Quantitative trait loci underlying the development of seed composition in soybean (Glycine max L. Merr.).

One hundred and forty-three F2:7 recombinant inbred lines (RILs) developed from the cross of soybean cultivars 'Charleston' and 'Dongnong 594' were analyzed for the quantitative trait loci (QTLs) underlying protein or oil content at 6 different developmental stages by composite interval mapping with a mixed genetic model. The genotype x environment (GxE) interactions of the QTLs were also evaluated. Nineteen (2004) and 33 (2005) unconditional QTLs underlying seed protein or oil content at the different developmental stages were mapped onto 8 and 9 linkage groups, respectively. The proportion of phenotypic variation explained by these QTLs ranged from 6.26% to 30.52% and from 5.38% to 28.47%, respectively. Fourteen (2004) and 21 (2005) conditional QTLs underlying seed protein or oil content were mapped onto 5 and 8 linkage groups, respectively. The proportion of phenotypic variation explained by these QTLs ranged from 2.97% to 29.68% and from 5.42% to 31.96%, respectively. The numbers and types of QTLs and the genetic effect for the two traits were different at each developmental stage. However, several genomic regions that simultaneously control the development of both traits were detected. The genetic effect on protein content and oil content was opposite for loci in the marker interval Satt335-SSatt334, reflecting a negative correlation of protein content and oil content. A G x E interaction effect of some QTLs underlying protein or oil content at different growth periods was observed.     

Mapping of quantitative trait loci for canopy-wilting trait in soybean (Glycine max L. Merr)

Drought stress adversely affects [Glycine max (L.) Merr] soybean at most developmental stages, which collectively results in yield reduction. Little information is available on relative contribution and chromosomal locations of quantitative trait loci (QTL) conditioning drought tolerance in soybean. A Japanese germplasm accession, PI 416937, was found to possess drought resistance. Under moisture-deficit conditions, PI 416937 wilted more slowly in the field than elite cultivars and has been used as a parent in breeding programs to improve soybean productivity. A recombinant inbred line (RIL) population was derived from a cross between PI 416937 and Benning, and the population was phenotyped for canopy wilting under rain-fed field conditions in five distinct environments to identify the QTL associated with the canopy-wilting trait. In a combined analysis over environments, seven QTL that explained 75?% of the variation in canopy-wilting trait were identified on different chromosomes, implying the complexity of this trait. Five QTL inherited their positive alleles from PI 416937. Surprisingly, the other two QTL inherited their positive alleles from Benning. These putative QTL were co-localized with other QTL previously identified as related to plant abiotic stresses in soybean, suggesting that canopy-wilting QTL may be associated with additional morpho-physiological traits in soybean. A locus on chromosome 12 (Gm12) from PI 416937 was detected in the combined analysis as well as in each individual environment, and explained 27?% of the variation in canopy-wilting. QTL identified in PI 416937 could provide an efficient means to augment field-oriented development of drought-tolerant soybean cultivars.     

Dehydration Injury in Germinating Soybean (Glycine max L. Merr.) Seeds

The sensitivity of soybean (Glycine max L. Merr. cv Maple Arrow) seeds to dehydration changed during germination. Seeds were tolerant of dehydration to 10% moisture if dried at 6 hours of imbibition, but were susceptible to dehydration injury if dried at 36 hours of imbibition. Dehydration injury appeared as loss of germination, slower growth rates of isolated axes, hypocotyl and root curling, and altered membrane permeability. Increased electrolyte leakage due to dehydration treatment was observed only from isolated axes but not from cotyledons, suggesting that cotyledons are more tolerant of dehydration. The transition from a dehydration-tolerant to a dehydration-susceptible state coincided with radicle elongation. However, the prevention of cell elongation by osmotic treatment in polyethylene glycol (−6 bars) or imbibition in 20 micrograms per milliliter cycloheximide did not prevent the loss of dehydration tolerance suggesting that neither cell elongation nor cytoplasmic protein synthesis was responsible for the change in sensitivity of soybean seeds to dehydration. Furthermore, the rate of dehydration or rate of rehydration did not alter the response to the dehydration stress.     

