Glycine max and Glycine soja are capable of cold acclimation

Soybean has been considered a cold intolerant species; based largely upon seed germination and soil emergent evaluations. This study reports a distinct acquisition of cold tolerance, in seedlings, following short acclimation periods. Diversity in cold responses was assessed in eight cultivars of Glycine max and six accessions of G. soja. All varieties of soybean significantly increased in freezing tolerance following acclimation. This study indicates soybean seedlings are indeed capable of sensing cold and acquiring cold tolerance. Germination rates after cold imbibition were negatively correlated with maturity group, but positively correlated with cold acclimation potential in G. soja. Seed fatty acid composition was varied between the species, with Glycine soja accessions containing about 2‐times more linolenic acid (18:3) than G. max. Furthermore, high levels of linoleic acid (18:2) in seeds were positively correlated with germination rates following cold imbibition in G. soja only. We suggest that domestication has not impacted the overall ability of soybean to cold acclimate at the seedling stage and that there is little variation within the domesticated species for ability to cold acclimate. Thus, this brief comparative study reduces the enthusiasm for the “wild” species as an additional source of genetic diversity for cold tolerance.     

Mapping and use of QTLs controlling pod dehiscence in soybean

While the cultivated soybean, Glycine max (L.) Merr., is more recalcitrant to pod dehiscence (shattering-resistant) than wild soybean, Glycine soja Sieb. & Zucc., there is also significant genetic variation in shattering resistance among cultivated soybean cultivars. To reveal the genetic basis and develop DNA markers for pod dehiscence, several research groups have conducted quantitative trait locus (QTL) analysis using segregated populations derived from crosses between G. max accessions or between a G. max and G. soja accession. In the populations of G. max, a major QTL was repeatedly identified near SSR marker Sat_366 on linkage group J (chromosome 16). Minor QTLs were also detected in several studies, although less commonality was found for the magnitudes of effect and location. In G. max × G. soja populations, only QTLs with a relatively small effect were detected. The major QTL found in G. max was further fine-mapped, leading to the development of specific markers for the shattering resistance allele at this locus. The markers were used in a breeding program, resulting in the production of near-isogenic lines with shattering resistance and genetic backgrounds of Japanese elite cultivars. The markers and lines developed will hopefully contribute to the rapid production of a variety of shattering-resistant soybean cultivars.     

Evolutionary studies of the soybean: the frequency and distribution of alleles among collections of Glycine Max and G. Soja of various origin

Summary Allelic frequencies at 10 loci common throughout the genus Glycine subgenus Soja were determined for 27 geographical area-species samples. The samples included 366 accessions of Glycine soja, the wild soybean, and 193 accessions of G. max, the domesticated soybean, from the USDA Soybean Germplasm Collection. The data indicate that the alleles for grey pubescence (t ₁), low seed coat peroxidase level (ep), and blunt pubescence tip (pb) probably arose as mutations during the domestication of G. max. The remaining seven loci studied(Fr, Pa ₁, Pa ₂, Fg ₁, Fg ₂, Fg ₃and Fg ₄)are polymorphic throughout the subgenus Soja; differences among collections of G. max and G. soja seem to be the result of differing selection pressures. A cluster analysis of allelic frequencies reveals two distinct groups within the subgenus corresponding to G. soja and G. max, Semi-wild accessions of G. max, while morphologically more similar to cultivated plants, clustered with samples of G. soja. The semi-wild accessions examined are thought to have arisen via hybridization between G. soja and G. max.Joint contribution: North Central Region, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, and Journal Paper No. J-9868 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa 50011; Project 2107.     

Characterizing morphological traits and estimating genetic relationship for intermediate soybean collected from South Korea

Twenty‐two wild, 16 intermediate and 20 cultivated soybean varieties were used to analyse relationships among the species of subgenus Soja, genus Glycine using 11 morphological traits and simple sequence repeat (SSR) markers. These genotypes using eleven agronomic characteristics were divided into three clusters: cluster I included 20 G. max, cluster II included 12 intermediate, and cluster III included 22 G. soja and four intermediate lines. Genetic relationships among the species of subgenus Soja showed three distinct clusters. Cluster I consisted of 20 G. max cultivars and two intermediate type lines, and cluster II consisted of 13 intermediate type and two G. soja lines; however, cluster III consisted of 20 G. soja and one intermediate type lines. These phenotypic and genetic data suggest that the intermediate type lines could be distinguished between G. max and G. soja lines. However, the intermediate type could not be classified as a new species.     

