CELLULAR CHANGES INDUCED BY XIPHINEMA VULGARE IN THE ROOTS OF CITRUMELO AND BY XIPHINEMA INTERMEDIUM IN THE ROOTS OF BERMUDA GRASS
Feeding by Xiphinema vulgare on Swingle citrumelo and Xiphinema intermedium on Bermuda grass induced pronounced disturbances of attacked roots. Both nematodes removed cell contents through perforation and lysis of consecutive cell walls and formed syncytia-structures. The differentiation zone in citrumelo and the meristematic region in Bermuda grass reacted hypersensitively to nematode injury. Ultrastructural evicende revealed that the membranes of subcellular organelles, and the plasma membrane in particular, were the primary targets of elicitor molecules in cells inside and outside the feeding site. The nuclear membrane was the most resistant to damage, except in affected meristems of Bermuda grass. X. intermedium feeding on parenchyma cells of the differentiating region in Bermuda grass caused hypertrophy of nuclei which became highly amoeboid. These modifications are very similar to those induced by other Xiphinema species in their hosts. Multinucleate cells were not induced because of the lytic process involving all the root cells.