THE INFECTIOUS TRANSCRIPTS OF SWEET CLOVER NECROTIC MOSAIC-VIRUS BIPARTITE GENOME CONSTRUCTED BY THE POLYMERASE CHAIN-REACTION

Based on the complete nucleotide sequences of sweet clover necrotic mo saic virus (SCNMV) genome, full-length cDNA clones derived from RNA-1 and RNA-2 were constructed by the polymerase chain reaction with prope r primers. RNA-1 and RNA-2 transcripts capped or uncapped with m7GpppG were efficiently generated, were infectious and induced symptoms iden tical with those caused by native viral RNAs when coinoculated to test plants Chenopodium quinoa, C. amaranticolor and Phaseolus vulgaris 'R ed Kidney' bean. However, infectivity of these transcripts were less t han that of the native viral RNA. In addition, the uncapped transcript s were less infectious than the capped transcripts, particularly on Re d Kidney bean. The progeny SCNMV particles derived from the transcript infection had infectivity similar to that of the native viral RNA-gen erated virions. Both the capped and the uncapped transcripts containin g an artificial poly(A)61 tail were not infectious.