Ent-555_Outline of Class Lectures_Edited_17-08-19.pdf
1. NEMATODES
If you've wandered around our exhibits much, you've seen many groups
described as living just about anywhere. That statement goes triple for
nematodes, who live not only in almost every geographic location on Earth, but
live in such extreme habitats as ice and hot springs, as well as living on or in
almost every other kind of animal and plant alive today. Free-living nematodes are
extremely abundant in soils and sediments, where they feed on bacteria and
detritus. Other nematodes are plant parasites and may cause disease in
economically important crops. Still others parasitize animals (including humans);
well-known parasitic nematodes include hookworms, pinworms, Guinea worm
(genus Dracunculus), and intestinal roundworms (genus Ascaris)
2. Nematodes could be
defined as aciliated,
pseudocoelomic,
unsegmented, bilaterally
symmetrical, triploblastic,
vermiform metazoa, generally
dioecious, with well developed
digestive & reproductive and
sensory systems, a less
developed excretory system,
lacking in circulatory &
respiratory systems; have a
serpentine movement on the
dorso ventral plane.
3.
4. Nematode –derived from a greek
word nema- thread, oides-worm like
Synonymies as round worms as cross
section at any point is round.
Members of Ecdysozoa and belongs
to division Bilateria .
Second most numerous animal next
to Arthropods(Waggoner, 2004)
Ubiquitous in nature
About 50 million nematodes are
found in a square meter of moderately
fertile soil depth of 0-30cm!
5. ♦Nematology is an important branch of biological science, which deals
with a complex, diverse group of round worms known as Nematodes
that occur worldwide in essentially all environments.
♦ The name nematode was derived from Greek words nema (thread)
and oides (resembling)
♦ Nematodes are also known as eelworms in Europe, nemas in the
United States and round worms by zoologists.
♦ Many species are important parasites of plants and animals,
whereas others are beneficial to agriculture and the environment.
♦ Nematodes that are parasites of man and animals are called
helminthes and the study is known as Helminthology.
♦ The plant parasitic forms are called nematodes and the study is
known as Plant Nematology.
6. Distribution of the
Nematodes over the globe
marine
50%
free living
25%
Animal and
human parasites
15%
Plant parasites
10%
Distribution of nematodes according to their habitat
7. HISTORY OF DEVELOPMENT OF PHYTONEMATOLOGY
Nematology research, like most fields of science, has its foundations in
observations and the recording of these observations. The earliest written
account of a nematode "sighting," as it were, may be found in the Pentateuch of
the Old Testament in the Bible.
In Vedas Nematodes were dealt in detail – its biology, ecology, management etc.,
The oldest reference of parasitic nematodes could be traced in China form 2700
BC.
In ancient civilization of the Mediterranean and Middle East, mention of parasitic
nematodes was made in 1553-1550 BC
8. HISTORY OF DEVELOPMENT OF PHYTONEMATOLOGY
● Before 1750, a large number of nematode observations were recorded, many by the
notable great minds of ancient civilization like, Hippocrates (ca. 420 B.C.), Aristotle (ca.
350 B.C.) etc. Celsus (ca 10 B.C.), Galen (ca. 180 A.D.) and Redi (1684) all described
nematodes parasitizing humans or other large animals and birds.
● Borellus (1653) was the first to observe and describe a free-living nematode, which he
dubbed the "vinegar eel;“
● The major contribution of advancement of nematology was the microscope. Tyson
(1683) used a crude microscope to describe the rough anatomy of the human intestinal
roundworm, Ascaris lumbricoides.
● The taxonomic studies were taking shape with Dujardin (1845), Deising (1851) , Bastian
(1865) in Europe.
● It must be also mentioned that in the same time in Europe good proportions of work
particularly in the aspect of nematode evolution was worked out by the Russian
Nematologist Paramanov
● In America the most important person for developing the science of nematology was
Nathan Augustus Cobb who is regarded all over the world as father of Nematology.
● Cobb was also fortunate to be succeeded by some outstanding students like, A. L.
Taylor, B. G. Chitwood, G. Thorne, J. R. Christie and G. Steiner.
● The great nematologist, Armand Maggenti was another star actor in this field.
9. Milestones in Nematology (International and
National):
First ever report of any PPN in the world – Anguina tritici by
Needham (1743)
Kuhn (1857) – Ditylenchus dipsaci
Schacht (1859) – 1st report of cyst nematode (Heterdera schacht
Report of root-knot nematode by Reverend M. J. Barkeley
(1855) and latter on by Goeldi (1887)
Kuhn (1881) – Potato cyst nematode (Heterodera rostochiensis)
Aphelenchoides frageri from Strawberry by D. S. Ritzemaboss
(1891)
10. Detection and description of Reniform Nematode by Linford and
Oliveira (1940)
First ever record of virus transmission by a nematode by D. J. Raski,
W. B. Hewitt and A. C. Goheen (1958)
First ever report of any PPN in the India as well as first ever report of
root-knot nematode in this country in Tea from Kerala by C. A. Barbar
(1901)
Report of Ufra disease causing nematode, Ditylenchus angustus by
Butler (1913) from erstwhile East Pakistan (Presently Bangladesh)
Aphelenchoides besseyi in rice by J. F. Dastur (1936) from erstwhile
Central Province (Presently MP), India
Milestones in Nematology (International and National):
11. Milestones in Nematology (International and
National):
Report of Golden Nematode of Potato (Heterodera
rostochiensis) from Ooti, T. N., India by F. G. W. Jones (1961).
Post Graduate degree programmes in Indian Agricultural
Research Institute started (1969)
Indian Journal of Nematology commenced publication (1971)
Foundation of NSI at New Delhi (1969)
12. Importance of Nematodes:
♦ Animal Parasitic Nematodes (APNs) cause serious damage
to cattle and human beings
♦ Entomopathogenic Nematodes (EPNs) are effectively
utilized against menacing insects
♦ Free living Nematodes (FLNs) have significant contribution
in soil recycling and thereby improving soil health
♦ Annual crop loss due to Plant Parasitic Nematodes (PPNs)
has been estimated nearly Rs. 5000.00 crores in India
13. CONTRIBUTION OF NEMATODES TO SOIL HEALTH
Given their central role in the soil food web and linkage to ecological processes,
nematodes can be a tool for testing ecological hypotheses and understanding
biological mechanisms in soil. It makes ecological sense to use nematodes as bio-
indicators of soil condition. Nematodes represent a central position in the soil food
web and correlate with ecological processes such as nitrogen cycling and plant
growth.
