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2015-11-16 18:59:50
Plant Path nematology

Show Answers:

  1. Who is the Father of U.S. nematology
    Nathan A. Cobb
  2. Name Free-living nematodes:
    • bacterial feeders:Caenorhabditis elegans
    • fungal feeders: Aphelenchus avenae
    • predatory nematodes: Mononchus
    • Animal-parasitic nematodes:  Ascaris suum
    • Plant-parasitic nematodes: Meloidogyne hapla
  3. What do all plant nematodes have?
    • Stylets
    • Functions:
    • Mechanical penetration of plant cell wallsIntroduction of nematode secretionsUptake of plant cell contents
  4. What are the different types of feeding habits?
    • Ectoparasitic: nematode does not enter the plant tissuesMigratorySedentary
    •  Endoparasitic: the entire nematode penetrates the roottissueMigratorySedentary
    • Semi-endoparasitic: the anterior part of the nematodepenetrates the root, but the posterior part remains in thesoil phase
  5. Symptoms of nematode infection:
    • Often times unspecific
    • Easily confused with physiological disorders and diseasescaused by other pathogens
    • Wilting
    • Stunting
    • Deformed growth
    • Yellowing
    • Stunted root systems or bushy roots
    • Leaf damage, seed damage, tuber damage Lesions, galls
  6. Examples of nematode disease with examples:
    • Nematodes that infect plants below groundRoot-knot nematodes (Meloidogyne)
    • Cyst nematodes (Globodera, Heterodera)Root-lesion nematodes (Pratylenchus)Burrowing nematodes (Radopholus)
    • Dry rot disease of yams (Scutellonema bradys)
    • Migratory ectoparasitic nematodes (Xiphinema, Longidorus,Belonolaimus, Trichodorus)
    • Semi-endoparasites (Rotylenchus reniformis
  7. Nematodes that infect plants above ground
    • Foliar nematodes (Aphelenchoides)
    • Seed gall nematodes (Anguina)
    • Stem and bulb nematodes (Ditylenchus)
  8. Diseases on trees caused by nematodes
    • Red ring disease of palms (Bursaphelenchus cocophilus)
    • Pine wilt disease (Pine wood nematode, Bursaphelenchus xylophilus)
  9. How to manage nematodes?
    • Difficult (wide host range, survival strategies)
    • Principles:
    • Avoidance
    • Healthy plants
    • Exclusion
    • Quarantines
    • Nematode-free seed, nematode-free propagative parts
    • Eradication
    • Steaming, solarization, sanitation, pasteurization, crop rotations, fallowing, trap crops, tillage, biofumigation
    • Biological control
    • Chemical control (soil fumigants and nonfumigant nematicides)
    • Protection
    • Genetic resistance
    • Crop rotation will not eliminate cyst nematode-it can survive for years without host
    • Fallow or planting a non-host broadleaf like pea, lentil, or chickpea may slow buildup
    • Control grassy weeds and break green bridge carryover
    • Best long-term solution will be resistance Cre genes.
  10. List the different ways nematodes reproduce:
    • Amphimictic: fusion of a male and female gamete
    • parthenogenic: female asexual reproduction
  11. Baermann funnel Nematode collection method:
    Baermann funnel- attach rubber tubing to bottom of the funnel with a clamp. place two pieces of tissues paper in the funnel then add the soil.  Add water to the funnel and let set for 1-2 days and observe.
  12. Whitehead tray Nematode collection method:
    • 1) collect soil from around plant roots
    • 2) wrap a small handful of soil in two layers of facial tissue
    • 3) place the wrapped soil in a small dish on top of a mesh or screen. Add water so that the mesh is slightly covered with water and the soil contacts the water.
    • 4) let sit 1-3 days to allow the nematodes to crawl out of the soil. Make sure the sample stays in contact with the water - do not let the dish become dry. Covering the dish with plastic wrap or foil will help prevent drying.
    • 5) remove the bundled soil from the dish and observe the water in the dish using a binocular dissecting microscope (you will even be able to see many nematodes with a magnifying glass
  13. Sieving and sucrose Nematode collection method:
    • . Mix soil sample and pass through coarse sieve to remove rocks, roots, etc.
    • 4. Take a 100 cc subsample of soil: pack lightly into beaker for uniformity.
    • 5. Remove sand and organic material:
    • a) Mix soil subsample in 500 ml water by pouring between beakers ten times.
    • b) Rinse residues in second beaker into beaker with sample.
    • c) Swirl beaker with sample; allow to stand for 15 seconds (sand settles).
    • d) Pour supernatant through 20/500-mesh stacked sieves.
    • e) Gently tap side of 500-mesh sieve to facilitate drainage.Note: Larger particles will remain in beaker; organic debris is caught on 20-mesh sieve; nematodes and silt are retained on 500-mesh sieve.
    • f) Using the coarse-spray water bottle, gently wash nematodes, etc. into one sector of the 500-mesh sieve.
    • g) Using the fine spray water bottle, wash sample into a centrifuge tube.
    • 6. Centrifuge: add water to centrifuge tubes to equalize volumes; place tubes in centrifuge in balanced pairs.a) Spin at 1700 rpm (810 g) for 5 minutes without using the brake.b) Allow to settle for 5 minutes.c) Aspirate supernatant to approximately 1 cm above pellet.d) Fill tubes with sucrose solution at room temperature.e) Stir with a spatula to break up pellet (must be completely dispersed).f) Spin sample: bring centrifuge up to 1000 rpm ( 280 g) in 30 sec, then apply brake.Note: Nematodes and clay are suspended in sucrose supernatant; silt and larger particles are in the pellet.
    • 7. Pour supernatant through 635-mesh sieve. Rinse gently with water and transfer to labeled vials using the fine spray water bottle.
  14. What are amphids?
    Sensory organs at anterior end