NaCl胁迫下野生和栽培大豆幼苗体内离子的再转运

采用NaCl根际处理和叶面饲喂^22Na方法,研究了野生大豆(Glycine soja)——耐盐的BB52、盐敏感的N23232和栽培大豆(Glycine max)——较耐盐的Lee68幼苗在盐胁迫及解除过程中对Na^ 、Cl^-的吸收和再转运。结果表明,在NaCl根际处理12h过程中,BB52和Lee68幼苗根对Na^ 、Cl^-吸收和向茎、叶的运输逐渐增加,10h时趋于稳定,Na^ 、Cl^-含量高低顺序是根＞茎＞叶。但N23232的Na^ 、Cl^-含量则是茎＞根＞叶。在用NaCl对根处理10h后再解除NaCl处理的0～36h内,BB52吸收的Na^ 、Cl^-较多地留于根部或转运至根茎过渡区,叶中较少。N23232吸收的Na^ 较多地转运至茎部,而Cl^-含量在幼苗各部分无差异。叶片饲喂^22Na 10h后,BB52吸收^22Na较N23232多,并较多地向根部运输。从离子再转运角度讨论了BB52的耐盐性。     

栽培和野生大豆及其杂交后代幼苗的耐氯性与多胺积累的关系

对经逐代耐盐性筛选的栽培和野生大豆杂交组合(‘Jackson’בBB52’)F4代‘JB185’株系及其亲本幼苗以不同浓度NaCl和等渗(-0.53 MPa)PEG-6000、NaCl、钠盐(无Cl-)和氯盐(无Na )溶液处理6d。结果表明:(1)随NaCl浓度的提高,3种遗传材料幼苗叶片相对电解质渗漏率和MDA含量均呈上升趋势,叶绿素含量除‘BB52’和‘JB185’在NaCl 50mmol/L处理时显著上升外,其余处理呈下降趋势,‘JB185’变化介于两亲本之间。(2)不同离子胁迫下,它们叶片相对电解质渗漏率和MDA含量较对照多表现增加趋势,其中‘BB52’和‘JB185’在钠盐(无Cl-)处理下的变化明显大于氯盐(无Na )处理。叶片中游离态和束缚态Put、Spd和Spm含量都较对照明显提高,但‘BB52’和‘JB185’在钠盐(无Cl-)处理下游离态(Spd Spm)/Put比值和束缚态多胺总量为3种盐处理中最低。表明‘JB185’与野生大豆‘BB52’种群一样对Na 敏感而对Cl-表现较强的耐性。     

氯化钠胁迫下野生和栽培大豆幼苗体内的多胺水平变化

以通用的较耐盐的栽培大豆Lee68品种和对盐敏感的野生大豆N23232种群为参照,研究了盐胁迫下耐盐野生大豆BB52种群幼苗体内多胺(PAs)组分、含量及多胺氧化酶(PAO)活性的变化。结果表明,盐胁迫下BB52幼苗根PAs中Put和Spm含量下降较Lee68和N23232显著,但Spd含量下降较少．BB52叶片PAs中Put含量下降,Spd上升,(Spd+Spin)／Put值增加和Put／PAs值降低幅度与耐盐性呈正相关趋势．盐胁迫下,各材料根和叶中PAO活性上升,N23232上升最明显．探讨了多胺水平与BB52耐盐性的关系。     

Restriction of Nodulation by Bradyrhizobium japonicum Is Mediated by Factors Present in the Roots of Glycine max

Reciprocal grafting experiments done using soybean plant introduction genotypes indicated that restriction of nodulation by Bradyrhizobium japonicum is determined by the genotype of the root and is dependent on plant growth temperature. Microscopic analyses indicated that the soybean plant introduction genotypes restrict nodulation of B. japonicum at symbiotic stages which occur both before and after the formation of nodule primordia.     

