Natural abundances of N-15 and C-13 indicating physiological responses in Petunia hybrida to infection by longidorid nematodes and nepoviruses

The effects of a) systemic virus infection (arabis mosaic and tomato black ring nepoviruses), b) ectoparasitic nematode feeding (Xiphinema diversicaud atum and Longidorus elongatus) and c) a combination of virus infection acid nematode feeding on the natural abundances of C-13 (delta(13)C) and N-15 ( delta(15)N) of nitrogen-starved Petunia hybrida were studied. Pathogen-indu ced effects were not confined to sites of virus infection or nematode feedi ng. Those treatments with nematodes feeding on Petunia hosts and those with a combination of virus infection and nematode feeding resulted in a deplet ion of shoot and root N-15 compared with controls. Virus-infected plants we re more N-15-enriched than those fed upon by nematodes which, in turn, were more N-15-enriched than those with both nematode and virus in combination. Shoot delta(13)C values from infected treatments were not significantly di fferent from controls. Although root delta(13)C was significantly different from controls in most treatments, absolute differences were small. Differe nces in delta(15)N between infected and control plants were probably caused by physiological responses to pathogen infection/feeding such as productio n of PR-proteins and/or release of nitric oxide.