Root Cortical Cell Spherical Bodies Associated with an Induced Resistance Reaction in Monoxenic Cultures of Meloidogyne incognita


  • D. Orion
  • W. P. Wergin
  • D. J. Chitwood


The root-knot nematode Meloidogyne incog'nita was monoxenically cultured on excised roots of soybean cv. Pickett and tomato cv. Rutgers in agar media containing either 0 to 1,600 [mu]g/ml ammonium nitrate or 0 to 100 [mu]g/ml urea. Observations with scanning and transmission electron microscopy indicated that an elevated concentration of ammonium nitrate or urea inhibited giant cell formation and suppressed nematode development in the infected soybean roots. In the tomato roots, concentrations of ammonium nitrate above 400 [mu]g/ml or urea above 25 [mu]g/ml inhibited giant cell formation and nematode development. Coincident with the nitrogen concentrations that suppressed giant cell formation was the appearance of electron-dense spherical bodies in the cortical parenchyma cells of both the soybean and tomato roots. These bodies, which were 1-4 [mu]m in diameter, appeared to form in the cytoplasm and migrate to the cell vacuole. Key words: Cortical cell, Glycine max, Lycopersicon esculentum, Meloidogyne incognita, nematode, nitrogen, root gall, root-knot nematode, scanning electron microscopy, spherical body, transmission electron microscopy.