AGRY 301

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AGRY 301
2013-04-02 16:17:27

Koch's Postulate
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  1. Koch's Postulates
    • 1. Associate- there must be a constant association between the pathogen and diseased individual
    • 2. Isolate: have to isolate the pathogen on pure media
    • 3. Inoculate: inoculate¬† pathogen to healthy host and must cause same symptoms
    • 4. Reisolate: to confirm it is the same pathogen
  2. Robert Koch
    • Nobel Prize in medicine 1905
    • not used to diagnose known diseases but unknown
  3. Gray mold of Strawberries
    • Botrytis cinerea
    • gets into the fruit at the beginning and then multiplies to rot
    • Select more resistant varities
    • fungicide spray
    • remove dead/dying leaves
  4. Rivers's modified Koch's Postulate
    • 1. Isolate virus from host
    • 2. Cultivation of the virus in cells of the host
    • 3. Proof of filterablity of infections entity
    • 4. Production of identical disease in original host
    • 5. Re-isolation of the virus
    • 6. Detection of an immune response in the host to virus infection
  5. Mechanical Inoculation of Plant Viruses
    • Mayer- inoculated with glass tubes
    • others scratching surface 1930, no system perfect
    • Holmes found some gentle wiping with infectious extract to work very well
    • Now rub with cheese cloth or fingers
  6. Determining host Range
    • just because a species doesn't show symptoms doesn't mean virus isn't multiplying
    • have to return inoculate on known host
    • may be a combination of two viruses
  7. Good Experimental host
    • 1. rapidly develop characteristic symptoms
    • 2. be a rapidly growing plat with large flat leaves
    • 3. be readily avaiable as genetically uniform seed
  8. Indicator hosts
    • host plants that give clear characteristic and consistent symptoms
    • what hypersensitivity- fast necrotic lesions, from of resistance
  9. Nicotiana tabacum
    hypersensitive to TMV
  10. TMV will survive
    • in infected plant debris in soil
    • on door knobs and water fauscets
    • on green house benches an dpots
    • on contaiminated seed coats
    • in herbaria >50 years
    • on lab coats for 3 yrs
  11. TMV is spread by
    • infectious plant sap on contaminated hand adn clothes and door knobs
    • infesed cutting, pruning tools, pots
    • infested water hoses and sprinklers
    • NOT by insects