A novel procedure for identifying a hybrid QTL-allele system for hybrid-vigor improvement, with a case study in soybean(Glycine max)yield

“Breeding by design” for pure lines may be achieved by construction of an additive QTL-allele matrix in a germplasm panel or breeding population, but this option is not available for hybrids, where both additive and dominance QTL-allele matrices must be constructed. In this study, a hybrid-QTL identification approach, designated PLSRGA, using partial least squares regression(PLSR) for model fitting integrated with a genetic algorithm(GA) for variable selection based on a multi-locus, multi-allele model is described for additive and dominance QTL-allele detection in a diallel hybrid population(DHP). The PLSRGA was shown by simulation experiments to be superior to single-marker analysis and was then used for QTL-allele identification in a soybean DPH yield experiment with eight parents. Twenty-eight main-effect QTL with 138 alleles and nine QTL × environment QTL with 46 alleles were identified, with respective contributions of 61.8% and 23.5% of phenotypic variation. Main-effect additive and dominance QTL-allele matrices were established as a compact form of the DHP genetic structure. The mechanism of heterosis superior-to-parents(or superior-to-parents heterosis, SPH) was explored and might be explained by a complementary locus-set composed of OD+(showing positive over-dominance, most often), PD+(showing positive partial-to-complete dominance, less often) and HA+(showing positive homozygous additivity, occasionally) loci, depending on the parental materials. Any locus-type, whether OD+, PD + and HA+, could be the best genotype of a locus. All hybrids showed various numbers of better or best genotypes at many but not necessarily all loci, indicating further SPH improvement. Based on the additive/dominance QTL-allele matrices, the best hybrid genotype was predicted, and a hybrid improvement approach is suggested. PLSRGA is powerful for hybrid QTL-allele detection and cross-SPH improvement.

Cd Distribution and Subcellular Localization in Leaf and Its Effects on Growth of Soybean(Glycine max) Seedlings

In order to investigate Cd accumulation, subcellular distribution, and local-ization in soybean seedlings leaves, soybean seedlings were cultivated in solution containing different concentrations of Cd. The results showed that most Cd associ-ated with the cellwal s and soluble fractions, and a minor part of Cd presented in mitochondria fractions, nuclear and chloroplast fractions, especial y exposure to high Cd concentrations. Under 20.00 mg/L Cd stress, Cd subcellular distribution fol owed a sequence as： soluble fractions （55.00%）＆gt;cellwal s （30.0%）＆gt;mitochondria fractions （8.21%）＆gt;nuclear and chloroplast fractions （6.79%）. Deposited Cd black particles were observed in cellwal s, chloroplasts, nuclei, and vacuoles through electrical microscope slice. This fact indicated that the cellwal s of soybean leaves were the first protecting organel es from Cd toxicity, and the cellwal s and soluble fractions were the main place for Cd storage. Due to Cd accumulated in the organel es, the intercellular space was enlarged and the subcellular structure was damaged, especial y for the chloroplasts.

Isolation and Characterization of a Mitochondrial atp6 Gene from Soybean (Glycine max)

Mitochondrial ATPase (mtATPase) complex plays vital roles in higher plants. It consists of a few subunits. In the present study, a new copy of the mtATPase subunit 6 (EC 3.6.1.34) gene (atp6) was cloned and characterized from Glycine max (L.) Merr., which has the shortest opening reading frame of 223 amino acids in all organisms examined and designated as the atp6 copy3 (atp6_3). PCR amplifications of the atp6_3 from 9 soybean cultivars combined with sequencing analysis suggested its wide occurrence in G. max . RFLP analysis of a RILs population implied that paternal inheritance of the atp6_3 might occur in G. max at undetermined frequency. Under salicylic acid (SA)_treated condition, the expression of the atp6 gene was significantly inhibited. The possible role of this inhibition was discussed.

