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.

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.

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.

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 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.

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.

Effect of Different Potting Mixtures on Growth and Yield of Soybean （Glycine max L.） and Soil Microbial Activity

Soybean （Glycine max： Fabaceae） is a mycotrophic （mycorrhizal） crop grown commercially for human consumption. Seven different fertilizer mixtures, namely cow dung, coir dust, mush room medium waste, saw dust, compost, decaying leaves and field soil with standard dose of NPK （control） were used for this experiment. The variety used was PM 25. Soil microbial activity was measured using CO2 evolution method. The experiment was carried out as a complete randomized block design with five replicates at the rate of eight plants per replicate. Average number of leaves on 25-day and 45-day old plants, shoot-length, root-length, number of pods per plant, wet weight of pod per plant, dry weight of pod per plant, plant wet weight, plant dry weight and seed dry weight per pod were measured. All management practices were conducted according to recommendations of the Department of Agriculture from seed germination to harvesting. Data were analyzed using SAS program （9.1.3）. Highest number of pods/plant （100, 124, 102, 106） and dry-seed-weight in g/plant （12, 14.8, 12, 12） were recorded in those grown in cow dung, compost, decaying leaves and inorganic mixture （control） whereas the lowest pod production （8.7 pods/plant） and seed dry weight （1.0 g/plant） was recorded in saw dust. Instead of inorganic fertilizer there is possibility to use organic potting mixtures like compost and decaying leaves which gave a significant difference in crop productivity as compared to other treatments. Significantly highest mean microbial activity was observed in potting media filled with coir dust.

大豆(Glycine max(L.) Merr.)叶片抗氧化酶对干旱及复水的响应机制

采用10%PEG-6000模拟干旱胁迫,研究了抗旱品种晋大74与不抗旱品种晋大75两种大豆幼苗在水分胁迫及复水后叶片MDA含量、O2-·含量、SOD、CAT、APX及POD等的活性变化,旨在揭示抗氧化酶对干旱及复水的响应机制。结果表明,在干旱胁迫下,两种大豆叶片MDA及O2-·,含量都高于对照,且晋大75增加幅度显著大于晋大74;复水后晋大74中MDA及O2-·接近于对照水平,表明旱后复水产生了补偿效应。干旱胁迫下,晋大74通过保持较高的SOD活性或较低的APX、CAT降幅以减弱活性氧伤害,而旱后复水过程中晋大74通过维持较高的SOD、APX、CAT酶活性,利用其协同作用有效清除活性氧,避免膜伤害。总之,耐旱品种在干旱及复水过程中具有更强的抗氧化修复能力。

Natural variations and geographical distributions of seed carotenoids and chlorophylls in 1167 Chinese soybean accessions

Understanding the composition and contents of carotenoids in various soybean seed accessions is important for their nutritional assessment.This study investigated the variability in the concentrations of carotenoids and chlorophylls and revealed their associations with other nutritional quality traits in a genetically diverse set of Chinese soybean accessions comprised of cultivars and landraces.Genotype,planting year,accession type,seed cotyledon color,and ecoregion of origin significantly influenced the accumulation of carotenoids and chlorophylls.The mean total carotenoid content was in the range of 8.15–14.72μg g–1 across the ecoregions.The total carotenoid content was 1.2-fold higher in the landraces than in the cultivars.Soybeans with green cotyledons had higher contents of carotenoids and chlorophylls than those with yellow cotyledons.Remarkably,lutein was the most abundant carotenoid in all the germplasms,ranging from 1.35–37.44μg g–1.Carotenoids and chlorophylls showed significant correlations with other quality traits,which will help to set breeding strategies for enhancing soybean carotenoids without affecting the other components.Collectively,our results demonstrate that carotenoids are adequately accumulated in soybean seeds,however,they are strongly influenced by genetic factors,accession type,and germplasm origin.We identified novel germplasms with the highest total carotenoid contents across the various ecoregions of China that could serve as the genetic materials for soybean carotenoid breeding programs,and thereby as the raw materials for food sectors,pharmaceuticals,and the cosmetic industry.

