2003

1. (25 points)

You are provided with nematodes extracted from the grass of the central quad on the UC Davis campus. (The instructor can attest that the soil is extremely compacted from the passage of millions of feet, activities of frisbee players, Whole Earth festivals, etc. You have probably often wondered about the creatures lingering below that hallowed turf).

a. Place an adult female plant-feeding nematode of any species on a microscope slide.

• Kill the nematode with gentle heat.
• Apply a coverslip.
• Seal the edge of the coverslip with fingernail polish to prevent the slide from drying out.
• Place the slide on the compound microscope and adjust the microscope to provide Köhler illumination.

b. Indicate on your exam sheet the Class and Order of your nematode.

c. Draw and label the component parts of the stylet and esophagus for this type of nematode (either from your specimen, or from your knowledge of anatomy and morphology, or both).

d. Call the instructor for examination of your nematode. If there is more than one nematode present in the microscope field, indicate the specimen you wish to have examined. Do not ask or expect the instructor to make the selection.

Only the nematode that you indicate initially will be considered.

Grading:

• adult female plant-feeder, good condition 15 points
• non-plant-feeder, good condition 8 points
• correct designation of Class and Order 2 points
• correct drawing and identification of stylet/esophagus 8 points
• points off for damage, distortion, dry slides, etc.

2. (15 points)

1. Describe acquisition, retention (retention sites, mechanism and retention period), and transmission of plant viruses by plant-feeding nematodes.
2. Which genera of nematodes transmit TOBRA viruses?
3. What are the shapes and sizes of the virus particles?
4. Describe the feeding structure of the nematode vectors of TOBRA viruses.

3.  (15 points)

1. Describe the distinguishing morphological and anatomical characteristics of the pin nematodes, Paratylenchus spp.
2. Describe the life cycle of these nematodes and indicate the feeding habits of each life stage.

4.  (20 points)

Provide a generalized drawing of a female nematode of the family Longidoridae in which males are rare.

• Label the features of the reproductive and digestive tracts.

• Provide the name of a nematode genus with the characteristics you have drawn.

• Indicate whether you expect this nematode to feed as an ectoparasite or an endoparasite, and why.

5.  (12 points)

Briefly describe the technique that you would use to separate the following nematodes from samples of soil or plant tissue:

a.  Pratylenchus vulnus in grape roots.

b.  Sting nematode (Belonolaimus sp.) in soil from a fallow field

c.  Mesocriconema xenoplax in soil from a walnut orchard.

6. (13 points)

Spiral nematodes (Helicotylenchus multicinctus) and burrowing nematode (Radopholus similis) are important parasites of bananas in central America.

• Describe the damage that these nematodes cause to the plant root system.
• Describe how this damage translates into crop loss.
• What methods are used to eliminate the nematode from planting stock?
• What methods are used to minimize the nematode damage in established plantations?