BOT350/550 Practical Study Guide
Isolation of Fungal Pathogens:
 Pathogens with which life strategy (e.g. facultative parasite) are incapable of growing on culture
media? Why?
 What is the purpose of surface sterilizing infected plant tissue before culturing it?
 Why isolate pathogens from the interface between healthy and diseased tissue rather than from the
diseased tissue itself?
 What is selective media? What is differential media? (Remember that media can be both selective
and differential)
 Why are antibiotics commonly added to isolation media for fungi?
 What special technique is often used to isolate soilborne Oomycetes? Why?
Koch’s Postulates:
 What is the purpose of Koch’s Postulates?
 What are the four steps of Koch’s Postulates? Note: “Determine the pathogen,” is not an
acceptable answer for postulate one.
Oomycetes (Water Molds):
 Know two features that distinguish Oomycetes from true fungi.
 Know: oospore, oogonium/antheridium, zoospore, and sporangium.
 Which of the above structures are asexual? Which are sexual or the direct product of sexual
reproduction?
 Which of the above is a resting or overwintering structure?
 Know how to recognize sporangia and oospores under the compound microscope.
 Why does wet, poorly drained soil often contribute to the establishment and spread of Oomycete
diseases?
 Diseases: white rust, downy mildew, late blight of potato, damping off.
Ascomycetes (Sac Fungi):
 Do Ascomycetes have septate or aseptate hyphae?
 Are they predominately haploid, diploid, or dikaryotic?
 Know: ascospores, ascus, ascocarps (cleistothecium/ascoma, perithecium, apothecium),
sclerotium, stroma, conidia, conidiophores (separate, synnema, sporodochium), asexual fruiting
bodies (acervulus, pycnidium).
 Which of the above are sexual structures? Which are asexual structures? (Remember that regular
or teleomorphic ascomycetes have both sexual and asexual structures while asexual or anamorphic
ascomycetes have only asexual structures)
 Which are overwintering structures?
 What is an anamorph? What is a teleomorph?
 How many ascospores does an ascus contain?
 Powdery Mildews have which of the three ascocarps?
 What three traits are used to key out powdery mildews?
 Be able to recognize asci, cleistothecia, perithecia, stroma, conidia/conidiophores, and asexual
fruiting bodies under the compound microscope.
 Diseases: eastern filbert blight, white mold, tar spot of maple, apple scab, ergot, powdery mildew,
grey mold, early blight, Verticillium wilt.
Basidiomycetes (Club Fungi):
 Are Basidiomycetes predominately haploid, diploid or dikaryotic?
 Are they septate or aseptate?
 Know: basidiospores, basidia (naked or in basidiocarps), basiodocarps, teleospores, telium,
spermatia, receptive hyphae, spermagonium, uredospores, uredium, aeciospores, aecium.
 Which of the above structures belong to ascocarp basidiomycetes? Which belong to rusts? Which
belong to smuts?
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Which of the above spores is the direct product of sexual reproduction? Which of the above are
overwintering structures?
For some rusts the only functional spore is the uredospores….how does a rust of this type
overwinter?
Be able to identify basidia with basidiospores, uredospores in uredia and teliospores in telia under
the comound microscope.
Define: macrocyclic, microcyclic, heteroecious, autoecious.
Are smuts monocyclic or polycyclic?
Diseases: rusts, smuts, wood rots/decays.
Bacteria:
 What are five methods used to diagnose bacterial diseases and identify bacteria?
 Define peritrichous and polar flagella.
 Know the basis of the gram stain test and the colors of gram positive and negative bacteria.
 Know the basis of the hypersensitivity response when testing for pathogenic bacteria, including
the importance of the type III secretion system.
 What characteristic of bacteria does the oxidation/fermentation test investigate?
 Diseases: soft rot and ring rot of potato, fire blight, crown gall.
Viruses:
 What are five methods used to diagnose viral diseases and identify viruses?
 Know the basics of how an ELISA test works.
 What is the difference between a local lesion host and a systemic host when conducting a viral
pathogenicity bioassay? How do the two differ in resistance?
 Diseases/symptoms: chlorotic mosaics (Tobacco Mosaic Virus), leaf curls, vein clearing, stunt
syndromes.
Botrytis Predisposition:
 Know why Botrytis is considered an example of a weak pathogen (i.e. know its life strategy).
 Why would the addition of rose petals or potato dextrose broth aid in the establishment of
Botrytis?
Race Identification of Wheat Strip Rust:
 Define race and differential cultivar.
 Do necrosis and chlorosis in wheat cultivars indicate susceptibility or resistance to a particular rust
race?
 How do r-genes fit in?
Biocontrol of Crown Gall:
 Know the importance of both Agrobacterium radiobacter and Agrobacterium tumefaciens in the
biocontrol experiment.
 What is the importance of the production of agrocin in A. radiobacter (K84).
 How does A. tumefaciens produce galls in host plants?
Nematodes:
 There are ten characteristics commonly used to identify nematodes…..know five.
 What is the importance of the stylet in plant parasitic nematodes?
 What is the difference between endoparasitic, ectoparasitic, sedentary, and migratory nematodes?
 What are two methods used to extract nematodes from roots or soil?
 Be prepared to key out or identify nematodes.
Electron Microscopy:
 The electron microscope is especially useful for viewing which major pathogen group?
 What differences are there between transmission electron microscopy (TEM) and scanning
electron microscopy (SEM)?
 What are positive and negative staining in TEM?