Under field conditions, bacterivorous and predatory nematodes are estimated to
contribute (directly and indirectly) about 8% to 19% of nitrogen mineralization in
conventional and integrated farming systems, respectively
Nematodes contribute to nitrogen mineralization indirectly by grazing on
decomposer microbes, excreting ammonium, and immobilizing nitrogen in live
biomass
Predatory nematodes also regulate nitrogen mineralization by feeding on
microbial grazing nematodes, a conduit by which resources pass from bottom to top
trophic levels
14. CONTRIBUTION OF NEMATODES TO SOIL HEALTH
Since the 1970s, nematodes have been used as environmental biomonitors for
aquatic systems. For example, Panagrellus redivivus has been used as a
biomonitors to detect toxin concentrations that affect molting and organism size
through stimulation, inhibition, or lethality, and provides a rapid bioassay that
costs less than 10% of a Salmonella bioassay. The nematode has been used to
determine toxic effects of about 400 single chemicals
BIOLOGICAL MODEL
The first multicellular animal to be sequenced was the free-living nematode
Caenorhabditis elegans (The C. elegans Sequencing Consortium 1998) and this
has built a technological platform from which to investigate innate immunity,
the generic science that underpins the biology of host-pathogen interactions..
The last 3 years represent a milestone for parasitic nematode genomics; in
addition to the release of a draft genome sequence of the human parasite
nematode Brugia malayi, the first two complete genomes of plant-parasitic
nematodes have been obtained, both from the root-knot nematode genus:
Meloidogyne incognita and M. hapla
15. LOSSES DUE TO ANIMAL PARASITIC NEMATODES:
Nematodes can sap energy, cause serious diseases, and even kill humans
and animals. Sheep, dogs, and cats are especially vulnerable.
They have a major, long-term impact (directly and indirectly) on human
health and cause substantial suffering, particularly in children
The World Health Organization (WHO) estimates that 2.9 billion people
are infected with nematodes
Parasitic nematodes such as hookworm suck blood and cause anemia.
Ascarids live in the intestines of people, pigs, and other animals, and
compete for nourishment with the host. Young ascarids migrate through the
hosts's body and cause a type of pneumonia. Trichinella spiralis causes
muscle pain and even death in people who eat insufficiently
cooked, infected pork. Brugia malayi, cause the mosquito-transmitted
lymphatic filariae.
16. LOSSES DUE TO ANIMAL PARASITIC NEMATODES:
Trichostrongyloid lungworm Dictyocaulus viviparus in cattle
sheep, goat, horse , donkey is world wide problem. These lungworms were
mentioned from Mexico (02424, 02952); Cuba (02739, 02914); Ecuador
(02437); Brasil (00607, 03937, 04229); India, (07103); India (02499); Korea
(02394, 03644); Taiwan (05945); Malaysia (04210); Philippines (03823);
Papua New Guinea (03060)
In a year round study it has been reported from India that prevalence of
nematode parasites like, Haemoncchus sp., Toxocara sp., Trichuris
sp., Strongyloides sp. and mixed infection was found to be
38.01, 27.68, 14.87, 11.98 and 7.43%, respectively. The infection rate in
buffalo, cattle and goat was 41.63, 32.18 and 51.94%, respectively.
17. COMMERCIAL USE OF EPNS
Constraints about the use of chemical insecticides have limited the availability of
control measures against soil-borne insect pests. Entomopathogenic nematodes of the
genera Steinernema and Heterorhabditis provide an environmentally safe and
economically reasonable alternative. Their life cycle and current production, storage
and formulation technology are now known to us. Their market An overview of their
safety, use in integrated pest management and current market potential was estimated
as US$10 million in 1994.
In Europe total revenues in the biocontrol market have reached approximately 200
million Euros. The sector with the highest turn-over is the market for beneficial
invertebrates with a 55% share, followed by microbial agents with approximately 25%.
The development of technology for mass production in liquid media significantly
reduced the product costs and accelerated the introduction of nematode products in
tree nurseries, ornamentals, strawberries, mushrooms, citrus and turf. Progress in
storage and formulation technology has resulted in high quality products which are
more resistant to environmental extremes occurring during transportation to the user.
18. ♦Annual crop loss in India due to PPN has been estimated more than
RS.3000.00 crores
♦ Brinjal – 16.67%, Cucurbits – 18.20%, Jute – 21.35%, Okra – 14.1%, Tomato –
27.21%, Rice – 10.54%, Pointed gourd - 44%
♦ A conservative estimation of global yield loss due to Plant Parasitic Nematodes
could be to the tune of 5% report in 2010
♦ In USA 100 billion dollars loss only for RKN has been reported in 2008
♦ In some regions in USA , more than 50% of fields are infested with root-knot
nematodes causing 3.54 % average yield loss or 778,703 bales worth $311.5
million. Many of the early cultivars were developed to control the M. incognita-
Fusarium wilt complex, and most commercial cultivars now have tolerance or very
high resistance to the fungus but no more than a low level of tolerance or
resistance to the root-knot nematode, M. incognita (Starr,1993). This is a serious
economic problem since M. incognita is ubiquitous and 70% of all cotton grown in
the U. S. is grown in the South
19. ♦ For the potato crop in the UK alone, it is estimated that the cyst
nematodes, Globodera rostochiensis and G. pallida, account for an
estimated ~$70 million per annum or 9% of UK production (DEFRA
2010).
♦ In the tropical and sub-tropical climates, crop production losses
attributable to nematodes were estimated at 14.6% compared with
8.8% in developed countries.
♦ Nematodes pave the way for concomitant pathogens; symptom
produced by different individual pest together appears as complex
symptoms – syndrome
♦ Plant Parasitic Nematodes have the ability to transmit plant disease
causing virus
20. Advantages of Plant Parasitic Nematodes
Symptoms produced by the plant parasitic nematodes are
often confusing and non-specific
Microscopic/submicroscopic size is advantageous to get escaped
at first sight.
