Soybean leaf rugose mosaic virus, a new soilborne virus in the family Potyviridae, isolated from soybean in Japan

Abstract

In 2005, soybean plants with severe mosaic and leaf rugose symptoms were found in Japan. The plants contained flexuous and filamentous virus-like particles with a modal length of 500 nm. Double-stranded RNA analysis revealed a single major band of ~7000 bp. Reverse transcription-PCR for Potyviridae diagnosis generated a 1.5-kbp cDNA fragment, which contained a partial NIb gene, a coat protein (CP) gene, a 3′-noncoding region, and a poly(A) tract. The CP gene consisted of 248 amino acids and had less than 40% amino acid sequence identity with CPs of other member in Potyviridae. The C-terminal region of the NIb gene had ~60% amino acid sequence identity with Barley mild mosaic virus and other Bymovirus isolates. The NIb amino acid sequence contained the GDD motif, while the CP had no motifs associated with aphid transmission. Phylogenetic analyses of the amino acid sequence of the CP core region showed that this virus was independent from other potyvirus genera. In a host range test, the virus infected 10 plant species in four families. The virus was not transmitted via seeds or aphids, but soybeans became diseased when grown in virus-infested soil. The characteristics of this virus suggest that it is not related to any of the previously described soybean viruses; thus, we tentatively propose the name soybean leaf rugose mosaic virus (SLRMV).