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Transcript
Nematode Workshop 1st Morning Session
Nematology 101:
Biology and Ecology
Deb Neher
University of Vermont
Dept. of Plant and Soil Science
[email protected]
http://www.uvm.edu/~dneher/
Soil Biological Indicators Lab
+1.0
Dr. Deborah Neher uses soil nematode & microarthropods for
monitoring soil quality and measuring progress of soil
remediation (http://www.uvm.edu/~dneher/)
moisture
bulk density
organic carbon
proturans
Oribatida
other mites
fungi
Isotomidae
Onychiuridae
clay
Pauropoda
Symphyla
EC
cellulose/lignin
DiplopodaL
sand
Homoptera
bacteria
HymenopteraA
HymenopteraL
pH
-1.0
cellulose
benzo[a]pyrene
5-ring
phenanthrene
fluoranthene
pyrene
-1.0
+1.0
Abundance of soil
animals per square
meter in European
grassland
General characteristics of nematodes
 Aquatic
 Unsegmented
 Appendageless
 Transparent
 Bilaterally symmetrical
 Generally bisexual
 Vermiform roundworms
 Non-coelomate
Meloidogyne hapla
 Biotrophs
Sensory organs
 No eyes, appendages
or segmentation
 Mechanosensory
 Chemosensory
Fig. 2. Spiral-shaped chemosensory
organs called amphids in an anterior
position of Achromadora sp.
collected from soil of Jumbo Valley
fen in Cherry County, Nebraska.
Phytonematode anatomy & morphology
 Well developed digestive &
reproductive & sensory
systems
 Lack circulatory & respiratory
systems
Nematode identification
Pratylenchus
Xiphinema
Criconemella
Physiological versatility
 Tolerate harsh habitats
avoid interspecific competition and many
environmental selection pressures
 Regulate uptake of O2 between 100 to 5%
 Permeable, hydrostatic skeleton
osmoregulation of Ca, Mg, K
 Tolerate pH from 1.6 to 11.0
 Temperatures from sub-zero to 60C +
Survival
Aphelenchus, anhydrobiosis
Head structures of soil nematodes
a) bacterivore
b) bacterivore
c) bacterivore,
predator
d) Fungivore and/or
herbivore
e) omnivore
f) herbivore
g) herbivore
h) predator
Predatory nematodes
 May feed on
nematodes,
protozoa, bacteria,
etc
Figure 5. Teeth of oral opening of predator Mylonchulus montanus (1000x
magnification), collected in soil with big blue stem in the Konza Prairie
(96W35’ 39N05’) near Manhattan, Kansas. Photograph is provided
courtesy of Peter Mullin/2000.
Bacterial-feeding nematodes
 Simple tubular
mouthpart
 Elaborate cuticle
around oral opening
Figure 4. Cuticle ornamentation of oral opening of Acrobeles ctenocephalus
(1000x magnification), collected in soil with little bluestem (Andropogon
scoparius) in the Konza Prairie (96W35’ 39N05’) near Manhattan, Kansas.
Photograph is provided courtesy of Peter Mullin/2000.
Paulo Vieira (Mactode publications)
Plant-parasitic nematodes
 Respond to CO2 & root
exudates
 Move few cm per day
 Probe with stylet
 Ecto-parasites
 Endo-parasites
 Lifecycle: 3 weeks (rootknot) to 2 yrs + (dagger)
Figure 3. Variation in morphology of spear-like structure in oral opening a) male plant-parasite Hoplolaimus galeatus (1000x
magnification) collected from soil with big bluestem (Andropogon gerardii Vitman) in the Konza Prairie (96W35’ 39N05’) near
Manhattan, Kansas, and b) female fungivore Enchodelus hopedorus (400x magnification) collected from the summit of Long’s Peak,
Colorado (105W35’ 40N16’). Photographs are provided courtesy of Peter Mullin/2000.
Plant-parasitic nematodes con’t
 Generalists or specialists
 Hosts range from 1 to
100’s
 All crop plants are
susceptible to at least
one nematode species
 Most are root parasites but species have adapted to
parasitize most plant tissues
 More damage can be associated with coarser
textured soils – sands (larger pore space)
Major impacts of nematodes
 Decomposition of organic matter and
recycling of nutrients (soil food web)
Major impacts of nematodes
 Decomposition of organic matter and
recycling of nutrients (soil food web)
 Biological control agents, esp. for insects
 Research biological models
 Diseases of animals and humans
(heartworm, Trichinosis, hookworm, etc.)
 Important plant pathogens
Other nematodes...
 Animal parasites
– Human: Night blindness,
Elephantiasis
– Pets: Hookworm
– Insects: biocontrol
 Caenorhabditis elegans
– Model system
– Studies of aging,
neurology, ecotoxicology
Major impacts of nematodes
 Decomposition of organic matter and
recycling of nutrients (soil food web)
 Biological control agents, esp. for insects
 Research biological models
 Diseases of animals and humans
(heartworm, Trichinosis, hookworm, etc.)
 Important plant pathogens
Morphology and relative size of major
plant-parasitic nematodes
Agrios
Types of Plant-Pathogenic Nematodes
Ectoparasites: feed from outside the plant
Migratory: moves, feeding from plant to plant (dagger)
Sedentary: remains on same plant (spiral)
Endoparasites: feed from inside the plant
Migratory: moves within and feeds on tissues (lesion)
Sedentary: remains within same plant and feeds at
specialized sites (root-knot)
Sedentary ectoparasite
(spiral)
Migratory ectoparasite
(dagger)
Essential Plant Pathology, 2006
Sedentary endoparasite
(root-knot)
NC State Univ.
Migratory endoparasite
(lesion)
Typical lifecycle of a plant-parasitic nematode
M
M
M
H
M
3rd stage juvenile
Meloidogyne
hapla
4th stage juvenile
Formation of giant cells and galls
J2 infect root
Egg
mass
2nd stage juvenile (J2)
mobile in soil
1st stage juvenile
Egg
Modified from Agrios, 1997
Lifecycle of Pratylenchus penetrans –
Root-lesion nematode
Agrios
Plant productivity
losses
Meloidogyne, Root knot
nematode damage
How do nematodes damage plants?
Direct feeding on plants (metabolic sinks)
Malformation of host tissues (morphological &
physiological)
Predispose host plant to physical stress
Provide entry for secondary pathogens
(disease complexes)
Breakdown of resistance to other pathogens
Vectoring of plant pathogens (virus & bacteria)
Suppression of beneficial organisms
Nematology 101:
Biology and Ecology
Questions?
Coming up next...signs and symptoms