NEMATOLOGY 100

Laboratory Exercise 17

Rev. 01/01/2020

Purpose:   Rhizosphere and soil biology in relation to nematode ecology and crop production (continued)

     1.   Powerpoint presentation and slides:  Organisms that exploit, compete with, or are antagonistic to plant-parasitic nematodes.

     2.   Nematodes extracted from various rhizospheres are provided.
          Gellan Gum plates (1.5%) are provided seeded with Meloidogyne incognita juveniles as prey.
          Hand pick nematodes that you think may be predators on the prey nematodes and place them in different regions of the plate.  Mark each region with a circle on the lower surface of the plate.  Observe for indications of predaceous behavior.  Save plates for further observation at the next lab period.
          Likely predators might include nematodes with a large open stoma (e.g., Mononchus - Order Mononchida), large nematodes with relatively short odontostyles (e.g., Discolaimus, Mesodorylaimus, Eudorylaimus, Labronema,  - Order Dorylaimida), small, fast-moving nematodes with slender stylets and enlarged metacorpus (e.g. Seinura - Order Rhabditida, Suborder Tylenchina, Superfamily Aphelenchoidea.

Order Mononchida is characterized by a strong, cuticularized stoma, predaceous and cannibalistic. Soil and freshwater, no marine forms.
Order Dorylaimida is characterized by movable mural tooth or hollow spear; all soil or freshwater inhabitants, no marine.
Order Diplogastrida is characterized by movable teeth in the stoma; predators, omnivores, bacterial and fungal feeders, insect associates; very muscular metacorpus and glandular postcorpus.
Order Rhabditida, Suborder Tylenchina - all have movable hollow stylet, the Aphelenchoidea have a prominent metacorpus.            

     3.  Faunal Analysis Project Reports

    4.  Soil suppressiveness test.  

• You are provided with microcosm cylinders packed with soil from hills above the Napa Valley, organic agriculture in the Salinas Valley and a sand control.  Three of the cylinders of each soil have been defaunated by heat, the other three retain their natural food web organisms.  All cylinders are covered at one end by a double layer of tissue.
• Pipette 500 J2 of Meloidogyne incognita suspended in 0.5ml water into each cylinder.
• After 24 hours of incubation, cylinders of each soil and treatment will be placed on a Baermann tray for nematode extraction.
• At the next class, determine the suppressiveness of each soil by the relative number of M. incognita J2 recovered from the faunated and defaunated treatments.

     5.   Videotapes:

• Theratromyxa weberi (Proteomixida--an ameba) catching Heterodera schachtii.
• Soil Sampling for Soybean Cyst Nematode

     6.   Introduction to the "double logistic model" for assessing nematode management strategies: Nemaplex demonstration.

     7.   In-class NEMAPLEX Exercise
          Main Menu:
            Select...Management and Decision Support   
               Select...Management Strategy Simulator
                  Use the double logistic simulation model to explore the effect of nematode management strategies, and their costs, that:
                   a) reduce the initial population;                      
                   b) reduce the rate of population increase; and
                   c) change the tolerance (carrying capacity) of the host to the nematode.                                        
                  Note the effect on the host, on the nematode population, and on the net crop value.
     

     8.   Faunal Analysis Reports - 5 minutes per student.

     9.   Homework Assignment:

             NEMAPLEX Exercise
                Select...Nematode Management
                  Review:  Principles of Nematode Management.
                           Tactics:  (Various tactics listed)    
                           Emerging Research Developments:  (Various topics listed).
           Return to Main Menu
         

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