2. Nematodes (from Greek nema
which means ‘thread’ and Latin
oid which means ‘like’) are
ubiquitous, thread like worm,
bilaterally symmetrical,
vermiform, unsegmented,
pseudocoelomate
animal.
6. Spend thier entire life cycle in soil, all life cycle stages,
including eggs in soil.
Only stylet is inserted into roots, body remains outside.
A vast majority of ectoparasites feed on root hairs and
epidermal cells.
Migratory ectoparasites
Feed outside of root, move cell-to-cell but do not enter
inside the root.
Remain vermiform, eggs are scattered in soil.
Examples:
Sting nematode - Belonolaimus
Dagger nematode - Xiphinema
Needle nematode - Longidorus
Stubby root nematode –Trichodorus,
Paratrichodorus
7.
8. Feed at a particular site for long time.
Very sluggish in movement.
May secrete an adhesive plug to fix their stylet at a particular
feeding point.
Examples:
Sheath nematode - Hemicycliophora arenaria
Sessile nematode - Cacopaurus pestis
9.
10. The anterior portion of the body of nematode is inserted inside
the plant tissue and the posterior part extents free into the soil.
Migratory semi-endoparasites
Remain vermiform
Do not establish a permanent feeding site in plant tissues and
move from one site to another frequently.
Eggs are not deposited in masses.
Examples:
Spiral nematode - Helicotylenchus
Lance nematode - Hoplolaimus
Stunt or Stylet nematode - Tylenchorhynchus
11.
12. Establish a permanent feeding site inside plant tissues.
Do not move after infection.
Eggs are deposited in masses around the female body
on root surface.
The posterior portion of the female body outside the roots
becomes swollen to varying degrees.
Examples:
Citrus nematode – Tylenchulus semipenetrans
Reniform nematode - Rotylenchulus reniformis
13.
14. The entire nematode is found inside the plant tissue.
Complete their entire life cycle inside plant tissues.
Migratory endoparasites:
These nematodes move in the cortical parenchyma of host
root.
While migrating they feed on cells, multiply and cause
necrotic lesions.
Eggs are scattered within the cortex.
Remain vermiform
Examples:
Lesion nematode - Pratylenchus
Rice root nematode - Hirschmanniella
Burrowing nematode – Radopholus similis
15.
16. These nematodes establish a permanent feeding site
inside plant tissues.
Do not move after infection
Eggs are deposited in masses around the body of
females on root surface
Examples:
• Root-knot nematode – Meloidogyne spp.
• Cyst nematode – Heterodera,
Globodera
17.
18. A. Above ground symptoms
B. Underground symptoms
A-Above ground symptoms
Discolouration of foliage:
• G. rostochiensis infested potato
plants show light green foliage.
19. Dead or devitalized buds:
• Aphelenchoides besseyi on
strawberry cause killing and dropping
off of flower buds
Crinkled or distorted stem and foliage:
• The wheat seed gall nematode,
Anguina tritici infests the growing
point of wheat seedling as a result
distortions in stem and leaves take
place.
20. Seed galls:
• Anguina tritici producing seed galls
in wheat.
Leaf spots:
• Aphelenchoides fragariae
forms angular spots on the leaf
of strawberry.
21. Root galls:
• Galling of roots is the most characteristic
symptom of attack of root knot nematodes,
Meloidogyne spp.
Root lesion:
• Hirschemanniella cause brown lesion on
rice root.
22. Reduced root system:
Nematode feeding on the root tips may kill the growing point
and stop the further elongation of root.
• Belonolaimus longicaudatus infecting
maize resulting in coarse roots.
• Xiphinema cause curling of roots
known as “Fish hook” symptom.
.
23. Excessive root branching:
• Meloidogyne hapla on tomato.
Root rot:
• Ditylenchus destructor cause
root rot in potato.
Editor's Notes
Motile (sinusoidal wave-like movement resulting from contractions in the longitudinal muscles)
Invertebrate (without a backbone)
Migratory ectoparasites: Feed at a particular site for a brief time and then move to the next site.
Such ectoparasites have a stout and long stylet relative to their small body size.
Juvenile,occur in soil and cause infection. After penetrating the root, they establish a permanent feeding site which usually involves the vascular tissue,lose the power of locomotion and become sessile. The body of adult female is enlarged manifold and becomes sac like, lemon shaped etc.
Symptoms caused by plant parasitic nematode can be divide into two categories:
Discolouration of foliage: Patchy yellow appearance in coffee due to Pratylenchus coffeae.
Dead or devitalized buds: The nematodes affect the terminal bud or the growing point and kill the plants and result in a blind plant.
Leaf spots: Foliar nematodes enter through stomatal openings and feed on the mesophyll tissue of leaves. Initially, the damage appears as a brown spot on the leaf surface, which gradually enlarges as the nematode infestation spreads, ultimately forming the angular spots.
Seed galls: some nematode of Anguina produce seed galls in cereals. At the time of floral initiation, the juveniles enter inside the floral primordia,develop into adult,deposit eggs inside and die. Such tissue form seed galls containg thousands of nematode juveniles.
Root lesion: The penetration and movement of nematodes in the root causes typical root lesions. The rice root nematode,Hirschemaniella also cause brown lesions on rice root. 2- Necrotic lesions induced by Radopholus similes in banana.
Root galls: Many other nematodes such as Xiphinema and Globodera rostochiensis also cause swelling on underground parts of their hosts.
Coarse root: Paratrichodorus spp. arrest the growth of lateral root & lead to a open root system with only main roots.
Stubby roots: Corn roots with "stubby-root" symptoms caused by Paratrichodorus minor.
Xiphinema retard the elongation of root & cause curling of roots k/a “Fish hook” symptom.
Excessive root branching: nematode infection may sometimes stimulate the plant to produce rootlets near the sites of penetrating resulting in excessive root branching.
Root rot: The nematodes feeds on the fleshly underground tissue and resulting in rotting of tissues(decaying of fleshly underground tissue )