The complete nucleotide sequences of both RNAs of oat golden stripe virus (OGSV) and a wheat-infecting furovirus isolate from France, previously thought to be soil-borne wheat mosaic virus (SBWMV), have been determined. Both viruses had a similar genomic organisation to SBWMV and Chinese wheat mosaic virus, the two other furoviruses previously sequenced but had <70% nucleotides identical to them. The French isolate has been named European wheat mosaic virus (EWMV). Phylogenetic analyses supported the recognition of these isolates as distinct viruses in the genus Furovirus. Analysis of the coat protein readthrough domain on RNA2 of all furoviruses strongly predicts two mutually compatible conserved transmembrane domains that may be significant for fungus transmission. The second of these regions is eliminated by a deletion in the isolate of OGSV studied. Leaky opal (UGA) stop codons occur on both RNAs of all four furoviruses characterised and, in common with most other leaky opal codons identified in plant viruses, they are followed by a CGG codon.

A sequence of 942 nucleotides, located in the helicase gene of RNA1 of a French isolate of soil-borne wheat mosaic virus (SBWMV), is presented. This sequence was compared with the corresponding sequences published for Nebraskan and Chinese isolates and showed a 74·8% and 73·4% identity, respectively, with these isolates, whereas the Nebraskan and Chinese isolates shared a 78·2% identity. A set of primers specific to the French SBWMV isolate was designed on the basis of this sequenced 942 nucleotide fragment. A primer set for wheat spindle streak mosaic virus (WSSMV) was designed from the published partial sequence of a French isolate. Both sets of primers were combined into a two-step multiplex reverse-transcription polymerase chain reaction, allowing simultaneous detection of both viruses in leaves of infected wheat samples. The amplification specificity of the two sets of primers was checked against isolates of SBWMV from Oklahoma and China, Indian peanut clump virus strains H, L and D from India, barley mild mosaic virus and barley yellow mosaic virus from France. SBWMV primers were specific for French isolates of this virus, whereas the primers designed from the sequence of a French isolate of WSSMV could also faintly detect barley yellow mosaic virus in barley plants. The RT-PCR technique was also compared with ELISA (enzyme-linked immunosorbent assay) on 100 wheat leaf samples collected from the field on the basis of symptoms, and was shown to be reliable and reproducible.

Some of the fields of an experimental farm situated in the Po Valley area (Ozzano, Bologna), utilized by the Department of Agronomy of the University of Bologna to assay different agronomic techniques were found to be severely infested by BaYMV and BaMMV. This provided us with an excellent opportunity to study the effects of different agronomic practices on BaYMV and BaMMV.