Virus-free Richards Early Italian and standard Italian prune (Prunus domestica) trees growing on various rootstocks were infected in their second year with PRSV (Prunus ringspot virus) isolates of differing severity and observed through their sixth year for PRSV and other symptoms.  Incidence of nonvirus symptoms (primarily leafspot-complex and fruit-gummosis) varied with rootstock and season.  A mild PRSV strain seldom induced symptoms, but other isolates produced characteristic symptoms in most scion-root combinations.  Incidence of PRSV symptoms was greatest the year following inoculation with typical latency ensuing thereafter.  No general correlation was observed in the incidence of leafspot-complex, fruit-gummosis, and PRSV symptoms, nor of PRSV infection with rootstock-suckering or wind-resistance.  The various conditions under study generally were more severe in Richards trees than in standard Italian trees.  With all factors considered, the best trees for both varieties were produced on the CEA-2 Myrobalan plum (P. cerasifera) rootstock.

Additional key words: genetic disorders, compatibility, PRSV incubation, leaf-curl, gum-spotting, leafspot-complex.