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 · –...
Part 2:Part 2:Disease Causing Agents
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
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!
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.
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
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
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…
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
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
Agents of Disease FungiDiseases caused by Ascomycetes
Agents of Disease ‐ Fungi
Agents of Disease FungiDisease cycle of Brown Rot (Monilinia fructicola)
Agents of Disease ‐ Fungiy ( f )
Agents of Disease ‐ FungiDisease cycle of Brown Rot (Monilinia fructicola)
Agents of Disease ‐ Fungi
Agents of Disease FungiDisease cycle of Apple Scab (Venturia inaequalis)
Agents of Disease ‐ Fungi
Agents of Disease ‐ FungiDisease cycle of Apple Scab (Venturia inaequalis)
Agents of Disease ‐ Fungi