Sedentary endoparasites

DISEASES OF ROOTS
SEDENTARY ENDOPARASITES
CLASS CHROMADOREA
Order Rhabditida
Suborder Tylenchina
Infraorder Tylenchomorpha
Family Meloidogynidae
Meloidogyne = Root-knot Nematodes
Most important nematodes in world agriculture

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Agrios

Stained Adult Female Meloidogyne
K.J. Merrifield

Meloidogyne spp.
Root-knot Nematode
Sedentary Endoparasite

Meloidogyne spp. = Root-knot Nematode
Eggs overwinter in the soil and in decaying root tissues.
The nematode molts from J1 to J2 within the egg.
Egg hatch does not require presence of root exudates.
K.J. Merrifield

Meloidogyne spp. = Root-knot Nematode J2
J2 hatches from egg = J2 and males are only stages in soil
and are recovered from soil samples
J.D. Eisenback
Nemaix 1

Meloidogyne spp. = Root-knot Nematode
J2 = only infective stage
Penetrate at root tip or in the region of elongation
Migrate through cortex and select feeding site
R.S. Hussey

Meloidogyne spp. = Root-knot Nematode
J2 begin feeding and become sedentary,
grow in thickness, becoming "sausage-shaped" and molt
to become J3. Develop further and molt to J4.
J2 J3 J4
E.C. Bernard

Meloidogyne spp. = Root-knot Nematode
The root's physiology is changed by the nematode and
"giant cells" form around the head
to nourish the nematode
N.T. Powell

Meloidogyne spp. = Root-knot Nematode
Female J4 molt and grow to a "pear-shaped" adult
with the posterior just beneath the root surface.
The root forms a gall around the female.
R.S. Hussey

Meloidogyne spp. = Root-knot Nematode
Males become "worm-shaped" again, developing within
the J4 cuticle like within an egg. The male emerges from
the J4 cuticle and leaves the root to search for a female.
Males are usually rare and have not been reported
for some species.
R.S. Hussey

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

Meloidogyne spp. = Root-knot Nematode
The gall may rupture as the female enlarges allowing the
male access to the female and allowing the female to lay
eggs into the soil. The female does not need to be
fertilized by the male to lay eggs.
R.S. Hussey

Meloidogyne spp. = Root-knot Nematode
Over 300 eggs are laid into a gelatinous matrix (egg sac)
which may be inside or outside the root tissues depending
on the position of the female. Eggs may hatch immediately
or remain until the following spring.
A typical life cycle
takes 3-4 weeks at
25-30 C.

Meloidogyne spp. = Root-knot Nematode
106+ species
99?% of all root-knot nematodes are:
Meloidogyne incognita 46%
Meloidogyne javanica 44%
Meloidogyne arenaria 7%
Meloidogyne hapla 6%

Meloidogyne incognita
Perineal Pattern
Used to determine species
H. H.Triantaphyllou

Multiple side roots may develop = "hairy root".
Meloidogyne spp. = Root-knot Nematode
Symptoms
Nematodes stimulate gall formation.
Galls with one nematode are about twice the
normal root diameter, multiple infections in same
location can create galls 1-2 cm in diameter.
M.A. McClure
Nemapix 1

Multiple side roots may develop = "hairy root“.
Lettuce Seeding Infected
with Meloidogyne hapla
Gall with lateral
branch roots
H.J. Jensen

Symptoms of Root
Knot Nematode
ize and shape of galls vary considerably between
pecies or races of nematodes and host species or
ultivar.

In light infections, roots may continue to grow past the
infection. However, in heavy infections, a mass of short,
swollen "clubbed" roots may develop.
H.R. Garriss

Roots often are heavier
than normal and become
nutrient "sinks"
diverting nutrients from
plant tops.
Symptoms of Root
Knot Nematode
on tomato
Rates of photosynthesis
are decreased .

