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Published byMartha Chadwick Modified over 10 years ago
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PLANT PATHOLOGY
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Plant disease Plant’s normal function is interrupted by a pathogen or the environment
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Plant disease Is this a disease?
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Biotic damage Caused by living pathogens or parasites
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Biotic damage Symptoms: visible expressions of plant reaction to the pathogen
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Biotic damage Signs: indications of disease from direct visibility of a pathogen –Actually seeing the pathogen
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DISEASE TRIANGLE Disease needs all three to develop –Only need to block one of them
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Pathogen Organisms capable of causing disease Fungus Bacteria Virus Other micro-organisms
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Pathogen Parasites: obtain food from living organisms (host)
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Pathogen Obligate parasite: require (obligated to) living plant cells as food to complete life cycle
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Pathogen Facultative parasite: obtain nutrition from either living or dead plants
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Pathogen Saprophyte: feeds on dead organic material on plant or in soil
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HOST Susceptible: no ability to retard or resist disease Susceptible plant tissue –Fertilization
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HOST Resistance: some ability to retard or tolerate disease
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HOST Immunity: complete resistance against disease
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ENVIRONMENT Moisture and temperature are the predominant factors
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ENVIRONMENT Moisture, water is critical Dry springs can reduce disease occurrence Often 24 to 48 hours continually wetness required Poor irrigation practice
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ENVIRONMENT Temperature, each pathogen has optimal range Predisposed condition of host Host is stressed, can’t defend
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FUNGUS The vast majority of plant diseases are fungal
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FUNGUS What is a fungus? Microscopic organisms that lack chlorophyll, cannot produce own food Multicellular organism that is threadlike in composition
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FUNGUS Enormous genetic variability due to rapid reproduction
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FUNGUS Species of fungi are subdivided into strains that are very specific in Plant species or cultivars Virulence Temperature range Moisture requirements
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SPORE Fungal seed Very distinct shape and size used to differentiate pathogens Single celled or multi-celled
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SPORE Asexual, not requiring the union of sexual parts to be produced Conidia
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SPORE Sexual, requiring union of sexual parts to be produced –Basidiospore, ascospore, oospore…
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SPORE Where do you see spores when a plant is infected? Leaf surface –Appears as mold (powdery mildew)
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SPORE Where do you see spores when a plant is infected? Fungal fruiting bodies Spore producing pockets Sporodochium, acervulus, pycnidium…
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HYPHAE Hyphae is what germinates out of the spore Branches out into tubular filaments
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HYPHAE Mycelium refers to all the hyphae as a whole, as the fungal body Inside the plant, or outside the plant under high moisture
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PLANT INVASION Fungus enters plant through any of the following Wounds –Mechanical, pruning or handling
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PLANT INVASION Wounds –Insects, vectors or egg laying
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PLANT INVASION Wounds –Naturally occurring Secondary roots rupture the main root when emerging Leaf scars
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PLANT INVASION Fungus enters plant through any of the following Natural openings –Lenticels
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PLANT INVASION Fungus enters plant through any of the following Direct penetration –Pushing through tissue –Resistance can come in the form of thicker cuticle or hairy leaf
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FUNGAL LIFE CYCLE Peach brown rot is used as an example
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FUNGAL LIFE CYCLE Overwinter, Disease is dormant in infected fruit and stems
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FUNGAL LIFE CYCLE Dissemination Disease produces spores (conidia) that are spread by wind and rain
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FUNGAL LIFE CYCLE Inoculation Spores contact susceptible blooms
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FUNGAL LIFE CYCLE Penetration Spore germinates and enters tissue directly
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FUNGAL LIFE CYCLE Infection Establishes hyphae in tissue and feeds on cells
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FUNGAL LIFE CYCLE Incubation period Time between infection and appearance of symptoms
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FUNGAL LIFE CYCLE Invasion Spreads from bloom to other parts of the plant within tissue
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FUNGAL LIFE CYCLE Dissemination…
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FUNGAL LIFE CYCLE Overwinter When temperature cools, fungus goes dormant
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Zombie Fungus http://www.h uffingtonpost.com/2011/0 9/14/zombie- caterpillars- virus_n_9622 56.html http://www.h uffingtonpost.com/2011/0 9/14/zombie- caterpillars- virus_n_9622 56.html http://www.h uffingtonpost.com/2011/0 9/14/zombie- caterpillars- virus_n_9622 56.html Brazilian rain forest Controls ants
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Infection pegs grow from body Shoots at passing ants
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