Heterodera avenae

Heterodera avenae Wollenweber, 1924.

Syn Heterodera schachtii var. avenae Wolienweber, 1924; H. schachtii subsp. maior 0. Schmidt, 1930; H. maior (0. Schmidt, 1930) Franklin, 1940. [Heterodera schachtii var. avenae Mortensen, Rostrup and Kolpin Ravn, 1908 = nomen nudum].

Measurements

Female:

L = 0.55-0.77 mm; breadth = 0.36-0.50 mm.

Male:

L = 1.07-1.59 (1.38) mm; a = 32-55 (45); b = 7-12 (9); b' = 5.5-6.8 (5.8); c =subterminal; T
40-50 (45); spear = 27-31 (28.5) mu; spicules = 33-38 (36) mu.

Second-stage larvae:

L = 0.52-0.61 mm (mostly within range 0.54-0.58 mm (mean 0.575 mm, after Franklin, 1951); breadth = 20-24 mu; tail length = 45-70 mu (usually 54-58 mu; spear = 24-28 mu (mean 27 mu, after Triffitt, 1929).

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Description

Female:

Adult lemon-shaped, with prominent neck and vulval cone. Lip region annulated, with 6 confluent lips and a labial disc. Spear straight to slightly arcuate, 26-32 mu long; basal knobs rounded. Median oesophageal bulbrounded, with a distinct valvular apparatus. Vulva a 12-13 mu longslit, may have gelatinous extrusion but eggs rarely if ever extruded. Zigzag, rugose cuticular surface pattern. Subcrystalline layer conspicuous, sloughing off as the dark brown cyst is formed. This layer now known to consist of cosanoic acids and their calcium salts (Brown et al., 1971). Vulval cone of cysts mainly occupied by hyaline vaginal structure. Bullae prominent, crowded beneath vulval cone. Ambifenestrate. Most cysts contain 200-250 eggs but large ones may contain more than 600 (Andersen, 1961). Average cyst-size 0.71 mm x 0.50mm (Triffitt, 1929). No yellow phase as the maturing cyst changes from white to dark brown (Franklin, 1951). Mean of 20 eggs from neotype locality (Aschersieben, Germany): 126 mu long, 56 mu wide.

Male:

Abundant, vermiform, length averaging 1.38 mm for 100 individuals (Franklin, 1951) but often much shorter - particularly those developing in H.avenae-resistant cereals. Body annules distinct, about 2 mu wide. Lateral fields with 4 incisures, outer bands usually areolated. Lipregion rounded, offset, with 4 to 6 (usually 5) annules; framework heavily sclerotized with conspicuously marked outer margins. Cephalids indistinct, anterior 1 to 2 and posterior 6 to 7 annules behind lip region. Anterior tapering part of spear sharply pointed, usually a little shorter than half the spear length; basal knobs of spear rounded, usually with flat, posteriorly sloping anterior surfaces. Orifice of dorsal oesophageal gland 3 to 6 mu behind spear base. Median oesophageal bulb oval with distinct vaivular apparatus. Oesophageal glands ventral and ventro-lateral to intestine; dorsal with larger nucleus located closely behind oesophago-intestinal junction, subventrals extending past the dorsal. Excretory pore near oesophago-intestinal junction. Hemizonid distinct, 2 to 3 annules long, usually 5 to 6 annules anterior to excretory pore but occasionally only one or 2 annules anterior. Hemizonion indistinct, 6 to 7 annules behind excretory pore. Spicules arcuate, with medium sized ventral flanges and notched end; together forming a narrow tube distally. Gubernaculum simple, slightly curved. Tail end usually twisted.

Second-stage larva:

Vermiform with a sharply pointed tail. Lip region rounded, offset, with 2-4 annules. Body annules distinct, averaging 1.5 mu wide near middle. Lateral fields about one-fourth as wide as body, with 4 incisures forming 3 bands; outer bands areolated. Spear well developed, with large, anteriorly flattened to concave basal knobs; its anterior tapering portion less than half its length. Median oesophageal bulb rounded, very muscular, with a large valvular apparatus. Oesophageal glands as described for the male, not filling the body cavity. Tail 3-4.5 times anal body width long; body contents extend 1-1.5 anal body width into tail cavity, hyaline portion 35-45 mu or about 1.5 spear lengths long. Lateral fields disappearing near middle of tail. Phasmids pore-like, distinct, just behind anal level. 1st- and 2nd-stage larvae folded 4 times within the egg.

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Type Host and Locality

Oats (Avena sativa), Aschersleben, East Germany (D.D.R.). No original type material designated. Neotype - cyst with eggs and larvae from Aschersleben, proposed by Franklin, Thorne & Oostenbrink (1959).

Systematic Position

Tylenchida: Tylenchoidea: Heteroderidae: Heteroderinae: Heterodera Schmidt, 1871. Top of Page

Illustrations

Fig.1. Heterodera avenae Wollenweber (from oats at Woburn, England)

A. Cysts
B. En face view of vulval cone of cyst.
C. Head ends of male
D. Head ends of male
E. Oesophageal region of male
F. Tail end of male
G. Entire male
H. Head end of 2nd-stage larvae
I-K. Tail ends of 2nd-stage larvae, an ceph = anterior cephalid, dn= dorsal oesophageal gland nucleus, gub = gubernaculum, hd = hemizonid, hn = hemizonion, mod = median oesophageal bulb, nr = nerve ring, ph = phasmid, p ceph = posterior cephalid, sp = spear, spic - spicules, svn = subventral oesophageal gland nuclei.