Life cycle strategies of plant-parasitic nematodes

LIFE CYCLE STRATEGIES OF NEMATODES
Plant Pathogens

LIFE CYCLE STRATEGIES OF NEMATODES
Root Pathogens
Ectoparasites = body remains outside of plant tissue
Endoparasites = whole nematode enters plant tissue
Migratory = move around throughout life
Sedentary = adult females feed in one location only

LIFE CYCLE STRATEGIES
Root Pathogens
Migratory Ectoparasites - feed outside of root, move
cell-to-cell but do not enter root.
Lance Nematodes
D.W. Dickson

LIFE CYCLE STRATEGIES OF NEMATODES
Root Pathogens
Needle Nematode
Migratory Ectoparasite
S. Edwards

LIFE CYCLE STRATEGIES
Root Pathogens
Migratory
Ectoparasites
= most common type of
plant parasite.
Includes all virus
vector nematodes.
Stylet
Head
Dagger Nematode
U. Wyss

LIFE CYCLE STRATEGIES
Root Pathogens
Sedentary Ectoparasites - head enters root but body
remains outside, no movement after this.
Reniform Nematode
R.B. Rebois

Citrus nematode
Tylenchulus semipenetrans
APS Slide Set #32

Tylenchulus semipenetrans = citrus nematode
Nematode molts
3 times to become
an adult
Posterior remains
in soil and female
swells with eggs
J2 penetrate
outer layers
of cortex

Tylenchulus
semipenetrans
Nurse Cells
APS Slide Set #33

LIFE CYCLE STRATEGIES
Root Pathogens
Migratory Endoparasites - tunnel inside root but
move back to soil and into new roots at will.
Root-lesion Nematodes
H. Jensen

Pratylenchus spp. – Root-lesion Nematode
All stages from J2 to
adult remain vermiform
and move in and out of
roots
J.D. Eisenback

Pratylenchus spp. – Root-lesion Nematode
Root-lesion nematode in cortical cell

Pratylenchus spp. – Root-lesion Nematode
Males are common in some species
while other species have few to no males

Pratylenchus spp. – Root-lesion Nematode
Eggs are usually laid in
root tissues but may be
deposited in soil as well

Root-lesion nematodes in roots
(migratory endoparasites with 6-9 week reproductive cycle)
juvenile
eggs

LIFE CYCLE STRATEGIES
Root pathogens
Sedentary Endoparasites - tunnel into root and establish
feeding site, females do not move but may rupture root as
they enlarge.
Root-knot nematode - gall forms
around nematode, eggs laid outside
Cyst nematode - no gall, nematode pops
out of root, eggs retained in body

Root-knot Nematode Eggs
First Molt Occurs in Egg
K. Merrifield

Meloidogyne second-stage juvenile (J2)
Hatches from egg = migratory stage in soil
Only infective stage.
G. Santo

Meloidogyne J2
J.D. Eisenback

Meloidogyne incognita J2
Infecting Cotton Root Tip
R.S. Hussey

Meloidogyne Juvenile Stages
All inside root
J2 J3 J4
E.C. Bernard

Meloidogyne incognita
Feeding on Giant Cells
N.T. Powell

Root Forms Gall Around Female
Eggs Are Laid in Egg Mass
R.S. Hussey

Meloidogyne incognita Adult Male
Coiled Inside 4 th Stage Juvenile Cuticle
Adult
Head
J4 Head
R.S. Hussey

Male Root-knot Nematode
Migratory stage in soil
G.S. Abawai

Stained Adult Female Meloidogyne
K. Merrifield

Eggs of Cyst Nematode May Stay
Protected Inside Cyst for Years
Ulrich Zunke

Some Cyst Nematodes
Require a “Hatching Factor”
From the Host Plant
Globodera rostochiensis
Eggs and J2s
U. Zunke

Heterodera glycines (Soybean Cyst Nematode)
J2 Infecting Soybean Root
J.D. Eisenback

J2 Infect Roots and Nematode
Develops Similar to Meloidogyne
D. Inglis

Females enlarge and emerge from root
while head stays buried in root and feeds
Mature Female
Potato Cyst
Nematode
Theirry Vrain

Roots Do Not Form
Galls Around
Cyst Nematodes
R.S. Hussey

Heterodera glycines on Soybean Roots
R.A. Motsinger

Golden Potato Cyst - Globodera rostochiensis
Pale Potato Cyst - Globodera pallida
Potato Cyst Nematodes Feeding on Root
Ulrich Zunke

Color Changes During Cyst Maturation
Globodera
J.A. Fox

Brown Cysts of Globodera
Opened to Expose Eggs and J2
J.A. Fox

LIFE STRATEGIES OF FOLIAR NEMATODES
Nematodes crawl up plant in film of water and/or
migrate inside plant to reach destination
Feeding strategies vary at different points of their life cycles:
Migratory ecto migratory endo sedentary endo
Examples:
- stem and bulb nematode
- foliar nematode
- seed gall nematode

WORLD’S MOST IMPORTANT
PLANT-PATHOGENIC NEMATODES
Weighted
Importance
Common Name Genus Life Cycle Strategy Ranking
Root-knot Meloidogyne Sedentary Endoparasite 1375
Root-lesion Pratylenchus Migratory Endoparasite 782
Cyst Heterodera Sedentary Endoparasite 606
Stem & Bulb Ditylenchus Diverse Strategies 251
Potato Cyst Globodera Sedentary Endoparasite 244
Citrus Tylenchulus Sedentary Ectoparasite 233
Dagger Xiphinema Migratory Ectoparasite 205
Burrowing Radopholus Migratory Endoparasite 170
Reniform Rotylenchulus Sedentary Ectoparasite 142
Spiral Helicotylenchus Migratory Ectoparasite 122

ROOT PARASITES
Migratory Ectoparasites - feed on outside of root, move from cell to cell but do
not enter the root. Example = dagger nematode
Sedentary Ectoparasites - head enters root but body remains outside, nematode
does not move after this. Example = citrus nematode ( also referred to as
semiendoparasites or ecto-endoparasites
Migratory Endoparasites - feed inside root, tunnel inside root and move back
into soil and to new root at will. Example = root-lesion nematode
Sedentary Endoparasites - tunnel inside root and establish feeding site, females
do not move and may rupture outside of root as they grow, adult males move back
into soil. Example = root-knot and cyst nematodes
ABOVEGROUND PARASITES
Nematodes that are parasites of stems, leaves or seeds may crawl up the plant in a
film of water on stems and leaves or migrate through tissues to reach their
destination. Some species may utilize several of the strategies above at different
points in their life cycle. Examples = stem and bulb nematode, foliar nematode,
seed gall nematode.

ROOT-LESION NEMATODE LIFE CYCLE
Pratylenchus spp.

Root-lesion Nematode