Vulval cone is a specific characteristic of which nematode?

Vulval cone is a specific characteristic of Heterodera sp. Nematode.
Heterodera is a genus of nematodes in the family of Heteroderidae. Members of the genus are obligate parasites and different species attack different crops, often causing great economic damage.
The genus is unique among nematode genera because of the ability of the female to transform into a tough, brown, cyst that protects the eggs which have been formed within her body.
Based on cyst morphology and characteristics of the vulval cone, species of Heterodera are placed into six groups that are Avenae, Cyperi, Schachtii, Sacchari, Goettingiana and Humuli.