Fine Mapping And Candidate Analysis Of Heading Date Genes On Wild Emmer Chromosome Arm 7BS

Heading date of wheat directly reflects the length of growth period of wheat varieties.Appropriate heading date plays a key role in maintaining high and stable yield of wheat.We used chromosome arm substitution line（CASL）to identify a QTL with LOD value of 7.68 and phenotypic contribution rate of9.14%on Chr7B of wild emmer.In this study,genome wide re-sequencing and transcriptome sequencing were used to identify the chromosome composition of CASL7BS;The possible QTL sites in early and late maturation mixing pool were detected by BSR-seq technique;according to the whole genome re-sequencing,In Del primer scanning（CASL7BS×CS）F_2:3 population was designed to fine map the heading date;the candidate genes were screened by transcriptome data at different stages of young panicle differentiation and annotation of CASL7BS whole genome re-sequencing gene.The main results are as follows:1.Through analysis of CASL7BS genome re-sequencing and transcriptome sequencing data,it was found that the homozygous SNPs of CASL7BS were mainly distributed in the interval of 20-500 Mb on Chr5A and 0-530 Mb on Chr7B.SSR primers were used to scan CASL7BS to confirm that 0-530 Mb fragment of Chr7B was replaced by wild emmer.2.BSR-seq data analysis mapped the highly reliable QTL located in 57-63 Mb on Chr7B,which was consistent with the previous mapping interval of 53-64 Mb.The fine mapping of heading date gene in（CASL7BS×CS）F_2:3 family was carried out by using polymorphic In Del markers designed by re-sequencing data.A QTL with LOD value of 10 and phenotypic contribution rate of 22%was located between 59 962 645-61 354 548 bp on Chr7B.4.The transcriptome sequencing analysis of four samples from different materials（CASL7BS and CS）showed that there were 615 differentially expressed genes in CASL7BS compared with CS.5.According to the annotation information of Chinese Spring reference gene,26 genes were found in 59-61 Mb of Chr7B.Combined with the genome-wide gene annotation and analysis of CASL7BS,six types of gene mutation were found in 26 genes,among which 25 genes had upstream promoter mutation,and 25 genes had upstream promoter mutation.A total of 13 genes were found to have mutations in cis-acting elements,including abscisic acid responsive element and gibberellin responsive element.Base mutations in cis-acting elements and protein coding region of CASL7BS gene may lead to differences in protein levels,which may affect the heading date of CASL7BS.