QTL Mapping Of Wheat Yield-related Traits And Preliminary Mining Of Candidate Genes Based On 55K Chip And RNA-seq Technology

Wheat(Triticum aestivum L.)is one of the most crucial food crops in the global.Maintaining the stable and increased yields of wheat is crucial for ensuring food production safety.Grain weight and type are closely related to wheat yield,and are controlled by multiple micro effect genes,as well as environmental factors.Therefore,mining QTLs related to grain weight and shape and developing efficient molecular markers are of great significance for cloning wheat yield-related genes and functional research,and for improving wheat yield molecular breeding.In this study,wheat cultivars P271 and Chinese spring and their 163 offspring of recombinant inbred lines were planted in Yangling and Weinan in Shaanxi province and Xuchang in Henan province from 2018 to 2020.Ear length,plant height,grain length,width,1000 grain weight and quality were measured.Wheat 55 K SNP array was used to detect genotypes of yield-related traits,construct a physical linkage map,and locate QTLs of yield-related traits.At the same time,we also observed the grain sections of two parents P271 and Chinese spring at 4,8,and 12 days after anthesis and analyzed the transcriptome.The main results are as follows:1.This study used wheat 55 K SNP array typing data to scan the whole genome of P271 and Chinese Spring and RIL populations,and constructed a high-precision genetic distance map of wheat.The genetic map contains 3,955 markers,genetic distance of3553.38 c M,the mean genetic distance 1.82 c M.Chromosome a contains 865 markers,the genetic distance is 1424.51 c M,the mean average genetic distance between markers is 1.65 c M;The B chromosome contains 63 markers,covering the genetic distance is 1141.89 c M,the mean genetic distance is 1.79 c M;D chromosome contains 452 markers,genetic distance is 986.97 c M,and mean genetic distance is 2.18 c M.2.Seven QTLs controlling the weight of 1000 grains,which are located on chromosomes 1A,4A,1B,4D,and 7B,respectively.QTGW-1A,QTGW-4A,QTGW-6B.1,QTGW-6B.2,and QTGW-7B have a positive impact on 1000 grain weight,while QTL loci in chromosomes 1B and 4D have a negative impact.There are 10 QTL loci related to grain length,which are distributed on 2D,3A,5A,5B,6B,7A,7B and 7D chromosomes respectively.The interval on QGL-2D and QGL-5A.1 has a high gene density,and the Genetic distance interval length is 6 c M and 4 c M.The corresponding chromosome region length is about 19.21 Mb and 11.58 Mb.The genetic interval of QGL-5B is only 1 c M,and the physical interval length is close to 0.11 Mb,which can explain 11.80% of the phenotypic variation rate.Eight QTL loci for grain width were identified,distributed on chromosomes 1A,1D,4A,5A,6B,and 6D.The interval of QGW-1A.1 is the longest.The Genetic distance interval length is 13 c M,and the corresponding physical interval is about18.04 Mb,which can explain 8.89% of the phenotypic variation rate.The genetic interval of QGW-1A.2 is only 1c M,and the physical interval length is about 0.55 Mb,which can explain 9.04% of the phenotypic variation rate.Six QTLs related to length/width ratio were identified and distributed on chromosomes 1B,2B,3A,4D,and 5A,respectively.The QTL on QGWR-5A.1 corresponds to the longest physical distance,approximately 1.48 Mb,and the physical interval length corresponding to QGWR-1B is the shortest,approximately0.02 Mb.3.By sequencing the transcriptome of the grains of the two parents at 4,8 and 12 days after anthesis,it was found about 584.2-1154.5 m 150 bp reads were obtained,and further identified that 85,056-87,701 genes came from this development period of the two wheat varieties.GO enrichment analysis showed that there were differences between the two varieties in cellular and metabolic processes.According to the KEGG pathway enrichment analysis,the differential genes between the two varieties at different development stages may be related to starch and sucrose metabolism,ribosome biosynthesis,amino acid biosynthesis,pyrimidine metabolism,plant hormone signal transduction,purine metabolism,phenylalanine biosynthesis,spliceosome and other pathways.4.We put the QTLs of all traits in the SNP array data together and obtained 6,379 genes after gene ID mapping.After comparing these genes with the previously analyzed expression difference gene analysis,we found that 18,12,8 and 68 differential genes were found in grain width,length/width ratio,grain length and 1000 grain weight compared with the transcriptome,and there were 7 genes between 1000 grain weight,grain width and the common differential genes of the transcriptome.By comparing the expression levels,it was found that Traes CS6D02G217800,Traes CS4D02G240700,Traes CS1A02G062700,and Traes CS7B02G442100 showed significant differences between P271 and CS,and the annotated functions of Traes CS6D02G217800 were similar to those of ethylene transcription factors.Traes CS4D02G240700 annotated functional glutamine synthetases,and Traes CS7B02G442100 was associated with E3 ubiquitin ligases,The functions annotated by Traes CS1A02G062700 are related to lipid transfer proteins or seed development,all of which are closely related to wheat grain yield.This study provides genetic resources for in-depth analysis of the mechanism of wheat yield formation.