Marker‐assisted backcrossing of a null allele of the α‐subunit of Soybean (Glycine max) β‐conglycinin with a Chinese soybean cultivar (a). The development of improved lines

The development of soybean varieties that lack the β‐conglycinin α‐subunit is an attractive goal because the β‐conglycinin α‐subunit negatively influences the nutrition and gelation of tofu and is a major allergen. To remove this undesirable allergen and simultaneously improve the seed nutritional value and food‐processing quality, marker‐assisted background selection (MABS) was used in backcross breeding to incorporate cgy‐2, a null phenotype version of the gene encoding the β‐conglycinin α‐subunit, from the donor line ‘RiB’ into the genetic background of the Chinese cultivar ‘Dongnong47’ (DN47), a popular high‐oil superfine seed soybean cultivar from Heilongjiang Province, China. In each F₂ (F₂, BC_nF₂) generation of the breeding programme, the offspring that carried the introgressed cgy‐2 were identified by sodium dodecyl sulphate–polyacrylamide gel electrophoresis and rescreened by MABS using simple sequence repeat markers to accelerate recurrent parent genome recovery. Of the 49 advanced backcrossing breeding lines (ABLs), the three best lines, ABL1, ABL2 and ABL3, were selected from the BC₁, BC₂ and BC₃ populations, respectively. The ABLs were evaluated for desirable agronomic characteristics, yield‐related traits, amino acid composition, free amino acid composition and tofu‐processing quality in the mature seeds. All of the ABLs lacked the α‐subunit but grew and reproduced normally without deleterious effects on physiological processes such as seed development and germination. The free amino acid content of ABL1 was significantly higher than that of ‘DN47’, with arginine (Arg) being particularly enriched. Compared to the recurrent parent ‘DN47’, the total protein content of the three ABLs was higher, the amino acid composition of the seed proteins was markedly modified and the yield and hardness of the tofu that was made from the ABLs were significantly increased. MABS combined with stringent phenotypic selection in a backcross breeding programme is a feasible strategy for the genetic engineering of seed protein components to produce allergenic subunit‐deficient variant alleles.     

Breeding and characterization of soybean Triple Null; a stack of recessive alleles of Kunitz Trypsin Inhibitor,Soybean Agglutinin,and P34 allergen nulls

Soybean (Glycine max) seeds contain bioactive proteins with antinutritional and immunological properties that affect metabolism and assimilation of nutrients. The presence of antinutritional proteins requires soybeans to be heat‐treated resulting in input energy costs. Nulls for bioactive seed proteins have been previously isolated from the USDA soybean collection, including Kunitz trypsin inhibitor (TI), soybean agglutinin (LE) and immunodominant soybean allergen P34 protein. Each of these nulls has the potential to partially address the concerns of soybean feed/food consumption. A stack of recessive nulls of TI, LE and P34 was created in a cv ‘Williams 82’ background termed ‘Triple Null’. Triple Null has a slight reduction of total protein compared with ‘Williams 82’ corresponding to aggregate contribution of TI, LE and P34 in the seed proteome. Triple Null's proteome analysis revealed P34 and TI nulls are frame‐shift mutants able to accumulate small amounts of authentic P34 and TI proteins. Triple Null has possible application as a conventional feed/food source and for immunotherapy to mitigate soybean allergenic response.     

Mapping quantitative trait loci (QTLs) underlying seed vitamin E content in soybean with main,epistatic and QTL × environment effects

Soybean (Glycine max (L.) Merr.) seed contains small amounts of tocopherol, a non‐enzymatic antioxidant known as lipid‐soluble vitamin E (VE). Dietary VE contributes to a decreased risk of chronic diseases in humans and has several beneficial effects on resistance to stress in plants, and increasing VE content is an important breeding goal for increasing the nutritional value of soybean. In this study, quantitative trait loci (QTLs) underlying VE content with main, epistatic and QTL × environment effects were identified in a population of F_5 : 6 recombinant inbred lines from a cross between ‘Hefeng 25’ (a low‐VE cultivar) and ‘OAC Bayfield’ (a high‐VE cultivar). A total of 18 QTLs were detected that showed additive main effects (a) and/or additive × environment interaction effects (ae) in different environments. Moreover, 19 epistatic pairs of QTLs were found to be associated with α‐tocopherol (α‐Toc), γ‐tocopherol (γ‐Toc), δ‐tocopherol (δ‐Toc) and total VE (TE) contents. The QTLs identified in multienvironments could provide more information about QTL by environment interactions and could be useful for the marker‐assistant selection of soybean cultivars with high seed VE contents.     

