[Mapping of fertility-restoring genes with main effects and epistatic effects for CMS-DA in rice]

A test-cross population was established for mapping genes conditioning fertility restoration for dwarf-wild-abortive cytoplasmic male sterility(CMS-DA) in rice. A recombinant inbred line(RIL) population consisting of 210 lines was derived from the cross Xieqingzao B/Miyang 46, in which Xieqingzao B is the maintainer line of CMS-DA Xieqingzao A, and Miyang 46 is the restorer line. Each of the RILs was crossed to Xieqingzao A, and the resulting F1s were used for phenotyping of the spikelet fertility in 1999 and 2000. A linkage map consisting of 129 RFLP and SSLP markers was constructed. QTLs having significant main effects and/or epistatic effects for spikelet fertility were determined with QTLMAPPER 1.0 of mixed linear model. Background genetic variation due to main and epistatic effects of important markers was controlled. Four QTLs having significant main effects for fertility restoration were detected. A major gene qRf-10-2 was located in interval RM258-RZ811 on the long arm of chromosome 10, and QTL qRf-1 displaying a moderate main effect was located in a position close to RG532 on chromosome 1. Two other QTLs were located on chromosome 5 (qRF-5) and the short arm of chromosome 10 (qRf-10-1), in which the main effect of qRf-5 bacame significant only in the absence of qRf-10-2. A significant digenic interaction was detected, which occurred between QTLs qRf-1 and qRf-5. No significant QTL by environmental interactions and epistasis by environmental interactions were detected. Analyses on the gene effects based on markers closest to the Rf genes were made, and multi-locus interactions were implied. The present results were also compared to a previous study on mapping fertility restoration genes in Milyang 46 for wild-abortive CMS Zhenshan 97A, and to other published reports. It was indicated that differences on the genetic control of fertility restoration among different rice populations were mainly attributed to variations on genes with minor main effects and epistatic effects.