This help them in accommodating/adopting under new
situation even may be adverse too
PPNs could be disseminated easily
Once established, it is very difficult to make a field free from
PPNs
Presence of PPN can only be ascertained through extraction
from soil or from plant samples following appropriate method
of sampling which depends on field situation
21. Nematodes have strong ability to adopt Cryptobiosis ( an
ametabolic state of life entered by an organism in response
to adverse environmental conditions such as
desiccation, freezing, and oxygen deficiency). Under the
cryptobiotic state, all metabolic processes stop preventing
reproduction, development and repair
Presence of PPN could be ascertained through soil/plant
sampling following appropriate method depending on
fielding situation
26. Classification of Nematodes on the
basis of habitat and mode of
feeding:
Classification According to habitat:-
♦ Marine ♦ Terrestrial
a) Plant Parasitic
b) Animal Parasitic
c) Free Living
d) Entomopathogenic
27. According to habitat PPNs are further
classified as:-
Below Ground Feeders –
♦ Attack the below ground parts of the plants.
♦ They have ability to survive in soil/plants in active stage.
♦ Produce symptoms both on the below ground and aerial parts
of the plants.
♦ Prefers sandy/sandy loam/loamy soil. However, some are able
to survive in clay soil or under submerged condition.
28. ♦ Symptom on the below ground parts of the plant may be; specific/
nonspecific.
♦ Symptoms on the aerial part of the plants due to below ground
feeding are nonspecific.
♦ Specific symptom on the roots is produced by -
► Root-knot nematodes (Meloidogyne sp.)
► Lesion nematodes/ burrowing nematodes/rice root nematodes
(Pratylenchus sp./Radopholus similis/ Hirschmanniella sp.)
► Stubby root nematodes (Trichodorus sp.)
34. Pointed gourd field uninfested (1) and infested (2) by
root-knot nematode
1
2
35.
36.
37.
38. Potato rot caused by Ditylenchus destructor
Onion bloat diseased caused by stem and bulb nematode
39.
40.
41.
42.
43.
44. ♦ Above Ground Feeders –
• Attack the above ground parts of the plants.
• Do not survive in soil in active stage.
• Produce specific symptoms on the aerial
part of the plants; e.g., Aphelenchoides
besseyi, Rhadinaphelenchus
cocophilus, Aphelenchoides
ritzemabosi, Anguina tritici, Ditylenchus
angustus
52. Classification According to mode of feeding :-
A. Ectoparasite B. Endoparasite C. Semiendoparasite
a) Sedentary a) Sedentary
b) Migratory b) Migratory
53. ►Ectoparasites – Feed on the plants from outside
of the plants
♦ Sedentary Ectoparasites - Feed on the plants from
a particular site remaining outside
of the plant
♦ Migratory Ectoparasites – Migratory in habit while
feeding on the plants from outside
54. ► Endoparasites – Draws nutrients from the plants
remaining inside the plants
♦ Sedentary Endoparasites - Draws nutrients from
within the plants from a particular
site.
♦ Migratory Endoparasites – While feeding move
through intercellular/intracellular
spaces
55. ► Semiendoparasites –
Feeding from the plant from a fixed
site while a part of the body remain
inside the plant and the rest remain
outside the plant
66. Ecology of an organism not only helps in
understanding the behaviour of the organisms in
nature but also helps in developing methods of
managing populations of the organisms by
manipulation of the environment.
Why nematode ecology is important???
Ecological studies on plant parasitic nematodes are
of paramount importance since these form the basis
of devising their management practices.
67. Management is based upon decision
making system and decision is taken on the
basis of information.
These information are about the interaction of
nematode with other biotic and abiotic factors
which means nematode and its ecology
Therefore management can be called as
applied ecology.
68. Nematode ecology includes both
biotic and abiotic factors of the
environment.
Nematode ecology includes
both biotic and abiotic
factors of the environment.
69. Ecology, Ecosystem and Environment
Ecology is the scientific study of the distribution and abundance of life and the
interactions between organisms and their natural environment. It includes the study of
properties of the living organisms and how these properties (biotic and abiotic) are
affected by interactions between the organisms and their environment.
Ecosystem is an ecological unit which includes all the organisms living in a particular
area and all the abiotic (non living) features of the local environment. It is a system that
includes all living organisms (biotic factors) in an area as well as its physical
environment (abiotic factors) functioning together as a unit within a definable boundary.
Environment of an organism includes physical properties, which can be described as the
sum of local abiotic factors such as sunlight, climate, and geology, and biotic
ecosystem, which includes other organisms that share its habitat. It is the conditions
surrounding an organism, including both abiotic factors (eg Temp, rainfall) and biotic
factors (eg predation, competition).
70. Nematode which attack the aerial parts of the plant
interact with their surroundings only.
Irrespective of the difference in habitats, the
environmental components may be abiotic- comprising of
the physical and chemical factors and the biotics -including
mainly the host plants and a galaxy of micro-organisms with
which the nematodes co-exist in the respective habitat.
Nematodes are entirely dependent on water for their
activities, because they cannot feed, move etc., unless there
is sufficient moisture.
As because most of the plant parasitic nematodes live in
soil, those are generally accounted in ecological studies.
71. Uniformly in
the field
Randomly
in the field
Clusters in
the field
The nematode populations are basically distributed
in the following ways
But because of its obligate parasitism
nematodes are forced to aggregate around
plant roots in clustered pattern.
72. In considering the nematodes’ environment,
one should think in terms of moisture and pore
size of the soil.
Changes in aeration, temperature, moisture
etc add to the complexity of the
environment.
Nematodes’ habitats may be a constantly
changing one or a static one.
73.
74. ♦ Above Ground Feeders –
• Attack the above ground parts of the plants.
• Do not survive in soil in active stage.
• Produce specific symptoms on the aerial part of
the plants; e.g., Aphelenchoides besseyi,
Rhadinaphelenchus cocophilus, Aphelenchoides
ritzemabosi, Anguina tritici, Ditylenchus angustus
81. ABIOTIC FACTORS IN NEMATODES
ENVIRONMENT:
The soil (edaphic) characteristics such as
temperature, moisture, aeration, chemicals, e
tc have a profound influence on the biology
and pathogenecity of plant parasitic
nematodes
82. Mobility of nematodes changed
considerably with soil structure or
pore distribution. This may
contribute to a more stable
positioning of nematodes around
the rhizosphere of their host
plants, and therefore increase the
possibility of successful
parasitization
83. The relative proportion of sand, silt
and clay determines the soil texture.
