A novel putative member of the family <i>Benyviridae</i> is associated with soilborne wheat mosaic disease in Brazil

Abstract

Soilborne wheat mosaic disease ( SBWMD ), originally attributed to infections by Soilborne wheat mosaic virus ( SBWMV ) and Wheat spindle streak mosaic virus ( WSSMV ), is one of the most frequent virus diseases and causes economic losses in wheat in southern Brazil. This study aimed to characterize molecularly the viral species associated with wheat plants showing mosaic symptoms in Brazil. Wheat leaves and stems displaying mosaic symptoms were collected from different wheat cultivars in Passo Fundo municipality, Rio Grande do Sul State, southern Brazil. Double‐stranded RNA was extracted and submitted to cDNA library synthesis and next‐generation sequencing. No sequences of SBWMV and WSSMV were detected but the complete genome sequence of a putative new member of the family Benyviridae was determined, for which the name wheat stripe mosaic virus (Wh SMV ) is proposed. Wh SMV has a bipartite genome with RNA 1 and RNA 2 organization similar to that of viruses belonging to Benyviridae . Wh SMV RNA 1 has a single open reading frame ( ORF ) encoding a polyprotein with putative viral replicase function. Wh SMV RNA 2 has six ORF s encoding the coat protein, the major protein (read‐through), triple gene block movement proteins ( TGB 1, 2 and 3) and ORF 6 (hypothetical protein). In addition to the genomic organization and nucleotide and amino acid sequence identities, phylogenetic analyses also corroborated that Wh SMV is a virus species of the Benyviridae . However, isolates of Wh SMV formed a clade distinct from members of the genus Benyvirus . It was also demonstrated that the plasmodiophorid Polymyxa graminis is associated with wheat roots showing SBWMD symptoms and infected by Wh SMV .