| Soybean is an important grain,oil and feed crop,and is widely cultivated worldwide.Two main goals of soybean breeding are high yield and high quality.Therefore,identification of the QTLs in regulating soybean yield and quality has great significance for soybean breeding towards to high yield and high quality.In addition,as an important organ of plants,root hair plays an important role in nutrients acquisition from soils.Therefore,understanding the genetic mechanisms of root hair has great significance for nutrient efficiency soybean breeding.In this study,F1,F2,F2:3 and RIL populations containing 150 F5:7 families derived from a cross between two soybean genotypes contrasting in root hair traits,RBC-HL×RBC-NH.A high-density genetic linkage map was constructed using these genetic materials,the genetic analysis and QTL mapping of 9 main agronomic traits and root hair traits of soybean were carried out.The results are as follows:（1）The results of genetic analysis showed that the genetic variations of 9 major agronomic traits ranged from 4.34%to 81.71%,the quality traits had lower variations than other traits,and the branch number had the highest variations.In addition,the heritability of these 9 traits ranged from 0.77 to 0.91,and the plant height showed the highest and the number of branches had the lowest heritability.The results displayed these 9 traits have a stable heritability and was less affected by environment.Therefore,they can be used for subsequent QTLs mapping analysis.The results of root hair genetic analysis showed that the F1 showed NH type,and the distribution of root hair trait in the progeny showed discontinuous distribution,which can be mainly divided into normal（NH）,intermediate（MH）and root hairless type（HL）,indicating that the root hair is controlled by a few genes.Furthermore,root hairs were consistent with the ratio that 15:1,7:8:1和3:1 in the F2,F2:3 and RIL populations,indicating that the root hair mutant phenotype is controlled by two independent genetic recessive locus,and the dominant genes of the two loci are functionally complementary.（2）High-density genetic map was constructed using re-sequencing and GBS techniques.First,a total of 2,209,573 variations were detected between parents RBC-HL and RBC-NH,including 1,996,740 SNPs and 212,833 Indels.A total of1,028,048 tags were generated including 536,416 effective tags,and the length of all the tags was 145,982,816,covering 7.8%of the genome.After strict screening,8,784bin markers were identified,and the total length of the constructed map was3,108.210 cM.The average distance between the markers was 0.354 cM.These results indicate that the constructed high-density genetic map can be used for further QTL mapping studies.（3）In total,36 putative QTLs were found to be associated with the 9 tested agronomic traits in two years.Among them,7 QTLs were identified for shoot architecture traits,and the LOD value was between 2.6227.25,which could explain the phenotypic variation between 7.7%56.7%.6 QTLs were identified for the yield per plant,and the LOD value was between 2.56 and 7.35,which could explain7.5%20.2%of variation.23 QTLs were identified for quality traits,and the LOD values ranged from 2.52 to 9.16,and the genetic contribution rate was 7.5%to 24.5%.In addition,QTL loci qPH19,qNN19,qGN17,qHW17,qPC13 could be stably detected in two years,suggesting that these trusted loci could be used for further fine mapping research,and the other QTLs need further confirmation.The results of QTL mapping of root hair traits showed that two major QTLs were detected on chromosomes 1 and 11,respectively,named qRHLa and qRHLb.The LOD values were 14.41 and 11.47,which explained 35.7%and 29.7%phenotypic variation.qRHLa and qRHLb covered 0.5 cM and 2.1 cM genetic interval,and 65 kb and 523 kb physical interval,respectively.（4）Candidate genes of qRHLa and qRHLb were cloned by map-based cloning.A total of 14 dCAPs polymorphic markers were developed,728 F2 plants were screened,and a total of 12 recombinant strains were identified.qRHLa and qRHLb was located in289 kb and1120 kb physical regions using genotype and phenotype.Furthermore,the evolution tree was constructed for the genes in these two physical intervals.The results showed that there were 7 pairs of homologous genes in the two intervals,and the similarity was between 86 to 97%,indicating that one pair of them could separately regulate the QTL locus qRHLa and qRHLb.In summary,36 putative QTLs were found to be associated with the 9 tested traits and 2 QTL loci qRHLa and qRHLb were associated with root hair.qRHLa and qRHLb were further mapped to the physical regions of289 kb and1120 kb,and seven pairs of homologous genes were identified as candidate genes.These research results provide candidate genes for soybean molecular breeding towards to high yield,high quality and nutrient efficient. |
