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Soybean provides large amounts of protein for human, and the most popular consumption pattern is tofu and soymilk. Recently, the demand of tofu and soymilk is increased, and the breeding of special variety becomes very urgent. To illustrate the genetic basis of these traits, 269 accessions were evaluated under six environments, and 32 associated SNPs were identified on nine chromosomes across multiple environments or conferring diverse traits. Of these SNPs, 16 were demonstrated by BLUP values. Seven adjacent‐SNPs were first identified to associate with tofu and soymilk weights in an 1.02‐Mb region on chromosome 8, which were verified by BLUP‐values. Meanwhile, four neighbouring SNPs in a 0.32‐Mb region on chromosome 12 were first identified to associate with these traits across multiple environments, of which three were detected in BLUP values. Furthermore, some candidate genes, that is, α‐glucan water dikinase Glyma.08G283700 and E3 SUMO‐protein ligase Glyma.12G071300, were screened out with differential expressions between the high‐ and low‐tofu/soymilk‐output accessions. Thus, these associated SNPs and candidate genes provide new insight into the genetic basis of tofu and soymilk processing quality in soybean. [ABSTRACT FROM AUTHOR]

Seed coat cracking (SCC) is a major factor that affects seed appearance quality, pathogen infection, humility absorption and seed storage in soybean. In view of this, a recombinant inbred line (RIL) population and a natural population were genotyped by SoySNP6K and were evaluated for type‐I SCC percentage. Eight QTLs were identified on six chromosomes with phenotypic variation explanations ranging from 3.46% to 34.71% in RIL population. Twenty‐three SNPs associated with cracking percentage were identified on eight chromosomes in natural population. More importantly, the association SNP ss715593768 in natural population was the left marker of qSCC‐C2‐1 in RIL population, which were detected across all of the environments and BLUP values. Two genes, Glyma.06G197300 and Glyma.06G202100, were proposed in this QTL region. These two genes showed differential expressions at seed developmental stages between RIL parents in the seed transcriptome sequencing and quantitative reverse transcription‐polymerase chain reaction (qRT‐PCR) analysis, and also showed differential expressions between two germplasms with different cracking percentage in natural population. Thus, the results provide novel insight into the genetic basis and molecular improvement of SCC in soybean. [ABSTRACT FROM AUTHOR]

Seed size and shape are important characteristics in soybean breeding, whereas the genetic basis are still unknown, which constrains the improvement of related traits. In view of this, one recombinant inbred line population was assessed for six related traits under four environments. In total, 10 QTLs controlling the related traits were identified, and five were detected across at least two environments, which located on chromosomes 2, 4, 6, 13, and 16 with phenotypic variation explained (PVE) 3.6% to 9.4%. Among them, qSS‐02 and qSS‐16 were identified to control four and five related traits with pleiotropic effects on chromosomes 2 and 16 across three and two environments, respectively. Meanwhile, qSS‐04 was detected to control all of the six related traits on chromosome 4 under four environments with PVEs 4.5% to 9.4%. Furthermore, the candidate genes, that is, Glyma.04G055100 (big grain protein) and Glyma.13G068500 (cytochrome P450), were screened out for their different expressions between population parents at different seed growth and developmental stages. Thus, these results could provide novel insights for the genetic basis of seed size and shape in soybean. [ABSTRACT FROM AUTHOR]

Soybean mosaic virus (SMV) is a serious disease in soybean production, and the cultivation of resistant variety is the irreplaceable strategy to decrease the virus damage. However, the progress of SMV molecular breeding is limited partly due to the diverse types of SMV strains, solely resistance to virus strain of variety and minor genetic effects of QTLs. In the present study, one major pleiotropic additive QTL, qSMV‐D1b, with phenotypic variation explained that 27.04%–54.23% was identified on chromosome 2, and the favourable allele was from the resistant parent "Qihuang30". Meanwhile, the allele analysis of the flanking markers showed that the favourable genotypes presented high resistance to SC3 and SC7 strains with lower disease index, while the unfavourable genotypes presented high sensitivity with higher disease index. Furthermore, six candidate genes, including four novel resistance genes, Glyma.02G121000, Glyma.02G123000, Glyma.02G123200 and Glyma.02G124700 with different expression levels between resistant and sensitive parents were discovered through transcriptome sequencing and confirmed by quantitative real‐time PCR. The resistance genes and the tightly linked molecular markers can be used for SMV breeding in soybean. [ABSTRACT FROM AUTHOR]