A cluster analysis of wild and domesticated soybean phenotypes

Summary Cluster analysis techniques were used to examine phenotypic variation within the USDA Soybean Germplasm Collection. This study included ten Plant Introductions each of the domesticated soybean, Glycine max (L). Merr., the wild soybean, G. soja Sieb. & Zucc., and a disputed species, G. gracilis Skvortz. G. max and G. soja were found to be morphologically distinct entities and G. gracilis was found to be conspecific with G. max. Because G. gracilis probably represents weedy races associated with the cultivated soybean and because gracilis phenotypes can be distinguished from G. max, the designation, G. max forma gracilis, is recommended.Joint contribution: North Central Region, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, and Journal Paper No. J-9389 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa 50011; Project 2107.     

Heterosis of interspecific soybean hybrids for traits related to N2 fixation

Summary Three greenhouse experiments were conducted to compare the performance of soybean (Glycine max (L.) Merr.), wild soybean (G. soja Sieb. et Zucc.), and soybean x wild soybean hybrids for traits relating to N₂ fixation including nodulation, acetylene reduction, nodule leghemoglobin concentration, and nitrogen (N) accumulation and dry matter (DM) accumulation. In all three experiments G. max generally exceeded G. soja in nodulation, acetylene reduction, and N and DM accumulation while the soybean possessed higher nodule leghemoglobin concentration. In Experiment I, the mean of the hybrids did not differ significantly from the G. max parent in nodule mass, acetylene reduction activity, nodule leghemoglobin concentration, or DM accumulation. The hybrids did exceed the soybean parent in N accumulation, thus demonstrating high parent heterosis. In Experiments IIA and IIB with a more carefully chosen set of G. soja parents, high parent heterosis of individual crosses was common. Across the three experiments average high parent heterosis was 34, 28, and 28%, respectively, for nodule mass, N accumulation, and DM accumulation. If one accepts the assumption that hybrid vigor results from the accumulation of dominant alleles, then these alleles could theoretically be accumulated via selection in a homozygous genotype. If this is true than the results of the experiments reported here suggest that interspecific soybean x wild soybean crosses could serve as sources of homozygous lines which would exceed currently available soybean cultivars in nodule mass, and N and DM accumulation.This work was supported in part by the USDA Competitive Grants Program, Grant 82-CRCR-1-1039 and Cooperative Agreement 58-32U4-2-370 between the U.S. Department of Agriculture and the Agronomy Department, University of Maryland, Scientific Article No. A-4648, Contribution No. 7644 of the Maryland Agricultural Experiment Station.     

Differences in Ion Accumulation and Salt Tolerance among Glycine Accessions

Salinity reduces crop yield by limiting water uptake and causing ion‐specific stress. Soybean [Glycine max (L.) Merr.] is sensitive to soil salinity. However, there is variability among soybean genotypes and wild relatives for salt tolerance, suggesting that genetic improvement may be possible. The objective of this study was to identify differences in salt tolerance based on ion accumulation in leaves, stems and roots among accessions of four Glycine species. Four NaCl treatments, 0, 50, 75 and 100 mm , were imposed on G. max, G. soja, G. tomentella and G. argyrea accessions with different levels of salinity tolerance. Tolerant genotypes had less leaf scorch and a greater capacity to prevent Na⁺ and Cl^? transport from soil solution to stems and leaves than sensitive genotypes. Magnitude of leaf injury per unit increase in leaf Na⁺ or Cl^? concentrations was lower in tolerant than in susceptible accessions. Also, plant injury was associated more with Na⁺ rather than with Cl^? concentration in leaves. Salt‐tolerant accessions had greater leaf chlorophyll‐meter readings than sensitive genotypes at all NaCl concentrations. Glycine argyrea and G. tomentella accessions possessed higher salt tolerance than G. soja and G. max genotypes.     

