Potato Spindle Tuber Viroid Does Not Complement Tobacco Mosaic Virus Temperature-sensitive Transport Function

1 Department of Virology, Moscow State University, Moscow 119899 and 2 Institute of Phytopathology, Moscow District 143050, U.S.S.R. In mixed infections, the potato spindle tuber viroid (PSTV) does not complement the transport function of the tobacco mosaic virus (TMV) Ls1 mutant, which has a temperature-sensitive transport function. This appears to be due to the fundamentally different mechanisms of virus and viroid transport. However, PSTV significantly enhances the accumulation of temperature-resistant TMV in mixed infections at a temperature non-permissive for Ls1. Keywords: PSTV, TMV, transport function Received 2 November 1988; accepted 27 February 1989.