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WELCOME
The science of life of
living organisms
including their
structure, function,
growth, origin,
evolution and
distribution
 Nematodes are dioceous or
amphigonus
 Male and female nematodes
occur in most species, but
reproduction without males i...
 The plant parasitic nematodes have 6 stages
in their life cycle.They are
1. Egg
2. First stage larva/juvenile (J1)
3. Se...
Embryogenesis occurs in two stage
in the first half of embryogenesis
Most of the cell division occurs.
In the second half,...
Egg
 is ovoid-shaped with 3 layers
and contains a single juveniles.
 The majority of eggs are of
similar size (50–100 μm...
CHAIN OF EVENTS FROM EGG TO EGG
Female lays eggs Eggs hatch
Juveniles moves at
random in soil wander
to root zone by
physi...
The length of the life cycle varies
considerably, depending on
nematode species, host plant, and
the temperature of the ha...
MOULTING
 Increase in body size as growth takes place between moults.
 The cuticle is shed and replaced four times durin...
In general, the process
involves three phases:
(i) the separation of the old cuticle from
the epidermis (apolysis);
(ii) t...
MOULTING
HATCHING
Essentially, the hatching process can be divided into three phases:
 changes in the eggshell;
 activation of th...
Flow diagram showing events in the hatching
process of second-stage juveniles
of Globodera rostochiensis after stimulation...
Enhanced juvenile
activity
Exploratory stylet
probing
Sub-polar slit cut in
eggshell by stylet
Juvenile hatches from
t...
 Migratory ectoparasitic
 Migratory endoparasitic
 Sedentary endoparasitic
 Semiendoparasitic
Ectoparasitic Nematodes
 Remains outside of the plant
and uses its stylet to feed from
the cells
 Uses strategy by which...
Migratory ectoparasitic
These are motile and feeds on
external surface cells of roots.
Eggs are laid in soils only
All mou...
Migratory Endoparasitic
Nematodes
 Spend much of their time migrating through root
tissues destructively feeding on plant...
ECTOPARASITIC ENDOPARASITIC
Sedentary Endoparasitic
 Most damaging nematodes in the
world have a sedentary endoparasitic
life style.
 The cyst nemat...
soybean cyst nematode (Heterodera glycines
Semi-Endoparasites:
Nematodes
 They are able to partially
penetrate the plant and feed at
some point in their life cycle....
 Many nematode species are able to survive
under extreme abiotic conditions at very low or
high soil temperatures (McSorl...
DORMANCY
 Subdivided into ‘quiescence’ and ‘diapause’.
 Quiescence is a spontaneous reversible response to
unpredictable...
DIAPAUCE
 Is a state of arrested development.
 For cyst and root-knot nematodes it is a strategy
to overcome cyclic long...
CRYPTOBIOSIS OR QUIESCENCE ’
 Ecological factors influencing nematode
ecology (soil pore size, aeration,
temperature, pH , light, moisture, osmotic
pr...
PORE SIZE
 Nematodes movement is influenced by pore size.
 Pore size must be more than width of nematode body (20
µ m).
...
SOIL AERATION
 Oxygen content in aerated soil: 18-21 % , co2 less than 1
%.
 Nematode activity increases with increase i...
Moisture
 Either too high or too low moisture levels affects the
nematode
 Tolerance levels to moisture may vary
 RKN &...
 The effect of soil moisture and soil particle size on the survival and
population increase of Xiphinerna index
(Sufian A...
Particle Size(μm) Final population
2 360 139
850 179
534 291
373 1020
250 1174
Sandy loam 1590
Soil moisture % Survival (%)
0 18.4
5 24.8
10 28.0
15 27.3
20 24.0
25 21.1
SOIL TEMPERATURE
 Temperature plays a major role in nematode activities like
hatching, reproduction, movement, multiplica...
pH
 Severely affects hatching
 Variation in nematode activity is mainly due to soil pH.
 Reduction in pH from 6 to 4 de...
OSMOTIC PRESSURE
 Juveniles of H.schactii shrink in conc NaCl solution.
 OP may act as stimulating agent eg. more RKN in...
