3 Plant Pathology & Koch's Postulates - Copy

3 Plant Pathology & Koch's Postulates - Copy - PP 315 /...

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PP 315 / 590J Lecture 3 Objectives Understand how major concepts in plant pathology developed through time and how they are still applied today. Start to think about what is involved in proving the presence of a causal relationship between a pathogen and disease and realize the steps involved in the laboratory. Diagnosis Now that we have reviewed what factors are required for a disease to occur, how do we determine what disease is present? diagnosis - the art and science of determining what disease is present on a plant Classical approach to Disease Diagnosis Field (natural setting) examination Pattern of disease distribution - uniform, random, systematic? Collection of suitable specimens - range of symptoms, etc. Laboratory examination 1. Observation of symptoms and/or signs present (Requires knowledge of what a healthy plant looks like) 2. Isolate from symptomatic tissue to determine if a pathogen is present (not all pathogens can be isolated or grown outside of the plant) 3. Identify the pathogen - HOW? - microscopic features - diagnostic kit - immunoassay (cost, reliability) - molecular tools (PCR, dot blots) 4. If the pathogen has not been reported from that host, you must conduct Koch's Postulates to prove that it is the cause of the disease. Koch's Postulates - Robert Koch Check out these extensive web sites on Koch's life and contributions to bacteriology and microbiology. http://www.nobel.se/medicine/laureates/1905/koch-bio.html http://web.ukonline.co.uk/b.gardner/Koch.htm Robert Koch was a medical doctor that almost gave up his career to travel and see the world. His wife gave him a microscope on his 28 th birthday and it opened a whole new world for him. He became fascinated with the bacterium that causes anthrax. He knew the little rods in blood of infected animals were bacteria and that he could reproduce the disease by putting the rods into a healthy animal. Remember, the
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This note was uploaded on 03/22/2008 for the course PP 315 taught by Professor Shew during the Spring '08 term at N.C. State.

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3 Plant Pathology & Koch's Postulates - Copy - PP 315 /...

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