Identification of a microsatellite marker linked to the fertility-restoring gene for a polima cytoplasmic malesterile line in Brassica napus L.
Polima cytoplasmic male sterility (pol CMS) has been widely used for exploiting heterosis in rapeseed breeding. The dominant restorer gene of pol CMS (Rfp) is found in the nucleus and is a key component of hybrid production by achieving F1 progeny with complete fertility restoration. To identify the molecular markers associated with the Rfp gene, a near isogenic line (NIL) population of 2,000 individuals segregating for the Rfp locus was generated by crossing and backcrossing for 12 times. This NIL population was used to screen Rfp markers by AFLP technique. Based on the sequence information of AFLP markers that have been identified in previous research, we identified a homologous region of Rfp locus in chromosome 1 of Arabidopsis. Then, six sequenced Brassica rapa BAC clones corresponding to this target region were chosen to design microsatellite (SSR) primer pairs. Twenty-two SSR markers were designed and one of them, KBrDP1, was verified in the 2, 000 NILs population and proved to be strongly linked to Rfp locus. The genetic distance between KBrDP1 and Rfp was 0.2 cM. KBrDP1 marker was found located on linkage group N9 of a published DH mapping population. This SSR marker was useful in marker assisted selection breeding of the elite pol CMS restorer lines in rapeseed.
Key words: Brassica napus, polima cytoplasmic male sterility, fertility restorer gene, microsatellite.