Identification And Mapping Of Restorer Genes In HL-type Maintainer Lines

Recently,three-line hybrid rice is widely used in hybrid rice production.In view of the great contribution made by three-line hybrid rice,there are a lot of researches having been con-ducted for uncovering the mechanism of male sterility and fertility restoration of sterile cyto-plasm.However,the exploration of major fertility-restoring(Rf)genes in restorer lines are mainly concerned,and there are few reports on minor Rf genes and Rf genes in sterile/maintainer lines,resulting in the insufficient ability to solve the problems in three-line hybrid rice breeding,such as the instability of sterile lines,the low breeding efficiency of maintainers and the different re-coverability of indica and japonica sterile lines with the same sterile cytoplasm.Therefore,it is of great significance to strengthen the study of Rf genes in maintainer lines,which would be of great benefit for breeding of three-line hybrid rice.In this study,YuetaiB and BT-SuqiuA,HL-SuqiuA,the wide compatibility japonica sterile lines were selected for identifying the Rf genes in HL-Type indica and japonica maintainers.The spikelet fertility of BT-SuqiuA/YuetaiB F1 and HL-SuqiuA/YuetaiB F1 plants were firstly observed for making sure whether HL-Type indica and japonica maintainers carried the Rf genes.Further,we constructed the iso-cytoplasmic restoring populations to locate the Rf genes,and the restorability of the target genes was evaluated by development of the iso-cytoplasmic restoring near-isogenic lines.The main results are as follows:(1)The natural spikelet fertility of BT-SuqiuA,HL-SuqiuA and HL-YuetaiA were 0,and the natural spikelet fertility of BT-SuqiuA/YuetaiB F1 and HL-SuqiuA/YuetaiB F1 plants were 34.32%and 30.04%,respectively.These results indicated that YuetaiB,the HL-type indica maintainer carried the Rf genes for BT-type and HL-Type cytoplasmic male sterile(CMS)lines and SuqiuB harborred the Rf genes for HL-Type cytoplasmic male sterile(CMS)lines.These identified Rf genes were dominant and had the gene interaction of complementary in the fertility restoration of HL-type CMS lines.(2)With 120 plants in BT-SuqiuA/YuetaiB F2 population,the Rf gene from YuetaiB was mapped on chromosome 10,and two markers,STSh-7 andSTS10-16,were linked with the target gene.Furthermore,the Rf gene was lacated into a region of 461.29 Kb between RM25613 and STSh-7 using a total of 580 plants in BT-SuqiuA/YuetaiB F2,F3 populations Rf1c was located,and this Rf gene was named as Rf1c temporarily.(3)In the present study,we proposed a strategy of development of iso-cytoplasmic restor-ing populations for mapping the Rf gene from SuqiuB,and a set of iso-cytoplasmic restoring lines(HL-SuqiuA/YuetaiB//YuetaiB BC4F1)were obtained.Using HL-SuqiuA/Yue-taiB//YuetaiB BC5F1 and BC5F2 populations,a Rf gene from SuqiuB was identified and the marker STS-3-10.9 on chromosome 3 was linked with the target gene.Accordingly,the identi-fied Rf gene from SuqiuB was a novel gene for the fertility restoration and was tentatively named as Rf23(t).Furthermore,using 1000 plants in HL-SuqiuA/YuetaiB//YuetaiB BC5F3 population,Rf23(t)was initially located between RM22 and STS-3-10.9,and the genetic distances between Rf23(t)and the two markers were 0.25 cM and 0.4 cM,respectively.(4)NILRf5,NILRf6 and NILRf23(t),three iso-cytoplasmic restoring near-isogenic lines with the background of HL-YuetaiA,were developed for evaluating the ability of Rf23(t)in the fertil-ity restoration of HL-type CMS line.These iso-cytoplasmic restoring near-isogenic lines for dif-ferent genes exhibited similar natural spikelet fertility,indicating that harbored the nor-mal restorability for the fertility restoration of HL-type indica CMS lines..