Chromosomal features revealed by comparison of genetic maps of Glycine max and Glycine soja

Recombination is a crucial component of evolution and breeding. New combinations of variation on chromosomes are shaped by recombination. Recombination is also involved in chromosomal rearrangements. However, recombination rates vary tremendously among chromosome segments. Genome-wide genetic maps are one of the best tools to study variation of recombination. Here, we describe high density genetic maps of Glycine max and Glycine soja constructed from four segregating populations. The maps were used to identify chromosomal rearrangements and find the highly predictable pattern of cross-overs on the broad scale in soybean. Markers on these genetic maps were used to evaluate assembly quality of the current soybean reference genome sequence. We find a strong inversion candidate larger than 3 Mb based on patterns of cross-overs. We also identify quantitative trait loci (QTL) that control number of cross-overs. This study provides fundamental insights relevant to practical strategy for breeding programs and for pan-genome researches.     

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.     

Screening of Glycine max and Glycine soja genotypes for multiple shoot formation at the cotyledonary node

Summary To identify genotypes which may give better plant regeneration responses in vitro, multiple shoots were induced from 155 Glycine max and 13 Glycine soja genotypes from maturity groups 000 to VII on B5 medium supplemented with 1 or 5 mol benzylaminopurine (BAP). The average number of shoots formed show genotype specific and hormone concentration specific responses, with number of shoots ranging from 1 to 12 for different genotypes. The results were reproducible with different seed lots of the same genotype and genotypes with similar genetic backgrounds responded in a similar fashion. No hybrid vigor was observed, except in one instance of F₁ hybrids between low shoot producers where the number of shoots obtained were higher than either parent. The root forming ability of cuttings of soybean plants grown in vivo showed general agreement with shoot forming ability in vitro. The ability to form multiple shoots appears to be genetically controlled.This research was supported by funds from the Illinois Agricultural Experiment Station and Agrigenetics Research Associates     

Physiological regulation of seed soaking with soybean isoflavones on drought tolerance of Glycine max and Glycine soja

In this study, the Glycine max Jackson cultivar (the relatively drought-sensitive) and the Glycine soja BB52 accession (the drought-tolerant one) were used as the experimental materials. Effects of seed soaking with exogenous soybean isoflavones (daidzin or genistin) on seed germination, and seedlings photosynthesis, relative electrolytic leakage, content of thiobarbituric acid reactive substances , and anti-oxidative activities were investigated under drought stress conditions. The results showed that, treatments of seed soaking with daidzin or genistin could improve seed germination, and alleviate cell damage, enhance anti-oxidative activities and photosynthesis in drought-stressed seedlings, therefore displayed mitigated effects on soybean drought injury, especially for the drought-sensitive G. max Jackson cultivar. Thus seed soaking with exogenous soybean isoflavones may be a usable approach to enhance drought tolerance of cultivated soybean in practice.     

Genetically determined enzyme polymorphism in soy varieties (Glycine max) and in wild soy (Glycine soja)

Analysis of 22 genetic-biochemical systems (42 loci) in 18 varieties of domestic soybean (G. max) and in 3 population of wild soybean (G. soja) was carried out. The part of polymorphous loci (P), intraspecies genetic differentiation (genetic distances--DN) were higher in domestic plants in comparison with wild ones (P = 45%, 17%: DN = 0.038-0.269, 0.059-0129). The preferable polymorphism of loci, coding the enzymes of glycolysis and Kreb's cycle was revealed in wild species. Domestic soybean had more polymorphous enzyme loci, which did not participate in glucose metabolism in comparison with wild species. The presence of the specific part of the gene pool in ancestor species, which was involved in soybean domestication and forming of varieties was discussed.     

Isolation and Characterization of Thiamin Pyrophosphotransferase from Glycine max Seedlings

Thiamin:ATP pyrophosphotransferase (EC2.7.6.2) activity from soybean (Merr.) seedlings grown for 48 hours was determined by measuring the rate of [2-¹⁴C]thiamin incorporation into thiamin pyrophosphate. With partially purified (11-fold) enzyme, optimal activity occurred between pH 7.1 and 7.3, depending on the buffer system that was used. Assays were routinely conducted at a final pH of 8.1 in order to minimize interference from competing reactions. Enzyme activity required the presence of a divalent cation, and a number of nucleoside triphosphates proved to be active as pyrophosphate donors. Apparent K_m values of 18.3 millimolar and 4.64 micromolar were obtained for Mg·ATP and thiamin, respectively. Among the compounds tested, pyrithiamin and thiamin pyrophosphate were most effective in inhibiting thiamin pyrophosphotransferase activity. Based on Sephadex G-100 gel filtration, soybean thiamin pyrophosphotransferase has a molecular weight of 49,000.     

