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Heterodera Schmidt, 1871
Tylenchus (Heterodera) (Schmidt, 1871)
Heterodera (Heterodera) (Schmidt, 1871)
Heterobolbus (Railliet, 1896)
Bidera (Krall' and Krall', 1978)
Ephippiodera (Shagalina and Krall', 1978)
Refer to Subfamily Diagnostics (Heteroderinae)
for taxonomic history and distinctions among related genera.
Slide show on Globodera
and Heterodera spp.
Cyst of Heterodera glycines
Female body forms a cyst.
Females: anterior neck-like region; swollen body shape -
lemon, round, or pyroid shape (about 0.5-0.6 mm diam).
Weak cephalic framework.
Moderate stylet with small rounded knobs.
enlarged and fills neck region.
ovaries coiled or reflexed.
Vulva subterminal; anus terminal.
Posterior region important taxonomically:
Pre-parasitic stage: vermiform J2, 300-500 µm long.
Heavily sclerotized head framework; head offset.
Stylet prominent with anteriorly-directed knobs.
Ventro-lateral overlap of esophageal glands over intestine.
Genital primordia visible.
Post-parasitic stages: swollen.
Stylet weak, sometimes not visible in 3rd and 4th
Developing gonads visible.
Males: Vermiform, 1-1.5mm length.
Sclerotized cephalic framework, rounded head
Strong stylet; knobs project forward.
Esophagus tylenchid, overlaps ventro-laterally.
Reproductive system monorchic.
Tail bluntly rounded.
[Ref: H. Ferris.]
By 2009, more than 40 species of the genus
Heterodera had been molecularly characterized by sequencing the ITS-rRNA
genes and by PCR-RFLP profiles. These tools are so far the best
available for identifying cyst-forming nematodes.
By restricting the lTS amplicons with one or a
combination of seven restrietion enzymes (AIuI, Aval, Bsh 12361, BsuRI,
C/ol, MvaI, and Rsal), h most of the agriculturally important eyst
nematode species can be distinguished.
When it is not possible to use sequences of
ITS-rRNA genes and PCR-RFLPs in diagnostic work, morphometrie
eharaeteristies are still useful.
Intraspeeifie polymorphism in the lTS
sequences can make identification diffieult and more eonclusive
moleeular identification tools are needed.
(Ref: Waeyenberge et al., 2009)
On the basis of cyst morphology and
characteristics of the vulval cone, species of Heterodera are
placed into six groups: Avenae, Cyperi, Schachtii, Sacchari,
Goettingiana and Humuli.
Worldwide, usually with the definitive hosts of each species.
Juveniles enter root to region of developing vascular tissues by direct penetration of cells.
Juveniles may feed from individual cells as they cut through cell walls while
migrating to permanent feeding site region.
The permanent feeding site is a syncytium which is stimulated in a cortical or endodermal cell. The syncytium
becomes multinucleate after 24 hours as adjacent cells merge. Cell wall
dissolution is through a combination of physical stress (nematode head movement)
and chemical action.
Syncytia associated with developing males are usually smaller than those
associated with females.
Large sectors of the developing root, including areas that would have become
vascular tissue are transfomed into syncytia. Syncytia have many plastids,
mitochondria, ribosomes, increased rough endoplasmic reticulum and enlarged
Cell wall protruberances increase the surface area of the cell membrane for
flow of solutes from the xylem to the syncytium - the transfer cell
configuration (Endo, 1975).
More than 50 genes are upregulated to some extent in the
development of giant cells (Meloidogyne) and syncytia (Heterodera/Globodera) (Gheysen and Fenoll, 2002). Both types
of feeding cells have the genome amplified as a result of multiple shortened
cell cycles; but the processes differ. Giant-cells go through repeated (acytokinetic)
mitosis. Syncytia undergo repeated S-phase endoreduplication
without mitosis or nuclear division.
root-knot nematode (Meloidogyne) feeding site there is repeated nuclear
division (S and M phases of the cell cycle) but no cell division; this is called acytokinetic mitosis or
karyokinesis without cytokinesis.
the cyst nematode (Heterodera, Globodera) feeding site, the S phase of the cell cycle is
activated but not the M phase.
the cells repeatedly go through the S-phase (endoreduplication) and
probably through parts of the G1 and G2 phases, but bypass
Mundo and Baldwin
showed that, in the Heteroderinae, syncytium formation and number varies
with nematode species and genus in the same plant.