HOST AND SOIL
CHEMICALS
 Addition of nitrogenous compounds to soil decrease the
population of nematodes.
 Eg P.penetrans...
THANK YOU
References
 Reproduction, Physiology and Biochemistry
DENIS J. WRIGHT1 AND ROLAND N. PERRY2
© CABI 2006. Plant Nematology...
nematology-nematode biology,ecology
nematology-nematode biology,ecology
nematology-nematode biology,ecology
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nematology-nematode biology,ecology

  1. 1. WELCOME
  2. 2. The science of life of living organisms including their structure, function, growth, origin, evolution and distribution
  3. 3.  Nematodes are dioceous or amphigonus  Male and female nematodes occur in most species, but reproduction without males is common.  some species are hermaphroditic .  Parthenogenesis: Eg. Meloidogyne, Heterodera, Tylenchulus. Intersexes are found in some genera like Meloidogyne and Ditylenchus
  4. 4.  The plant parasitic nematodes have 6 stages in their life cycle.They are 1. Egg 2. First stage larva/juvenile (J1) 3. Second stage larva/juvenile (J2) 4.Third stage larva/juvenile (J3) 5. Fourth stage larva/juvenile (J4) and 6. Adult
  5. 5. Embryogenesis occurs in two stage in the first half of embryogenesis Most of the cell division occurs. In the second half, the Embryo elongates markedly and synthesizes the cuticle
  6. 6. Egg  is ovoid-shaped with 3 layers and contains a single juveniles.  The majority of eggs are of similar size (50–100 μm long and 20–50 μm wide) and morphology.  Eggs between 50 and 500 eggs per female, depending on the nematode species and their environment, but some can produce more than 1,000 eggs.  Juveniles hatch from eggs that are laid by the adult female  These juveniles are similar to adults.
  7. 7. CHAIN OF EVENTS FROM EGG TO EGG Female lays eggs Eggs hatch Juveniles moves at random in soil wander to root zone by physical and chemical stimuli,aggregate at root surface Penetration, invasion of tissue,moults,adults
  8. 8. The length of the life cycle varies considerably, depending on nematode species, host plant, and the temperature of the habitat. Generally Life cycle from egg to egg completes in 20-40 days . Ex; 1month :RKN 2weeks:foliar nematode 1year :dagger nematode During summer months when soil temperatures are 80 to 90ᵒF, many plant nematodes complete their life cycle in about four weeks
  9. 9. MOULTING  Increase in body size as growth takes place between moults.  The cuticle is shed and replaced four times during the life cycle.  some species of Longidorus and Xiphinema have only three juvenile stage.  In Aphelenchus hamatus, the moulting process from fourth- stage juvenile (J4) to adult took 12–13 h to complete (Wright and Perry, 1991).
  10. 10. In general, the process involves three phases: (i) the separation of the old cuticle from the epidermis (apolysis); (ii) the formation of a new cuticle from the epidermis; and (iii) the shedding of the old cuticle (ecdysis)..
  11. 11. MOULTING
  12. 12. HATCHING Essentially, the hatching process can be divided into three phases:  changes in the eggshell;  activation of the juvenile; and  eclosion (or hatch from the egg).  In many species, such as Meloidogyne spp., activation of the juvenile appears to precede, and may even cause, changes in eggshell structure.  in others, such as G. rostochiensis, alteration of eggshell permeability characteristics appears a necessary pre-requisite for metabolic, and consequent locomotory changes in the juvenile.  Hatching of nematodes is reviewed in detail by Jones et al. (1998) and Perry (2002)
  13. 13. Flow diagram showing events in the hatching process of second-stage juveniles of Globodera rostochiensis after stimulation with potato root diffusate  Hatch stimulation  Unhatched quiescent juvenile in cyst  Ca2+-mediated change in eggshell permeability  Loss of trehalose from the perivitelline fluid  Uptake of water by juvenile  Juvenile becomes metabolically active
  14. 14. Enhanced juvenile activity Exploratory stylet probing Sub-polar slit cut in eggshell by stylet Juvenile hatches from the egg Further water uptake to full hydration Emergence of juvenile from the cyst
  15. 15.  Migratory ectoparasitic  Migratory endoparasitic  Sedentary endoparasitic  Semiendoparasitic
  16. 16. Ectoparasitic Nematodes  Remains outside of the plant and uses its stylet to feed from the cells  Uses strategy by which they can graze on numerous plants.  Very susceptible to environmental fluctuations and predators.  Have extremely long stylets
  17. 17. Migratory ectoparasitic These are motile and feeds on external surface cells of roots. Eggs are laid in soils only All moults takes place in soils /root. All stages are motile and feeds on roots. Causes terminal galls in the roots and cause severe stunting of the root system Ex: Stubby root nematode
  18. 18. Migratory Endoparasitic Nematodes  Spend much of their time migrating through root tissues destructively feeding on plant cells .  Cause massive plant tissue necrosis.  All motile stages are infective.  Secondary infection by bacteria and fungi (Zunke 1991).  Examples are Pratylenchus (lesion nematode), Radopholus (burrowing nematodes) and Hirschmanniella (rice root nematode).