Mapping and validation of a dominant salt tolerance gene in the cultivated soybean(Glycine max) variety Tiefeng 8

Salt is an abiotic stress factor that strongly affects soybean growth and production. A single dominant gene has been shown to confer salt tolerance in the soybean cultivar Tiefeng 8.The objective of the present study was to genetically map the salt-tolerance gene in an F2:3population and a recombinant inbred line(RIL) population derived from a cross between two cultivated soybeans, Tiefeng 8(tolerant) and 85-140(sensitive). The F2:3families and RILs were treated with 200 mmol L-1Na Cl to evaluate salt tolerance. The F2:3population showed 1(42 tolerant): 2(132 segregating): 1(65 sensitive) segregation, indicating a single dominant gene for salt tolerance in Tiefeng 8. A sequence-characterized amplified region(SCAR) marker from a previously identified random amplified polymorphic DNA(RAPD)marker and four insertion/deletion polymorphism(In Del) markers were developed within the mapping region. Using these markers along with SSR markers, the salt-tolerance gene was mapped within 209 kb flanked by SCAR marker QS08064 and SSR marker Barcsoyssr_3_1301 on chromosome 3. Three markers that cosegregated with the salt tolerance gene and SCAR marker QS08064 were used to genotype 35 tolerant and 23 sensitive soybean accessions. These markers showed selection efficiencies of 76.2% to94.2%. The results indicate that these markers will be useful for marker-assisted breeding and facilitating map-based cloning of the salt tolerance gene in soybean.

Effects of salinity on activities of H^+-ATPase, H^+-PPase and membrane lipid composition in plasma membrane and tonoplast vesicles isolated from soybean(Glycine max L.) seedlings

The effects of NaCl stress on the H +-ATPase, H +-PPase activity and lipid composition of plasma membrane(PM) and tonoplast(TP) vesicles isolated from roots and leaves of two soybean cultivars(Glycine max L.) differing in salt tolerance(Wenfeng7, salt-tolerant; Union, salt-sensitive) were investigated. When Wenfeng7 was treated with 0.3%(W/V) NaCl for 3 d, the H +-ATPase activities in PM and TP from roots and leaves exhibited a reduction and an enhancement, respectively. The H +-PPase activity in TP from roots also increased. Similar effects were not observed in roots of Union. In addition, the increases of phospholipid content and ratios of phospholipid to galactolipid in PM and TP from roots and leaves of Wenfeng7 may also change membrane permeability and hence affect salt tolerance.

Analysis of QTLs for the Trichome Density on the Upper and Downer Surface of Leaf Blade in Soybean [Glycine max (L.) Merr.]

Trichomes （plant hairs） are present on nearly all land plants and are known to play important roles in plant protection, specifically against insect herbivory, drought, and UV radiation. The identification of quantitative trait loci （QTL） associated with trichome density should help to interpret the molecular genetic mechanism of soybean trichome density. 184 recombinant inbred lines （RILs）, derived from a cross between soybean cultivars Kefeng 1 and Nannong 1138-2 were used as segregating population for evaluation of TDU （trichome density on the upper surface of leaf blade） and TDD （trichome density on the downer surface of leaf blade）. A total of 15 QTL were detected on molecular linkage groups （MLG） A2, Dla, Dlb, E and H by composite interval mapping （CIM） and among all the QTL, qtuA2-1, qtuD 1 a-1, qtuD lb-2, qtuH-2 qtuE-1, qtdDlb-2, and qtdH- 2 were affirmed by multiple interval mapping （MIM）. The contribution ofphenotypic variance of qtuH-2 was 31.81 and 29.4% by CIM and MIM, respectively, suggesting it might be major gene Ps loci. Only 10 pairs of main QTL interactions for TDU were detected, explained a range of 0.2-5.1% of phenotypic variations for each pair for a total of 22.8%. The QTL on MLG Dlb affecting trichome density were mapped near to Rsc-7 conditioning resistance to SMV （soybean mosaic virus）. This study showed that the genetic mechanism of trichome density was the mixed major gene and polygene inheritance, and also suggested that the causal nature between trichome density and other agronomic traits.

