Improvement of combining ability in traits of parents is an important strategy for enhancing heterosis level in rice. Using japonica restorer line Wuyujing 3R as the donor parent for RM208-180 band with high combining ability in productive panicle and Ninghui 8 as the receptor parent in japonica rice, four improved restorer lines with the homozygous 180 bp band at RM208 site and the genetic background of Ninghui 8 were obtained through crossing, backcrossing, selfing and the SSR molecular marker-assisted se...