  19. 19. ECTOPARASITIC ENDOPARASITIC
  20. 20. Sedentary Endoparasitic  Most damaging nematodes in the world have a sedentary endoparasitic life style.  The cyst nematodes (Heterodera and Globodera) and the root-knot nematodes (Meloidogyne).  Juveniles becomes sedentary because their somatic muscles atrophy.  The juveniles feed, enlarge and molt three times to the adult stage.  The large feeding cells formed by these nematodes plug the vascular tissue of the plant making it susceptible to water stress.
  21. 21. soybean cyst nematode (Heterodera glycines
  22. 22. Semi-Endoparasites: Nematodes  They are able to partially penetrate the plant and feed at some point in their life cycle.  nematodes swell and do not move.  risk of death if their host plant dies  EX: Rotylenchulus reniformis,  Tylenchulus semipenetrans
  23. 23.  Many nematode species are able to survive under extreme abiotic conditions at very low or high soil temperatures (McSorley, 2003;Treonis and Wall, 2005) or at 0% relative humidity (Wall andVirginia, 1999).  To survive unfavourable conditions, some nematodes are able to suspend development and survive in a dormant state until favourable conditions return.  (D.J.Wright and R.N. Perry)
  24. 24. DORMANCY  Subdivided into ‘quiescence’ and ‘diapause’.  Quiescence is a spontaneous reversible response to unpredictable unfavourable environmental conditions and release from quiescence occurs when favourable conditions return.  Quiescence can be facultative or obligate.  Adverse environmental conditions and the types of quiescence they induce include  Cooling (cryobiosis), high temperatures (thermobiosis), lack of oxygen (anoxybiosis), osmotic stress (osmobiosis) and dehydration, or desiccation, (anhydrobiosis). (D.J. Wright and R.N. Perry)
  25. 25. DIAPAUCE  Is a state of arrested development.  For cyst and root-knot nematodes it is a strategy to overcome cyclic long-term conditions .  Obligate diapause is initiated by endogenous factors and can be relieved by the J2 receiving exogenous stimuli for a required period of time.  Nematodes can undergo obligate diapause only once in their life.  Facultative diapause is initiated by exogenous, rather than endogenous, stimuli and terminated by endogenous factors after a critical period of time (D.J. Wright and R.N. Perry)
  26. 26. CRYPTOBIOSIS OR QUIESCENCE ’
  27. 27.  Ecological factors influencing nematode ecology (soil pore size, aeration, temperature, pH , light, moisture, osmotic pressure, chemicals, decomposing plant material ).
  28. 28. PORE SIZE  Nematodes movement is influenced by pore size.  Pore size must be more than width of nematode body (20 µ m).  Ideal soils: Sandy loam soils  Sandy soils: Less porosity & Less total pore volume  Clay soils : Greater porosity & Greater total pore volume  Rode : showed that the migration of juveniles of Globodera rostochiensis toward potato plants was greatest in sandy soil, intermediate in loamy soil, and least in clay soil.
