QTL Mapping Of Stigma Exsertion And Fine Mapping Of Fertility Gene OsFMS8 In Rice

Rice（Oryza sativa L.）is the main food crop in China.More than half of the population lives on rice.In order to meet the continuous demand of the growing population for grain yield,rice breeders have made unremitting efforts to cultivate high-yield hybrid rice,which can greatly increase the yield of rice and solve the problem of food crop shortage in China.Three line hybrid rice is made up of male sterile line,restorer line and maintainer line.At present,the stigma exsertion rate of Wild Abortive male sterile lines widely used in China is low,which is not conducive to large-scale hybrid seed production and limits the popularization of hybrid rice.In addition,the molecular mechanism of stigma exsertion in rice is also a developmental biology problem.The analysis of the molecular mechanism will provide a theoretical basis for hybrid rice seed production.This paper is divided into two parts:QTL mapping of stigma exsertion in rice and fine mapping of fertility gene Os FMS8.In the first part,a F₂population derived from the cross between ZH493（a family of Gui9-5B/Reyan 2）with high percentage of exserted stigma and 02428（a Japonica Rice Variety with low percentage of exserted stigma）was used to construct a molecular genetic map covering the whole genome by using 226 pairs of SNP markers evenly distributed on 12 chromosomes of rice,The main results are as follows1.A molecular linkage map of 226 SNP markers covering the whole rice genome was constructed.The total length of the map was 2374.21 c M,and the average distance between adjacent markers was 10.51 c M.2.In 2019 and 2020,we investigated the distribution of stigma exsertion rate in F₂and F_2:3populations derived from the cross between"ZH493/02428"parents.A total of 21 QTL controlling stigma exsertion rate in rice were detected by using the constructed genome-wide molecular linkage map.Five QTL controlling the percentage of single exserted stigma were located on chromosome 1,4 and 12,respectively,which explained the phenotypic variation rate between 8.52%and 22.28%;Eleven QTL controlling the percentage of dual exserted stigma were located on chromosome 1,2,4,6,8 and 12,respectively,which explained the phenotypic variation between 3.73%and 12.80%;Five QTL controlling the percentage of total exserted stigma were located on chromosome 1,4and 12,respectively,which explained that the phenotypic variation rate ranged from10.11%to 24.13%.3.Correlation analysis showed that percentage of single exserted stigma,percentage of dual exserted stigma and percentage of total exserted stigma were highly correlated.The correlation coefficient was 0.81 between percentage of single exserted stigma and percentage of dual exserted stigma rate were significantly positively correlated,the correlation coefficient was 0.96 between percentage of single exserted stigma and percentage of total exserted stigma were significantly positively correlated,the correlation coefficient was 0.77 between percentage of dual exserted stigma and percentage of total exserted stigma were significantly positively correlated.4.The results showed that q PDES6 controling the percentage of dual exserted stigma in rice,which was located on the molecular markers RM527-RM3183 of chromosome 6,and its explained phenotypic variation rate is 12.77%.This locus has not been mapped in previous studies,so it is speculated that this locus may be a new QTL.In the second part,cytological observation was carried out on the sterile mutant Os FMS8 with Zixiangnuo as the genetic background,and the F₂population was constructed by crossing the sterile heterozygous plant with Xudao 9,and the fertility genes were precisely located by using the segregation population1.The male sterile mutant Osfms8 was obtained from the field mutation of Zixiangnuo.In the vegetative growth stage,the phenotype of the mutant Osfms8 was not significantly different from that of the wild type,but in the mature stage,the spikelet setting rate of the mutant Osfms8 was only 21.29±4.25%,which was significantly lower than that of the wild type 82.86±1.96%.Through I₂-KI staining,it was found that the pollen of the mutant was the same as that of the wild type,and the starch could accumulate normally;the pollen germination experiment in vivo further proved that the pollen had the ability of normal germination,indicating that the pollen of mutant has normal function.2.Genetic analysis showed that the low fertility phenotype of Osfms8 was controlled by a single recessive gene.The mutant Osfms8 heterozygous plant was used as female parent to cross with japonica rice variety Xudao 9,and 155 extreme plants with the same phenotype as the mutant parent were selected from F₂population.First,10 extreme plants were initially located between the two indel molecular markers G-2 and G-38 on the short arm of chromosome 8,and then new molecular markers were designed,Further mapping to the 735 kb region of G-7 and G-29 will lay a good foundation for the cloning of fertility gene.