Effects of high oleic acid soybean on seed yield,protein and oil contents,and seed germination revealed by near‐isogeneic lines

Typical soybean oil is composed of palmitic, stearic, oleic, linoleic and linolenic acids. High oleic acid content in soybean seed is a key compositional trait that improves oxidative stability and increases oil functionality and shelf life. Using a marker‐assisted selection method, near‐isogenic lines (NILs) of G00‐3213 for the high oleic trait were developed and yield tested. These NILs have various combinations of FAD2‐1A and FAD2‐1B alleles that were derived from the same backcrossing populations. The results indicated that G00‐3213 NILs with both homozygous mutant FAD2‐1A and FAD2‐1B alleles produced an average of 788 g/kg oleic acid content. The results also demonstrated that possessing these mutant alleles did not cause a yield reduction. Furthermore, seed germination tests across 12 temperatures (12.8–32.0°C) showed that modified seed composition for oleic acid in general did not have a major impact on seed germination. However, there was a possible reduction in seed germination vigour when high oleic seeds are planted in cold soil. The mutant FAD2‐1A and FAD2‐1B alleles did not hinder either seed or plant development.     

Genotypic lipoxygenase variation in soybean seeds and response to nitrogen nutrition

Decreasing the lipoxygenase content of soybean (Glycine max (L.) Merr.) seed is a prerequisite for its increased use in human foods. These investigations aim to analyse the variation of lipoxygenase contents in relation to the genotype or the nitrogen nutrition of the plant. Four genotypes from a divergent selection for N₂ fixation and the recurrent parent, Weber, were grown in pots, and two Bradyrhizobium japonicum strains (G.49 and SMGS1) were used. Dinitrogen fixation was estimated in situ using the acetylene–reduction assay. The lipoxygenase activity was determined polarographically on seeds taken from plants grown under controlled conditions in the presence or absence of symbiotic N₂ fixation. The large genotypic variation observed for the lipoxygenase contents was enhanced by high N₂ fixation. The variation range of lipoxygenase contents, which was obtained through the combination of the genotypic variation and the N₂ fixation activity, was relatively large with a ratio of 2 on a seed dry–weight basis and a ratio of 2.6 when the total proteins were considered. Decreased lipoxygenase content and increased total protein content can thus be considered in parallel in a genetic context, together with more efficient N₂ fixation.     

Molecular characterization of a β-conglycinin deficient soybean

Summary The soybean seed storage protein β-conglycinin has a low amino acid score, shows lower functional gelling properties compared with glycinin and contains a major allergen. The wild soybean (Glycine soja Sieb et Zucc.) QT2 lacks all the subunits of β-conglycinin, and this deficiency is controlled by a single dominant gene Scg-1 (suppressor of β-conglycinin). Scg-1 was introduced into a soybean cultivar Fukuyutaka from QT2 and this near-isogenic line was designated as QY7-25. Segregation analyses of the progeny derived from a cross between QY7-25 and the wild type did not show any significant changes caused by Scg-1 in the germination ratio and seed weight. Low amounts of mRNAs for the α ’, α and β subunits of β-conglycinin were detected by RT-PCR in QY7-25. We revealed that an α subunit mRNA expressed from a region which replaced with mutant line in the near-isogenic line QY7-25 by single nucleotide polymorphisms analysis. In addition, an abnormal splicing event in a cDNA clone for the β subunit isolated from immature seed of QY7-25 was observed. Southern analysis using the coding region of α ’ subunit gene as a probe revealed a polymorphism between QY7-25 and wild type and this genotypes co-segregate with the deficiency of β-conglycinin subunits. These results suggest that the β-conglycinin deficiency might be controlled by a claster region of β-conglycinin subunit genes. In the present study, no agronomical disadvantage in QY7-25 was observed, confirming that Scg-1 is a valuable gene for soybean breeding.     