Effects of Zn2+ and niflumic acid on photosynthesis in Glycine soja and Glycine max seedlings under NaCl stress

The effects of two anion/Cl^? channel inhibitors, Zn²⁺ and niflumic acid (NA), on seedling photosynthetic and fluorescent parameters of two Glycine soja populations (salt-tolerant BB52; salt-sensitive N23227) and Glycine max cultivar (salt-tolerant Lee68) were studied and compared under salt stress. Treatments with Zn²⁺ and NA only (10, 20 μmol L^?1) were also imposed for comparisons. Results showed that, there were non-toxic and non-nutritional effects of Zn²⁺ and NA treatments alone on seed germination and seedling growth of soybeans. Under 150 mmol L^?1 NaCl for 6 d, leaf chlorophyll and carotenoid contents, net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), transpiration rate (Tr), and the maximum photochemical efficiency of photosystem II (PS II) (F_v/F_m) except the stomatal limitation (Ls) significantly decreased in three kinds of soybean seedlings when compared with their control plants. The NaCl stress plus additional 20 μmol L^?1 Zn showed an obvious enhancement of leaf chlorophyll and carotenoid contents, P_n, G_s, C_i and Tr, especially for the G. max cultivar Lee68, but the supplementation of 20 μmol L^?1 NA showed the reverse effects.     

Ribonuclease activity of Glycine max and Glycine soja sprouts as a marker adaptation to copper sulphate and zinc sulphate toxicity

Environmental pollution caused by anthropogenic activities has increased agricultural land contamination with heavy metals which is harmful to plant and human health. Increased metal accumulation in the soils may trigger competition between toxic metals and essential nutrients for absorption by plants and consequently leads to the development of oxidative stress. Soybean plants have a delicate system of defense mechanisms. We assume that the influence of heavy metals on plant growth as a whole can be traced through a change in the activity of enzymes. We studied the stress-reducing reaction against the toxic effects of copper sulphate and zinc sulphate, identified different endurance classes, and observed differences in the biochemical adaptation i.e. ribonuclease (RNase) activity in the wild and cultivated soybean sprouts. Sulphates of both zinc and copper at maximum permissible concentration and double maximum permissible concentration affected the multiple forms of RNase and its specific activity in the wild and cultivated soybean sprouts (grown for 1, 3, 5, and 7 days). Wild soybean sprouts had higher RNase activity as compared to cultivated soybean sprouts. It is shown that the limits of endurance for wild soybean during intoxication are observed on days 1, 3 and 5, while for cultivated soybean they vary depending on the type of toxicant and its concentration. Sulphates of copper and zinc affect the wild and cultivated soybean sprouts in a time and dose-dependent manner.     

Nodulation of Glycine max by Six Bradyrhizobium japonicum Strains with Different Competitive Abilities

