Heterodera schachtii Schmidt, 1871
Sugarbeet Cyst Nematode
Head small, neck
expanding rapidly, then cylindrical; excretory
`shoulder' where body swells to nearly spherical shape
terminating in vulval cone, with anus dorsally
sub-terminal. Head skeleton weak.
Stylet slender with small knobs.
Median esophageal bulb prominent, spherical.
glands overlapping intestine
Paired ovaries long and much coiled.
A few eggs are deposited in a gelatinous matrix, but most retained in
Cuticle basically three-layered, superficially covered
with a reticulum of ridges (for detailed structure see
Shepherd, Clark & Dart, 1972).
Cyst: When the female dies, the
cuticle becomes tanned, brown, tough and minutely rugose, forming a
protective envelope, the cyst, containing 500-600 eggs.
Cysts of H. schachtii can be distinguished from
those of other species of the genus by their shape and
the features of the vulval cone.
The terminal vulval slit
is about as long as the `vulval bridge' which is flanked
on either side by a kidney-shaped thin area of the cyst
wall that breaks down in older cysts leaving 2 apertures
or `semi-fenestrae' separated by the `vulval bridge.'
Within the cone are the remains of the vagina attached to
the side walls by the `under-bridge' and a number of
irregularly arranged, dark brown `bullae' situated a
short distance below the vulval bridge. These features
and the morphology of the second stage juveniles are
useful for identifying cysts extracted from soil (Cooper,
1956; Mulvey, 1960; Hesling, 1965).
The surface of mature females and newly-formed cysts
is encrusted with a white waxy material referred to as
the `sub-crystalline layer' which soon falls off the cyst
when it is loose in the soil. The layer has been
investigated in some species of the genus and is probably
formed from fatty acids produced by a fungus living
symbiotically on products excreted by the female nematode
when feeding (Brown et al., 1971).
Second-stage juveniles: Head offset,
hemispherical, with 4 annules; robust, hexaradiate
skeleton; small amphid
apertures in lateral sectors close
to mouth opening.
Body annules 1.4 µm wide in spear region and 1.7 µm
at midbody. Lateral
field with 4 incisures.
Stylet moderately heavy with prominent,
Esophagus as in male, but median
bulb more prominent;
dorsal gland duct opening 3-4 µm behind spear base.
Anus obscure, about 4 anal body-widths from terminus.
Tail acutely conical with rounded tip; a distinct hyaline
terminal section 1-1.25 times the stylet length.
Genital primordium with 2 nuclei, located slightly
behind mid-body. Phasmids obscure, just post-anal.
field with 4 longitudinal incisures,
Head offset, dome-shaped, with 3 or 4 annules (Allen,
1952) and hexaradiate skeleton with lateral sectors
slightly narrower than sub-laterals; small slit-like amphid
apertures in lateral sectors close to oral
opening. Anterior cephalids
at second, posterior at sixth
to eighth annule behind head constriction.
Stylet well developed with knobs concave anteriorly.
Esophagus cylindrical, expanding midway to a fusiform
bulb with valve;
isthmus encircled by nerve ring.
glands overlying intestine
ventro-laterally, the dorsal gland duct joining the
espohageal lumen about 2 µm behind spear base, the 2
sub-ventrals opening into median bulb lumen close behind
pore 2 to 3 body-widths behind median bulb; hemizonid
6 to 10 annules in from of pore.
Spicules curved, slightly knobbed
notched at tip; gubernaculum
Egg hatch: Heterodera schachtii
Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:
Distributed throughout Europe from Spain to Finland and Eire
to Bulgaria. Also recorded in Soviet Union, Turkey, Israel; in
U.S. in both eastern and western states; in Canada, Australia,
and South Africa.
pest in California Nematode Pest
Feeding site establishment and development
typical of the genus.
Chenopodiaceae, especially Beta vulgaris. Cruciferae,
all varieties of Brassica oleracea, including cabbage,
cauliflower, brussels sprouts, and cruciferous weeds.
A few eggs are deposited externally in a gelatinous matrix, but most
are retained in
the female body.
