Molecular mapping of the fertility restoration locus Rf1 in sunflower and development of diagnostic markers for the restorer gene

Fertility restoration by dominant nuclear genes is essential for hybrid breeding based on cytoplasmic male sterility (CMS) to obtain heterotic effects and high seed yields. In sunflower, only the PET1 sterility inducing cytoplasm has been used in commercial hybrid breeding until now. This particular male sterility was derived from an interspecific hybrid Helianthus petiolaris × H. annuus. For the recent work we used the segregating population RHA325(CMS) × HA342, based on the PET1 cytoplasm. Molecular markers were mapped within 1.1 cM around the restoration locus Rf1. At the distal side, the marker OP-K13_454 mapped at a distance of 0.9 cM and E32M36-155R at 0.7 cM from Rf1. At the proximal side the markers E44M70-275A, E42M76-125A and E33M61-136R were mapped at 0.1, 0.2, and 0.3 cM from the restorer locus, respectively. These markers provide an excellent basis for a map based cloning approach and for marker-assisted sunflower breeding.