Histopathology of Soybean Roots Infected with Heliocotylenchus dihystera.

Soybean roots infected with Helicotylenchus dihystera in a greenhouse were stained with acid fuchsin in lactophenol or sectioned and stained with safranin and fast green. Adults and larvae were observed in semi-endoparasitic and endoparasitic feeding positions. Adults, larvae and eggs were observed within the root cortex posterior to the region of maturation. Small brown lesions, affecting the walls of six to ten cells, were observed in the immediate vicinity of the nematode. Endoparasitic nematodes were usually coiled within the walls of one or two cells. Cytoplasm of the infected cells appeared normal, and there was no indication of nuclear proliferation. Walls of the infected cells were thickened and llgnified, but there was no indication of swelling or giant cell formation. Uncoiled nematodes usually were aligned parallel to the vascular tissue, but were not consistently oriented with respect to the root apex. Nematodes moved through cell walls rather than between them; however, no persistent burrows were observed.