Graft-induced changes in soybean storage proteins. I. Appearance of the changes

Summary Genetic changes induced by grafting were observed in soybean storage proteins, involving the 11S acidic subunit composition and Kunitz trypsin inhibitor. Changes from Gly ₁ Gly ₁to Gly ₁ gly ₁involved the 11S acidic subunit, and those from Ti ⁰Ti⁰ to Ti ³Ti⁰ involved the KTI in the first progeny (G₁S₁) in the scion (Gly ₁ Gly ₁ Ti ⁰Ti⁰, var. Kinzu) grafted onto var. Raiden (gly ₁ gly ₁ Ti ³ Ti ³). The progenies G₁S₂ and G₂S₁ from the seeds that had been changed segregated for both proteins. However, the segregation ratio in the progenies were different from those of the F₂'s from the sexual crosses between Kinzu and Raiden used for grafting. These findings show that the changes (changed genes) were transmitted to the progenies in an unstable manner.     

Identification and validation of an over‐dominant QTL controlling soybean seed weight using populations derived from Glycine max × Glycine soja

Heterosis, or hybrid vigour, has been used to improve seed yield in several important crops for decades and it has potential applications in soybean. The discovery of over‐dominant quantitative trait loci (QTL) underlying yield‐related traits, such as seed weight, will facilitate hybrid soybean breeding via marker‐assisted selection. In this study, F₂ and F_2 : 3 populations derived from the crosses of ‘Jidou 12’ (Glycine max) × ‘ZYD2738’ (Glycine soja) and ‘Jidou 9’ (G. max) × ‘ZYD2738’ were used to identify over‐dominant QTL associated with seed weight. A total of seven QTL were identified. Among them, qSWT_13_1, mapped on chromosome 13 and linked with Satt114, showed an over‐dominant effect in two populations for two successive generations. This over‐dominant effect was further examined by six subpopulations derived from ‘Jidou12’ × ‘ZYD2738’. The seed weight for heterozygous individuals was 1.1‐ to 1.6‐fold higher than that of homozygous individuals among the six validation populations examined in different locations and years. Therefore, qSWT_13_1 may be a useful locus to improve the yield of hybrid soybean and to understand the molecular mechanism of heterosis in soybean.     

Identification of low lectin mutants in soybean

Lectin is one of the known antinutritional factors that deteriorate the soybean protein quality and development of cultivars with low lectin content will help to improve nutritional quality of soybean [Glycine max (L.) Merrill]. Therefore, attempts were made to induce mutations for low lectin content in the cultivar ‘MACS 450’. Soybean cultivar ‘MACS 450’ was subjected to combination treatments of γ‐rays and ethyl methane sulphonate (EMS) with an objective to induce variability for low lectin content. The treatments of different combinations of γ‐rays and EMS were 50 Gy + 0.2% EMS, 50 Gy + 0.4% EMS, 100 Gy + 0.2% EMS and 100 Gy + 0.4% EMS. Of the 3200 treated M₁ seeds sown, 16 400 M₂ plants were raised. In M_2, 72 plants were identified for low lectin content [<40 × 10⁵ haemagglutination unit (HAU)/mg] and were carried up to M₅ generation. In M₅ generation, lectin content in ‘MACS 450’ was 39.23 to 50.0 × 10⁵ HAU/mg, and was compared with the nine true breeding lines identified having low lectin content, ranging from 2.3 × 10⁵ to 27.46 × 10⁵ HAU/mg. Three mutants were found to possess very low lectin content (ranging from 2.0 × 10⁵ to 3.0 × 10⁵ HAU/mg). Thus, the identified mutant lines with low lectin content will greatly improve soybean protein quality, thereby reducing financial burden on the soybean industry for processing soybean meal and also making it suitable for human consumption. All the mutants showed normal seed development, having soluble protein content similar or higher than that in the parent (32.0 mg/ml). This indicates that the change in lectin content does not have any negative impact on the plant growth and protein content.     

Identification of quantitative trait loci controlling soybean seed weight in recombinant inbred lines derived from PI 483463 (Glycine soja) × ‘Hutcheson’ (G. max)

The objective of this study was to identify quantitative trait loci (QTLs) controlling 100‐seed weight in soybean using 188 recombinant inbred lines (RIL) derived from a cross of PI 483463 and ‘Hutcheson’. The parents and RILs were grown for 4 years (2010–2013), and mature, dry seeds were used for 100‐seed weight measurement. The variance components of genotype (a), environment (e) and a × e interactions for seed weight were highly significant. The QTL analysis identified 14 QTLs explaining 3.83–12.23% of the total phenotypic variation. One of the QTLs, qSW17‐2, was found to be the stable QTL, being identified in all the environments with high phenotypic variation as compared to the other QTLs. Of the 14 QTLs, 10 QTLs showed colocalization with the seed weight QTLs identified in earlier reports, and four QTLs, qSW5‐1, qSW14‐1, qSW15‐1 and qSW15‐2, found to be the novel QTLs. A two‐dimensional genome scan revealed 11 pairs of epistatic QTLs across 11 chromosomes. The QTLs identified in this study may be useful in genetic improvement of soybean seed weight.     