Vascular damage disturbs water & nutrient uptake
so infected plants are stunted, wilt easily and often
have signs of nutrient deficiency, potassium.
R.A. Motsinger

In old infections, roots may decay and plants are
more susceptible to attack by other pathogens.
A. Mani
Nemapix 2

Forking of Tap Root and
Hairy Root Caused
by Melodogyne hapla
H.J. Jensen

Columbia Northern
Uninfected Root-knot Root-knot Uninfected
External Symptoms of Root-knot Nematode

Root-knot Infection sites in Potato

M.A. McClure

Root-knot Infection Site in Potato Tuber
G. Santo
Body of Female
Discoloration From Egg
Mass And Tissue Reaction

Discoloration is increased when
root-knot infected potato tissue is fried

Meloidogyne spp. = Root-knot Nematode
Control
Crop rotation is effective but not always practical.
Resistant cultivars exist for some crops but are
species or even race specific. Examples: lima beans,
peaches, soybeans, tobacco and tomatoes.
Fumigant and nonfumigant chemical nematicides are
frequently used on high cash value crops.
Trap crops, flooding, fallowing, solarization, green
manures, and heat treatment of bulbs are also used
in special instances.

DISEASES OF ROOTS
SEDENTARY ENDOPARASITES
CLASS CHROMADOREA
Order Rhabditida
Suborder Tylenchina
Infraorder Tylenchomorpha
Family Hoplolaimidae
Heterodera = Cyst Nematodes, 67+ species
Globodera = Cyst Nematodes, 12? species
Both genera have species that can be devastating
Life cycles of both genera are similar

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Agrios

T.O. Powers

Photo from Tom Powers

Disease cycle of the cyst nematode Heterodera glycines
Agrios

Some Cyst Nematodes
Require a “Hatching Factor”
From the Host Plant
Globodera rostochiensis
Eggs and J2s
U. Zunke
Nemapix 1

Heterodera glycines (Soybean Cyst Nematode)
J2 Infecting Soybean Root
J.D. Eisenback
Nemapix 1

Juveniles become sedentary while feeding, swell
and go through molts to become adults
J.D. Eisenback
Nemapix 1

Production of extensive syncytia is induced by the
nematode to support feeding.
B. Endo
Nemapix 2

Adult females enlarge and since root tissue does not expand
around them, they break through the root surface.
Some eggs are laid outside the body in an egg mass.
Caubel
Nemapix 2

Most eggs are retained within the body
E.C. McGawley
Nemapix 1

Mature “lemon-shaped” females of Heterodera die and
become dislodged from the root where they may remain
for many years.
J.D. Eisenback
Nemapix 1

Globodera are similar to Heterodera
but are round in shape.
Mature Female
Potato Cyst
Nematode
Theirry Vrain

Color Changes During Cyst Maturation
Globodera
J.A. Fox

Structure of the vulval cone is used to determine species
of Heterodera
Side View
End View
J.D. Eisenback
Nemapix 1

Cyst Nematodes - Symptoms
Side roots may be initiated and an infected root may
have a "bewiskered" appearance often called "hairy
root".
Yields may be dramatically reduced.
Plants are often severely stunted and may even die if
water stressed.
Plants wilt more easily than normal, uninfected plants.
Disease complexes can occur with other plant pathogens.

Heterodera schachtii on Red Beet
Note White Cysts and Hairy Root
Cysts are a “sign”, not a symptom
Closeup of roots
K.R. Barker

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

Potato Cyst Nematodes Reduce Plant Growth
Yield Loss Can Be as High as 80%
Bonsak Hammeraas

Heterodera schachtii
on Cabbage
D.W. Dickson

Cyst Nematodes - Control
Fumigant and nonfumigant chemical nematicides.
Some resistant cultivars of certain crops are available
but are often race specific and if they are used too
often, can "select" for populations that are capable of
reproducing on them.

Plot of Soybean Cyst Resistant Soybeans Growing
in a Field Infested With Heterodera glycines

Cyst Nematodes - Control
Long rotations with nonhost crops. Some eggs have
remained viable in soil for 15 years, or more, in the
absence of a host crop.
Rotations and use of resistant cultivars are sometimes
regulated and enforced by governments.
Early planting i.e. sugarbeets can be planted early and
get a jump on nematode populations. Can have an
adequate root system developed that can tolerate
nematodes when it becomes warm enough for them to
become active.

Questions?
Globodera pallida
Slide From Tom Powers

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

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