2004

You are provided with nematodes extracted from a walnut orchard interplanted with alfalfa

a. Place an adult female plant-feeding nematode of the Order Tylenchida 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)

The composite nematode drawing is extracted from a paper by Gerald Thorne in the 1943 volume of the Proceedings of the Helminthological Society of Washington.  We did not study this genus in class but it is a parasite of walnut.

Here is a key to the component parts of the drawings:

A.  Anterior portion of an early juvenile stage. B. Posterior of male. C. Anterior of male. D. Male copulatory structures. E. Face view of female.

H. Developing female juvenile. I. Young female after last molt. J. Female without fully-developed egg. K. Gravid female.

(i) What is the probable feeding habit of this nematode? (give reasons).

(ii) In which order of the Nematoda would you place this genus, and why?

(iii) Use the appropriate letter to label structures on the drawings. Only label each structure one time - on the drawing in which it is most obvious.

3.  (10 points)

1. List the ways in which nematodes cause damage to plants.
2. What are the aboveground signs of nematode damage?
    

4.  (15 points)   

Briefly describe the technique that you would use (and why you would use it) to detect the presence of the following nematodes in a sample:

   a. Pratylenchus penetrans (lesion nematode) from lily bulbs.
   b. Pin nematode (Paratylenchus sp.) in fallow soil in which onions will be planted.
   c. Scutellonema bradys (a spiral nematode) from stored yam.
   d. Mesocriconema xenoplax (ring nematode) in a peach orchard.

   e. Stubby root nematode (Paratrichodorus minor) in soil from a cotton field.

5.  (10 points) 

Describe the life history, feeding habits and mode of parasitism of the rice root nematode (Hirschmanniella oryzae).  What is the longevity of this nematode under adverse conditions and how would you create such conditions?

6.  (10 points)

1. Which genera of nematodes transmit NEPO viruses? 
2. What are the morphological characteristics of NEPO viruse particles?
3. Give an example of a NEPO virus disease, the plant host, and the nematode vector.

7.  (15 points)

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

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