Abstract
Eighteen pseudorecombinants were constructed in vitro by exchanging the three genomic RNA segments between pairs of three strains of cucumber mosaic virus (CMV). Inoculation of the CMV strains and the pseudorecombinants to 10 selected host plant species revealed that infection and symptom expression in a plant can be a complex interaction of the genetic material of the virus with that of the host genome. Whereas some host reactions were determined only by either RNA-2 and some by RNA-3, others were the results of the interaction of both these RNA species. Furthermore, some host reactions resulted from the interactions of any two, or perhaps even all three RNA segments of the virus.