Identification and fine mapping of qSW2 for leaf slow wilting in soybean

Drought is one of the abiotic stresses limiting the production of soybean(Glycine max).Elucidation of the genetic and molecular basis of the slow-wilting(SW)trait of this crop offers the prospect of its genetic improvement.A panel of 188 accessions and a set of recombinant inbred lines produced from a cross between cultivars Liaodou 14 and Liaodou 21 were used to identify quantitative-trait loci(QTL)associated with SW.Plants were genotyped by Specific-locus amplified fragment sequencing and seedling leaf wilting was assessed under three water-stress treatments.A genome-wide association study identified 26 SW-associated single-nucleotide polymorphisms(SNPs),including three located in a 248-kb linkage-disequilibrium(LD)block on chromosome 2.Linkage mapping revealed a major-effect QTL,qSW2,associated with all three treatments and adjacent to the LD block.Fine mapping in a BC_(2)F_(3) population derived from a backcross between Liaodou 21 and R26 confined qSW2 to a 60-kb interval.Gene expression and sequence variation analysis identified the gene Glyma.02 g218100,encoding an auxin transcription factor,as a candidate gene for qSW2.Our results will contribute significantly to improving drought-resistant soybean cultivars by providing genetic information and resources.

MicroRNAs Involved in the Pathogenesis of Phytophthora Root Rot of Soybean (Glycine max)

Phytophthora root rot is one of the most prevalent diseases in the world,which can infect the seedlings and plants,with substantial negative impact on soybean yield and quality.MicroRNAs （miRNAs） are a class of post-transcriptional regulators of gene expression during growth and development of organisms.A soybean disease-resistance variety Suinong 10 was inoculated with Phytophthora sojae race No.1,and the specific miRNA resistant expression profile was acquired by microarray for the first time.Different expressional miRNAs have been found after comparing the results of the treated sample with the control sample.Furthermore,the target genes of different expressional miRNAs were predicted.Two miRNAs,cbr-mir-241 and ath-miR854a,regulated the disease-resistance process directly through their targets,some enzymes.Another two miRNAs,gma-miR169a and ath-miR169h,participated in disease-resistance regulation as transcription factors.Similarly,one miRNA,ptc-miR164f,has been reported to regulate the plant development.All of these studies would be served as the foundation for exploring the resistance mechanism.

Genetic Analysis of Combining Abilities and Heterosis for the Contents of Soybean Isoflavone and Its Components Among the Soybean Varieties [Glycine max (L.) Merr.]

The genetic analysis of soybean isoflavone content and its components were carried out based on the NC Ⅱ matingdesign in eight soybean varieties. The results showed that the isoflavone contents and its components of soybean seedare quite differences among the tested materials, the contents of isoflavone and daidzein are controlled not only byadditive effects and but also by non-additive effects, while the content of genistin is dominated by non-additive effects,and genistein, glycitin and daidzin are mainly controlled by additive effects. There are significant differences in thecontents of isoflavone and its components among the combinations derived from different parents. Results also indicatedthat the tested traits are negatively heterosis except for the contens of daidzein and daidzin are positively heterosis basedon the data of the GCA and SCA in average heterosis values. In this research we have a suggestion that soybean varietywith high isoflavone should be used as one of the parents in the breeding program, and it is the best choice that thecombinations crossed between two high isoflavone varieties or a high variety and a low one.

Genetic diversity center of cultivated soybean(Glycine max) in China——New insight and evidence for the diversity center of Chinese cultivated soybean

Information on the center of genetic diversity of soybean（Glycine max） will be helpful not only for designing efficient strategies for breeding programs, but also for understanding the domestication and origin of this species. Here, we describe an analysis of genetic diversity based on simple-sequence repeat（SSR） variations within a core collection of 2 111 accessions of Chinese soybean landraces. Prior to the diversity assessment, the geographic origin of each accession was mapped. The map was then divided into grids each 2.5° in latitude and 5° in longitude. We found two regions that had higher number of alleles（NA） and greater polymorphic information content（PIC） values than the others. These regions are adjacently located within grid position of 30°–35°N×105°–110°E, which includes the valley of the middle and lower reaches of the Wei River, and the valley of the upper reaches of the Hanjiang River. It was also observed that in many regions, genetic diversity decreased with the increase in distance from the center. Another region, in northern Hebei Province（115°–120°E×40°–42.5°N）, was observed having higher diversity than any surrounding regions, indicating that this is a sub-center of soybean diversity. Based on the presented results, the domestication and origin of soybean are also discussed.