  29. 29. SOIL AERATION  Oxygen content in aerated soil: 18-21 % , co2 less than 1 %.  Nematode activity increases with increase in oxygen concentration but decreases with increase in co2 concentration  Lowest level of oxygen requirement for host and nematode : 3-5 %  Detrimental level to nematodes is above 5%  Eg: xiphinema americanum more sensitive to long oxygen exposure  the aeration and pore size of sandy soils increase nematode viability
  30. 30. Moisture  Either too high or too low moisture levels affects the nematode  Tolerance levels to moisture may vary  RKN & Burrowing nematode sensitive to dessication  Stem and bulb nematode resistant  Egg masses, cysts,galls are resistant to high moisture  Ideal level : Field condition
  31. 31.  The effect of soil moisture and soil particle size on the survival and population increase of Xiphinerna index (Sufian A. SULTAN and Howard FERRIS) (Department of Agricultural Sciences, Al1 Najah National University, West Bank, Israel, and Department of Nematology, University of California, Davis, CA 95616, USA)  The interaction of soil moisture on survival and subsequent reproductive potentiial of Xiphinema index,and the effect of sand particle size on population increase, were studied under greenhouse conditions.  In the absence of a host, fewer than 10 %of the nematodes survived for 60 days even under favorable (intermediate) moisture conditions. Survival was very low in both saturated and dry soils.  In the presence of a host, population increase of the nematode was highest in sandy loam and in fine sands of 250 μm particle size.  Population increase was low in coarse sand of particle size534 μm and larger. Root damage to host plants was directly related to the increase in nematode population.
  32. 32. Particle Size(μm) Final population 2 360 139 850 179 534 291 373 1020 250 1174 Sandy loam 1590
  33. 33. Soil moisture % Survival (%) 0 18.4 5 24.8 10 28.0 15 27.3 20 24.0 25 21.1
  34. 34. SOIL TEMPERATURE  Temperature plays a major role in nematode activities like hatching, reproduction, movement, multiplication, survival, feeding etc.  5-15 ºc :most nematodes inactive  15-30ºc: optimum  30-40ºc :most nematodes inactive  Eg : H.rostochiensis  Invading host : 15-16ºc, cyst emergence : 21-25ºc, Development : 18-24ºC.
  35. 35. pH  Severely affects hatching  Variation in nematode activity is mainly due to soil pH.  Reduction in pH from 6 to 4 decreases the emergence of juveniles of H. rostochiensis.  At 3 and 10.6 juveniles of RKN juveniles repells  Inhibitory levels are < 5 and > 8  E.g.. P . Penetrans opt :5.5-5.8 LIGHT Light has no or little effect on phytonematodes Mostly spend their lives in darkness UV light is known to be lethal
  36. 36. OSMOTIC PRESSURE  Juveniles of H.schactii shrink in conc NaCl solution.  OP may act as stimulating agent eg. more RKN in high saline soils.  Exposure of RKN juveniles to 1M salt solution ineffective.  Osmotic destruction of nematodes eg. M.arenaria.  Most nematodes can tolerate upto 10 atmosphere.
  37. 37. HOST AND SOIL CHEMICALS  Addition of nitrogenous compounds to soil decrease the population of nematodes.  Eg P.penetrans .  Applications of sodium nitrate and ammonium nitrate to soil reduced hatching, penetration and cyst development in H.glycines on soyabean.
  38. 38. THANK YOU
  39. 39. References  Reproduction, Physiology and Biochemistry DENIS J. WRIGHT1 AND ROLAND N. PERRY2 © CABI 2006. Plant Nematology (eds R.N. Perry and M. Moens) (Division of Biology, Faculty of Life Sciences, Imperial College London)  The effect of soil moisture and soil particle size on the survival and population increase of Xiphinerna index Sufian A. SULTANa nd Howard FERRIS (Department of Agricultural Sciences, Al1 Najah National University, West Bank, Israel, and Department of Nematology, University of California, Davis, CA 95616, USA) The History of Nematodes Blaxter, M.L., P. De Ley, J.R. Garey, L.X. Liu, P. Scheldeman, A. Vierstraete, J.R. Vanfleteren, L.Y. Mackey, M. Dorris, L.M. Frisse, J.T. Vida, K.W. Thomas, K.W. 1998. (A molecular evolutionary framework for the phylum nematoda)
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