Exam 1 Flashcards
disease
abnormal functioning of an organism
characteristics of disease
-injurious (causes harm to plant)
-progressive
plant disease triangle
-susceptible plant
-pathogen capable of disease
-favorable environment
symptoms
expression of disease by a plant as a response to activities of a pathogen
biotic agents
living agents including pathogens
abiotic agents
non living agents
pathogens
organisms that cause disease in living host
-include fungi, virus, bacteria, nematodes
infectious
transmitted from 1 plant to another
pathogen signs
pathogen structures or products on or in diseased plants
fungi signs
spores and fruiting bodies
bacteria signs
bacterial ooze
virus signs
inclusion bodies
nematode signs
can be extracted from the roots or soil
host range
set of species in which pathogen can cause disease
abiotic agents
-non infectious
-could be damage from herbicide, fertilizer, heat/cold
-symptoms all the same on all plant species in area
-no pathogen signs
environmental factors
-recent temps
-rainfall or irrigation
-light or shade
-soil characteristics, like ph or soil type
-fertilizers, herbicides, fungicides, etc
-presence of other organisms
saprophytes
organisms that obtain their nutrients from dead organic matter
biotrophs
-obligate parasites
-have narrow host range
-cannot grow as saprophytes
-attack healthy host tissue at any stage
-kill host cells slowly
-penetrate directly via natural openings
-mildews, rusts, virus, nematodes
necrotrophs
-bacterial fungi
-have wide host range
-can grow as saprophytes
-attack young, weak, or senescent tissues
-kill host cells rapidly by producing toxins or enzymes
-penetrate through wounds or natural openings
-anthracnose, cankers, fruit rot, leaf spots and blights, root rot, vascular wilt
hemibiotrophs
-live part of cycle in living tissue and then kill plant and continue to live in dead tissue
-ex. Phytophora infestans
stages in disease cycle
inoculation
penetration
infection
growth and reproduction
dispersal of pathogen
survival of pathogen
inoculation
-primary inoculum: initiates infection (first step in disease cycle)
-secondary inoculum: 2nd set of inoculation that occurs at later stage of disease cycle
penetration
-direct penetration: pathogen creates entry point using structures (appressoria and haustoria (teeth))
-penetration through wounds
-through natural openings (stomata, lenticels, hydathodes)
infection
-establishment of pathogen within host cells to obtain nutrients
-infection courts: where infection starts
-successful infection will produce symptoms
-incubation period: time interval between inoculation and appearance of symptoms
growth and reproduction
-pathogen grows and multiplies in infected host
-fungi: spores
-virus: replicate within cell
-nematodes: eggs
dispersal of pathogen
-wind, rain, people, animals, insects, machinery
-spores of fungus can be dispersed through all methods
plant pathology
study of what causes plant disease, why they occur, and how to control them
ergotism
poisoning from ergot alkaloids
ergot alkaloids
mycotoxins produced by fungus claviceps
ergot symptoms
-presence of sclerotia instead of grains, produces ergot alkaloids that causes ergotism in humans
-caused by claviceps fungus
-host is rye
coffee rust
-fungus hemilela vastatix
-affects arabica and robusta coffee
-lesions on leaves which affects photosynthesis
-severe defoliation can kill trees
underdevelopment
-stunting of plants, leaves
-shortened internodes
-inadequate chlorophyll production
-caused by many types of pathogens
overdevelopment
-overgrowth of leaf tissue causes thickening or distortion
-galls form on all plant parts, caused by many pathogens
-in roots: nematodes
-on stem: bacteria
fungal leaf spots
-tissue necrosis
-usually round, not vein limited
-may have alternating zones of light/dark tissue
-sporulation or mycelia may be evident
bacterial leaf spots
-tissue necrosis
-often dark and water soaked
-often vein limited, giving angular shape
-bacterial flow observed under microscope
fruit rots
–tissue necrosis
-firm or soft and watery
-colors vary
-fungal sporulation may be present
-fungal and bacteria causes
cankers
-tissue necrosis
-localized necrotic lesions
-sunken or swollen or both
-mainly caused by fungi and bacteria
-can be caused by mechanical injury
root rots
-tissue necrosis
-root lesions
-darkening and softening of roots
-yellowing of foliage and stunting of plants
-fungal and bacterial causes
blight
-tissue necrosis
-rapid and complete chlorosis, browning and then death of plant tissues
-fungal and bacterial causes
damping off
-tissue necrosis
-rapid death of seedlings and cuttings
-stem infected at soil line, seedling topples
-caused mainly by fungus
wilting
-response to disruption of transport of water in plant due to invasion of xylem or roots by phloem
-mainly fungal and bacterial causes
mosaic
-caused by virus
-irregular patches of discolored tissue
-often with distortion to tissue
ringspot
-on leaves and fruit
-distinct ring shaped lesions, often in concentric zones
-caused by viruses
abiotic causes of change in appearance
-chemical damage and nutritional deficiencies
symptom variability
-diseased plants may have more than one problem (and more than one pathogen)
-pathogens have varying levels of virulence
-environmental conditions can affect symptoms
-host genetics and physiology can affect symptoms (resistant, tolerant, or susceptible)
fungal signs (more in depth)
-shape of fruiting body aids in fungal identification
-tissue location may help differentiate between species