ATP Sulfurylase Activity in the Soybean [Glycine max (L.) Merr.

ATP sulfurylase activity was assayed in soybean leaf extracts. A simple, rapid assay system using molybdate as an analogue of sulfate was developed. The assay was coupled to inorganic pyrophosphatase. The high pyrophosphatase level in soybean leaf extracts obviated the necessity of adding this enzyme to the assay system. ATP sulfurylase has a pH maximum above 7.5, uses molybdate and ATP as substrates, and requires magnesium ions for activity.     

Mapping quantitative trait loci associated with chlorophyll a fluorescence parameters in soybean (Glycine max (L.) Merr.)

Chlorophyll a fluorescence parameters can provide qualitative and quantitative information about photosynthetic processes in chloroplasts. JIP-test and modulated fluorescence (MF) parameters are commonly used chlorophyll a fluorescence parameters. This study was conducted to identify quantitative trait loci (QTLs) associated with JIP-test parameters, MF parameters, and photosynthetic rate (P_N), and to examine the relationships among them in soybean (Glycine max (L.) Merr.). Pot and field experiments were performed to evaluate 184 recombinant inbred lines (RILs) for five JIP-test parameters (ABS/RC, TR_o/ABS, ET_o/TR_o, RE_o/ET_o, and PI_ABS), four MF parameters (Fv/Fm, Fv′/Fm′, ΦPSII, and qP), and P_N. Significant correlations were commonly observed among JIP-test parameters, MF parameters, and P_N. QTL mapping analysis identified 13, 9, and 4 QTLs for JIP-test parameters, MF parameters, and P_N, respectively, of which 13 were stable. Four major genomic regions were detected: LG A2 (19.81 cM) for JIP-test parameters, LG C1 (94.31 and 97.61 cM) for P_N and MF parameters, LG M (100.51 cM) for JIP-test and MF parameters, and LG O (30.61–49.91 cM) for P_N, JIP-test, and MF parameters. These results indicate that chlorophyll fluorescence parameters, especially ΦPSII and qP, could play an important role in regulating P_N, and that JIP-test and MF parameters could be controlled by the same or different genes. The QTLs identified in this study will help in the understanding of the genetic basis of photosynthetic processes in plants. They will also contribute to the development of marker-assisted selection breeding programs for photosynthetic capacity in soybean.     

Quantitative trait loci associated with oligosaccharide and sucrose contents in soybean (Glycine max L.)

Oligosaccharides and sucrose are very important nutritional components in soybean seeds. However, little information is available about their inheritance. We used molecular markers to identify the genomic regions significantly associated with the quantitative trait locus (QTL) that controls oligosaccharide and sucrose contents in segregating F_2:10 Rl lines. Two related, but independent, QTLs were identified for oligosaccharides — near marker satt546 on linkage group (LG) D1b+W and satt278 on LG L. Four others, for sucrose content, were located at LG B1 (satt197), D1b+W (satt546), and L (satt523 and satt278). Finally, we found two common QTLs, on LG D1b+W and L, that are associated with both oligosaccharides and sucrose.     

Nitrate Reduction by Roots of Soybean (Glycine max [L.] Merr.) Seedlings

Studies were conducted with 9 to 12 day-old soybean (Glycine max [L.] Merr. cv. Williams) seedlings to determine the contribution of roots to whole plant NO(3) (-) reduction. Using an in vivo -NO(3) (-) nitrate reductase (NR) assay (no exogenous NO(3) (-) added to incubation medium) developed for roots, the roots accounted for approximately 30% of whole plant nitrate reductase activity (NRA) of plants grown on 15 mm NO(3) (-).Nitrogen analyses of xylem exudate showed that 53 to 66% of the total-N was as reduced-N, depending on the time of day of exudate collection. These observations supported enzyme data that suggested roots were contributing significantly to whole plant NO(3) (-) reduction. In short-term feeding studies using (15)N-NO(3) (-) significant and increasing atom percent (15)N excess was found in the reduced-N fraction of xylem exudate at 1.5 and 3 hours after feeding, respectively, which verified that roots were capable of reducing NO(3) (-).Estimated reduced-N accumulation by plants based on in vivo -NO(3) (-) NR assays of all plant parts substantially over-estimated actual reduced-N accumulation by the plants. Thus, the in vivo NR assay cannot be used to accurately estimate reduced-N accumulation but still serves as a useful assay for relative differences in treatment conditions.     