野生大豆(Glycine soja)YD63和栽培大豆(G. max)ZD19茎秆解剖结构比较

以野生大豆YD63和栽培大豆ZD19为研究对象,通过组织化学方法观察茎秆解剖结构的差异,分析和阐述这些解剖结构与功能和环境适应性间的关系,旨在为大豆抗逆性研究提供解剖学依据。结果表明:1.野生大豆表皮毛和腺毛多于栽培大豆,且角质层厚度、表皮厚度和表皮比例均大于栽培大豆,表皮和外皮层细胞的木质化和木栓化程度也高于栽培大豆;2.野生大豆皮层、韧皮部、木薄壁组织和髓的比例均大于栽培大豆,茎秆机械强度降低,可塑性升高,抗逆性增强;3.栽培大豆木质部、木纤维和总纤维比例均大于野生大豆,并且表皮细胞壁、韧皮纤维壁、木纤维壁和导管壁厚度均大于野生大豆。栽培大豆组织木质化的比例大于野生大豆,茎秆的机械强度升高,可以更好地维持直立生长和形态构建;4.栽培大豆微管形成层的细胞层数和厚度均大于野生大豆。栽培大豆木质部的比例大于韧皮部的比例,而野生大豆两者比例基本相同;5.野生大豆韧皮部厚壁组织几乎是连续分布,仅在髓射线处中断,而栽培大豆是不连续的,呈片状分布,野生大豆韧皮部厚壁组织的比例大于栽培大豆;6.野生大豆导管壁强度(t/b)2和小导管比例大于栽培大豆,水分运输的安全性较高,但野生大豆木质部的连通性和水分运输的效率低于栽培大豆。

Sampling Survey and Identification of Races of Soybean Cyst Nematode (Heterodera glycines Ichinohe) in Huang-Huai Valleys

Soybean cyst nematode （SCN Heterodera glycines Ichinohe） is one of the most important nationwide soybean diseases in China. A total of 38 soil specimens or locations in the area was sampled and tested for SCN races during 2001-2003 for the inspection of race distribution in Huang-Huai Valleys. A map of race distribution was constructed according to the data from both the present study and the published reports cited. Three areas, namely, the area of southeast to Jinan in Shangdong Province; the area of northern Henan Province and its border region to south of Hebei Province; and the area of Luohe, Zhoukou of Henan Province and Fuyang of Anhui Province mainly infested with Race 1 were identified. Race 4 was predominant in Shanxi Province, Beijing and the adjacent area of Henan, Shandong, and Anhui provinces, and the delta of Huanghe River in Shandong Province. Race 2 was mainly found in Liaocheng, Dezhou of Shangdong Province and Shijiazhuang of Hebei Province, and Jiaozuo and Huojia of Henan Province. Race 7 was distributed in the west part of Jiaodong Peninsula of Shandong Province and Kaifeng, Huaxian, Wenxian of Henan Province. Race 5 was found and scattered in Hebei and Henan Province. Race 9 was found in Shangqiu of Henan Province, which was reported for the first time in China. It can be seen that Race 1 and Race 4 were the two predominant races in Huang-Huai Valleys, and that research should focus on developing resistant cultivars of these races. There might exist other races in an area with some predominant races. The race substitution in the past decade was not obviously found, therefore, the results should be meaningful to future breeding for resistance to SCN in Huang-Huai Valleys.

Rapid HPLC Method for Determination of 12 Isoflavone Components in Soybean Seeds

It is important to determine the isoflavone components by high-performance liquid chromatography （HPLC） for the molecular assistant selection of isoflavone in soybean. Based on the standard samples of 12 isoflavone components, the isoflavone components were analyzed using the determination of absorbance peaks method by HPLC. The results showed that there were different maximum ultraviolet （UV） absorbance for the aglycones of daidzein, glycitein, and genistein, which were at 250, 257, and 260 nm, respectively. A linear gradient elution of acetonitrile （13-30%） containing 0. 1% acetic acid as a mobile phase was applied on a YMC-C18 column at 35℃. The 12 isoflavone components were determined using the UV detector by HPLC. We concluded that this is a rapid and precise method which adapted to determine the large numbers of samples with microanalysis.