When the female dies, the
cuticle becomes a tanned, brown, tough protective envelope, the cyst, containing the
eggs. The cysts become detached from the host root and
remain in the soil, the contained eggs (often numbering
500 to 600) remaining viable for at least 6 years (Thorne, 1923).
In the cysts, the eggs become embryonated at the first stage
juveniles molt to the second, infective stage. These individuals
may remain dormant in the eggs for several years, but some hatch
every year and emerge from the cysts into the soil.
Optimum temperature for hatching is 25 C, and for subsequent
movement in the soil, 15 C. Optimum soil moisture is intermediate
between saturated and dry (Wallace, 1963).
Hatching is stimulated by exudates from roots of host and some
non-host plants, but also takes place to a lesser extent in the
absence of plants.
The J2 are attracted to plant roots, enter behind the root
tips and take up a feeding position close to the stele. If the
plant is a suitable host, it forms syncytia on which the nematode
feeds and develops to maturity.
The optimum temperature for growth and reproduction is 21-27
C, and development takes about 17 days. The fourth stage female
swells greatly, rupturing the root tissues, but remaining fixed
at the head; it molts and becomes flask-shaped and white, and at
this stage, the subcrystalline layer begins to form.
Males are attracted to the females (Green, 1966), fertilize
them, and the females then produce from the vulva the gelatinous
material into which some of their eggs are laid.
When feeding finishes, the females die, the cuticle becomes
tanned and protects the eggs inside from desiccation.
The eggs develop, and infective second-stage juveniles hatch 5
weeks after the roots were first invaded, and can start a second
generation if suitable host roots are available.
One to 2 generations can be produced per year in temperate
regions; up to 5 generations per year in Imperial Valley
(California) sugarbeet fields (heat-unit dependent - Thomason
Fife, 1962). [Ref: CIH Descriptions of Plant-parasitic Nematodes,
Set 1, No. 1 (1972) and H. Ferris]
Second-stage juvenile (J2) enters lateral roots which may
cease to grow or die and are replaced by others resulting in a
Plants wilt, top growth and yields are reduced, initially in
patches which spread with repeated crops.
Interactions occur - Rhizoctonia solani is more
pathogenic to sugarbeets in the presence of H. schachtii
due to rupture of root cortex providing ingress and syncytia
constituting favorable sites for infection.
Rotation: Six-year crop rotation in Europe -
some nematodes survive the first year of rotation, but population
decreases each year over the next 5 years. Legumes, especially
alfalfa, aid reduction in populations in rotations (Steele &
The University of California. has recommended that beets
be planted every 4 to 6 years, with no crucifers planted in the
Historically, fields were monitored by sugar companies (Holly
Sugar) in the Imperial Valley. In a non-infested field, beets may
not be grown for more than two years in succession.
Source: I.J. Thomason
(1,3-D) applied at rate of 20 gal/acre
[overall treatment at 10-12 gal/acre-row (U.C.) is effective].
Temik applied at 30 lb/acre has been used with success in
Host-Plant Resistance: There are sources of
resistance in Beta procumbens and B. patellaris,
but problems of genetic compatability and chromosome number.
However, resistant cultivars are under development at the USDA
Research Station in Salinas (Bob Lewellyn, Plant Breeder).
Resistant sugarbeets have been produced by transgenic methods in Europe (Wegelin,
Biological Control: A fungal
parasite of eggs and cysts, Dactylella oviparasitica, is an effective
agent if at high enough levels of the soil. The population levels decline
in more than one year of a non-host crop of H. schachtii. A
viable strategy may be to grow a crop relatively toleran to H. schachtii
in a sugarbeet rotation sequence (Ole Becker, Pers. Com.).
[Ref: CIH Descriptions of Plant-parasitic Nematodes,
Set 1, No. 1 (1972)]
Wegelin, Tanja. 2002. Bestimmung von Funktion und Wirkungsweise des Hs1pro-1
Nematodenresistenzgens aus Beta procumbens.
Schriftenreihe des Instituts fÃƒÆ’Ã‚Â¼r Pflanzenbau und PflanzenzÃƒÆ’Ã‚Â¼chtung, Christian-Albrechts-UniversitÃƒÆ’Ã‚Â¤t
zu Kiel,1435-2613 ;26