NUCLEOTIDE-SEQUENCE RELATIONSHIPS OF DOUBLE-STRANDED RNAS IN FLAX RUST, MELAMPSORA-LINI

Flax rust, Melampsora lini strain SP6, contains 11 double-stranded (ds ) RNA molecules with a total length of about 25 kbp. The dsRNAs are in herited in three genetic units: the L unit comprising a single 5.2 kbp dsRNA and contained within a 40-nm virus-like particle, and the A and B units each consisting of five dsRNAs (A1-A5, and B1-B5) ranging in size from 1.2 to 2.7 kbp. This paper reports the isolation of a cDNA l ibrary representing 10 of the 11 dsRNAs. By nucleic-acid hybridization techniques it has been shown that all ten sequences are unique showin g no detectable cross-hybridization with any other dsRNA present in th e rust. A near full-length sequence of 1932 bp of the B3 dsRNA is repo rted and contains several open reading frames, the largest of which co mprises most of the molecule.