Fine Mapping Of Flag Leaf Width QTL-qFlw-5B In Wheat And Its Application In Breeding

Flag leaf is an important photosynthetic organ of wheat,which can provide 20-30%dry matter for wheat seeds.The size and morphological characteristics of flag leaf directly affect the yield of wheat.In the previous research,qFlw-5B(a quantitative trait locus related to flag leaf width)was detected using the recombinant inbred line population(KJ-RILs)constructed by Kenong 9204 and Jing 411,which explains9.9-19.8% of the phenotypic variation and covers a genetic distance of 6.5 c M.In this study,we tend to fine map qFlw-5B and analyze its selection and application in wheat breeding.The results will lay a theoretical foundation for the clone and molecular breeding application of qFlw-5B,which is of great significance for genetic improvement of flag leaf and yield traits in wheat.The main results of this study are as follows:1.We identified 109322 single nucleotide polymorphisms(SNPs)and insertion-deletions(In Dels)by using the genome resequencing data of Kenong 9204 and Jing 411.There were 584 In Dels(≥5 bp)in the target region.Based on their sequence difference information,we developed 11 pairs of polymorphic In Del markers for the genotype identification of secondary mapping populations.2.Two secondary mapping populations were constructed using residual heterozygotes KJ033 and KJ391 Near-isogenic lines(NIL-KN9204 and NIL-J411)as well as important recombinant materials were obtained by genotype identification.Combined with multi-environment phenotype data,qFlw-5B was finally located in the physical interval between 596.605104-599.018603 Mb,which containing 16 candidate genes.3.The flag leaves of NIL-KN9204 and NIL-J411 were used for transcriptome sequencing analysis at heading and filling stages,and the gene Traes KN5B01HG44150 was differentially expressed in both of the two stages.Sequence analysis showed that there were five different bases of Traes KN5B01HG44150 between NIL-KN9204 and NIL-J411,which led to four amino acid mutations,and might eventually lead to the changes of gene function.Functional annotation showed that Traes KN5B01HG44150 was a protein encoding ribosome-binding ATPase Ych F.Combined with the above data,it was preliminarily inferred that Traes KN5B01HG44150 was the candidate gene of qFlw-5B.4.The near-isogenic lines in KJ033 and KJ391 lines were used to analyze the genetic effects of qFlw-5B,respectively.Based on the analysis of near-isogenic lines of the two lines,qFlw-5B can significantly increase plant height,thousand kernel weight and grain width.The results of paraffin section showed that the wider flag leaf of NIL-KN9204 was mainly caused by the bigger vesicular cells and the more vascular bundles.5.We genotyped 244 natural population using molecular markers closely linked to qFlw-5B.Combined with multi-environmental phenotypic data,the genetic effects of qFlw-5B was analyzed.The results showed that Hap-J411 could significantly increase the yield per plant,and the proportion in the natural population is increased year by year.The above results showed that the excellent allele of qFlw-5B has been selected in the breeding process.In summary,this study fine-mapped qFlw-5B within a region of 2.4 Mb by constructing a secondary mapping population.The candidate gene was preliminarily identified by transcriptome sequencing,sequence difference analysis and gene function annotationand the genetic effect of qFlw-5B was analyzed based on near-isogenic lines.Combined with the genotype and phenotype of 244 materials,the genetic effect and selection application of qFlw-5B in breeding were analyzed.This study laid a theoretical foundation for gene clone of qFlw-5B,and provided marker resources for molecular-assisted breeding of flag leaf width in wheat.