Identification of novel QTL associated with soybean isoflavone content

Soybean isoflavones are essential secondary metabolites synthesized in the phenylpropanoid pathway and benefit human health. In the present study, highresolution QTL mapping for isoflavone components was performed using specific-locus amplified fragment sequencing(SLAF-seq) with a recombinant inbred line(RIL) population(F5:7) derived from a cross between two cultivated soybean varieties, Luheidou 2(LHD2) and Nanhuizao(NHZ). Using a high-density genetic map comprising 3541 SLAF markers and the isoflavone contents of soybean seeds in the 200 lines in four environments, 24 stable QTL were identified for isoflavone components, explaining 4.2%–21.2% of phenotypic variation.Of these QTL, four novel stable QTL(qG8, qMD19, qMG18, and qTIF19) were identified for genistin, malonyldaidzin, malonylgenistin, and total isoflavones, respectively. Gene annotation revealed three genes involved in isoflavone biosynthesis(Gm4CL, GmIFR, and GmCHR) and 13 MYB-like genes within genomic regions corresponding to stable QTL intervals, suggesting candidate genes underlying these loci. Nine epistatic QTL were identified for isoflavone components, explaining 4.7%–15.6% of phenotypic variation. These results will facilitate understanding the genetic basis of isoflavone accumulation in soybean seeds. The stable QTL and tightly linked SLAF markers may be used for markerassisted selection in soybean breeding programs.

Effect of Phosphorus Fertilization to P Uptake and Dry Matter Accumulation in Soybean with Different P Efficiencies

Phosphorus （P） is an essential element for plant growth and yield. Improving phosphorus use efficiency of crops could potentially reduce the application of chemical fertilizer and alleviate environmental damage. Soybean （Glycine max （L.） Merr.） is sensitive to phosphorus （P） in the whole life history. Soybean cultivars with different P efficiencies were used to study P uptake and dry matter accumulation under different P levels. Under low P conditions, the P contents of leaf in high P efficiency cultivars were greater than those in low P efficiency cultivars at the branching stage. The P accumulation in stems of high P efficiency cultivars and in leaves of low P efficiency cultivars increased with increasing P concentration at the branching stage. At the late podding stage, the P accumulation of seeds in high and low P efficiency cultivars were 22.5 and 26.0%, respectively; and at the mature stage were 69.8 and 74.2%, respectively. In average, the P accumulation in whole plants and each organ was improved by 24.4% in high P efficiency cultivars compared to low P efficiency cultivars. The biomass between high and low P efficiency cultivars were the same under extended P condition, while a significant difference was observed at late pod filling stage. At the pod setting stage, the biomass of high P efficiency cultivars were significant greater （17.4%） than those of low P efficiency cultivars under high P condition. Meanwhile, under optimum growth conditions, there was little difference ofbiomass between the two types of cultivars, however, the P agronomic efficiency and P harvest index were significant higher in high P efficiency cultivars than those in low P efficiency cultivars.

