QTL Mapping And Candidate Gene Mining For The Leaf Morphological Traits Using Cultivated×Wildsoybean Recombination Inbred Line Population JLRIYC

Appropriate soybean leaf shape is of great significance for high soybean yield.For soybean dense planting and intercropping with other crops;competition for water,nutrients and light,to reduce the mutual shading between the leaves,and to meet the photosynthesis requirements for the quality and quantity of light are major constraints in production.In this study,Changling wild soybean（narrow leaf,low nitrogen fixation efficiency wild soybean）and Yiqianli（broad leaf,high nitrogen fixation efficiency Landraces）were used to construct a recombinant inbred line population JLRIYC containing 199 lines,to explore changes in different parts of the plant,genetic variation and the relationship between traits.The high-density genetic map was developed and main QTLs were identified that controls leaf shape related traits.At the same time,the differentially expressed genes were analyzed based on the transcriptome data of the leaf between the parents,and SNPs and InDels were mined in the transcriptome to develop genetic markers.Combining QTL mapping and mining candidate genes explored leaf shape regulation mechanisms.This broadens genetic information resources for soybean genetics and genome research.The main results are as follows:（1）Phenotypic variation of leaf shape related traits in JLRIYC population:It was found that in the cultivated ×wild soybean recombinant inbred line population JLRIYC,the leaflet traits of the middle leaflet of the compound leaf have larger variation at the top of the plant than the middle and bottom and the highest heritability.In the leaves at the top leaf position,leaf length and leaf width showed a very significant positive correlation,0.91,and leaf width and leaf shape showed a very significant negative correlation,which was0.49.The heritability of leaf width and leaf shape was higher than that of leaf length,for 81.0%,84.0%and 52.1%respectively.There was relatively large progressive segregation of the leaf shape,indicating that the superior alleles controlling the leaf shape of the upper leaf came from different parents.（2）QTL mapping of leaf shape related traits in JLRIYC population:A total of 40 QTLs were identified for leaf length,leaf width and leaf shape at the top,middle and bottom leaf position of the plant,of which 24 were newly discovered,and the R2 of a single QTL was 3.9-36.6%.The QTL confidence intervals overlapped together to form four multi-effect QTL clusters that contain multi-trait main effect QTLs.（3）Genetic analysis and PCR marker mapping verification of the main QTL cluster Cluster-16:There was a major QTL cluster on chromosome 16 that controls leaf width and leaf shape.The alleles that increase leaf width and reduce leaf shape came from Yiqianli.Cluster-16 mainly affected leaf shape through leaf width.Cluster-16 is only located in the top leaf position and it is speculated that it is involved in the regulation of leaf development in the later stages of soybean growth.The seed number per pod was not significant between parents,and no QTL was identified.So seed number per pod is not related to Cluster-16,which is different from the known In gene that controls the leaf shape and the seed number per pod simultaneously.Through PCR molecular marker encryption,the mapping result was verified,and two PCR molecular markers BARCSOYSSR₁6₀796 and Gm16PAV0653 which were closely linked to Cluster-16 that can be used for markerassisted selection.（4）Analysis of parental transcriptome sequence variation:From the top leaves of R1 phase of Changling wild soybean and Yiqianli,parents of JLRIYC population,transcriptome sequencing was performed;the sequence variation of the transcriptome was excavated to analyze the main types of sequence variation.It was found that 2640 InDel mutations could be used for the development of PCR markers equal or bigger than 5bp.The distribution of SLAF markers and InDel mutations on chromosomes are complementary each other and can to increase the marker density.The SNPs and InDels discovered by these transcriptome sequencing can broaden the genetic information resources for soybean genetics and genome research.（5）Analysis of the gene differential expression between parents and mining of candidate genes for leaf shape related traits:9826 differentially expressed genes were found among parents.They were enriched in processes such as membrane composition,protein activity,transport,reproductive development,and abiotic stimulation.At the same time,the differentially expressed genes and effective mutations of genes in the 4 main QTL clusters were analyzed,and a total of 9 genes were obtained Glyma.02G115200,Glyma.02G122000,Glyma.16G122500,Glyma.19G217800,Glyma.19G221700,Glyma.19G220800,Glyma.19G222000,Glyma.02G119600 and Glyma.16G122700.In addition,all sequence variations in Cluster-16 were analyzed,and four candidate genes Glyma.16G121300,Glyma.16G122200,Glyma.16G123100 and Glyma.16G123700 were screened.These 13 genes are the most likely to participate in the regulation of leaf development and can be used as the major candidate genes for further functional research.