大豆结荚习性、荚色和种皮色相关野生片段分析

结荚习性、荚色和种皮色是大豆的重要形态性状,与进化密切相关。利用由151个家系组成的野生大豆(Glycinne soja Sieb et Zucc.)染色体片段代换系(CSSL)群体(SojaCSSLP1),通过不同表型CSSL组间比对,分别检测到与结荚习性、荚色和种皮色相关的1个、3个和2个野生片段(基因)。其中,5个野生片段(基因)分别与前人在栽培豆中检测到的无限结荚Dt₁、荚色L₁、荚色L₂、绿种皮G和黑种皮i基因相对应,说明野生大豆与栽培大豆间、栽培大豆与栽培大豆间在这些片段上均存在等位变异分化,是与大豆进化相关的基因/片段。另一个与荚色相关的Satt273野生片段能使大豆表现黑荚,可能是本研究的新发现,但还需进一步验证。     

A Line with Four-Seeded Pods Derived from an Interspecific Hybrid in Soybean

The cultivated soybean, Glycine max (L.) Merr., was crossed with its proposed wild progenitor, Glycine sofa (Seib. & Zucc.), to create useful genetic variability. A few plants with increased frequency of four-seeded pods were identified in a segregating generation derived from this interspecific cross. One of them had about 45 percent four-seeded pods per plant, whereas Glycine max and Glycine soja accessions used as parents in this study had only 8.0 and 5.1 per cent four-seeded pods per plant, respectively. The established line finally had 32.5 per cent four-seeded pods per plant, which is substantially higher as compared to either of the parents. Obviously, the genes which are responsible for this character are not expressed in the parental population.     

Development of a chromosome segment substitution line population with wild soybean (Glycine soja Sieb. et Zucc.) as donor parent

Chromosome segment substitution line (CSSL) population is potential in precisely detecting and pyramiding genes/QTL/segments due to the genetic background noise removed. To exploit and utilize the favorable wild alleles, a CSSL population with 151 lines (SojaCSSLP1) was generated using a wild soybean (Glycine soja Sieb. et Zucc.) N24852 as donor parent and the elite cultivar NN1138-2 as its genetic background. An improved CSSL construction strategy was used, i.e. continuous backcross after initial crossing followed with alternation of backcross and selfing combined with marker-assisted selection based on pedigree DNA pools and phenotypic differences among pedigrees. The SojaCSSLP1 with an average recovery ratio of 95.7?% of the NN1138-2 genome could cover the entire genome of wild soybean. Four wild alleles/segments for each of the two wild characteristics, longer plant height (PH) and more number of nodes on main stem (NN), in a total of six segments, were detected with additive effects all positive. Among them, Satt243 on Chr.10 and Sat_286 on Chr.19 associated with both PH and NN while Satt338 and SOYGPATR on Chr.4 and Satt314 neighboring with Satt192 on Chr.12 had the former and latter on each chromosome associated with PH and NN, respectively. That could explain the high positive correlation between the two traits (r?=?0.88). Compared with those in the literature, three QTL/segments for PH and one for NN were detected also among cultivated soybeans, indicating allele differentiation happened not only between wild and cultivated but also among cultivated soybeans. Therefore these QTL/segments might be the key ones to explain the domestication and evolution of soybean. In addition, SojaCSSLP1 should be also potential in studies for multiple wild traits due to its broad variation.     

Genetic characterization of group A acetylsaponin‐deficient mutants from wild soybean (Glycine soja Sieb. and Zucc.)

Group A acetylsaponins are the main causative components for bitter and astringent tastes of soybean (Glycine max). In this study, we examined the genetic nature of the absence of group A acetylsaponins in 12 Korean wild soybean (Glycine soja) accessions. In all 12 accessions, the coding region (1431‐bp) of Sg‐1 locus was identical with Sg‐1^a, which adds the xylose sugar moiety at the terminal position of the C‐22 sugar chain of SS‐A, except one nucleotide (G→A change) at +948th position. This point mutation results in change of one amino acid from tryptophan (TGG) to stop codon (TGA). We observed that the mutated Sg‐1 was controlled by a single recessive gene (sg‐1^0‐a1). This gene was mapped between BARCSOYSSR_07_1561 and BARCSOYSSR_07_1598 on soybean chromosome 7. Our study demonstrated that the mutated Sg‐1 gene in Korean wild soybeans is genetically different from those identified in Japanese soybean cultivar ‘Kinusayaka’ and wild soybean JP‐36121. We believe that the new Sg‐1 mutants can also be utilized to produce a new soybean variety without bitter and astringent properties.     