Yield stability studies of soybean (Glycine max (L.) Merrill) under rhizobia inoculation in the savanna region of Nigeria

Soybean (Glycine max (L.) Merrill) production is expanding into temperate and tropical environments. Yield stability studies under rhizobia inoculation were investigated in 24 soybean genotypes over two successive growing seasons at three agro‐ecological zone of Nigeria, during the 2015–2016 rainy seasons. Treatments were arranged in a split‐plot design and replicated three times. Treatments were 24 soybean genotypes and three levels of rhizobia inoculation. Results indicated that the variation of genotypes and inoculation on percentage emergence, height, number of leaves, number of branches per plant, total biomass yield, above‐ground biomass and seed yield was significant (p = .05). The effects of genotypes (G), environment (E) and G × E interactions on seed yield were also significant. Two soybean genotypes (TGx 1989‐45F and TGx 1990‐110FN) were identified as the most promising in relation to yield stability. Of the three locations, Abuja produced the least interaction effects followed by Igabi and may be most appropriate environments for large‐scale soybean production. Appropriate inoculation of soybean with inoculants (LegumeFix and or NoduMax) should be encouraged in farmer's field.     

Saponin polymorphism in the Korean wild soybean (Glycine soja Sieb. and Zucc.)

Seed saponin composition of 3025 wild soybean (Glycine soja Sieb. and Zucc.) accessions collected from nine regions of Korea was analysed by thin‐layer chromatography to determine its polymorphic variation and geographical distribution and find mutants in saponin components. The saponin composition of seed hypocotyls was primarily divided into seven phenotypes, designated as Aa, Ab, AaBc, AbBc, Aa+α, AaBc+α and AbBc+α. The predominant phenotypes were AaBc (55%), Aa (33%), AaBc+α (7.5%) and Aa+α (3.3%). The frequencies of Ab, AbBc and AbBc+α were very low (0.3‐0.5%). Codominant alleles Sg‐1^a and Sg‐1^b and dominant allele Sg‐4 occupied 98.6, 1.1 and 63.3%, respectively. Alleles Sg‐3 and Sg‐5 were found to be dominant in all the analysed accessions except the mutants. Three accessions were discovered as mutants via LC‐PDA/MS/MS. The accession CWS0115 did not produce saponin Aa and Ax, CWS2133 did not produce saponin Aa and Ab and CWS5095 did not produce any group A saponins. These newly determined mutants might be utilized in producing a new soybean variety with good taste as well as in biosynthetic studies.     

Characterization of genotype by environment interactions in soybean breeding programmes of southeast Europe

Southeast Europe is Europe's major production area of soybean of maturity groups (MG) 0, I and II, but genotype by environment interaction (GEI) for soybean traits in this region is still not characterized. The objective of this study was to characterize GEI in soybean grown in Croatia for seed yield, protein and oil content. Fourteen soybean cultivars of MG 0 and I were evaluated at 15 environments. In the combined anova , genotypes, environments and GEI were significant. All three seed traits were more affected by year than by location and seed yield and protein content were more sensitive to environmental changes than oil content. Genotype by environment interaction is generally of less importance than effects of genotypes and years, especially for oil content. High‐yielding genotypes had values of regression coefficient (b) close to 1, indicating that they were not responsive to extreme environments, either positive or negative. Means and b values were not correlated for yield and negatively correlated for protein and oil content, probably because of low‐input practice in the region. The absence of recognizable differences in means, b values and principal component scores of ammi analysis between two MGs for all traits indicated that soybean cultivars of MG 0 may be recommended for growing in the region because they responded similarly to environmental changes as do full‐season genotypes of MG I.     

