Molecular mapping of a fertility restoration locus (Rfm1) for cytoplasmic male sterility in barley (Hordeum vulgare L.)

The Rfm1a gene restores the fertility of msm1 cytoplasmic male-sterile line s in barley. We identified three RAPD markers linked to the Rfm1 locus (CMN B-07/800, OPI-18/900, and OPT-02/700) using isogenic lines and segregating BC1F1 and F-2 populations. Using a previously developed linkage map of barl ey, we located CMNB-07/800 and OPT-02/700 beside MWG2218 on chromosome 6HS. The linkage between MWG2218 and the Rfm1 locus was demonstrated using the segregating BC1F1 and F-2 populations. To confirm the chromosomal locations of these markers, we converted them to STSs and tested against two sets of wheat-barley chromosome addition lines. These STS markers, CMNB-07/800, OP T-02/700, and MWG2218, were amplified only in the addition lines possessing the chromosome 6H, thereby providing additional evidence the Rfm1 locus is located on chromosome 6H. Homoeologous relationships among fertility resto ration genes in Triticeae are discussed.