The full nucleotide sequence of the S RNA segment of Melon yellow spot virus (MYSV) was determined to be 3232 nucleotides long and to have every feature of the S RNAs of tospoviruses reported so far. From an amino acid sequence comparison of nonstructural proteins (NSs), MYSV is most closely related to two tospoviruses in serogroup IV. MYSV had nucleotide and amino acid sequence identities over 96% with Physalis severe mottle virus in all regions of S RNA except in an intergenic region and in deduced open reading frames, including that on complementary strand RNA.