Moisture Loss as a Prerequisite for Seedling Growth in Soybean Seeds (Glycine max L. Merr.)

Rosenberg, L. A. and Rinne, R. W. 1986. Moisture loss as a prerequisitefor seedling growth in soybeanseeds (Glycine max L. Merr.).—J.exp. Bot. 37: 1663–1674. As soybean seeds [Glycine max (L.) Merr.] develop, they undergoa change in seed moisture. When excised prematurely from thepod and planted, seeds do not exhibit seedling growth until63 d after flowering (DAF) when the seed moisture has fallenbelow 60%. In contrast, seed germination (radicle protrusion)can occur when seeds as young as 35 DAF (68–79% moisture)are excised, but this germination docs not lead to comparableseedling growth frequencies unless seeds are first given a moistureloss treatment to artificially reduce their moisture below 60%.A moisture loss treatment applied at 35 DAF thus enables seedto undergo the transition from germination (cell expansion)to seedling growth (cell division and expansion) to the extentthat treated immature seed have a vigour index comparable toseeds matured on the plant (100%). The pattern of protein synthesisin vivo was examined in 35 DAF seed using [³⁵S]-methionine incorporation.When moisture loss treatment was applied for 24 h to 35 DAFseeds, seeds synthesized several new polypeptides when comparedwith untreated seeds at the same developmental stage. The sameseed samples showed 0% seedling growth in the absence of moistureloss treatment and 80% seedling growth when the treatment hadbeen applied. Moisture loss from soybean seeds appears to bea prerequisite for the synthesis of new proteins which may bepart of the metabolic process or processes that allow the soybeanseed to undergo the transition from seed germination to seedlinggrowth. Key words: Moisture loss, germination/growth, soybean     

Protein Modification and Utilization of Starch in Soybean (Glycine max L. Merr.) Seed Maturation

Seeds of soybean (Glycine max L. Merr.) harvested at variousstages of development and allowed to dry in intact pods undergoa maturation process and are viable. Defatted powders of seedharvested 24–66 d after flowering were extracted to yieldbuffer-soluble and alkali-soluble proteins. Imposition of amaturation process increased the level of buffer-soluble proteinsbut had no effect on the disulflde content of these proteins.After undergoing maturation, seeds showed an accumulation ofbuffer-soluble polypeptides in the molecular weight range of43–94 kD. Maturation may be associated with the synthesisof specific polypeptides having a molecular weight of approximately85 kD. Alkali-soluble proteins, which represents the storageproteins, did not show any responses to maturation. Their quantityincreased substantially during seed development and the disulfidelevel was only half that of buffer-soluble proteins, attaininga maximum value of 10.9 mol S per 10⁵ g protein. Matured seedat all harvest dates had a final starch content close to thatof normal seed, 10–20 mg g^–1, and soluble sugarswere maintained at quite high levels, 51–83 mg g^–1.The metabolic program for synthesis and degradation of starchseems quite rigidly followed and is independent of harvest dateor of attachment to the parent plant. Soybean seeds retain considerablesoluble proteins and soluble sugars throughout maturation, andthese collectively may be important in maintaining a desiccationresistant structure.     

