nematology 101: biology and ecology deb neher university of vermont dept. of plant and soil science...
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Nematology 101: Biology and Ecology
Nematology 101: Biology and Ecology
Deb Neher
University of Vermont
Dept. of Plant and Soil Science
[email protected]://www.uvm.edu/~dneher/
Nematode Workshop 1st Morning Session
Soil Biological Indicators Lab
Dr. Deborah Neher uses soil nematode & microarthropods for monitoring soil quality and measuring progress of soil remediation (http://www.uvm.edu/~dneher/)
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cellulose
EC
cellulose/lignin
organic carbon
moisture
pH
pyrene
phenanthrenefluoranthene
5-ring
clay
benzo[a]pyrene
sand
bulk density
Hym enopteraL
Sym phylaPauropoda
O nychiuridae
other m itesfungi
O ribatida
proturans
Hym enopteraA
bacteria
D ip lopodaL
Isotom idae
Hom optera
Abundance of soil animals per square meter in European grassland
General characteristics of nematodesGeneral characteristics of nematodes
Aquatic
Unsegmented
Appendageless
Transparent
Bilaterally symmetrical
Generally bisexual
Vermiform roundworms
Non-coelomate
BiotrophsMeloidogyne hapla
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.
Sensory organsSensory organs
Well developed digestive & reproductive & sensory systems
Lack circulatory & respiratory systems
Phytonematode anatomy & morphologyPhytonematode anatomy & morphology
Nematode identificationNematode identification
Pratylenchus Xiphinema Criconemella
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 +
Physiological versatilityPhysiological versatility
Aphelenchus, anhydrobiosis
SurvivalSurvival
a) bacterivore
b) bacterivore
c) bacterivore, predator
d) Fungivore and/or herbivore
e) omnivore
f) herbivore
g) herbivore
h) predator
Head structures of soil nematodesHead structures of soil 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.
Predatory nematodesPredatory 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.
Bacterial-feeding nematodesBacterial-feeding nematodes
Paulo Vieira (Mactode publications)
Respond to CO2 & root exudates
Move few cm per day
Probe with stylet
Ecto-parasites
Endo-parasites
Lifecycle: 3 weeks (root-knot) 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 nematodesPlant-parasitic nematodes
Generalists or specialists
Hosts range from 1 to 100’s
All crop plants are susceptible to at least one nematode species
Plant-parasitic nematodes con’tPlant-parasitic nematodes con’t
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 nematodesMajor impacts of nematodes
Decomposition of organic matter and
recycling of nutrients (soil food web)
Major impacts of nematodesMajor 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...Other nematodes...
Animal parasites– Human: Night blindness,
Elephantiasis– Pets: Hookworm– Insects: biocontrol
Caenorhabditis elegans– Model system– Studies of aging,
neurology, ecotoxicology
Major impacts of nematodesMajor 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
Agrios
Morphology and relative size of major plant-parasitic nematodesMorphology and relative size of major plant-parasitic 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)
Types of Plant-Pathogenic NematodesTypes of Plant-Pathogenic Nematodes
Migratory endoparasite (lesion)
Sedentary endoparasite (root-knot)
Migratory ectoparasite (dagger)
Sedentary ectoparasite (spiral)
Essential Plant Pathology, 2006 NC State Univ.
Typical lifecycle of a plant-parasitic nematodeTypical lifecycle of a plant-parasitic nematode
H
M
MM
M
Egg1st stage juvenile
2nd stage juvenile (J2) mobile in soil
J2 infect root
Formation of giant cells and galls
3rd stage juvenile 4th stage juvenile
Egg mass
Modified from Agrios, 1997
Meloidogyne hapla
Agrios
Lifecycle of Pratylenchus penetrans – Root-lesion nematode
Lifecycle of Pratylenchus penetrans – Root-lesion nematode
Meloidogyne, Root knot nematode damage
Plant productivity lossesPlant productivity losses
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
How do nematodes damage plants?How do nematodes damage plants?
Nematology 101: Biology and Ecology
Nematology 101: Biology and Ecology
Questions?Questions?
Coming up next...signs and symptoms