Map-based cloning of a novel QTL qBN-1 influencing branch number in soybean[Glycine max(L.)Merr.]

Branch number(BN)is an important agronomic attribute related to the plant architecture,adaptability,and yield of soybean.To date,few studies ofBNhave been conducted to elucidate its genetic background.We aimed to localize genetic factors affecting BN using segregating populations derived fromthe high-branching cultivar‘Kennong24’(KN24)and the low-branching cultivar‘Kenfeng19’(KF19).Composite interval mapping analysis detected a QTL(qBN-1)on chromosome 6 between the SSR markers BARCSOYSSR_06_0993 and BARCSOYSSR_06_1070 using an F2 population.To fine-map qBN-1,a RIL population was developed and genotyped with 14 SSRmarkers located in the QTL region.qBN-1 was localized to a 115.67-kb interval flanked by markers BARCSOYSSR_06_1048 and BARCSOYSSR_06_1053.The QTL was further confirmed using backcross populations of size 1305(BC2F2 with KN24 as a recurrent parent)and 1712(BC3F2 with KF19 as a recurrent parent).The fine-mapping region of qBN-1 contained only two candidate genes,Glyma.06G208800 and Glyma.06G208900,whose expression patterns were investigated by qRT-PCR.Compared to Glyma.06G208800 gene expression,Glyma.06G208900 showed the highest expression of the two genes and showed a significant difference in expression between high-and low-branching genotypes in either axillary meristem or shoot apical meristem,and showed opposite expression patterns in the two tissues at V4 and R1 stages.These results identify Glyma.06G208900 as a novel candidate gene controlling BN.Taken together,the results of this study provide a foundation for cloning and functional analysis of the qBN-1 gene and for the improvement of BN bymarker-assisted selection in soybean breeding.

Genetic Analysis of Embryo, Cytoplasm and Maternal Effects and Their Environment Interactions for Isoflavone Content in Soybean [Glycine max (L.) Merr.]

Soybean seed products contain isoflavones （genistein, daidzein, and glycitein） that display biological effects when ingested by humans and animals. These effects are species, dose and age dependent. Therefore, the content and quality of isoflavones in soybeans is a key factor to the biological effect. Our objective was to identify the genetic effects that underlie the isoflavone content in soybean seeds. A genetic model for quantitative traits of seeds in diploid plants was applied to estimate the genetic main effects and genotype x environment （GE） interaction effects for the isoflavone content （IC） of soybean seeds by using two years experimental data with an incomplete diallel mating design of six parents. Results showed that the IC of soybean seeds was simultaneously controlled by the genetic effects of maternal, embryo, and cytoplasm, of which maternal genetic effects were most important, followed by embryo and cytoplasmic genetic effects. The main effects of different genetic systems on IC trait were more important than environment interaction effects. The strong dominance effects on isoflavone from residual was made easily by environment conditions. Therefore, the improvement of the IC of soybean seeds would be more efficient when selection is based on maternal plants than that on the single seed. Maternal heritability （65.73%） was most important for IC, followed by embryo heritability （25.87%） and cytoplasmic heritability （8.39%）. Based on predicated genetic effects, Yudou 29 and Zheng 90007 were better than other parents for increasing IC in the progeny and improving the quality of soybean, The significant effects of maternal and embryo dominance effects in variance show that the embryo heterosis and maternal heterosis are existent and uninfluenced by environment interaction effects.

Effects of potassium deficiency on photosynthesis and photoprotection mechanisms in soybean(Glycine max(L.)Merr.)

