| The flag leaf is an important photosynthetic organ of wheat,and the appropriate size of flag leaves can improve the photosynthetic efficiency,thereby increasing wheat yield potential.Wheat related species contain abundant genetic resources,and it is an effective way to excavate flag leaf-related traits resources to improve wheat flag leaf morphology.In this study,a recombinant inbred line population（AM）was developed based on the cross between Sichuan tetraploid landrace Ailanmai and wild emmer wheat LM001.A genetic map was constructed based on a wheat 55K single nucleotide polymorphism（SNP）array.Combined with the phenotypic data of the six different environments,the major QTL controlling flag leaf length（FLL）and flag leaf width（FLW）were identified.Furthermore,molecular markers were developed based on the genotypes of wheat 660K SNP array to densify the genetic map and verify the genetic effect of the major QTL in different genetic backgrounds.The predicted candidate genes provide new gene resources for construction of ideal leaf type in wheat.The main results are as follows:1.Phenotype identification of flag leaf-related traits.The phenotypic data of the AM population and parents were obtained at six different environments in five years.The data of FLL and FLW showed an approximate normal distribution in all environments.Except for individual environment,both FLL and FLW of Ailanmai were significantly higher than that of LM001.The broad-sense heritability of FLL and FLW were 0.71 and 0.80,respectively.2.Mapping QTL for flag leaf-related traits.A total of 15 QTL for FLL and FLW were detected in six different environments.Seven of them controlled the development of the FLL,and eight controlled the development of the FLW.Among the 15 QTL,QFll.sau-AM-4B.2and QFlw.sau-AM-4B.4 were co-localized in the same interval.QFlw.sau-AM-4B.4 was a major QTL controlling the development of FLW,which positive alleles was from Ailanmai,and explained 10.65-37.20%of the phenotypic variation.3.Validation of major QTL for flag leaf-related traits.Comparing with the physical intervals of the previously reported major FLW loci,QFlw.sau-AM-4B.4 may be a new and major QTL for FLW.Then,the closely linked KASP marker KASP-AX-108756198 was used to successfully verify the genetic effect of the major QTL in two F3 populations.KASP-AX-108756198 can be further used in marker-assisted selection breeding to accelerate the construction of ideal leaf type in wheat.4.Candidate gene prediction of major QTL for flag leaf-related traits.Based on flanking markers,QFlw.sau-AM-4B.4 was blasted against reference genomes of durum wheat,wild emmer,and Chinese spring,and some high-confidence genes were predicted.The results showed that there were thirteen high-confidence genes in the durum wheat physical interval,of which nine genes were orthologs genes.The expression pattern analysis showed that four of the orthologs genes were highly expressed in flag and other leaves.The sequence alignment between the two parents revealed that there was no difference in the promoter of TRITD4Bv1G196680,but there were two missense mutations in the coding region.For TRITD4Bv1G197020 and TRITD4Bv1G197070,there were difference in the promoter,and there was one missense mutation and no missense mutation in the coding region,respectively.The expression levels of TRITD4Bv1G196680 was significant difference between line containing only favorable alleles of QFlw.sau-AM-4B.4 and line without favorable alleles of any major loci for FLW,and expression difference was not detected for the other two genes.Therefore,TRITD4Bv1G196680 might be a candidate gene of QFlw.sau-AM-4B.4,but further fine mapping and functional analysis are needed for verification. |
