The RNA 5 of Prunus necrotic ringspot virus is a biologically inactive copy of the 3 '-UTR of the genomic RNA 3

In addition to the four RNAs known to be encapsidated by Prunus necrotic ri ngspot virus (PNRSV) and Apple mosaic virus (ApMV), an additional small RNA (RNA 5) was present in purified preparations of several isolates of both v iruses. RNA 5 was always produced following infection of a susceptible host by an artificial mixture of RNAs 1, 2, 3, and 4 indicating that it was a p roduct of viral replication. RNA 5 does not activate the infectivity of mix tures that contain the three genomic RNAs (RNA 1 + RNA 2 + RNA 3) nor does it appear to modify symp;om expression. Results from hybridization studies suggested that RNA 5 had partial sequence homology with RNAs 1, 2, 3, and 4 . Cloning and sequencing the RNA 5 of isolate CK 57/1-M of PNRSV, and the 3 ' termini of the RNA 1, RNA 2 and RNA 3 of this isolate indicated that it w as a copy of the 3' untranslated terminal region (3'-UTR) of the genomic RN A 3.