Potassium is an important nutrient element requiring high concentration for photosynthetic metabolism.The potassium deficiency in soil could inhibit soybean（Glycine max（L.） Merr.） photosynthesis and result in yield reduction.Research on the photosynthetic variations of the different tolerant soyben varieties should provide important information for high yield tolerant soybean breeding program.Two representative soybean varieties Tiefeng 40（tolerance to K^＋ deficiency） and GD8521（sensitive to K^＋ deficiency） were hydroponically grown to measure the photosynthesis,chlorophyll fluorescence parameters and Rubisco activity under different potassium conditions.With the K-deficiency stress time extending,the net photosynthetic rate（Pn）,transpiration rate（Tr） and stomatal conductance（Gs） of GD8521 were significantly decreased under K-deficiency condition,whereas the intercellular CO2 concentration（Ci） was significantly increased.As a contrast,the variations of Tiefeng 40 were almost little under K-deficiency condition,which indicated tolerance to K^＋ deficiency variety could maintain higher efficient photosynthesis.On the 25 th d after treatment,the minimal fluorescence（F0） of GD8521 was significantly increased and the maximal fluorescence（Fm）,the maximum quantum efficiency of PSII photochemistry（F√Fm）,actual photochemical efficiency of PSII（φ（PSII））,photochemical quenching（qp）,and electron transport rate of PSII（ETR）were significantly decreased under K^＋ deficiency condition.In addition,the Rubisco content of GD8521 was significantly decreased in leaves.It is particularly noteworthy that the chlorophyll fluorescence parameters and Rubisco content of Tiefeng 40 were unaffected under K^＋ deficiency condition.On the other hand,the non-photochemical quenching（qN） of Tiefeng 40 was significantly increased.The dry matter weight of Tiefeng 40 was little affected under K^＋ deficiency condition.Results indicated that Tiefeng 40 could avoid or relieve the destruction of PSII caused by exceeded absorbed solar energy under K-deficiency condition and maintain natural photosynthesis and plant growth.It was an essential physiological mechanism for low-K-tolerant soybean under K-deficiency stress.

Effect of Gamma Irradiation on Morpho-Agronomic Characteristics of Soybeans (<i>Glycine max</i>L.)

Mutation breeding in crop plants is an effective approach in improvement of crop having narrow genetic base such as soybean. The main objective of the present study is to determine the effect of different doses of gamma irradiation on different morpho-agronomic characteristics. Agronomic traits that were analyzed included;grain yield, number of pods/plant, number of seeds/plant and weight of 100 seeds and numbers of days to 50% flowering. Morphometric characterization of the descriptive data included plant height, stem diameter, number of leaves/plant, leaflet length, leaflet width, number of ramifications/plant, and pod length and width at 3 lodge stage. The results of the present study revealed that the two gamma irradiation doses used (0.2 kGy and 0.4 kGy) decreased significantly most of agronomic and morphological traits evaluated in M1 populations. Different effects of 0.2 kGy and 0.4 kGy irradiation were observed in M2 populations with significant increase of grain yields and yield components in all the three soybean varieties. In general, a significant decrease or no changes of morphological traits were observed for the two irradiation doses in M2 populations. The levels of changes varied among varieties. Potential high yielding mutants were identified in progenies of irradiated seeds.

Genome-wide association with transcriptomics reveals a shade-tolerance gene network in soybean

Shade tolerance is essential for soybeans in inter/relay cropping systems.A genome-wide association study(GWAS)integrated with transcriptome sequencing was performed to identify genes and construct a genetic network governing the trait in a set of recombinant inbred lines derived from two soybean parents with contrasting shade tolerance.An improved GWAS procedure,restricted two-stage multi-locus genome-wide association study based on gene/allele sequence markers(GASM-RTM-GWAS),identified 140 genes and their alleles associated with shade-tolerance index(STI),146 with relative pith cell length(RCL),and nine with both.Annotation of these genes by biological categories allowed the construction of a protein–protein interaction network by 187 genes,of which half were differentially expressed under shading and non-shading conditions as well as at different growth stages.From the identified genes,three ones jointly identified for both traits by both GWAS and transcriptome and two genes with maximum links were chosen as beginners for entrance into the network.Altogether,both STI and RCL gene systems worked for shade-tolerance with genes interacted each other,this confirmed that shadetolerance is regulated by more than single group of interacted genes,involving multiple biological functions as a gene network.

