Feeding Plug Formation in Soybean Roots Infected with the Soybean Cyst Nematode

Abstract

The ultrastructure of the early stage of syncytium development in soybean roots attacked by Heterodera glycines was examined to determine the interaction between the host syncytium and the nematode feeding apparatus. One day after inoculation, an electron-dense plug-like deposit was observed between the extended stylet of the nematode and the syncytial wall of the host. During the feeding process, the plug appeared to form a seal between the extended stylet and the cell wall. Four days after inoculation, the plug remained in the opening of the cell wall after the stylet was withdrawn during the normal molting process. The plug apparently has continuity with secretions that apparently flow from the amphidial canals, the openings of the inner labial receptors and the stylet vestibule. The plug consists of an electron-dense fibrillar mass that forms a structure that may be comprised of nematode secretions and cell wall deposits, both of which are limited by the plasmalemma of the syncytium.