The root nodule locations of six Bradyrhizobium japonicum strains were examined to determine if there were any differences which might explain their varying competitiveness for nodule occupancy on Glycine max. When five strains were added to soybeans in plastic growth pouches in equal proportions with a reference strain (U.S. Department of Agriculture, strain 110), North Carolina strain 1028 and strain 110 were the most competitive for nodule occupancy, followed by U.S. Department of Agriculture strains 122, 76, and 31 and Brazil strain 587. Among all strains, nodule double occupancy was 17% at a high inoculum level (10⁷ CFU pouch⁻¹) and 2% at a low inoculum level (10⁴ CFU pouch⁻¹). The less competitive strains increased their nodule representation by an increase in the doubly occupied nodules at the high inoculum level. Among all strains, the number of taproot and lateral root nodules was inversely related at both the high and low inoculum levels (r = −0.62 and −0.69, respectively; P = 0.0001). This inverse relationship appeared to be a result of the plant host control of bacterial infection. Among each of the six strains, greater than 95% of the taproot nodules formed at the high inoculum density were located on 25% of the taproot length, the nodules centering on the position of the root tip at the time of inoculation. No differences among the six strains were observed in nodule initiation rates as measured by taproot nodule position. Taproot nodules were formed in the symbiosis before lateral root nodules. One of the poorly competitive strains (strain 76) occupied three times as many taproot nodules as lateral root nodules when competing with strain 110 (nodules were harvested from 4-week-old plants). Among these six wild-type strains of B. japonicum, competitive ability evidently is not related to nodule initiation rates.     

TnphoA-induced symbiotic mutants of Bradyrhizobium japonicum that impair cell and tissue differentiation in Glycine max nodules

Bradyrhizobium japonicum WM1, an ethylmethane-sulfonate-induced derivative of B. japonicum 110spc4 with reduced phosphatase activity but normal symbiotic properties, was randomly mutagenized using TnphoA. From about 1000 purified single colonies, approximately 300, preferentially those with enhanced phosphatase activity, were inoculated onto soybean seedlings to test their symbiotic traits. Sixteen strains were either completely Fix? or possessed markedly reduced acetylene reduction activity (Fix^red). Contrary to expectations, hybridization of total DNA of these strains to a transposonspecific DNA probe showed that many contained no transposon. Apparently these strains had gained resistance towards kanamycin spontaneously rather than through the introduction of TnphoA. However, in five mutant strains, two hybridizing BamHI fragments of different sizes were detected, as expected. All strains performed acetylene reduction under ex planta conditions, indicating that mutations had not occurred in nif or fix genes. A more than 50-fold increased specific activity of alkaline phosphatase was observed in strain 132, indicating the synthesis and secretion of a polypeptide fused to 'PhoA. Light and electron-microscopic analyses showed that in nodules induced by strain 132 (Fix^red) the infected cells of the central tissue were vacuolated. In some of these cells callose deposition was observed, indicating plant defense reactions. Nodules induced by mutant 184 were infected by bacteroids only in a few cells of the central tissue as isolated clusters, whereas the majority of cells remained uninfected. The concentration of phosphoenolpyruvatecarboxylase protein within the infected tissue was significantly reduced and starch granules accumulated. In both strains TnphoA insertions were identified to be the reasons for the observed phenotypes. These mutant strains should be helpful for studying the influence of the microsymbiont on the differentiation and colonization of infected cells in soybean nodules.     

野生大豆种子雨的研究

对野生大豆种子雨的时空动态及其与外界天气情况关系的初步研究表明,在野 生大豆整个种子雨的历程中,出现３个较为明显的炸荚和种子散落的高峰,并且峰的出现 与天气晴朗（相对湿度）相关,而与气温相关性不大．野生大豆种子雨的空间分布格局主要 是野生大豆种子炸荚的自身习性（炸荚弹力）和荚本身在植株上的空间分布有关,而与风 向（风力≤７级）关系不大．     

Protoplasts Culture and Plant Regeneration of Soybean (Glycine max L. and G. soja)

Protoplasts were isolated enzymatically from immature cotyledons of soybean. The protoplasts divided to form calli in the K8P liquid medium. The calli further grew to 2–3 mm on the solid K8 medium and were transferred onto the MSB medium (MS minerals+B5 organic components+0.5–1.0 mg/l 2,4-D+0.2–0.5 mg/l BA) to obtain compact and nodular calli. Shoot formation was initiated on M1 medium (MSB medium with 0.15 mg/1 NAA, and BA, KT and ZT, 0.5 mg/l of each, 500 mg/1 CH). Differentiation frequency was 13.6–24.2%. Plants have been regenerated from protoplasts of immature cotyledons in 2 cultivars, and normal pods were obtained from them.