Comparative analysis of different methods revealing the involvement of proteins during ageing of rice seeds

Seed longevity is a very important characteristic controlling seed quality. However, the mechanism underlying this characteristic is poorly understood. In this study, 'FH7185', a storable rice variety, the germination rate of which was 66.63%, much higher than the control after artificial ageing under relative humidity 88% and 42°C for 21 days. Different methods were applied to reveal the involvement of proteins during ageing of rice seeds. In total, 35 differential proteins were identified from 2D‐PAGE, and 3,719 proteins from iTRAQ analysis. A comparison of these two methods showed that not all protein types could be detected on the 2D‐PAGE gels, and the dynamic range was somewhat limited. So the comprehensive proteome map from the iTRAQ analysis was used to identify the quantitatively regulated proteins that played roles in seed longevity, and found that the most marked change was the increased abundance of many metabolic enzymes, especially the ones involved in α‐linolenic acid metabolism in the embryos during ageing. OsLOX2 and OsLOX3 had a negative effect on seed longevity, which were lower in FH7185 than the control. The dehydrogenase (LOC_Os07g44430) which played a major catalytic role in lipid peroxidation, also changed significantly during ageing. Therefore, OsLOX2, OsLOX3 and Loc_OS 07G44430 may be involved in the regulation of seed longevity with a synergistic effect.     

大豆7S球蛋白α-亚基缺失型种质创新

采用常规杂交育种方法,人工去雄、授粉,以10份综合农艺性状优良的黑龙江省主栽品种(或优良品系)为母本、亚基组成为(α'+α+11S酸性亚基)-缺失型育种材料日B为父本进行有性杂交。将F1杂交种南繁,单粒点播、单株收获得到F2代分离群体。聚丙烯酰胺凝胶电泳(SDS-PAGE)法分析表明,F1代杂交种子7S球蛋白α'-与α-亚基的表现型全部为正常型。在杂交F2代种子中获得了具有中国大豆遗传背景的α-缺失、(α+A1aA1bA2)-缺失、A3-缺失、(α'+A4)-缺失和(α'+α)-缺失的贮藏蛋白亚基组成新类型种质,为我国大豆蛋白组分育种选择提供了重要的中间材料。     

Interaction Amongst Soybean [Glycine max (L.) Merrill] Genotype, Soil Type and Inoculant Strain with Regard to N2 Fixation

The nitrogen (N₂)‐fixing bacterial inoculant strain for soybean [Glycine max (L.) Merrill] is not indigenous to South African soils. The interaction between soybean genotype, soil type and inoculant strain, however, has a definite influence on soybean production and compatibility should be optimized. This paper reports a growth chamber study using three different soybean genotypes (Barc‐9, Avuturda and Talana), three Bradyrhizobium japonicum inoculant strains (WB108, WB112 and WB1) and three soil types (Avalon, Arcadia and sand) to evaluate the effectiveness of N₂ fixation by different genotype × soil type × inoculant strain combinations, using different measuring parameters. These parameters included nodule fresh mass (NFM), amount of N₂ fixed (P_fix), as determined by the ureide method, seed protein content (SPC), average seed mass per plant (SMP) and average foliar N content (FNC). The comparison amongst the three‐way interactions, genotype × soil type × inoculant strain, did not differ significantly for the parameters used. Significant two‐way interactions were soil × inoculant for FNC, P_fix and SMP; soil × genotype for FNC and SMP, and inoculant × genotype for FNC (P < 0.05). The soil × inoculant strain interaction was significant for P_fix (P < 0.05). NFM, P_fix, FNC, SMP and SPC correlated positively with soil pH and negatively with soil clay content and soil NO₃^– and NH₄⁺ content (P < 0.05). SPC was significantly different (P < 0.05) for soil type, genotype and inoculant strain. P_fix and NFM did not reflect the protein content of the seeds, indicating that nodule evaluation should be used with caution as a N₂ fixation parameter. Low soil pH and high mineral N content inhibited N₂ fixation. NFM correlated negatively with the clay content of the soil. This finding confirms that soybean production in South Africa can be improved by appropriate selection of genotypes and inoculant strains for their compatibility in different soils.     

