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Melon yellow spot virus: A Distinct Species of the Genus Tospovirus Isolated from Melon

First author: Shizuoka Agricultural Experiment Station, 678-1 Tomioka, Toyoda, Shizuoka, 438-0803, Japan; second author: Kyushu National Agricultural Experiment Station, 2421 Suya, Nishigoushi, Kikuchi, Kumamoto, 861-1192, Japan; third author: Faculty of Agriculture, Yamaguchi University, 1677-1 Yoshida, Yamaguchi, 753-8515, Japan

A tospovirus-like virus recovered from netted melon was transmitted by Thrips palmi in a persistent manner but had different cytopathological features from tospoviruses previously reported. Viral nucleocapsid (N) was purified with two protective reagents, 2-mercaptoethanol and L-ascorbic acid, and RNA extracted from the viral nucleocapsid was used for genomic analysis. The virus had a genome consisting of three single-stranded RNA molecules. The open reading frame on the viral complementary strand, located at the 3′ end of the viral S RNA, encoded the N protein. The 3′ terminus of this RNA also contained an eight-nucleotide sequence similar to the conserved sequence at the 3′ end of genomic RNA molecules of tospoviruses. These features of the viral genome are identical to those of tospoviruses; therefore, this virus is considered to belong to the genus Tospovirus. Its N protein comprised 279 amino acids and had a molecular mass of 31.0 kDa. Comparisons of its amino acid sequence with those of known tospoviruses revealed less than 60% identity. This melon virus is concluded to be a distinct species in the genus Tospovirus, and the name Melon yellow spot virus is proposed.