Most nematodes prefer sandy loam to
loam soil.
Meloidogyne doesn’t prefer soil more
than 40% clay and over 50% silt
contain.
84. Well drained light soils and more
pore spaces are better suited for
most nematode species due to easy
locomotion and better oxygenation
certain nematode species prove
more pathogenic in light textured
soils.
Nematodes in
soil
85. Nematodes movement is also greatly influence
depending on water film in pore space and particle
diameter.
Best movement in pore space diameter with
nematode body is equal to 3:1
86. IMPACT OF SOIL DEPTH
Top 1-2 cm soil of field normally contain a few
nematodes but next below 20-30cm layer of soil is
reach in nematodes fauna.
At deeper nematodes population gets stability but
number is less
At deeper depth oxygen availability to nematodes
is also less
87. IMPACT OF TEMPERATURE
Most plant parasitic nematodes have
optimum thermal requirements between 15
and 300C.
Temperature determines the rate of
various physiological activities of nematodes
It determines the occurrence and
seasonal variation on number or activity of
nematodes.( even in same genus)
88. M. hapla prefers temperate climate condition
where as M. incognita, M. javanica, M.
arenaria prefers mostly tropical climate.
Pratylenchus penetrans, P. vulnus are
abundance in cooler region. P. thornii occur
both in cooler and warmer region. P. zeae
common in warmer region
89. Thermotype :
When different population of
same species exhibit different
requirement of the temperature,
these species are called thermo types
Meloidogyne javanica required
25-300 C for growth and reproduction
but for egg and juvenile survival is 10-
150 C optimum temperature
90. Responses to temperature of a
population of Meloidogyne javanica
from Tanzania were examined. The
minimum time to complete one
generation was determined over a
temperature range from 18-300 C.
(Madulu et al.,1994).
Irrigating the plots before covering
slightly decreased mean soil
temperatures compared with the
covered, dry plots and greatly increased
egg survival. (Madulu et al.,1994).
91. Impact of soil moisture
Nematodes are essentially aquatic animal.
It require a thin film of water for their biological activities.
Their movement is largely control by surface tension.
Excessive moisture resulting low friction tends to inhibit
the locomotion of nematodes in soil
92. Extreme dry conditions also inhibit nematode movement
due to surface tension of thin water films around soil
particles
Movement is best between 40% to a little below field
capacity.
Most nematodes can withstand flooding for short
periods but some nematodes like Hirschmaniella spp.
thrive well in flooded soils of rice fields.
93. Population of Hemicycliophora arenaria in citrus has
been recorded to decline when irrigated at 7 days
interval
Root galling in tobacco could be reduced to 50% if
irrigated at 20-25 days interval than at 6-7 days interval
Improving water holding capacity of soil by addition of
organic matter & rainfall or additional irrigations
during crop growth improves the tolerance of crops
94. In slowly drying soil and plant
debris, many nematodes become
quiescent and they also have high
adaptation to moisture stress.
(anhydrobiotic)
Anhydrobiosis help nematodes to
tolerate and resist environment
extremities.
95. In the anhydrobiotic state, nematodes are capable of
surviving desiccation, as well as extreme cold
Nematodes in anhydrobiosis lose 95–99% of their body
water content and cease metabolic activity (Crowe and
Madin 1975).
These and other physiological changes are accompanied by
morphological change – a coiling of the body that has been
used to identify anhydrobiotic individuals in laboratory (Higa
and Womersley 1993) and field studies (Townshend 1984)
96. Parasites of above ground plant parts like the species of
Ditylenchus Sp., Anguina Sp., Aphelenchoides Sp. prefer high
humidity in crop canopy and thin moisture film on stem and
leave surface.
It has been reported that A. besseyi could survive at all the
stages under anhydrobiotic condition by coiling its body at
room temperature (15 to 350 C) for more than 25 months.
97. In hydrated condition, the
Anguina tritici die at freezing or if
exposed to 50 C but in
anhydrobiotic stage they can
survive even in liquid nitrogen at
-180 C ֯
◌ and exposure to 105 C ֯
◌
for 2 mins.
98. Seed infected by seed gall nematode and healthy seed of wheat
Larvae multiplication and proliferation of Anguina tritici
99. Under anhydrobiotic condition nematode are difficult to detect
Triggering PPNs to anhydrobiosis may help to manage them as each
alternate desiccation and rehydration results loss of energy by
nematodes which is ultimately quite detrimental for nematodes.
100. IMPACT OF AERATION
In extreme low oxygen concentration nematode
become quiscent.
Aeration influence the hatching of juvenile,
development, movement of nematode.
101. The available oxygen and carbon dioxide determine the
rate of respiration of nematodes.
The concentration gradient of carbon dioxide is known to
attract PPNs. The CO2 released by the host plants during
respiration acts as cue for the nematodes.
102. Soil inhabiting nematodes are aerobic organism
but they are able to survive for considerable
period of micro aerobic or even in anaerobic
condition.
Oxygen concentration below 2% inhibit
hatching of Aphelenchoides spp. and
Ditylenchus spp.
Excess moisture reduced oxygen supply leading
to quiscent and death of nematodes
103. Effect of Fertilizer application:
Nitrogenous Fertilizer has effect in two phases on soil nematodes:-
Following fertilizer application some toxic matters like ammonia
may release which reduce nematode populations. But nitrate does
not have any inimical effect on soil dwelling nematodes. There are
several reports of decrease of nematode populations immediate
after application of nitrogenous fertilizers.
Application of fertilizers stimulates root and shoot growth & their
tolerance to nematode damage
Increase in level of potash and phosphorus in the soil have been
found to have relation with nematode increase.
104. Effect of Organic Matter application:
Organic matter in soil determines the water holding capacity, pH, soil
aggregation, cation exchange capacity, plant nutrient etc. In the process of
decomposition organic matter release several compounds like, phenols,
aldehyde, fattyacid, amino acids, sulphide, ammonia etc. which are toxic to
nematodes.