Isolation and Characterization of Storage Protein Subunit-null-dwarf Mutants in Soybean(Glycine max(L.) Merr.)

Dwarfing is useful to reduce plant height,when breeding high-yielding and non-lodging crops.In this study,a set of natural storage protein subunit-null dwarf mutants of soybean was reported that showed strongly reduced plant stature and deficiency in various 7S and 11S subunits,designated as snd1 mutants.Under normal growth conditions,the snd1 mutants showed a severe dwarf phenotype,with plant height of about 25 cm.Compared with wild-type DN47,the mutant snd1 exhibited no obvious morphological differences at the early stage of development.All the snd1 mutants examined had fewer nodes and shorter than normal internodes;the leaves were similar in shape to normal parents,but were dark-green at the mature stage.The flower size was similar to DN47;however,the flowering period was shorter than in the wild-type.Significant variation was noted for protein content,oil content of the seeds and size of seeds(weight of 100 seeds)among 17 snd1 dwarf lines.Genetic analysis indicated that the dwarfism of snd1 was controlled by a single recessive gene.The snd1 dwarf mutant had markedly different dynamic levels of the endogenous hormones gibberellin(GA),brassinosteroid,indole-3-acetic acid and abscisic acid,at the seedling stage.Exogenous GA3 treatment led to recovery of the plant height phenotype of the snd1 mutant;GA3 at 0.1 mm had the largest effect on enhancing plant height.Using molecular markers,snd1 gene was approximately mapped in an interval of 603 kb between markers Satt166 and Satt561 on chromosome 19.Snd1 mutant provided valuable material for hypoallergenic soybean breeding and the snd1 gene might be a novel gene related to plant height in soybean.

Proteomic Studies of Petal-specific Proteins in Soybean [Glycine Max(L.)Merr.] Florets

A survey of petal-specific proteomes of soybean(Glycine max(L.) Merr[Non-italic].) was conducted comparing protein expression profiles in different petals. Two-dimensional polyacrylamide gel electrophoresis reference maps of protein extracts from standard petals(SP), lateral wings(LW), keel petals(KP), and reproductive organs(RO)(a mixture of stamen and carpel) were obtained. Protein expression in the three petal types was compared using Image Master TM 2 D platinum 6.0 software. This indicated that the proportion of homologous proteins between SP and LW was 59.27%, between SP and KP was 61.48%, and between LW and KP was 60.05%. Within a mass range of 6.5-200.0 ku and pH 4.0-7.0, approximately 590, 646, 544, and 700 protein spots were detected in SP, LW, KP, and RO, respectively. A total of 82 differentially expressed proteins were detected. Sixty-four of these detected spots were differentially expressed and showed more than 2-fold changes in abundance; of these 64 proteins, 26 showed increased expression and 38 showed decreased expression. Among these spots, single organ-specific proteins were also identified.They were ID 49(60.9 ku), ID 45(50.0 ku), and ID 46(40.5 ku) in RO, ID 98(42.0 ku) in SP, and ID 05(29.0 ku) in KP. A total of 14 protein spots from 82 differentially expressed proteins were identified with LC-MS/MS. Further protein identification was conducted using the SwissProt and NCBInr databases. The identified proteins and their putative functions were discussed further. This was the first study reporting the comparison of petal protein profiles of soybean florets using proteomics tools.

