QTL Mapping For Grain Weight Based On SLAF-seq And Fine Mapping Of A QTL For Grain Weight On Chromosome 1B In Wheat

Wheat is one of the major food crops in the world,and high yield has always been an important goal of wheat breeding.Thousand-grain weight is one of the three elements of yield composition.Mapping QTLs for 1000-grain weight,grain length and grain width will contribute to accelerate the progress of wheat high-yield molecular pyramiding breeding.In this study,a recombinant inbred line(RIL,163 lines)population derived from the cross of Jing 411 × Hongmangchun 21 were used for mapping QTLs controlling 1000-grain weight,grain length and grain width using high-density genetic linkage map constructed by SLAF-seq technology,and wheat 660 K SNP array was used to develope CAPS markers for fine-maping QTL.The main results are as follows:1.The final linkage map consists of 6,763 polymorphic SLAFs on wheat 21 chromosomes which spans 1,233.91 c M,with an average distance of 0.18 c M between adjacent markers.2.Five QTLs for thousand-grain weight were detected on chromosomes 1B,2A,3B,4B and 7A,and the phenotypic variation explained range from 4.22% to 19.55%.Particularly,two QTLs on chromosomes 1B and 2A were detected in more 6 environments,and located within the interval Marker24473338-Marker23668938 and Marker19034760-Marker186-81956,respectively,and the corresponding physical locations 647Mb-675 Mb and 40Mb-62Mb;three QTLs for grain length were detected on chromosomes 1B,2A and 4B,explaining 6.76%-19.60% of the phenotypic variation,and the correspond-ing physical position intervals were 647Mb-675 Mb,40Mb-62 Mb and 638Mb-643 Mb,respectively;one QTL for grain width was located on chromosome 2A with the phenotypic variations of 12.58%-26.68% across environments,and the physical position was 40Mb-62 Mb.3.To finely locate the major QTL on chromosome 1B,three CAPS markers were developed in the target region Marker24473338-Marker23668938,and a stable QTL was narrowed within the interval JHMfe I-Marker24708085(about 320 kb),explaining 5.70%-16.11% of the phenotypic variation.Using both the natural population consisted of 369 wheat varieties and linkage population derived from Jing411×Hongmangchun21 cross,we validated effects of the CAPS marker JHMfe I on grain weight,grain length,and grain width.The average grain weight,grain length,and grain width of wheat varieties carrying the allele JHMfe I-a were significantly higher than those carrying the JHMfe I-b,indicating that the CAPS marker newly developed can be efficiently used for high-yield molecular breeding in wheat,also provides important information for cloning of the candidate gene.4.Seven candidate genes were predicted within the interval JHMfe I-Marker24708085 on chromosome 1B: Traes CS1B01G722100 LC encoding 4-hydroxy-Tetrahydrodipicolinate synthase;Traes CS1B01G722200 LC encoding BTB and TAZ domain protein 4;Traes CS1B01G722300 LC encoding Omega-6 fatty acid desaturase,endoplasmic reticulum isozyme 2;Traes CS1B01G722400 LC encoding F-box/RNI-like superfamily protein;Traes CS1B01G722500 LC encoding THO complex subunit 4;Traes CS1B01G722600 LC encoding Transposon protein,putative,CACTA,En/Spm sub-class;Traes CS1B01G425700 encoding Ubiquitin.Especially the three proteins encoded by Traes CS1B01G722200 LC,Traes CS1B01G722400 LC and Traes CS1B01G425700 are involved in the ubiquitin proteasome pathway.Therefore,the three genes were considered as candidates in the target region.