Recombinant DNA molecules containing cDNA of a sweet potato feathery mottle virus severe strain (SPFMV-S) RNA genome were constructed and the partial nucleotide sequences were determined for three DNA inserts, which cover 4.2 kb from the 3'-terminus excluding the poly (A) tail. This region of the genome consists of an open reading frame of 1340 amino acids (a.a) and a 3'-non-translated region of 224 nucleotides. The protein products expected were 6K(2) (53 a.a.), NIa (435 a.a.), NIb (521 a.a.) and CP (315 a.a.). Among NIa, NIb and coat proteins, the NIb protein was found to be the most conserved (59-68%) when compared to the corresponding proteins of other distinct potyviruses.