Pedigree analysis of the transmission of a double-stranded RNA in barley cultivars

The barley cultivar Barsoy (Hordeum vulgare L.) contains an unusual 13.1 kb cellular double-stranded ribonucleic acid (dsRNA). This non-viral dsRNA is efficiently transmitted by both egg and pollen in crosses with dsRNA-free cultivars. The pedigree of Barsoy was reconstructed and tested for dsRNA occurrence and sequence similarity in an effort to determine the origin and distribution of this molecule. The ancestors of Barsoy barley were tested for the presence of dsRNA by CF-11 cellulose chromatography and agarose electrophoresis. Of 31 ancestral cultivars tested, eight contained a dsRNA with electrophoretic properties similar to the one from Barsoy. A cDNA probe made with Barsoy dsRNA revealed that the dsRNAs isolated from related cultivars have similar nucleotide sequences. The dsRNA was found in four out of five of the oldest ancestors of Barsoy tested. One of these cultivars, Nakano Wase, was introduced to the US from Japan for breeding purposes in 1911. These results support a theory for vertical transmission of the dsRNA from generation to generation and suggest that the molecule has been maintained in barley cultivars for over 80 years.