Organic matter enhance the soil fertility status and thereby increase the
root and shoot growth of plants as well as the tolerance limit of plants to
nematodes.
Organic matter acts as a good substrate for many soil inhabiting
microbes many of which are antagonistic to the PPNs.
Different kind of organic matters vary in their performance in reducing
PPNs. However, Neem cakes, neem leaf dust, crop residues, saw dust, cow
dung, urine, poultry manure and different oil seed cakes have been found
very useful for the purpose.
105. BIOTIC FACTORS IN NEMATODES’
ENVIRONMENT
The biotic factor influencing
nematodes include plant, soil fauna
and micro flora. Some of which
support nematodes while others are
antagonist and competitive to
nematodes.
106. HOST PLANT
Crops and cropping patterns influence
plant parasitic nematode populations
tremendously.
A plant species which supports the
multiplication of a nematode species is
called its host.
107. Hosts’ characteristics determine the rate of
invasion, development, reproduction and population
density of nematode.
The multiplication rate of a nematode species may
be very high on a plant species, while some other
plant species may not be very favourable for
nematode multiplication.
108. At the same time, plant suffer some amount of
damage due to nematode as damage to the host
increase with the increase in population of
nematode
On the basis of damage to the
host and reproduction of
nematode parasite, the host has
been classify as
Tolerant, Intolerant, good, poor,
resistance and antagonistic
109. Good Host –
Suffer comparatively more
damage, allows high
reproduction rate,
higher ceiling or
Equilibrium Population Graph
Poor Host & Resistant Hosts – Suffer lesser damage, support lesser nematode
population, lower ceiling or equilibrium
Intolerant Host - invaded by the nematodes and suffers extensive damage,
ceiling
110. Tolerant Host – allows may allow high reproduction rate and
supports large population but suffers no damage
Non Host - dose not allow nematode invasion or reproduction.
Consequent on that reaction nematode population
density declines as it would happen in fallow land.
Antagonistic Host - causes greater harm to nematode population
in comparison to fallow. Some antagonistic
crops like African marigold, Sesame, mustard
etc., release toxic root diffusates where as
some like, Crotolaria juncea, C. spectabilis
allow nematodes to invade but do not allow to
attain sexual maturity and there by population
build up is inhibited
111. Host differential is used in
identification of genus, races or
pathotype of species of
nematode which help in the
management of nematodes.
When a particular host is preferred
by a species of a genus or by a race
or pathotype of a species but not
prefer by other species of that
genus or other races or pathotype
of the same species is called host
differential.
Host differentials are utilized for identifying different species of a
genus or races/ pathotypes of a species
112. Nematode genus/
species/race/pathotype
Host Differentials
Tomato
(Pusa ruby)
Cotton
(Delta pine -61)
Tobacco
(NC – 95)
M. incognita - race1 + - -
M. incognita – race2 + - +
M. incognita – race3 + + -
M. incognita – race4 + + +
M. arenaria - race1 + - +
M. arenaria – race2 + - +
M. javanica + + +
M. hapla - + - +
UTILIZATION OF HOST DIFFERENTIALS
113. Host-Parasite Interactions- Extra corporeal digestion – Giant Cell
formation
Synchronized Adaptation of Nematode with the Development of
Host:-
Stimuli emanated from the roots of the plant many times determine the time
of hatching of nematodes as happens in potato and Globodera sp.
Many cases Cyst Nematodes’ maturity coincide with drying up of the crop
and the cysts fall on the soil
Heterodera cajani produces more eggs in egg sack during active
growing stage of crop but starts to produce more eggs in cysts coinciding
with the senescence of the plants
114. Root exudates play vital role in influencing nematode
hatching, and attraction towards the plant roots.
example : Globodera, Heterodera
Yellow Cyst nematode , Globodera spp.
115.
116. Interactions with other micro organisms
Degree of damage to the particular crop is influenced by
the plant species or cultivar, nematodes species, level
of population density and the prevailing environment
around the host and nematode.
117. Nematodes interact with different pathogen to aggravate the
degree of damage and instead of producing a symptom
produce syndrome (complex symptom)
Plant parasitic nematodes are involved in all shorts of interaction with
other micro-organism (fungi, bacteria, viruses) leading disease
complexes, in which nematodes may play the role of inciter, aggravator or
a vector.
118. PPNs can cause damage indirectly with
other micro-organism (fungi, bacteria,
viruses) leading to the formation of disease
complexes manifested as Syndrome.
A disease complex is produced through a
synergistic interaction between two
organisms
119. It seems reasonable to expect that infection by
one pathogen may alter the host response to
subsequent infection by another (Taylor, 1990)
Ecological interactions affect the reproduction
capacity of the individual nematode population
This interaction may be beneficial or detrimental
to one or all interacting nematodes or there may
be no effect on either
120.
121. The competitive interaction does not involve
predation, parasitism, or pathogenesis but result
from the differential capacity to reproduce, to
consume food, to occupy space
In ectoparasitic and migratory endoparasitic
interaction, migratory endoparasites are antagonistic
to ectoparasites.
122. Nematodes suppressed by fungus
Fungus suppressed by nematode
Fig. Nematodes trap by fungus-Arthrobotrys oligospora
Fig: Nematode feeding on fungus
123. According to the theory of
competitive exclusion, two species
cannot occupy the same ecological
niche (Gause,1934)
Interaction may occur between
species that occupy different
niches if they are in close
proximity or simply feeding on the
same root system (Brewer ,1978;
Norton ,1978)
Fungal trapping
nematode
124. Role played by nematodes in disease
complexes:
Mechanical wounding agents
Host modifiers
Rhizosphere modifier
Resistance breaker
Vectors of pathogens
125. In agro ecosystem, most of the plant parasitic
nematodes are found in rhizospheric soil and many
of them are proved to have great impact economic
crop losses.
These losses are increased more when the PPNs
interact with other pathogens such as fungi and
bacteria, viruses by developing disease complex.
