Ultrastructural response of potato roots resistant to cyst nematode Globodera rostochiensis pathotype Ro1

Histological and ultrastructural changes in the potato cvs Diamant, Anosta and Morag, three days after inoculation with second stage juveniles of Globodera rostochiensis pathotype Rol, were identical. The cells involved in nematode feeding were already transformed into a highly metabolic syncytium. Protein storage in form of crystalline bodies were detected in the plastids contained in the syncytial cells. It is assumed that these crystalline bodies are formed as a consequence of an osmotic imbalance in the cells caused by the nematode invasion of resistant roots. The hypersensitive host reaction was evident seven days after nematode inoculation and was characterized by an extensive necrosis lining the syncytium. Syncytial cells showed an involution of the cytoplasmic content while the nucleus and nucleolus were severely affected, indicating inactivation of the transcription mechanism. The mechanism of resistance to the Rol pathotype in the three potato cultivars was determined to be antibiosis, expressed as resistance to the survival and reproduction of the nematode.