Examination of Le and lele Genotypes of Glycine max (L.) Merr. for Membrane-Bound and Buffer-Soluble Soybean Lectin

Membrane fractions from seedlings of four soybean [Glycine max (L.) Merr.] lines were examined by radioimmunoassay and hemagglutination assay for the 120,000 dalton soybean lectin. Two of the lines (Sooty and T-102) are genotypically lele and lack buffer-soluble soybean lectin; the remaining two lines (Beeson and Harosoy 63) are Le and produce seeds that contain the lectin (Su et al. 1980 Biochim. Biophys. Acta 629: 292-304). Both Triton X-100 (0.5% v/v) and nonidet P-40 (0.05% v/v) solubilized soybean lectin from membrane fractions of Le cotyledons. Triton X-100 interfered substantially with the assay of protein and hemagglutinating activity and was unacceptable for use in quantitative measurements. The nonidet P-40-solubilized soybean lectin from Le cotyledons was consistently present both in washed 13,000g and 82,500g membrane fractions, but it accounted for less than 1.5% of the total (buffer-soluble plus membrane-bound) soybean lectin. The membrane lectin was purified by the affinity chromatography procedure devised for soluble soybean lectin, and it was immunologically indistinguishable from authentic soybean lectin. Membrane fractions from Le cotyledons contained insignificant amounts of radioisotope-labeled soybean lectin that had been added during homogenization, and purified membrane fractions did not bind the lectin in the presence of the hapten, d-galactose. These controls make it unlikely that the membrane soybean lectin was of cytoplasmic origin. Soybean lectin and other hemagglutinins were not present in buffer-soluble or membrane fractions from lele cotyledons or from roots and hypocotyls of any of the lines.     

Effect of Sowing Time on the Incidence of Bud Blight in Soybean (Glycine max L. Merr.)

The incidence of soybean bud blight in soybeans in Brazil is sporadic in most of the production areas but is endemic in a few others. Tobacco streak virus (TSV), the causal agent, is transmitted by thrips. The vector population starts declining everytime the amount of accumulated rain is over 300 mm. A four year trial (1986—1990) indicated that by delaying the sowing time it was possible to drastically reduce the incidence of the disease, allowing farmers to grow a cash crop. Significant correlations were observed between percentage of infection, number of days with rain, total of accumulated rain and total of thrips surveyed. A multiple linear regression (y = 23.93 + 0.7 × 1—0.06 × 2) that accounted for 80 % of the variation was obtained, considering percentage of infected plants (y), total of thrips (×1) and total of accumulated rain (×2). Results indicated that farmers should sow during the month of December, in areas where the disease is endemic.     

低磷对大豆主根伸长生长的影响

文章采用卷纸培养和分层琼脂培养的方法,研究磷对大豆主根伸长影响的结果表明:低磷[0.2 μmol(KH2PO4)·L-1]显著促进大豆主根伸长,特别是延长大豆主根根尖至最新侧根间的距离;组织切片表明,低磷对主根伸长的促进主要是通过延迟主根伸长区的分化实现的,并且低磷对主根的促进作用不受亚磷酸盐的影响.琼脂分层培养的结果表明,在磷分布不均匀的条件下,低磷影响主根的仲长生长,上层或下层不施磷的大豆主根伸长均有增加.     

Ein Beitrag zur Systematik der Sojabohnen (Glycine max (L.) Merr.)

Ohne ZusammenfassungHerrn ProfessorStubbe in Dankbarkeit zum 60. Geburstag.     

Stimulation of Pod and Ovule Growth of Soybean, Glycine max (L.) Merr. by 6-Benzylaminopurine

Flowers at distal nodes on soybean racemes usually fail to setpods and subsequently abscise. Physiological and histologicalstudies were performed to determine the influence of 6-benzylaminopurine(BAP) on distal pod development. The pedicels of fully openedflowers on terminal racemes of field-grown IX93-100 soybeanplants were treated three times with 200 mg kg^-1 BAP in lanolinover a 6-d period. Racemes were then excised and ³²P uptakewas recorded for each flower position within a raceme; histologicalfeatures of pedicels and ovules also were determined. Applicationof BAP increased pod and ovule length, width and weight at allfour distal nodes (D, D-1, D-2, D-3) relative to controls treatedwith lanolin. Length and width of parietal endosperm cells weresmaller in BAP-treated ovules at the most proximal node beingstudied (D-3), and greater numbers of parietal endosperm cellswere observed at D-1 and D-3 nodes when compared to lanolincontrols. Smaller amounts of starch were found in suspensorcells, endosperm, and integuments of lanolin-treated ovules,and starch depletion over time was observed within starch sheathsof pedicels from lanolin-treated pods when compared to BAP-treatedtissues. BAP-treated racemes had more ³²P uptake at the fourmost distal nodes. A higher rate of uptake (cpm mg^-1 f. wt)was evident in ovules than in ovary tissues. These results suggestthat for racemes otherwise destined to abscise, applicationof BAP promotes pod set and growth by stimulating ovule development.Copyright1993, 1999 Academic Press Pod, ovule soybean, abscission, 6-benzylaminopurine     

