title: Ability of Rf5 and Rf6 to Restore Fertility of Chinsurah Boro II-type Cytoplasmic Male Sterile Oryza Sativa (ssp. Japonica) Lines.
abstract: BACKGROUND
  Three-line Oryza sativa (ssp. japonica) hybrids have been developed mainly using Chinsurah Boro II (BT)-type cytoplasmic male sterility (CMS). The Rf1 gene restores the fertility of BT-type CMS lines, and is the only fertility restorer gene (Rf) that has been used to produce three-line japonica hybrids. Using more Rf genes to breed BT-type restorer lines may broaden the genetic diversity of the restorer lines, and represents a viable approach to improve the heterosis level of BT-type japonica hybrids.
  
  
  RESULTS
  We identified two major Rf genes from '93-11' that are involved in restoring the fertility of BT-type CMS plants. These genes were identified from resequenced chromosome segment substitution lines derived from a cross between the japonica variety 'Nipponbare' and the indica variety '93-11'. Molecular mapping results revealed that these genes were Rf5 and Rf6, which are the Rf genes that restore fertility to Honglian-type CMS lines. The BT-type F1hybrids with either Rf5 or Rf6 exhibited normal seed setting rates, but F1plants carrying Rf6 showed more stable seed setting rates than those of plants carrying Rf5 under heat-stress conditions. Furthermore, the seed setting rates of F1hybrids carrying both Rf5 and Rf6 were more stable than that of F1plants carrying only one Rf gene.
  
  
  CONCLUSIONS
  Rf6 is an important genetic resource for the breeding of BT-type japonica restorer lines. Our findings may be useful for breeders interested in developing BT-type japonica hybrids.
authors.affiliation: Jiangsu Key Laboratory of Crop Genetics and Physiology/Co-Innovation Center for Modern Production Technology of Grain Crops, Key Laboratory of Plant Functional Genomics of the Ministry of Education, College of Agriculture, Yangzhou University, Yangzhou, 225009, China.
authors.forename: Honggen
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Jiangsu Key Laboratory of Crop Genetics and Physiology/Co-Innovation Center for Modern Production Technology of Grain Crops, Key Laboratory of Plant Functional Genomics of the Ministry of Education, College of Agriculture, Yangzhou University, Yangzhou, 225009, China.
authors.forename: Jianlan
authors.initials: J
authors.lastname: Che
authors.affiliation: Jiangsu Key Laboratory of Crop Genetics and Physiology/Co-Innovation Center for Modern Production Technology of Grain Crops, Key Laboratory of Plant Functional Genomics of the Ministry of Education, College of Agriculture, Yangzhou University, Yangzhou, 225009, China.
authors.forename: Yongshen
authors.initials: Y
authors.lastname: Ge
authors.affiliation: Jiangsu Key Laboratory of Crop Genetics and Physiology/Co-Innovation Center for Modern Production Technology of Grain Crops, Key Laboratory of Plant Functional Genomics of the Ministry of Education, College of Agriculture, Yangzhou University, Yangzhou, 225009, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Pei
authors.affiliation: Jiangsu Key Laboratory of Crop Genetics and Physiology/Co-Innovation Center for Modern Production Technology of Grain Crops, Key Laboratory of Plant Functional Genomics of the Ministry of Education, College of Agriculture, Yangzhou University, Yangzhou, 225009, China.
authors.forename: Lijia
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Jiangsu Key Laboratory of Crop Genetics and Physiology/Co-Innovation Center for Modern Production Technology of Grain Crops, Key Laboratory of Plant Functional Genomics of the Ministry of Education, College of Agriculture, Yangzhou University, Yangzhou, 225009, China.
authors.forename: Qiaoquan
authors.initials: Q
authors.lastname: Liu
authors.affiliation: Jiangsu Key Laboratory of Crop Genetics and Physiology/Co-Innovation Center for Modern Production Technology of Grain Crops, Key Laboratory of Plant Functional Genomics of the Ministry of Education, College of Agriculture, Yangzhou University, Yangzhou, 225009, China.
authors.forename: Minghong
authors.initials: M
authors.lastname: Gu
authors.affiliation: Jiangsu Key Laboratory of Crop Genetics and Physiology/Co-Innovation Center for Modern Production Technology of Grain Crops, Key Laboratory of Plant Functional Genomics of the Ministry of Education, College of Agriculture, Yangzhou University, Yangzhou, 225009, China. sztang@yzu.edu.cn.
authors.forename: Shuzhu
authors.initials: S
authors.lastname: Tang
keywords: BT-type CMS; Fertility restorer gene (Rf); Gene mapping; Japonica; Restoration ability