Accumulation of potato virus Y is enhanced in Solatium brevidens also infected with tobacco mosaic virus or potato spindle tuber viroid

The accumulation of potato virus Y?(PVY?) and potato leaf roll virus (PLRV) was studied in plants of Solanum brevidens co-infected with each of six viruses or a viroid. Virus could not be detected by ELISA in plants of S. brevidens infected solely with PVY. However, accumulation of PVY was increased c. 1000-fold in plants doubly infected with tobacco mosaic virus or potato spindle tuber viroid (PSTVd). PVY titres in doubly infected plants of S. brevidens were between 1% and 0.1% of those found in the PVY-susceptible interspecific Solanum hybrid DTO-33. Double infections of 5. brevidens by PVY and alfalfa mosaic virus or potato viruses M, S, T or X did not significantly enhance PVY accumulation. Accumulation of PLRV was not enhanced in plants co-infected with any of the six viruses or PSTVd.