The hypersensitive response of Prunus domestica to the Plum pox virus (PPV) was investigated in a model system by in vitro grafting of virus free and virus infected plums with hypersensitive genotypes to confirm the results obtained ex vitro. Shoot-tips were grafted onto rootstocks with a V-cut at the scion. Successful graft union formation ranged from 80 to 90{%}. The defense mechanism was observed by macroscopic observations. Furthermore, the intergrowth of root and scion was microscopically observed with special respect to the occurrence of hypersensitive reactions in single cells. PPV infected scions grafted onto hypersensitive rootstocks showed a macroscopically visible hypersensitive reaction as necrotic lesions on the leaves, leading to the death of the scion. All hypersensitive genotypes showed an accumulation of phenol vacuoles in cells close-by the graft union. The cells died a short time after the formation of tissue bridges between the two grafting partners. In contrast, no abnormalities in the establishment of graft unions between virus infected plants with PPV sensitive genotypes could be observed. The macroscopically visible symptoms and the histological observations correspond with former results obtained in ex vitro graftings.     «

The hypersensitive response of Prunus domestica to the Plum pox virus (PPV) was investigated in a model system by in vitro grafting of virus free and virus infected plums with hypersensitive genotypes to confirm the results obtained ex vitro. Shoot-tips were grafted onto rootstocks with a V-cut at the scion. Successful graft union formation ranged from 80 to 90{%}. The defense mechanism was observed by macroscopic observations. Furthermore, the intergrowth of root and scion was microscopically o...     »