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definition of disease
injurious alteration of one or more physiological processes in a living system caused by the continuous irritation of a primary causal factor or factors.
disease triangle
environment, host, pathogen
biotroph vs necrotroph
obligate parasite vs facultative parasite or facultative saprophyte.
disease cycle
primary inoculum, dispersal of inoculum, infection court, infection and colonization, survival

OR

after infection and colonization:  secondary inoculum, infection court, infection and colonization
Koch's postulates:
1.  pathogen must consistantly be associated w/diseased plant
2.  pathogen must be isolated
3.  disease reproduced by inoculation
4.  pathogen re-isolated from inoculated plant.
symptom vs sign
symptom is indication of disease by reaction of the host, e.g., canker, leaf spot, wilt.

sign is indication of disease from direct observation of a pathogen or its parts.
biotrophic pathogen
obligate parasite
haustorium
specialized branch of a pathogen for absorbing nutrients from inside host cells
incubation period vs latent period
time between infection and symptoms vs time between infection and production of propagules by pathogen.
3 monocyclic diseases
dutch elm
stinking smut of wheat
verticillium wilt
3 polycyclic diseases
apple scab
coffee rust
late blight of potato and tomato
monocyclic vs polycyclic
disease cycle carried out in a single season without production of secondary inoculum
vs
secondary inoculum produced during growing season
symptoms and pathogens of necrotic spot, blight, blotch, needle cast, and scab
round to oval spots (fungi)
agular spots (bacteria or nematodes)
signs symptoms and pathogen of anthracnose
dark, sunken leasions
white superficial mycelium and powdery conidia
dark, round chasmothecia filled with asci and ascospores

ascomycetes
signs symptoms and pathogen of powdery mildew
white superficial mycelium and powdery conidia
dark, round chasmothecia filled with asci and ascospores

ascomycetes
signs symptoms and pathogen of downy mildew
sporangiophores and sporangia in downy tufts, often on the lower surface of the leaf
oospores in infected tissue
necrotic areas on leaves and/or fruit

oomycetes
signs symptoms and pathogen of rust
variously colored spores, but powdery, orange- to rust-colored urediniospores are seen most often

basidiomycetes
signs symptoms and pathogen of smut
black, powdery teliospores
often distorted growth

basidiomycetes
signs symptoms of virus disease
mosaic, mottle, ringspots, veinbanding, yellowing
damping-off
infection of seeds and seedlings, leading to death.  caused mostly by fungi.
Apple Scab:
host, pathogen, symptoms/signs,
host:  apple, crabapple
pathogen:  Venturia inaequalis (ascomycete)
Symptom/signs:  olive-green lesions early, scabs later, when severe defoliation.
Apple Scab
pathogen, disease cycle, management
pathogen:  Ventura inaequalis
Disease cycle:  polycyclic.  survival spores overwinter in fallen leaves, ascospores infect young leaves, conidia secondary infection.
Management:  fungicide, removal of fallen leaves, some resistant cultivars
Late Blight
host, pathogen, symptoms/signs, disease cycle
host:  potato, tomato
pathogen:  Phytophthora infestans (oomycete)
Symptoms/signs:  lesions, blight, white mildew, reddish tubers during early stages.
disease cycle:  polycyclic.  zoospores or germ tube, sexual rep oospores, survive as mycelium in tubers or oospores.
genus of bacteria causing spot of pepper and tomato
Xanthomonas
Venturia
ascomycete, apple scab
Phytophthora
oomycete
late blight, POC root disease, sudden oak death
Xanthomonas
bacteria,
spot of pepper and tomato
Colletotrichum
ascomycete
anthracnose of turfgrass, apple, etc
chasmothecia
overwintering fruiting bodies of powdery mildew (ascomycetes).  dark brown to black round structures.  No natural opening.  ruptures.
heteroecious
multiple hosts
macrocyclic
rust fungi that produce all 5 stages of spores
demicyclic
rust fungi that produce all spore stages except urediniospores
microcyclic
rust fungi that produce only teliospores and basidiospores
autoecious
rust producing all stages of spores on single host
Albugo
white rust (oomycete) obligate parasite
Puccinia
stem rust of wheat and barley, macrocyclic
Tilletia
smut of wheat, basidiomycete, monocyclic
spores smuts are known for
teliospores
Fusarium
wilt, Panama disease, head blight, etc.  ascomycete.
two vascular wilt diseases caused by fungi transported by insects.  genus of fungi
dutch elm disease
oak wilt

Ophiostoma (ascomycete)
Ceratocystus
phytoplasma, spiroplasmas
phloem-inhabiting bacteria.
fastidious bacteria
plant vascular parasites requiring complex media to isolate
Chryphonectria
chestnut blight.  ascomycete
Gaeumannomyces
take-all root rot (ascomycete)
Armillaria
root rot (basidiomycete)
Thielaviopsis basicola
black root rot (basidiomycete)
Pythium
root disease (oomycete)
Rhizoctonia
root lesions, turgrass brown patch and yellow patch (basidiomycete)
Sclerotium
southern blight, root rot, stem and crown disease (basidiomycete)
Monolinia
brown rot of stone fruits (ascomycete)
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