Molecular loci associated with seed isoflavone content may underlie resistance to soybean pod borer (Leguminivora glycinivorella)

Soybean pod borer (SPB) (Leguminivora glycinivorella (Mats.) Obraztsov) causes severe loss of soybean (Glycine max L. Merr.) seed yield and quality in some regions of the world, especially in north‐eastern China, Japan and Russia. Isoflavones in soybean seed play a crucial role in plant resistance to diseases and pests. The aim of this study was to find whether SPB resistance QTL are associated with soybean seed isoflavone content. A cross was made between ‘Zhongdou 27’ (higher isoflavone content) and ‘Jiunong 20’ (lower isoflavone content). One hundred and twelve F_5:10 recombinant inbred lines were derived through single‐seed descent. A plastic‐net cabinet was used to cover the plants in early August, and thirty SPB moths per square metre were put in to infest the soybean green pods. The results indicated that the percentage of seeds damaged by SPB was positively correlated with glycitein content (GC), whereas it was negatively correlated with genistein (GT), daidzein (DZ) and total isoflavone content (TI). Four QTL underlying SPB damage to seeds were identified and the phenotypic variation for SPB resistance explained by the four QTL ranged from 2% to 14% on chromosomes Gm7, 10, 13 and 17. Moreover, eleven QTL underlying isoflavone content were identified, and ten of them were encompassed within the same four marker intervals as the SPB QTL (BARC‐Satt208‐Sat292, Satt144‐Sat074, Satt540‐Sat244 and Satt345‐Satt592). These QTL could be useful in marker‐assisted selection for breeding soybean cultivars with both SPB resistance and high seed isoflavone content.     

硫素对不同基因型大豆球蛋白组成及含量的影响

为了探讨施硫量对不同基因型大豆7S和11S球蛋白亚基组成及含量的影响,寻找不同基因型大豆品种最佳施硫水平,以期提高大豆籽粒球蛋白的含量,改善期品质。选用在黑龙江省种植面积较大的‘黑农48’（高蛋白）、‘黑农37’（中间型）和‘黑农44’（高油）3种大豆作为试验材料。采用盆栽种植,每个品种设S1、S2、S3、S4 4个S处理（即每千克土壤分别施单质硫0、0.02、0.04、0.06 g）。采用SDS-PAGE凝胶电泳方法,对成熟大豆籽粒球蛋白亚基组成和含量2个指标进行研究。结果表明：在3个大豆品种中,7S球蛋白由α′、α、γ、β 4个亚基组成;11S球蛋白由酸性亚基和碱性亚基组成;各种亚基分子量在品种间的差异不显著。同一品种不同处理中均以S3水平下蛋白含量最高,对不同品种施用硫肥时,以高油品种提高球蛋白含量效果显著。施用硫肥对3个大豆品种的7S和11S球蛋白各种亚基组成都没有影响,对分子量的大小影响很小。施用硫肥对3个大豆品种中的7S和11S球蛋白和亚基含量有显著影响,适宜的施用硫肥有利于提高各品种球蛋白和亚基的含量。     

Identification of quantitative trait loci underlying soybean (Glycine max [L.] Merr.) seed weight including main,epistatic and QTL × environment effects in different regions of Northeast China

Seed weight (SW) is the important soybean (Glycine max [L.] Merr.), yield component and also affected the quality of soybean‐derived foods. The aim of this study was to identify the quantitative trait loci (QTL) underlying SW through 112 recombinant inbred lines (RILs) derived from the cross between “Zhongdou27” (G. max, designated by its bigger seed size, 21.9 g/100 seeds) and “Jiunong 20” (G. max, smaller seed size, 17.5 g/100 seeds). Phenotypic data were collected from this RIL population after it was grown in the sixteen tested environments. A total of eight QTL (QSW1‐1, QSW2‐1, QSW2‐2, QSW5‐1, QSW15‐1, QSW17‐1, QSW19‐1 and QSW20‐1) were identified, and they could explain 4.23%–14.65% of the phenotypic variation. Among these eight QTL, three QTL (QSW1‐1 located on the interval of Sat_159‐Satt603 of chromosome (Chr) 1 (LGD1a), QSW19‐1 located on the interval of Sat_340‐Satt523 of Chr 19 (LGL) and QSW20‐1 located on Sat_418‐Sat_105 of Chr 20 (LGI)) were newly identified and could explain 4.235%–10.08%, 8.45%–13.49% and 8.08%–10.18% of the phenotypic variation, respectively. Six of the eight identified QTL including QSW2‐2, QSW5‐1, QSW15‐1, QSW17‐1, QSW19‐1 and QSW20‐1 exhibited a significant additive (a) effect, while two QTL (QSW2‐1 and QSW19‐1) only displayed significant additive‐by‐environment (ae) effects. A total of four epistatic pairwise QTL for SW were identified in the different environments. These eight QTL and their genetic information obtained here were valuable for molecular marker‐assisted selection and the realization of a reasonable SW breeding programme in soybean.