Complexity of the Argentina mild strain of barley stripe mosaic virus

Barley stripe mosaic virus (BSMV) is known to have unusual strain-specific variations in the number of high molecular weight RNAs that can be resolved by gel electrophoresis. Analysis with recombinant DNA clones has revealed that all strains contain three distinct hybridizing species of RNA, which we now designate α, β and y. The α- and β-RNAs are about 4200 and 3650 nucleotides (NT), respectively, but the γ-RNAs vary in size depending on the strain. The γ-RNA of the Type strain is 3650 NT, and is difficult to resolve from β-RNA by gel electrophoresis. However, the γ-RNA of the North Dakota 18 (ND18) strain is 3250 NT and is clearly separated from β-RNA. The results presented below show that the Argentina mild (AM) strain contains a mixture of γ-RNAs of 3650, 3250, and 2900 NT. The 3650- and 3250-NT γ-RNAs appear to be functional because AM subclones containing either 3650- or 3250-NT γ-RNA can be isolated from plants inoculated with low concentrations of virus. The 2900-NT γ-RNA is probably not capable of functioning as a genomic RNA because this RNA is not a component of any of the AM subclones.