Zhang Honggen, Che Jianlan, Ge Yongshen, Pei Yan, Zhang Lijia, Liu Qiaoquan, Gu Minghong, Tang Shuzhu
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.
Rice (N Y). 2017 Dec;10(1):2. doi: 10.1186/s12284-017-0142-9. Epub 2017 Jan 21.
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.
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 F hybrids with either Rf5 or Rf6 exhibited normal seed setting rates, but F plants carrying Rf6 showed more stable seed setting rates than those of plants carrying Rf5 under heat-stress conditions. Furthermore, the seed setting rates of F hybrids carrying both Rf5 and Rf6 were more stable than that of F plants carrying only one Rf gene.
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.
三系粳稻杂种主要利用包台（BT）型细胞质雄性不育（CMS）培育而成。Rf1基因可恢复BT型CMS系的育性，是用于培育三系粳稻杂种的唯一育性恢复基因（Rf）。利用更多的Rf基因培育BT型恢复系可能会拓宽恢复系的遗传多样性，是提高BT型粳稻杂种优势水平的可行途径。
我们从‘93-11’中鉴定出两个参与恢复BT型CMS植株育性的主要Rf基因。这些基因是从粳稻品种‘日本晴’和籼稻品种‘93-11’杂交衍生的重测序染色体片段代换系中鉴定出来的。分子定位结果表明，这些基因是Rf5和Rf6，它们是恢复红莲型CMS系育性的Rf基因。携带Rf5或Rf6的BT型F杂种表现出正常的结实率，但在热胁迫条件下，携带Rf6的F植株的结实率比携带Rf5的植株更稳定。此外，同时携带Rf5和Rf6的F杂种的结实率比只携带一个Rf基因的F植株更稳定。
Rf6是BT型粳稻恢复系育种的重要遗传资源。我们的研究结果可能对有兴趣培育BT型粳稻杂种的育种者有用。