Identification of a novel seed size associated locus SW9-1 in soybean

Seed size is one of the vital traits determining seed appearance, quality, and yield. Untangling the genetic mechanisms regulating soybean 100-seed weight (100-SW), seed length and seed width across environments may provide a theoretical basis for improving seed yield. However, there are few reports related to QTL mapping of 100-SW across multiple ecological regions. In this study, 21 loci associated with seed size traits were identified using a genome-wide association of 5361 single nucleotide polymorphisms (SNPs) across three ecoregions in China, which could explain 8.12%–14.25% of the phenotypic variance respectively. A new locus, named as SW9-1 on chromosome 9 that explained 10.05%–10.93% of the seed weight variance was found significantly related to seed size traits, and was not previously reported. The selection effect analysis showed that SW9-1 locus has a relatively high phenotypic effect (13.67) on 100-SW, with a greater contribution by the accessions with bigger seeds (3.69) than the accessions with small seeds (1.66). Increases in seed weight were accompanied by increases in the frequency of SW9-1T allele, with >90% of the bred varieties with a 100-SW >30 g carrying SW9-1T. Analysis of SW9-1 allelic variation in additional soybean accessions showed that SW9-1T allele accounting for 13.83% of the wild accessions, while in 46.55% and 51.57% of the landraces and bred accessions, respectively, this results indicating that the SW9-1 locus has been subjected to artificial selection during the early stages of soybean breeding, especially the utilization of SW9-1T in edamame for big seed. These results suggest that SW9-1 is a novel and reliable locus associated with seed size traits, and might have an important implication for increasing soybean seed weight in molecular design breeding. Cloning this locus in future may provide new insights into the genetic mechanisms underlying soybean seed size traits.

Effects of Lipoxygenase Null Genes of Soybean in Controlling Beany-flavor of Soymilk and Soyflour

The flavor of the soymilk and soyflour obtained from the lipoxygenase mutant isolines was concentrated by simultaneous distillation and extraction (SDE), and its constituents were identified by gas chro-matography (GC) and gas chromatography-mass spectrometry. Results showed that the same 24 flavor constituents were isolated in both soymilk and soyflour, and most of them were aldehydes and alcohols. Lox2 was most responsible for the production of the volatile and beany-flavor components, and Lox1 less responsible. Lox3 was least responsible and can reduce the yield of hexanal. Either Lx1 or Lx2 could significantly reduce the volatile and beany-flavor, and Lx3 could significantly increase the yield of hexanal. Primary and secondary interactions existed among the null mutant genes, and the major effects and interactions could be affected by processing conditions. The isoline with triple lipoxygenase null genes yielded the least volatile and beany-flavor components, and the isoline without the lipoxygenase gene Lx3 produced the greatest amount of the volatile and beany-flavor components. The amounts of volatile and beany-flavor components produced by the other isolines were between that of the isoline with triple lipoxygenase null genes and the isoline without lipoxygenase gene Lx3. According to the correlation analysis, the hexanal amount could be used as an index in evaluating the importance of lipoxygenase isozymes in the yield of beany-flavor compounds, and the effects of the different types of lipoxygenase null mutants in controlling beany-flavor compounds. The cultivars with triple lipoxygenase null genes will be a quality raw material for soy food processing.

Constitutive expression of feedback-insensitive cystathionine γ-synthase increases methionine levels in soybean leaves and seeds

Soybean （Glycine max （L.） Merr.） is a major crop that provides plant-origin protein and oil for humans and livestock. Al- though the soybean vegetative tissues and seeds provide a major source of high-quality protein, they suffer from low con- centration of an essential sulfur-containing amino acid, methionine, which significantly limits their nutritional quality. The level of methionine is mainly controlled by the first unique enzyme of methionine synthesis, cystathione y-synthase （CGS）. Aiming to elevate methionine level in vegetative tissues and seeds, we constitutively over-expressed a feedback-insensitive Arabidopsis CGS （AtD-CGS） in soybean cultivars, Zigongdongdou （ZD） and Jilinxiaoli 1 （JX）. The levels of soluble methionine increased remarkably in leaves of transgenic soybeans compared to wild-type plants （6.6- and 7.3-fold in two transgenic ZD lines, and 3.7-fold in one transgenic JX line）. Furthermore, the total methionine contents were significantly increased in seeds of the transgenic ZD lines （1.5- to 4.8-fold increase） and the transgenic JX lines （1.3- to 2.3-fold increase） than in the wild type. The protein contents of the transgenic soybean seeds were significantly elevated compared to the wild type, suggesting that the scarcity of methionine in soybeans may limit protein accumulation in soybean seeds. The increased protein content did not alter the profile of major storage proteins in the seeds. Generally, this study provides a promising strategy to increase the levels of methionine and protein in soybean through the breeding programs.

