Root Cortical Cell Spherical Bodies Associated with an Induced Resistance Reaction in Monoxenic Cultures of Meloidogyne incognita.
The root-knot nematode Meloidogyne incognita was monoxenically cultured on excised roots of soybean cv. Pickett and tomato cv. Rutgers in agar media containing either 0 to 1,600 mug/ml ammonium nitrate or 0 to 100 mug/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 mug/ml or urea above 25 mug/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 mum in diameter, appeared to form in the cytoplasm and migrate to the cell vacuole.
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