126. Nematode Interactions
►Nematode-fungus – Synergistic and antagonistic
► Nematode-bacteria – Synergistic and antagonistic
► Nematode-virus – Transmission by the nematodes
► Nematode-nematode – Synergistic and antagonistic
► Nematode-insect – Entomopathogenic Nematode (EPN)
► Nematode- mite
127. Nematode-Fungus
► Synergistic-
• Wilt fungus – Fusarium oxysporum – M. incognita increase wilt in
cotton, tomato, tobacco. Even variety of cotton resistant to
Fusarium wilt succumbed to wilt when root-knot nematode is
present there in the soil.
• In peas, early yellowing and root rot is dependent upon the
presence of Hoplolaimus uniformis and Fusarium oxysporum f.
pisi race 3.
• Pratylenchus penetrans and Trichoderma viridae cause more
reduction in root and shoot growth in lucerne than either
organism alone.
128. Nematode-Fungus
► Synergistic-
Tylenchulus semipenetrans increases root decay by Fusarium
sp. in lemon.
Adverse effect of Rhizoctonia solani on non-emergence of
cauliflower seedlings is greatly increased when the seedlings
are infested by the fungus along with Tylenchorhynchus
brassicae.
129. Nematode-Fungus
► Antagonistic
• M. incognita & Paecilomy ces lilacinus – egg parasite 70% root
gall could be reduced in potato.
• Mycorrhiza (Glomus mossae/ G. fasciculatus) & root-knot
nematode.
• In tomato nematode control was more effective by the fungus than
even by carbofuran.
• Predacious fungi – Dacty laria sp., (constricting ring), Arthrobotry s
sp. etc. (sticky network).
130. Nematode-Bacteria
► Synergistic
• In tobacco, when plants are exposed to M. incognita by 3-4 weeks
prior to exposure to Pseudomonas solanacearum, wilt problem is
more severe than exposure to only bacteria or bacteria-nematode
simultaneous
• In tomato, presence of root knot nematode along with P.
solanacearum increase the wilt problem
• In lucerne wilt caused by Cory nebacterium insidiosum is greatly
increased by the stem nematode, Dity lenchus dipsaci. Even the wilt
resistant varieties of lucerne become susceptible due to present of the
nematode
• In wheat tundu disease is caused by Anguina tritici and
Cory nebacterium michiganense (= tritici)
131. Nematode-Bacteria
► Antagonistic
• The bacteria, Pasteuria penetrans has
been found very effective in reducing
population of root-knot, reniform and citrus
nematodes
132. Nematode-Virus
► Two group of viruses depending on the basis of their particle
shape are transmitted by PPNs.
♦ NEPO (Nematode transmitted viruses with polyhedral particles) -
transmitted by - Xiphenema sp. , Longidorus sp. &
Paralongidorus sp.
♦ NETU (Nematode transmitted viruses with tubular particles) –
transmitted by –Trichodorus sp. and Paratrichodorus sp.
133. Nematode-Virus
► Transmission by both - Juvenile & adults.
► Feb. & Oct. are the best months for this transmission.
Persistence
♦ Grapevine fan leaf virus can persist for 8 months in X. index
♦ Tobacco ring spot virus can persist up to 49 wks. in X. americanum
134. Nematode-nematode
♦Meloidogy ne graminicola and Heterodera ory zicola
♦ Roty lenchulus reniformis and Ty lenchulus semipenetrans on
grapevine
♦ Root-knot nematodes and Reniform nematodes
► Predation by Predatory Nematodes namely, Mononchus
sp., Mylenchus sp., Diplogaster sp. etc on PPNs
136. Nematode-Mite
►Predation of M. incognita by Mesostigmatid mites
► Predation of Aphelenchoides ritzemabosi,
Meloidogy ne javanica, Heterodera avenae,
Xiphenema index by Rhizoglyphus echinopus.
► Predation of Aphelenchus avenae by Tyrophagus
putrescentiae
137. • Plant nematodes develop sophisticated system to
parasitize the plants
•have developed diversified defensive strategies
•fail to develop normally if the feeding sites do
not form
•successful and balanced host-parasite
relationship requires
•plant cue attract nematodes
•establishment of feeding site and reproduction
by nematode
•response of the host.
139. Plant Host
The Plant’s Reaction to the Nematode
Nematode
“Parasite”
Various stages of feeding process
can disturb integrity of host
Feedback
effect on plant
Consumption
140. STEPS INVOLVE IN FEEDING
PROCESS
• Attraction
perceive stimuli and attracted to plant
•Penetration
- caused by repeated mechanical thrusting
and insertion of stylet
- migration of nematodes through tissue
141.
142. Contact made, stylet inserted.
Injection of predigestive enzymes,
plant hormones, etc.
After waiting period, ingestion of cell
contents.
Cell may collapse, stylet withdrawn.
Typical Nematode Feeding Process
143. 1. Endo parasitic nematode
a) Sedentary endoparasite: Root knot nematode
(Meloidogyne spp.), Cyst nematode (Heterodera sp)
etc.
b) Migratory endoparasite: Root lesion nematode
(Pratylenchus spp.), Burrowing nematode
(Radopholus spp.)
2. Semi-endo parasitic nematode: Reniform
nematode (Rotylenchulus reniformis)
3. Ecto parasitic nematode: Foliar nematode
(Aphelenchoides spp)
Classification of nematode(depending
on the feeding behavior)
144. Stylet penetration is important in
damaging host tissue by sedentary
endoparasites which use the stylet
to puncture a large enough opening to
permit entry.
SEDENTARY ENDOPARASITE AND
SEDENTARY ECTOPARASITE
145. MIGRATORY ENDOPARASITE
Migratory endoparasites move
through the tissues, feeding on cells
as they go, leaving tunnels and
cavities behind them. In these
cases, mechanical damage to the plant
may be great.
147. The single insertion of a stylet by many
migratory ectoparasites which feed on
surface tissues actually causes little damage.
Migratory ectoparasites with large stylets
that feed on subsurface tissues cause more
damage.
More disturbance is actually caused by
the "feeding process"
MIGRATORY ECTOPARASITE
148. HOST PARASITE RELATION OF
SEDENTARY ENDOPARASITE
ROOT KNOT NEMATODE :
Different species of genus Meloidogy ne
- M. incognita, M. javanica, M.
arenaria, M. hapla etc.
HOSTS: potato, chillies, tomato, okra,
carrot, beans, grapes, papaya, cotton,
jute, ground nut, sunflower, tea, coffee
etc.
