Genetic Dissection Of Stem Water-soluble Carbohydrate Content In Bread Wheat And Development Of Molecular Markers

Stem reserved water-soluble carbohydrates(WSC)contribute 10–50% of the grain yield(GY)in common wheat(Triticum aestivum L.),and improvement of stem WSC content(SWSCC)is a promising approach to improve GY.Fructans are the predominant components of stem reserved WSC and the hydrolysis of fructans play an important role in modulation SWSCC.In the present study,a natural population comprising 166 wheat accessions from the Yellow and Huai Valleys Winter Wheat Zone(YHWZ)in China and a doubled haploid(DH)population containing 174 lines derived from Yangmai 16/Zhongmai 895 were each planted in four environments.The SWSCC at 10,20 and 30 days post-anthesis,indicated as WSC10,WSC20 and WSC30,respectively,and thousand-kernel weight(TKW)were investigated.Genotypes of the natural population were identified using the wheat 660 K and 90 K SNP arrays and a high-density physical map was constructed,and genome-wide association studies(GWAS)using TASSEL(mixed linear model,MLM)and FarmCPU software,were conducted to identify SWSCC and TKW associated loci.Genotypes of DH population were obtained using the wheat 660 K SNP array and a high-density linkage map was constructed to mapping SWSCC and TKW associated loci.In addition,the 1-FEH genes,which are the key genes in hydrolysis of fructans,were cloned and functional markers were developed based on the identified haplotypes of the genes.The main results and conclusions are summarized as follows:1.The broad-sense heritability for WSC10,WSC20 and WSC30 were as high as 0.90,0.87 and 0.85,respectively,so it would be effective to improve SWSCC by MAS.WSC10 and WSC20 were significantly correlated with TKW with correlation coefficients of 0.63 and 0.59,so it is promising to improve SWSCC by improving WSC10 and WSC20.2.A total of 62 stable SWSCC-related loci were identified by GWAS,covering 36,24 and 19 loci for WSC10,WSC20 and WSC30,respectively,with 16 associated with SWSCC at two or three time-points.Among the 62 loci,36 are potentially new,and 13 were associated with both SWSCC and TKW,and 12 other loci were located at similar positions with previously reported GY-related QTL.The identified loci set a basis for further dissecting the genetic architecture underlying WSC-and GY-related traits.Five KASP markers were developed based on the representative markers for WSC and TKW related loci,and they could be effectively used for SWSCC and TKW improvement.3.Linear regression analysis using the representative markers of the identified WSC loci indicated that pyramiding favorable WSC alleles could effectively improve SWSCC and TKW.In past 70 years,the SWSCC and TKW of the wheat cultivar from YHWZ were improved,which was supported by the pyramided WSC-increasing alleles.The favorable allele frequencies of pleotropic loci associated with WSC and TKW were increased in recent years,and there are still spaces for further improvement for some loci.Cultivars from Henan and Shandong provinces,which are two main high-yield wheat producing provinces in China,showed higher SWSCC and possessed more favorable WSC alleles.4.In the DH population,5,2 and 1 loci/locus were identified for WSC10,WSC20 and WSC20,respectively.The favorable alleles for 6 loci were from Zhongmai 895.Three of the loci were consistent with those identified in the natural population.The WSC10 and WSC20 related loci on 2DL and the WSC20 and WSC30 loci on 1BS were pleotropic loci simultaneously affecting SWSCC at two time-points.The WSC loci on 2DL,4DS,7BL and 7DS showed pleotropic effect on TKW.The candidate genes for WSC loci on 4DS,7BS and 7DS might be the plant height gene Rht-D1,and the vernalization genes Vrn-B2 and Vrn-D3,respectively.5.Three new haplotypes of the 1-FEH gene on 6A were identified,they encode two peptides.Based a missense mutation in the first exon,a KASP marker 1-FEH-AM1 was developed and validated to be effective for improvement of WSC10.In addition,sequencing of 1-FEH genes for more than 10 materials indicated that there may be no polymorphism for 1-FEHs on 6B and 6D for the wheat materials from YHWZ.The present study provide a genome-wide landscape of the genetic architecture of SWSCC,identified a panel of valuable loci associated with both SWSCC and TKW,gave a new insight into the relationship between WSC and GY,and explored the theoretical basis for co-improvement of WSC and GY.The validated linkage and functional markers are of high values for future breeding targeting for WSC and GY improvement.