Association mapping of iron deficiency chlorosis loci in soybean (Glycine max L. Merr.) advanced breeding lines

Association mapping is an alternative to mapping in a biparental population. A key to successful association mapping is to avoid spurious associations by controlling for population structure. Confirming the marker/trait association in an independent population is necessary for the implementation of the marker in other genetic studies. Two independent soybean populations consisting of advanced breeding lines representing the diversity within maturity groups 00, 0, and I were screened in multi-site, replicated field trials to discover molecular markers associated with iron deficiency chlorosis (IDC), a major yield-limiting factor in soybean. Lines with extreme phenotypes were initially screened to identify simple sequence repeat (SSR) markers putatively associated with the IDC. Marker data collected from all lines were used to control for population structure and kinship relationships. Single factor analysis of variance (SFA) and mixed linear model (MLM) analyses were used to discover marker/trait associations. The MLM analyses, which include population structure, kinship or both factors, reduced the number of markers significantly associated with IDC by 50% compared with SFA. With the MLM approach, three markers were found to be associated with IDC in the first population. Two of these markers, Satt114 and Satt239, were also found to be associated with IDC in the second confirmation population. For both populations, those lines with the tolerance allele at both these two marker loci had significantly lower IDC scores than lines with one or no tolerant alleles.     

Quantitative content of total polar lipids in soybean seeds Glycine max (L.) Merr]

The exhaustive extraction of lipids from soybean seeds in the native state, separation of polar lipids and determination of their functional groups (ester and phosphate) revealed that dry seeds may contain 36,7 mumole (+/- 4,6%) of polar lipids and 25,9 mumole (+/- 1.1%) phospholipids per gramme.     

A Pod Leakage Technique for Phloem Translocation Studies in Soybean (Glycine max [L.] Merr.)

Radioactive photosynthetic assimilates, translocated to a soybean (Glycine max [L.] Merr. `Fiskeby V') pod can be measured directly by excising the stylar tip of the pod under 20 mm ethylenediaminetetraacetate solution (pH 7.0) and allowing the material to leak into the solution. Pods at the source node received approximately 50% of the ¹⁴C exported from the source leaf to the pod and leaked approximately 1 to 3% of this into the solution. More than 90% of the ¹⁴C that leaked from the pods was found in the neutral fraction and, of this, about 93% was in sucrose. Fifteen amino acids were identified in the leakage including: alanine, arginine, asparagine, γ-aminobutyric acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, phenylalanine, serine, threonine, tyrosine, and valine. The majority of the ¹⁴C in the basic fraction was found in serine (30%) and asparagine (23%). The inorganic ions K, Ca, P, Mg, Zn, and Fe were found in the leakage component. Nitrate was not detectable in the collected leakage solution. The absence of NO₃⁻ and the large proportion of the label in sucrose suggest a possible phloem origin for most of the material. The technique provides an uncomplicated, reproducible means of analyzing the material translocated into and through the soybean pod, as well as following the time course of label arrival at the pod.     

l-Arginine and l-Canavanine Metabolism in Jack Bean, Canavalia ensiformis (L.) DC. and Soybean, Glycine max (L.) Merr

Studies have been conducted with the arginase (l-arginine amidinohydrolase, EC 3.5.3.1) of two legumes: jack bean, Canavalia ensiformis (L.) DC., a l-canavanine-containing plant and soybean, Glycine max, a canavanine-free species. Analyses of the arginase obtained from gradient-purified mitochondria of these legumes revealed that the arginine-dependent (ADA) and canavanine-dependent activities (CDA) were localized within this organelle.