Soybean provides irreplaceable protein and oil. Pods and seeds are essential soybean harvested organs. To illustrate the genetic basis of pod‐ and seed‐related traits, a natural population was assessed for eight related traits under four environments. In all, 15 associated SNPs were identified across multiple environments or controlling various traits, and 11 were verified through BLUP. Two SNPs on chromosome 15 were associated with six traits across multiple environments. Two SNPs on chromosome 2 were also associated with six traits under multiple environments. Significant phenotype differences between favourable and unfavourable alleles/haplotypes under four environments were detected. Significant association of pod length SNP and large‐pod phenotype (pod length ≥4.5 cm) was detected. The genetic basis of elite germplasms was analysed, and 'Chuxiu' possessed all of the 15 favourable alleles with best phenotype. Some candidate genes participating in cell wall structural remodelling, gibberellin and ethylene pathways were selected with different expressions in pod developmental stages. These results provided novel insights into genetic basis and molecular markers/candidate genes for soybean fresh pod and seed genetic improvement. [ABSTRACT FROM AUTHOR]

Soybean is important throughout the world not only due to the high seed protein and oil but also owing to the seed isoflavone. To improve the isoflavone concentration in seeds, detecting and mining the stable and reliable quantitative trait loci (QTLs) and related genes in multiple environments and genetic backgrounds become more and more important. In view of this, a F recombinant inbred line (RIL) population of 345 lines derived from a cross between Zheng 92116 and Liaodou14 (ZL) was genotyped using 1739 polymorphic SNP and 127 SSR markers in this study and was phenotyped for individual and total seed isoflavone in four environments over 2 years. In total, 48 additive QTLs, which explained 3.00-29.83% of seed isoflavone variation, were identified. Of them, eight QTLs ( qDA1_1, qGA1_1, qTIA1_1, qDA1_2, qGA1_2, qTIA1_2, qDA1_3, qTIA1_3) with phenotypic variation explained (PVE) ranging from 14.09 to 28.59% for daidzin, genistin, and total isoflavone were located on the same region of linkage group (LG) A1. These QTLs were further verified in another RIL population derived from Zheng 92116 × Qihuang 30 (ZQ). Meanwhile, the other four overlapping QTLs on linkage group B1, which were associated with glycitin content ( qGLB1_1, qGLB1_2, qGLB1_3, qGLB1_4) and explained 16.52 to 29.83% of phenotypic variation, were also verified using the ZQ population. Moreover, the individuals with different genotypes at the common flanking SNP markers for these QTLs on LGs A1 and B1 in the two mapping populations showed significant different isoflavone content, which further validate the QTL mapping results. And also, some candidate genes might participate in the isoflavone biosynthesis processes were found in these stable QTL regions. Thus, the novel and stable QTLs identified and verified in this study could be applied in marker-assisted selection breeding or map-based candidate genes cloning in soybean seed isoflavone genetic improvement in future. [ABSTRACT FROM AUTHOR]

Soybean is important throughout the world due to its high seed protein and oil, while the quality and quantity of seed amino acids need to be improved. To improve the multiple amino acid concentrations in soybean simultaneously, detecting and utilizing the pleiotropic quantitative trait loci (QTL) and related genes become increasingly important. In view of this, a F6:7 recombinant inbred line population was genotyped using 1739 polymorphic SNP and 127 SSR markers in the present study and was phenotyped for seventeen types of amino acids simultaneously. In total, twelve co-located or overlapped pleiotropic additive QTL clusters, which explained 2.38-16.79% of the amino acid variation, were identified. Of them, one novel pleiotropic QTL cluster with a phenotypic variation explained ranging from 8.84 to 16.79% for ten kinds of amino acid contents (glycine, alanine, isoleucine, leucine, valine, methionine, aspartic acid, glutamic acid, lysine and phenylalanine), was located at the same position on linkage group D2, and the confidence interval was only 0.8 cM. Moreover, the individuals in this family-based population (345 lines) and another cultivar-based population (254 varieties) with different genotypes at the common flanking markers for this QTL cluster showed significantly different amino acid contents, which further validated the QTL mapping results. Additionally, some candidate genes that might participate in the amino acid biosynthesis process were found in these pleiotropic QTL regions. Thus, novel pleiotropic QTL clusters could be applied in marker-assisted selection breeding or map-based candidate gene cloning in soybean for multiple amino acid genetic improvements in seed in the future. [ABSTRACT FROM AUTHOR]