Since nematodes in the Heteroderidae become sedentary from the late second
stage onwards (except for the metamorphosis to males), the feeding site in the
plant must be maintained in a condition favorable for perhaps five or six weeks
to allow the nematode to fulfill its reproductive potential. Besides
stimulation of the cell cycle events,
(PTI) responses must be suppressed. The Hg30C02
effector protein of
glycines which may be involved in active
suppression of host defenses. The same gene occurs in H. schachtii (Smant and Jones, 2011; Hamamouch et al., 2012).
Several forms of delayed hatch and diapause exhibited.
1. Host-mediated hatch in response to host root exudates. Vary in
degree of response to hatching factors:
a) Very sensitive - hatch in
water only 5% of that in host root
G. rostochiensis, H. carotae, H. cruciferae, H. humuli
b) Intermediate - hatch in
water 10-50% of that in diffusate.
H. schachtii, H. trifolii, H. galeopsidis.
c) Insensitive - apparently not
stimulated by diffusate.
H. goettingiana, H. avenae, H. glycines. H. avenae
period to break diapause.
Artificial hatching agents include Aminoacridine (Rivanol) and ZnCl for H. schachtii.
Ecological factors also influence hatch: temperature, moisture, aeration,
osmotic potential, pH, etc.
J2 enters near root tip and takes position in cortex with head near vascular
cylinder. Moves intra- and intercellularly towards vascular
During development, female breaks through cortex to surface so that most of
the body of adult female remains outside root.
Sugarbeet cyst nematode molts at 6, 12, and 15 days after entering root;
matures in 19 days at 25 C.
Males are needed for reproduction in most species.
Eggs are retained in cysts, but some are deposited in egg masses in many
species. Distended uterus enlarges to fill body; eggs are packed in mucoid
Cysts undergo a color change as they mature - from white to brown - due
to action of polyphenol oxidase on polyphenols in the cyst wall. The wall
remains permeable to chemicals and dissolved oxygen.
Cyst drops-off of root when dead; mucoid packing disappears.
H. schachtii - about 2 generations per year in Europe.
about 3 generations per year in northern California.
about 5 generations per year in the Imperial Valley.
H. glycines - about 5 generations per year in North Carolina.
Little mechanical injury due to the parasitism, body of female on outside of
the root and no cell division stimulated.
Branch rootlets may be stimulated near the point of infection.
General debilitation and reduction in efficiency of the root system.
Chlorosis, stunted growth, wilted plants.
Management strategies vary with species and biology.
Management of this genus is usually difficult due to prolonged
viability. Possibilities include prevention, crop rotation, soil fumigation,
use of resistant
varieties, and use of clean seed sources.
Endo, B. 1976. In Vistas on Nematology
Gheyson, G. and C. Fenoll. 2002. Gene expression in nematode feeding
sites. Ann. Rev. Phytopathol. 40: 191-219.
Mundo-Ocampo, M., Troccoli, A., Subbotin, S.A., Cid, J.D., Baldwin, J.G.,
Inserra, R.N. 2008. Synonymy of Afenestrata with Heterodera supported by
phylogenetics with molecular and morphological characterisation of H. koreana
comb. n. and H. orientalis comb. n. (Tylenchida: Heteroderidae). Nematology
Waeyenberge, L., Viane, N., Subbotin,
S.A., Moens, M. 2009, Molecular identification of Heterodera spp., an
overview of fifteen years of research. Pp 109-114 in Riely,
I.T., Nicol, J.M., Dababat, A.A. First
Workshop of the International Cereal Cyst Nematode InitiativeCereal cyst
nematodes: status, research and outlook. CIMMYT.