Evaluation of wild perennial Glycine species for resistance to soybean cyst nematode and soybean rust

The genetic base for soybean cultivars is narrow compared to most other crop species. Twenty-seven wild perennial Glycine species comprise the tertiary gene pool to soybean that may contain many genes of economic importance for soybean improvement. We evaluated 16 accessions of G. argyrea, G. clandestina, G. dolichocarpa, and G. tomentella for resistance to Heterodera glycines (HG), also known as the soybean cyst nematode, and to multiple isolates of Phakopsora pachyrhizi, the causal fungus of soybean rust. All 16 accessions were classified as resistant to H. glycines HG Type 2.5.7, based on number of cysts per root mass with plant introductions (PIs) 483227, 509501, 563892, and 573064 (all G. tomentella) void of any cysts indicating no reproduction by this pest. All 16 accessions had an immune reaction to one isolate of P. pachyrhizi. Regardless of isolate, no sporulating uredinia were observed on G. argyrea (PI 505151) and G. tomentella (PIs 483227, 509501, and 573064). These results demonstrate that some accessions within the perennial Glycine species harbour resistance to both H. glycines and P. pachyrhizi and would be good candidates for wide hybridization programs seeking to transfer potentially unique multiple resistance genes into soybean.     

Stability of elevated α-linolenic acid derived from wild soybean (Glycine soja Sieb. & Zucc.) across environments

Previous studies reported that omega-3 fatty acid and α-linolenic acid are important compounds that prevent cardiovascular disease and cancer in humans. Soybean [Glycine max (L.) Merr.] oil typically contains ~8 % α-linolenic acid (ALA). Elevated (~15 %) ALA content in seed oil is a trait of wild soybeans (G. soja Sieb. and Zucc.). Decreasing the ratio of linoleic acid (LA) to ALA to 4:1 or lower (compared to the ratio of 6 or 7:1 found in commercial soybean seed) should have health benefits for humans. This study was conducted to determine the environmental stability of elevated ALA acid recombinant inbred lines (RILs) derived from a cross of PI 483463 (wild soybean with 15 % ALA) and Hutcheson (cultivar with 9 % ALA). The fatty acid profile analysis from nine environments showed that the content of ALA for the RILs 156, 159 and 166 ranged from 10.7 to 15.7, 14.0 to 15.8, and 14.8 to 15.8, and averaged 13.9, 14.9, and 15.2 % respectively. The contents of ALA from these RILs and the wild soybean parent showed consistently higher than cultivated check soybeans. Two of the three RILs with elevated ALA content and ratios of <4:1 LA to ALA were as stable in ALA content as the high and low linolenic acid parents across growing environments. This indicates that lines with elevated ALA content developed from wild soybean PI 483463 are stable in ALA across environments and would be useful in improving soybeans with lower LA to ALA ratios.     

大豆结荚习性、荚色和种皮色相关野生片段分析

结荚习性、荚色和种皮色是大豆的重要形态性状,与进化密切相关。利用由151个家系组成的野生大豆(Glycinne soja Sieb et Zucc.)染色体片段代换系(CSSL)群体(SojaCSSLP1),通过不同表型CSSL组间比对,分别检测到与结荚习性、荚色和种皮色相关的1个、3个和2个野生片段(基因)。其中,5个野生片段(基因)分别与前人在栽培豆中检测到的无限结荚Dt₁、荚色L₁、荚色L₂、绿种皮G和黑种皮i基因相对应,说明野生大豆与栽培大豆间、栽培大豆与栽培大豆间在这些片段上均存在等位变异分化,是与大豆进化相关的基因/片段。另一个与荚色相关的Satt273野生片段能使大豆表现黑荚,可能是本研究的新发现,但还需进一步验证。     

大豆属Soja亚属植物花粉形态的比较观察

对野生、半野生、半栽培、栽培大豆花粉进行了光学显微镜和扫描电镜的观察。发现不同进化类型大豆花粉的沟、内孔及纹饰存在明显的差异，可以做大豆分类、进化研究的重要依据。     

DNA fingerprinting in soybean (Glycine max (L.) Merrill) with oligonucleotide probes for simple repetitive sequences

Summary Soybean DNA fingerprints were analyzed by digoxigenin-labeled oligonucleotide probes complementary to simple repetitive sequences. The clearest and most polymorphic patterns were obtained with (AAT)₆ as a probe, with which all 47 soybean cultivars tested could be distinguished. However, DNA fingerprints of individuals within cultivars showed the same pattern. Using (CT)₈, (GAA)₅ or (AAGG)₄ as probes, clear polymorphic patterns among cultivars and accessions in the subgenus Soja (Glycine max and Glycine soja) were not observed, while quite different patterns were found in accessions in the subgenus Glycine. The results suggest that G. max and G. soja are closer in their genome structure. DNA fingerprints of reciprocal crosses between cultivars and accessions in the subgenus Soja were similar, and contained bands of both parents. In an F₂ population from these crosses, such bands segregated in a Mendelian fashion.     

