT PATHOGEN
Favorability Abundance
Duration Virulance
Escapes Resistance
HOST
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The Disease Cycle (6)
- Overseasoning & Survival
- Production of Inoculum
- Dissemination of Inoculum
- Inoculation of Plant and Prepenetration
- Penetration and Ingress
- Infection, Colonization, and ...
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Monocyclic Diseases
& 3 examples
- 1 cycle per season
- Dutch elm disease
- Verticillium wilt
- Monosporascus root rot
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Dutch elm disease
Ceratocyctis ulmi
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Verticillium wilt
Verticillium albo-atrum
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Monosporascus root rot
Monosporascus cannonballus
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Polycyclic diseases
& 3 examples
Multiple cycles per season
- Coffee rust
- Potato late blight
- Apple scab
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Soybean rust
Phakopsora pachyrhizi
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Apple scab
Venturia inaequalis
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5 "rights" for infection
- Host
- Inoculum
- Infection court
- Time
- Environmental conditions
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5 ways plant pathoges infect
- Wounds
- Naturan openings
- Direct penetration
- Stylets
- Vectors
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5 Direct penetration ways of pathogens
- Adhesion
- Germ tube
- Appresorium
- Infection peg
- Haustorium
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Fire blight of Apple/Pear
G, Flagella? Hosts?
Symptoms? Infection Court?
Management? Survival?
- Erwinia amylovoraG neg rod, Peritrichous Apples/Pears
- Rapid death of leaves, twigs; cankers on twigs/limbs
- Nectarthodes/floowers, 2 via wounds, stomates
- Tolerant cv, removal of infected, antibiotic or copper sprays
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Thomas Burrill
- pear blight
- first to establish bacteria could cause plant disease
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Erwin F Smith
- Est reputation of US trained plant pathologists
- 8th President of APS
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L R Jones
- pectinolytic enzymes
- 1st President of APS
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Bacterial Soft Rot
G, Flagella? Hosts?
Symptoms? Infection Court?
Management? Survival?
- Pectobacterium (E) carotovoraG neg rod, Peritrichous Soft fleshy tissue/manyplts
- Watery, smelly rot
- Wounds, natural openings
- Avoind wounding, store at cool dry temps, chlorine dips
- In hose tissue, soil, insects, tools, prop plant parts
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Crown Gall
G, Flagella? Hosts?
Infection Court?
Survival?
- Agrobacterium tumefaciensG neg rod, Amphitrichous Dicots, 93 families
- Only via fresh wounds
- galls and rhizosphere soil
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Citrus canker
G, Flagella? Hosts?
Infection Court?
- Xanthomonas axonopodis pv. citriG neg rod, single polar flagellum #ous spec citrus
- Req warm moist conditions, enters stomates & wounds
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Histological
cellular level
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Father of Plant Pathology
Heinrich Anton de Bary
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Hydrathode
Specialized leaf structure used for guttation; leaf opening at terminus of vein.
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Hypertrophy vs Hyperplasia
increase in size vs increase in numbers
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Tyloses
Envaginations of hte xylem parenchyma cells resulting in 'balloon like structure' that blocks water flow.
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Xylella fastidiosa
Plant transpires until it runs out of water
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Haustoria
pushes in without rupturing the cell & absorbs nutrients so as to not kill the cell to quickly
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5 ways pathogens survive
- Oospores
- Chlamydospores
- Sclerotium
- Cysts
- Perithecia
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