Introduction to Plant Pathology Part2 MG09 - Merced Countycemerced.ucanr.edu/files/40652.pdf · –...
Transcript of Introduction to Plant Pathology Part2 MG09 - Merced Countycemerced.ucanr.edu/files/40652.pdf · –...
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Part 2:Part 2:Disease Causing Agents
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Agents of DiseaseAgents of Disease
Fungi: 8,000 known pathogenic species
i 100 000 dicausing 100,000 diseases
Viruses: 1000 differentViruses: 1000 different viruses causing 10,000 or more diseasesmore diseases
Nematodes: 500 species
Bacteria: 275 species
Parasitic Plants: only 5‐6 yplants that are of concern
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Agents of DiseaseAgents of Disease
Single crops are affected by many diseases!
Tomatoes can be attackedTomatoes can be attacked by more than 40 species of fungi, 7 spec es o u g ,bacteria, 16 viruses, and several nematodes!
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Agents of Disease FungiCharacteristics of Fungi
Agents of Disease ‐ FungiCharacteristics of Fungi• Filamentous eukaryotic
organisms that have chitinand glucans in the cell walland glucans in the cell wall
• Filamentous growth is called hyphae, and a mass of growth is called mycelium
• Reproduction is by spores –Reproduction is by spores both assexual and sexual
• Classification is by sexual stagesstages
• Many faces of fungi –mushrooms, diseases, wood rotters, etc.
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Agents of Disease ‐ FungiAgents of Disease Fungi
Ecology of Fungi:
• Saprophytic fungi breakdown woody biomass (majority)– Recycle organic matter
– Forested ecosystems, ycompost piles
• Some parasitic fungi can “White Rotter” “Brown Rotter”p gcause disease and some can be beneficial
White Rotter Brown Rotter
Photos from:
– Mycorrhizae, endophyteshttp://monticellolabs.com/FungalStain.html
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Agents of Disease Fungi
Bi h i f f i
Agents of Disease ‐ Fungi
Biochemistry of fungi• Produce many “extracellular
metabolites”:metabolites :– Enzymes– ToxinsToxins– Hormones
• Compounds when associated pwith plant disease are called virulence factorsC l i i l d i• Complex organisms involved in many processes – necessary for life on Earth – “Garbage men” of gthe ecological world
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Agents of Disease FungiAgents of Disease ‐ Fungi
Fungi and Plant Disease• Disperse through spores,
fragmented hyphae, contaminated soil and tools, vectors and many morevectors, and many more
• Survive as spores, sclerotia, rhizomorphs and myceliumrhizomorphs, and mycelium infested plant debris
• Cause plant symptoms of p y psmuts, molds, cankers, galls, leaf curls, soft rots, root rots, scabs, and more…
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Agents of Disease FungiAgents of Disease ‐ Fungi
Classification of fungal pathogens
• Ascomycetes
• Basidomycetes
• Chytridiomycetes
• Zygomycetes
• Imperfect fungi
• “Fungal‐Like” organismsGroups of fungi are differentiated by
– Oomycetesp g y
morphological features, and by DNA sequences.
Tree from: www.pfdb.net/myhtml/genosp_dermato.html
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Agents of Disease FungiAscomycetes
Agents of Disease ‐ FungiAscomycetes
– Sac fungi – produce sexual spores in a sac
• Typically have 8 ascosporesin an ascus
– Reproduces asexually asReproduces asexually as well
– Produces very distinct structures that are used forstructures that are used for identification
– Imperfect fungi are typically grouped with ascomycetes
– Most common fungalMost common fungal diseases
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Agents of Disease FungiDiseases caused by Ascomycetes
Agents of Disease ‐ Fungi
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Agents of Disease FungiDisease cycle of Brown Rot (Monilinia fructicola)
Agents of Disease ‐ Fungiy ( f )
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Agents of Disease ‐ FungiDisease cycle of Brown Rot (Monilinia fructicola)
Agents of Disease ‐ Fungi
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Agents of Disease FungiDisease cycle of Apple Scab (Venturia inaequalis)
Agents of Disease ‐ Fungi
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Agents of Disease ‐ FungiDisease cycle of Apple Scab (Venturia inaequalis)
Agents of Disease ‐ Fungi