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Who is the Father of U.S. nematology
Nathan A. Cobb
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
What do all plant nematodes have?
- Mechanical penetration of plant cell wallsIntroduction of nematode secretionsUptake of plant cell contents
What are the different types of feeding habits?
- Ectoparasitic: nematode does not enter the plant tissuesMigratorySedentary
- Endoparasitic: the entire nematode penetrates the roottissueMigratorySedentary
- Semi-endoparasitic: the anterior part of the nematodepenetrates the root, but the posterior part remains in thesoil phase
Symptoms of nematode infection:
- Often times unspecific
- Easily confused with physiological disorders and diseasescaused by other pathogens
- Deformed growth
- Stunted root systems or bushy roots
- Leaf damage, seed damage, tuber damage Lesions, galls
Examples of nematode disease with examples:
- Nematodes that infect plants below groundRoot-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
Nematodes that infect plants above ground
- Foliar nematodes (Aphelenchoides)
- Seed gall nematodes (Anguina)
- Stem and bulb nematodes (Ditylenchus)
Diseases on trees caused by nematodes
- Red ring disease of palms (Bursaphelenchus cocophilus)
- Pine wilt disease (Pine wood nematode, Bursaphelenchus xylophilus)
How to manage nematodes?
- Difficult (wide host range, survival strategies)
- Healthy plants
- Nematode-free seed, nematode-free propagative parts
- Steaming, solarization, sanitation, pasteurization, crop rotations, fallowing, trap crops, tillage, biofumigation
- Biological control
- Chemical control (soil fumigants and nonfumigant nematicides)
- 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.
List the different ways nematodes reproduce:
- Amphimictic: fusion of a male and female gamete
- parthenogenic: female asexual reproduction
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.
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
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.
What are amphids?
Sensory organs at anterior end
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