AbstractNorthern blot analysis with cDNA probes to RNA-3 (1 kb) of RBDV revealed extensive sequence homology with RBDV RNA-2 (2.2 kb). Nucleotide sequencing showed that RNA-2 contains 2 large open reading frames (ORFs), of 1074 (5′ ORF) and 822 (3′ ORF) bases. The 3′ ORF is virtually identical in sequence to RNA-3, which encodes the Mr 30 509 (30 kDa) coat protein. The 5′ ORF encodes an Mr 38 860 (39 kDa) protein which slightly resembles the 32 kDa protein encoded by RNA-3 of alfalfa mosaic virus (AlMV). RBDV RNA-2 resembles AlMV RNA-3 in being bicistronic and encoding a coat protein at the 3′ end. Comparing RNA-1 and RNA-2 of RBDV, only the 18 3′-terminal nucleotides are identical in sequence but the 3′-terminal 71 nucleotides of each RNA species have the potential to form similar stem-loop structures.