149. Brown egg mass produced by RKN female
Root knot nematode female and egg mass
150. FEEDING SITE
o J2 penetrate root tissue behind root cap
o Migrate intercellularly in cortex to region of cell
differentiation
o Increase level of oxidoreductive (a chemical reaction between two
substances in which one substance is oxidized and the other
reduced) enzyme activity
o Place their heads in the periphery of vascular tissue and rest of the
body in the cortex
153. CHANGES IN THE HOST PLANT DUE TO
ROOT KNOT NEMATODE
o Susceptible plants show morphological and
physiological changes.
o Development of elaborate, permanent
feeding sites called GIANT CELLS.
154. WHAT IS GIANT CELL ?
Giant cells are highly specialized
cellular adaptations, induced and
maintained in susceptible hosts by
feeding of root knot nematode.
155. WHY THEY NEED TO DEVELOP GIANT
CELLS ?
Juveniles fail to develop normally
without this unique host response
and feed without killing the host cells.
A continuous supply of food is
required for their nourishment &
development. Therefore formation of
GIANT CELL is essential for successful
host parasite relationship.
156. • Tissues preferred
for development
of giant cells are
primary phloem
or adjacent
parenchyma
• Each juvenile feed
on five to six cells.
cross section of root
• Feeding transform these cells into elaborate nutritive.
GIANT CELL
158. ANATOMY OF GIANT CELLS
• Nuclei of giant cell become irregularly lobed
amoeboid in for
• Golgi apparatus, mitochondria, ribosome,
polypore, endoplasmic reticulum are abundant
• Central vacuole disappear, small vacuoles
increase in number in cytoplasm
159. • Wall of giant cell apparently continuous
without any gap or perforation
• Plasmodesmata are found in thin
portion of wall
160. • Root knot nematode requires about a
month to reach maturity
• Infective juvenile increase in size by 1000
times during the development
• Total biomass is much larger than any
giant cell on which it feeds
• to accomplish such tremendous growth
must draw bulk of nutrients.
161. PHYSIOLOGY OF GIANT CELL
• Nematode draws nutrient from half dozen giant cells
surrounding nematode’s head
• Giant cells act as transfer cell
• Increase in surface area of Plasmalemma in giant
cell, facilitate transport of solute.
• Large quantity of solutes transfer from surrounding tissue
to the giant cell.
162. NEMATODE DEVELOPMENT
J2 undergo several morphological changes
Esophageal glands of nematode release
glandular substances, some membrane
bound granules
They are involve in egg hatching, juvenile
penetration, eliciting giant cell formation.
163. MORPHOLOGICAL CHANGES OF
PLANTS DUE TO ROOT KNOT
FEEDING:
Galling
◊One of the earliest host responses to
"root-knot nematodes" is the galling of
plant roots.
◊Steler parenchyma cells and pericycle
cells undergo hyperplasia
◊Surrounding cortical cells become
hypertrophied
174. FEEDING HABIT AND
PARASITISM
• Obligate sedentary endoparasite
• Stylet protrusion
• J2 settles in the region of vascular tissue
• Penetrate adjacent cell
• Ingestion of cell content with alternate
stylet protrusion and pumping of
metacorpus
• Esophageal gland content release through
stylet
176. PHYSIOLOGICAL CHANGES DUE TO
NEMATODE FEEDING
• Multinucleate syncytia is formed
• Syncytia forms from merging
hypertrophied adjacent cells
• Enlargement of plasmodesmata between
cells
• Dissolution of cell wall
177. • Nematodes draw nutrients from syncytia
• Host in response replaces cell nutrients
• Due to prolong feeding syncytia increases
in size
• Hyperplasia occur in surrounding tissue
• Cytoplasm become dense
178. •Loss of central vacuole with
replacement of several small
vacuoles
•Mitochondria, plastid, golgi
apparatus become abundant
•Syncytia may have one or more
nuclei
•Nucleus become multilobed
179. COMPARISONS
ROOT KNOT NEMATODE
i. Sedentary endoparasite
ii. J2 hatches from the egg
and migrate in search for
suitable host
iii. They always penetrate
the root just above the
root tip
iv. After entering they
migrate intercellularly
v. They induce several giant
cells embeded in a gall
CYST NEMATODE
i. Sedenatary endoparasite
ii. J2 hatches from the egg
and migrate in search for
suitable host
iii. They have the preference
for this part of root, they
are more flexible
iv. They migrate
intracellularly
v. Generate
syncytium, through
merger of up to 200 cells
180. ROOT KNOT NEMATODE
vi. Growing nematodes feed
from several giant cells
vii. For giant cell induction
they select 2 to 12
parenchymatic xylem cells
located in differentiation
zone of root.
CYST NEMATODE
vi. They feed from a single
syncytium
vii. They induce syncytia in
various tissues. E.g.-oat
cyst nematode (H. avenae)
and the beet cyst
nematode (H. schachtii)
usually select a pericycle
or procambium cell, cortex
cell is selected by the
potato cyst nematode
182. HOST PARASITE RELATION OF
MIGRATORY ENDOPARASITEs
» ROOT LESION NEMATODE: species
of genus Pratylenchus :
P. penetrans, P. vulnus, P. zeae, P.
coffeae, P. indicus, P. thornei etc.
» HOSTS:
coffee, citrus, banana, rice, tea, fruits,
wheat, grapes etc
183. Root lesion nematodes penetrate through cell walls causing
cavities to be formed by the collapse of cortical cells on which
they fed. Thus the effects on the plant are local lesions of necrotic
cells extending 1 mm in either direction. This necrotic reaction
probably results from the release of toxic substances by the
action of nematode enzymes on host substrates.
184.
185. FEEDING
•Ubiquitous in nature
•Nematode migration within the plant
both inter and intra cellularly
•Feeding is restricted to the cortex
•Sometimes enter the vascular tissue in
later stages of infection
189. HOST RESPONSE
• small, elongate, water soaked, then
brown to black lesions, on young feeder
roots
• lesions enlarge, coalesce and girdle the
root
• roots branching, elongation and volume
are reduced
• Root Browsing is associated with the
oxidation of phenols
190. ABOVE GROUND SYMPTOMS
• symptoms resemble those
malnutrition, water and nutrient
deficiency.
