Mapping Of A Nuclear Fertility Restorer Gene With SSR For T-type Cytoplasmic Male Sterility In Wheat

Cytoplasmic male sterility (CMS) is a widespread, maternally inherited trait in higher plants. It is caused by lesion or rearrangement of mitochondrial genome and can be restored by nuclear genes termed as restorer of fertility (Rf) genes which reduce or remove the deleterious effects caused by CMS-associated mitochondrial genes. CMS/Rf systems greatly facilitate hybrid seed production profiting from heterosis, because the laborious handwork of emasculation is eliminated.T-type CMS, an important type of CMS in wheat, derives from using T. timopheevi as the female parent in recurrent backcrosses with T. aestivum., resulting in incompatibility between T. timopheevi mitochondria and the T. aestivum nucleus. T-type CMS is more stable for environment than other CMS in wheat, but it is difficult to obtain excellent restorer lines in view of narrow restorer sources and the need of multitudinous Rf genes. For the utilization in hybrid seed production, it is important to research the Rf genes.In this study microsatellite markers were used to characterize fertility restorer genes of a restorer line of PR143 for T-type CMS in hexaploid wheat. The F2 populations of BAU 95A/PR143 were used to map the nuclear fertility restorer (Rf) gene for T.timopheevi (T-type) cytoplasmic male sterility (CMS). The two parents and two BSA (bulked segregant analysis) bulks with extremely sterile and fertile plants were used to screen microsatellite (SSR) primers. In about 280 pairs of Xgwm SSR primers and 40 of Xwmc, 6 pairs primers of Xgwm18, Xgwm273, Xgwm456, Xgwm582, Dupw267, Xgwm264 were tested for polymorphism between the parental lines and between the 2 bulks, which were amplified in the whole F2 populations of 300 individuals. In the online database "Grain Genes" (http://wheat.pw.usda.gov), some SSR primers near XgwmlS and Xgwm273 linked tightly to a Rf gene were amplified and detected, and it was found that Barc61, Barcl37, Barcl88, Wmc222, Xgwm11, Xgwm131, Xgwm153 and Xgwm274 had diversities between the parental lines. They were used for amplification in about 190 F2 populations chosen randomly from the whole F2 populations for genetic mapping in the chromosome IBS. By interval mapping of MAPMAKER the genetic map with 11 SSR markers was done. In order they were Barc61- Xgwm131- Xgwm11- Barc137- Xgwm18- Xgwm273-Dupw267- Xgwm582- Xgwm456 with the distance of 38.9 cM-19.0 cM-7.2 cM-7.7 cM-5.9 cM-2.0 cM-7.9 cM-10.3 cM and Xgwml53-Barc188 with 23.7 cM in the chromosome 1BS. The Rf gene whose variance-explained was about 87.5% was located in a section of 7.7 cM distance between Barcl37 and Xgwml8 in the chromosome 1BS by composite interval mapping of MAPMAKER, and the distance from the Rf gene to Xgwm18 and Barc137 were about 2.6 cM and 5.1 cM respectively.