Heterodera zeae
Koshy, Swarup, and Sethi, 1971
Corn Cyst Nematode
Photo Gallery- Maryland specimens
SEM Photo Gallery- Maryland specimens
Photo Gallery- Pakistan specimens
Molecular Diagnostics 

H. zeae was initially described by Koshy et al. (1971). Subsequently Golden and Mulvey (1983) redescribed females, cysts and juvenile specimens from Maryland, USA and India, using scanning electron microscopy.  The general description given here embodies those reported by these authors who should be consulted for more detailed descriptions with measurements and comparisons.  Details of embryonic and post-embryonic stages of the life cycle with measurements of the larvae at different developmental stages were reported by Shahina and Maqbool (1989).

Adult females
Adult females are swollen, lemon-shaped and pearly-white in colour with a distinctly protruded vulva, a thin cuticle (7.9 um) thickest at the neck-body junction, with a zigzag external pattern anteriorly, but appearing wavy around the vulval cone with broken transverse lines interspersed with longitudinal lines.  The head has two annules, the second larger than the first.  The stylet is slender with fairly developed anteriorly flattened knobs.  It has a long neck and a large rounded median bulb, with well-developed valve plates.  The excretory pore is placed posterior to the head tip and is at the level of oesophageal gland lobe.  The oesophageal gland is in a single lobe and is variable in size and shape.  Two ovaries are present.  The mature females are filled with eggs in various stages of development.  The vulval cone is well developed with a fairly long vulval slit.  The anus is very small, indistinct and placed close to the vulva.  An egg sac is present which is generally small but is in some cases one third to one half of the body length.  Most of the eggs are retained in the body and only a few in the egg sac.

The cyst is lemon-shaped, with protruding neck and vulva.  It is light-brown in colour, thin walled and without a subcrystalline layer.  The cyst wall pattern on the body proper is in the form of a zig-zag pattern.  The vulval cone is prominent.  The end-on view of the vulval cone shows concentric lines of cuticular ridges around the vulval slit and fenestra.  Fenestrae are ambifenestrate with the two semifenestrae separated by a vulval bridge and surrounded by a wide 'basin'.  The anus is indistinct.  Bullae are present, the characteristic arrangement for H. zeae including four finger-like bullae in a distinct formation immediately below the underbridge.  The underbridge is simple, short and thin, and is found in all but a few of the cysts examined.  Immediately below the finger-like bullae are a number of randomized bullae.  The vulval slit is fairly long.

Second-stage juveniles
The second-stage juveniles are vermiform and cylindrical, tapering at both ends.  The head has 4-5 annules, with a moderately developed cephalic framework.  The stylet is slender with slightly anteriorly directed knobs.  According to Koshy et al. (1971) the length of stylet was about 20-25 um (23.0 + 0.26 um), whilst Golden and Mulvey (1983) reported that larval stylets from India and Maryland, USA, were continuously found to average about 20.0 um.  The dorsal oesophageal gland opens close (4-5 um) to the base of the stylet.  There is a distinct median valve with well developed valve plates. The basal part of the oesophagus extends as a glandular lobe overlapping the anterior region of the intestine, mostly laterally and dorsally.  The hemizonid is distinct, located closer to the excretory pore and is 1-2 annules in length.  The anus is distinct.  Phasmids are small but conspicuous.  The lateral field has four lines.  The tail is short, hyaline and terminal with an acutely rounded terminus.
Mulvey and Golden (1983) compared two isolates- their measurements are as follows:
H. zeae
Body length
Lateral lines
Stylet length
Tail length
Hyline terminal length
410 + 40
23.3 + 0.3
41.0 + 1.1
24.0 + 0.7
Maryland, USA
431 + 14
19.9 + 0.4
44.2 + 2.4
21.9 + 1.7
(16.8 - 25.2)
4.3 + 0.4

The egg shell is hyaline, without cuticular markings.  According to Koshy et al. (1971), the majority of eggs measure about 105 -110 um in length and 35-38 um in width. Measurements given by Golden and Mulvey (1983) include length 97-105 um (102.6 + 2.1 um) and width 37.8 - 47.2 um (43.3 + 2.6 um).

The males of H. zeae are very rare and detailed descriptions were made for the first time by Hutzell (1984) from a culture originating from cysts collected in Kent, Maryland, at the site of the first known infestation in the USA.
(Description- CABI Crop Protection Compendium CD-Rom 2000)