Soybean Response to Weed Residues in the Soil

Soybean production systems that return plant residues to the soil surface are gaining in popularity. As these practices become more widespread, more crop and weed residues are being introduced into the upper soil profile. Greenhouse studies were conducted to determine the effects of varying concentrations of Palmer amaranth and pitted morningglory plant residues (aboveground portion of the plant) on soybean production. The study was arranged in a completely randomized experimental design with five treatments and five replications. Palmer amaranth and pitted morningglory residues were incorporated into soil at 20,000, 40,000, 80,000 and 160,000 ppm. Inert plastic residue at the same residue levels was included as a check. Soybean dry weight, leaf area and leaf tissue nutrient content were recorded during the study. A decrease in soybean dry weight and leaf area was observed as Palmer amaranth residue in the soil increased. Palmer amaranth residues of 160,000 ppm and 80,000 ppm in the soil significantly reduced soybean dry weight by 69% and 59%, respectively, and soybean leaf area by 60% and 57%, respectively. In contrast, pitted morningglory and inert plastic residues had no observable effect on soybean growth and development. This study demonstrated Palmer amaranth residues in the soil impacted early season soybean growth and development.

Effect of GmLEC1-A Expression on ABA Content at Germination Stage in Soybean(Glycine max)

LEAFY COTYLEDON1(LEC1) is a key regulator of seed maturation, which gives embryos the ability to withstand desiccation. In this study, a novel transcription factor that is homologous to LEC1 in soybean(Glycine max) was isolated from Dongnong 50 by homologous cloning and was named as GmLEC1-A(GenBank accession number: MF681785). Sequence analysis showed that GmLEC1-A contained conserved B regions, which were functional domains of H4 factor. The relative expression level of GmLEC1-A was the highest in seeds of the soybean cultivar Dongnong 50. To verify the function of GmLEC1-A, ectopic expression of Arabidopsis thaliana and over-expression of soybean plants were generated. In Arabidopsis, the expression of GmLEC1-A restored the tolerance of lec1 mutant to seed drying, indicating that GmLEC1-A was a functional homolog of LEC1,and it might regulate the maturation phase of seed development. In soybean, over-expression of GmLEC1-A caused slower growth and lower germination rates as compared to that of wild-type soybeans. Furthermore, over-expression of GmLEC1-A seemed to increase the level of endogenous abscisic acid(ABA) at the germination stage. These results suggested that GmLEC1-A had a function in regulating ABA content at the germination stage.

Identification of Co-dominant SSR Markers Associated with Genes Controlling α'- and cr-subunit-null β-conglycinin Phenotypes in Soybean (Glycine max (L.) Merr.)

Studies have shown that the three subunits of β-conglycinin are the main potential allergens of soybean sensitive patients.And β-conglycinin has adverse effects on nutrition and food processing.So solation and production of lines with lowerβ-conglycinin content has been the focus of recent soybean breeding projects.Soybean lines with deficiency in one or all subunits of β-congIycinin have been obtained.An effective and rapid system to identify such mutations will facilitate genetic manipulation of the β-conglycinin subunit composition.Here,two segregating F2 populations were developed from crosses between Cgy-1/cgy-1(CC),anα'-lacking line(△α'),and DongNong 47(DN47),a wild-type(Wt)Chinese soybean cultivar with normal globulin components,and Cgy-2/cgy-2(CB),an a-lacking line(△α),and DN47.These populations were used to estimate linkage among the egy-1(conferring α'-null)and cgy-2(α-null)loci and simple sequence repeat(SSR)markers.Seven SSR markers(Sat_038,Satt243,Sat_307,Sat_109,Sat_231,Sat_108 and Sat_190)were determined to co-scgregate with cgy-1,and six SSR markers(Satt650,Satt671,Sat_418,Sat_170,Satt292 and Sat_324)co-segregated with cgy-2.Linkage maps being composed of seven SSR markers and egy-1 locus,and six SSR markers and the cgy-2 locus were then constructed.It assigned that the egy-1 gene to chromosome 10 at a position between Sat_307 and Sat_231,and the cgy-2 gene to chromosome 20 at a position between Satt650 and Satt671.These markers should enable map-based cloning of the egy-1 and cgy-2 genes.For different subunit-deficiency types[α'-null,α-null and(α'+α)-null types],the two sets of SSR markers could also detect of polymorphism between three normal cultivars and seven related mutant lines.The identification of these markers is great significance to the molecular marker-assisted breeding of soybean/9-conglycinin subunits.