• symptoms noticed in patches of stunted
growth with yellow leaves
• Mature leaves turn yellowish and
brown, and drop off in summer
191. SOME SPECIFIC SYMPOTOMS
• Pratylenchus coffeae :brown irregular dry
rot, 1-2 cm or even 5cm deep, deep
cracks, corky appearance, exposed dark
brown rotted areas
• roots turning yellow, then brown, rotten
lateral roots, stunting, chlorosis of young
leaves, loss of young shoots, gradual wilt
and premature death
•Pratylenchus penetrans :Symptoms include
chlorosis and twig die-back
193. • Pratylenchus thornei :Roots are infested
but without any browning or lesion.
Stunting, chlorosis and necrosis of leaves.
Pratylenchus thornei damage in the root cortex of
tomato
195. HOST PARASITE RELATION OF
• BURROWING NEMATODE: Radopholus spp
• HOSTS: banana, black
pepper, coconut, ginger, turmeric etc
PENETRATION AND FEEDING
• They may spend its entire life in host roots
• infests only the healthy, succulent feeder root
tips.
• penetration through epidermis they occupy an
intercellular position in the cortical parenchyma
197. • feeding and destroying the cytoplasm of
the neighbouring cells
• cell wall breakdown, and as a result,
cavities are developed along the entire
length of the root
• cavities enlarge, coalesce and are formed
into lateral tunnels running up to
endodermis
• The stele is not invaded
198. • reddish brown lesions are formed
throughout the cortex
• decay and death of distal roots
• extensive cavities are formed in the cortex
by destroying the parenchymatous cells
three to four weeks after penetration
199. SYMPTOMS
• On banana- Causes ‘toppling over’ of
banana. ‘banana decline’ disease
• On coconut- decline, stunting, yellowing,
reduction in leaf size, delay in flowering,
reduced yield
• On black pepper- entire foliage become
yellow, leaf and spike shedding, cessation
of growth and die back
205. Adult female of reniform nematode is an
obligate, sedentary semi-endoparasite.
Young female infective stage
Common name ‘reniform’ is derived from
the kidney-shaped mature female.
Development from J2 to pre adult occurs
without feeding.
206.
207. HOST PARASITE RELATION
• Young females initiate infection by destroying
epidermal cells
• migrates intracellularly to the stele
FEEDING:
The nematode is mainly a phloem feeder in
good host
Phloem cells near head are extensively damaged
and enlarged in young root
Confined to pericycle cells on medium and poor
host
209. HOST RESPONSE
• Hyperplasia, hypertrophy and cell wall
thickening
• Dense granulation of cytoplasm
• Enlargement of nucleus
• Formation of syncytia
• Syncytia are formed in pericycle zone
• Inhibit formation of lateral cortical
parenchyma
210. • Hypertrophied cells form ring around
vessels
• In sweet potato syncytia comprise 7-10
cells
• In soybean 100-200 modified cells formed
a cocave, diamond shaped region,
centering initial feeding cell.
211. The citrus nematode penetrates deeply into the root cortex where
its head becomes surrounded by a 'feeding site', consisting of 6-10
altered cortex cells called 'nurse cells'. These cells have dense
cytoplasm and enlarged nuclei and nucleolus (64-125 times normal
volume) but the cells are not multinucleate. Older nurse cells
develop abnormally thick walls but are of normal size, and
immediately adjacent cells show no morphological changes.
Eventually these nurse cells disintegrate into a mass of necrotic
tissue. Thus the external symptoms of citrus nematode infection
of the roots is the presence of extensive necrotic regions where the
nematodes penetrate and feed, but no abnormal root swelling.
The branch roots do have a rough, irregular, somewhat
shortened appearance.
212. The stubby root nematode rasps the epidermis and hypodermis with its
stylet and causes superficial but characteristic browning of tissues. This
rasping causes a shallow puncture through the cell wall. The nematode
removes only part of the cytoplasm and does not kill the cell, but this
damage is sufficient to cause the root to lose its meristematic activity.
Hence the roots have a 'stubby' appearance
Other ectoparasitic nematodes, e.g., the dagger nematodes, cause
hyperplasia and hypertrophy of plant roots resulting in swollen root tips
due to retarded meristematic activity, hyperplasia of cortical
parenchyma, and maturation of the root tip region, which could include
lateral root formation. The root often becomes non-functional, or grows at
a reduced rate.
HOST PARASITE RELATION OF ECTO PARASITIC NEMATODE
213. The stem nematode on lucerne, clover, and narcissi causes a
massive host cell response at great distances from itself. The
infected plants are dwarfed and mis-shapened. The cells of
infected tissues separate due to the nematode secreting an
enzyme which dissolves the middle lamellae of cell walls, and
undergo marked hypertrophy. Cavities appear in the cortex and
the epidermal cells enlarge. This marked host cell response
can be caused by only a few nematodes.
The nematode has a adhesive Polysaccharide feeding tube
which becomes firmly attached to root, and nematode has to
writhe and twist to detach. Nematodes may appear as a fringe
around root tip. Nurse cells increase in volume, and walls
thicken; some cells are multinucleate. Cells collapse when
depleted and are pushed to the surface by meristem activity, thus
providing a continuous supply of new food cells for the
nematode. Root-tip galls are formed by increase in cell divisions
(hyperplasia), giving rise to enlarged cortex.
214. HOST PARASITE RELATION OF
ECTO PARASITIC NEMATODE
CHRYSANTHEMUM FOLIAR NEMATODE
: (Aphelenchoides spp)
• penetrate through the stomata
• Occupy intercellular spaces
• Mesophyll cells break down
• Large cavity forms
216. The seed and stem gall nematodes stimulate gall formation in
leaves and flowering parts of grasses. These galls develop by
hypertrophy and hyperplasia of parenchyma tissue and usually
have a central cavity containing the nematodes. There are no
specialised 'nurse cells' or cell types. But one species stimulates
the production of a well differentiated structure resembling a
cynipid gall with an inner lining of nutritive cells surrounded by a
zone of sclerenchymatous tissue, with strongly thickened cell
walls. It is remarkable that such an elaborate gall can arise as
a result of the presence of a single parasitic nematode.
