Ultrastructural Responses in Sugarbeet to Heterodera Schachtii

Abstract

Second stage juveniles of Heterodera schachtii Schmidt entered the roots of sugarbeet (Beta vulgaris L.) by penetrating meristematic cells of the root tip. The juvenile body was often found lying parallel to the root axis in tunnels formed within the cortex during nematode migration. Three days after entering the root, the lip region of the nematode was located beyond the endodermal cells, which were not completely differentiated. Nematode penetration caused mechanical damage to host tissues, evident as a necrotic ring, involving endodermal cells and three layers of the vascular tissue. The empty space around the juvenile permitted the movement of its lip region, allowing it to vary the site of stylet insertion in the feeding area of the vascular parenchyma, which as a result of the feeding was transformed into a syncytium. The occurrence of bundles of tubes at the site of stylet insertion, indicates that they may be produced repeatedly in the syncytial cells (Rumpenhorst, 1984).