Four degenerate oligonucleotide primers derived from conserved regions of the genome of potyviruses have been designed. A combined assay of reverse transcription and the polymerase chain reaction utilizing these primers on total RNA extracted from Ipomoea purpurea infected with a sweet potato feathery mottle virus isolate from China (SPFMV-CH), amplified a 1.35 kb and a 830 bp fragment. These amplified fragments were cloned into the Bluescript plasmid and sequenced. The comparison of the sequence of the N-terminal part of the coat protein of SPFMV-CH with those published for two other strains of SPFMV, showed a strong relationship between SPMV-CH and -RC.