Development Of Chromosome Segment Substitution Lines Derived From Japonica(NingJing 4)/Indica(N22) And Detection Of Hybrid Sterility Loci

Rice is one of the most important food crops in the world,which provides staple food for more than half of the world’s population.With the rapid growth of the world’s population,food production needs to increase by another 50%to fully meet the needs.At the same time,in recent years,global climate change,global warming and extreme weather have brought great challenges for food security.The results showed that the utilization of heterosis between indica and japonica subspecies is one of the most promising effective ways to achieve rice yield breakthroughs in a short period of time.However,the problem of hybrid sterility in the cross between indica and japonica has seriously hindered the effective utilization of this advantage.Therefore,it is of great significance to explore the quantitative trait locus（QTL）of indica-japonica hybrid sterility and analyze their genetic mechanism for the utilization of heterosis between indica and japonica subspecies.Hybrid sterility is a quantitative trait controlled by multiple loci.It is difficult to study it directly by using F₂ segregation population,especially the cloning and mechanism analysis of hybrid sterility genes.Compared with background parents,chromosome segment substitution lines are only different in substitution segments,which is a good genetic material for the complex quantitative traits research.In this study,in order to analyze the genetic mechanism of hybrid sterility,we use molecular marker-assisted selection to construct the chromosome segment substitution lines,which the Ningjing 4 as the recipient parent and N22 as the donor parent.The result of the study are as follows:（1）Among 992 pairs of SNP primers in the laboratory were used to screen polymorphic markers between Ningjing 4 and N22.A total of 487 pairs of SNP markers were screened,accounting for 49.1%of the total number of marks.Then,according to the physical position of each marker on the chromosomes,131 pairs of polymorphic primers were selected according to the physical position of each marker on the chromosomes,and the linkage map of molecular markers was constructed by using Ici Mapping software.On the basis of previous studies,Ningjing 4 was used as the recurrent parent for backcrossing,and 378 BC₃F₁families of“Ningjing 4/N22”were obtained.Combined with molecular marker-assisted selection,a total of 157 lines were screened,and each line containing at least one chromosome segment of N22.The construction of chromosome segment substitution lines is preliminarily completed.（2）The hybrid sterility QTL were detected using the above-mentioned substitution line population.First,the spikelet fertility and pollen fertility of the BC₃F₁ population were statistically analyzed,and four QTLs affecting the spikelet fertility were detected on chromosomes 5,7 and 11,respectively.Among the four QTL loci that affect the spikelet fertility,the LOD score of one locus on the 11 chromosome is 9.94,and the percent of phenotypic variation explained（PVE）is 11.56%.Two QTLs affecting pollen fertility were detected on chromosome 5 and chromosome 11.Four QTLs affecting the spikelet fertility could explain about 23%of the phenotypic variation,and the two detected QTLs affecting the pollen fertility could explain about 16%of the phenotypic variation.It is a long-term work to refine and perfect the chromosome segment substitution lines of“Ningjing 4/N22”.The use of CSSL can effectively discover the QTL loci of hybrid sterility between indica and japonica subspecies,analyze the molecular genetic mechanism of these loci,and provide a theoretical basis for overcoming the sterile problem of heterosis utilization in rice.