Genetic and molecular bases of photoperiod responses of flowering in soybean

Flowering is one of the most important processes involved in crop adaptation and productivity. A number of major genes and quantitative trait loci (QTLs) for flowering have been reported in soybean (Glycine max). These genes and QTLs interact with one another and with the environment to greatly influence not only flowering and maturity but also plant morphology, final yield, and stress tolerance. The information available on the soybean genome sequence and on the molecular bases of flowering in Arabidopsis will undoubtedly facilitate the molecular dissection of flowering in soybean. Here, we review the present status of our understanding of the genetic and molecular mechanisms of flowering in soybean. We also discuss our identification of orthologs of Arabidopsis flowering genes from among the 46,367 genes annotated in the publicly available soybean genome database Phytozome Glyma 1.0. We emphasize the usefulness of a combined approach including QTL analysis, fine mapping, and use of candidate gene information from model plant species in genetic and molecular studies of soybean flowering.     

Genetic studies on saline and sodic tolerances in soybean

Salt-affected soils are generally classified into two main categories: saline and sodic (alkaline). Developing and using soybean (Glycine max (L.) Merr) cultivars with high salt tolerance is an effective way of maintaining sustainable production in areas where soybean growth is threatened by salt stress. Early classical genetics studies revealed that saline tolerance was conditioned by a single dominant gene. Recently, a series of studies consistently revealed a major quantitative trait locus (QTL) for saline tolerance located on linkage group N (chromosome 3) around the SSR markers Satt255 and Sat_091; other minor QTLs were also reported. In the case of sodic tolerance, most studies focused on iron deficiency caused by a high soil pH, and several QTLs associated with iron deficiency were identified. A wild soybean (Glycine soja Sieb. & Zucc.) accession with high sodic tolerance was recently identified, and a significant QTL for sodic tolerance was detected on linkage group D2 (chromosome 17). These studies demonstrated that saline and sodic tolerances were controlled by different genes in soybean. DNA markers closely associated with these QTLs can be used for marker-assisted selection to pyramid tolerance genes in soybean for both saline and sodic stresses.     

Molecular mapping of QTLs for domestication-related traits in cowpea (V. unguiculata (L.) Walp.)

Understanding the genetic basis underlying domestication-related traits (DRTs) of cowpea (Vigna unguiculata (L.) Walp.) is important since the genome has experienced divergent domestication and in addition it is also useful to utilize the wild germplasm efficiently for improving different traits of the cultivated cowpea. Quantitative trait loci (QTLs) for DRTs were identified in a population of 159 F₇ recombinant inbred lines derived from a cross between a domesticated cowpea (V. unguiculata (L.) Walp.) variety, 524B, and a wild accession, 219. Using the constructed linkage map, QTLs for 10 DRTs were analysed and mapped. QTLs for seed, pod and flower related traits were detected. Subsequently, QTL for ovule number was also identified. To our knowledge, this is the first time a QTL for this trait has been observed. QTLs for DRTs show co-localization on three linkage groups and pleiotropy or close linkage of genes for the traits is suggested in these chromosome regions. The information gained in this study can be used for marker-assisted selection of domestication-related QTLs in cowpea and enhance understanding of domestication in the genus Vigna.     

Genetic diversity of wild and cultivated soybeans growing in China revealed by RAPD analysis

To evaluate the genetic diversity and to clarify the genetic relationships of wild and cultivated soybeans growing in China, 21 wild soybean accessions and 27 cultivated soybean landraces were analysed by using the random amplified polymorphic DNA method. The data show that wild soybean has a higher genetic variation than cultivated soybean, indicating that genetic variation has been reduced by domestication of wild soybean. Based on Nei's genetic similarity coefficient, all the accessions were classified into two major clusters, corresponding to wild and cultivated varieties of soybean. Furthermore, within each species, the accessions tend to form sub‐clusters that are in agreement with their geographical origins, demonstrating that an extensive geographical genetic differentiation exists in both species. For cultivated soybean, the varieties from the same geographical region but with different seasonal types were found to have closer genetic relationships than varieties from different geographical regions but with the same seasonal type. This result indicates that geographical differentiation plays a key role in the genetic differentiation of both wild and cultivated soybeans. Cultivated soybean varieties with different seasonal types in a region might have been established mainly from the local genotypes.