Synergistic interaction of NaCl and Cd on growth and photosynthetic parameters in soybean genotypes differing in salinity tolerance

The effects of salinity （50 mmol/L NaCI） and Cd （1 μmol/L CdCl2） as sole and combined on growth and photosynthetic parameters were studied using two soybean genotypes, Huachun 18 and NGB. The concentrations of Cd^2＋, Zn^2＋, Ca^2＋, Mg^2＋, K^＋ and Na^＋were also determined in seeds and pods. Huachun 18 suffered a more serious decrease than NGB in net photosynthetic rate （P,） in the treatments of salinity stress alone and combined stress （NaCl＋Cd）, showing that it is relatively sensitive to salinity. The decrease in P, caused by salt stress in Huachun 18 was mainly due to the reduced total chlorophyll content and photosynthetic efficiency （the ratio of variable fluorescence to maximal fluorescence, Fv/Fm）, whereas the decease in NGB was mainly related to reduced stomatal conductance （Gs）, The combined stress of both Na and Cd did not induce further decrease in photosynthesis and fluorescence in the two genotypes relative to salt or Cd stress alone. Greater change in the pod concentrations of Zn^2＋, Ca^2＋, Mg^2＋, K^＋ and Na^＋was detected under salt stress for Huachun 18 than for NGB. The results suggested that the interactive effect of NaCl-Cd on growth and nutrient uptake differs between the two soybean genotypes.

Studies on the Correlations Between Isoflavone Contents in Soybean Seed and the Eco-Physiological Factors

The soybean cultivar Yudou25 was sown at 5 locations of Henan Province on 13 differentdates in 2001 and 2002. The data of isoflavone contents for the 109 samples of soybeanseed and 33 eco-physiological factors including meteorological factors, soil nutritionand altitudes were received and used for statistical analysis. The step-wise regressionwas used to screen the correlated factors, which significantly effected isoflavonecontents. Results showed that 9 eco-physiological factors were highly correlated withisoflavones. Low mean temperature, high diurnal temperature range at seed filling andmaturity, more sunlight hours and low mean temperature at emergence were favorable toisoflavone accumulation. The rainfall at emergence showed a nonlinear relationship withisoflavone content and its optimum value was 75 mm for isoflavone formation. Low diurnaltemperature range at branching, high organic matter and low sulfur content in soil weresuitable for the formation of isoflavones. The isoflavone contents would not be affectedby other eco-physiological factors in this study.

A novel TIR-NBS-LRR gene regulates immune response to Phytophthora root rot in soybean

Phytophthora root rot(PRR),caused by Phytophthora sojae,is a devastating disease of soybean.The NBSLRR gene family is a class of plant genes involved in disease resistance.miRNA mediates plant response to biotic stresses by regulating the expression of target genes at the transcriptional or post-translational level.Glyma.16G135500,encoding an NBS-LRR-type protein,is a target of gma-miR1510 that responds to pathogen infections.We cloned and overexpressed Glyma.16G135500(naming it GmTNL16)and knocked down mi R1510 using short tandem target mimic technology to identify the roles of the GmTNL16/gma-mi R1510 pair in the interaction of soybean and the oomycete.By overexpressing GmTNL16 in transgenic hairy roots of soybean,we showed that biomass of P.sojae was lower in overexpressing hairy roots than in control roots.Thus,miR1510 expression was reduced upon P.sojae infection,reflecting the induced expression of GmTNL16 conferring resistance to P.sojae in soybean.Differentially expressed genes were enriched in plant-pathogen interaction,plant hormone signal transduction,and secondary metabolism by RNA sequencing analyze.In particular,jasmonate and salicylic acid pathway-associated genes,including JAZ,COI1,TGA,and PR,responded to P.sojae infection.All of these results indicate that the GmTNL16/gma-miR1510 pair participates in soybean defense response via the JA and SA pathways.