Supernodulating Soybean Research Articles

Nodulation number tempers the relative importance of stochastic processes in the assembly of soybean root-associated communities

Identifying the ecological forces that structure root-associated microbial communities is an essential step toward more sustainable agriculture. Legumes are widely utilized as model plants to study selective forces and their functioning in plant-microbial interactions owing to their ability to establish mutualism with rhizobia. Root nodules act as symbiotic organs to optimize the cost-benefit balance in this mutualistic relationship by modulating the number of nodules. However, it is not known whether the number of nodules is related to the structure of root-associated bacterial communities. Here, the root-associated bacterial communities of soybean grown in native soil by means of soybean cultivars with super- or normal nodulation were investigated across four developmental stages. We compared ecological processes between communities and found decreased relative importance of neutral processes for super-nodulating soybean, although the overall structures resembled those of normal-nodulating soybean. We identified the generalist core bacterial populations in each root-associated compartment, that are shared across root-associated niches, and persist through developmental stages. Within core bacterial species, the relative abundances of bacterial species in the rhizosphere microbiome were linked to host-plant functional traits and can be used to predict these traits from microbes using machine learning algorithms. These findings broaden the comprehensive understanding of the ecological forces and associations of microbiotas in various root-associated compartments and provide novel insights to integrate beneficial plant microbiomes into agricultural production to enhance plant performance.

Pot experiment suggests that the low yields of a super-nodulating soybean (Glycine max L. En-b0-1) was not caused by N2 fixation activity of nodules itself.

Pot experiment suggests that the low yields of a super-nodulating soybean (Glycine max L. En-b0-1) was not caused by N2 fixation activity of nodules itself.

Salinity Tolerance of Super-Nodulating Soybean Genotype En-b0-1

Salinity stress causes various physiological dysfunctions in soybean (Glycine max (L.) Merr.). For example, reduced nitrogen (N) uptake due to salt-induced depression of nodule formation severely limits soybean growth and yield. Super-nodulating soybean genotypes were previously identified by their superior N2 fixation and photosynthesis. Here, we have tested our hypothesis that the super-nodulating En-b0-1 genotype is more salinity tolerant than a normal-nodulating genotype. The super-nodulating genotype and its parental normal-nodulating cultivar Enrei were grown in pots and subjected to saline conditions during the pre-flowering and reproductive growth stages. Under saline conditions imposed during pre-flowering, En-b0-1 formed heavier nodules, resulting in greater N uptake, higher photosynthetic activity, and greater biomass production compared with Enrei. Saline treatment increased the concentrations of sodium (Na) and chlorine (Cl) in all plant parts regardless of genotype; but in En-b0-1, the concentrations of these elements in shoots were significantly lower, while those in roots and nodules were higher than in Enrei. When the salinity treatment was imposed during the reproductive growth stages, En-b0-1 maintained higher N uptake, leading to better alleviation of salinity-induced yield reduction than in Enrei. The super-nodulating genotype En-b0-1 was more tolerant to salinity than its parental normal-nodulating cultivar, due to its superior nodulation and prevention of excessive accumulation of Na and Cl in shoots, which were retained in roots and nodules, thus supporting our hypothesis.

Growth and Yield of a Supernodulating Soybean Cultivar “Sakukei 4” in Miyagi Prefecture

Growth and Yield of a Supernodulating Soybean Cultivar “Sakukei 4” in Miyagi Prefecture

根粒超着生ダイズ品種作系４号の生育・収量に対する高地下水位の影響―開花結実習性への影響について―

根粒超着生ダイズ品種作系４号の生育・収量に対する高地下水位の影響―開花結実習性への影響について―

Effect of Waterlogging During Vegetative Stage On Growth And Yield in Supernodulating Soybean Cultivar Sakukei 4

The Supernodulating Soybean Cultivar Sakukei 4 Was Previously Characterized By Its Superior Capabilities of Nitrogen (N) Fixation and Photosynthesis, and Was Expected To Be High Yielding. Since The N Absorption By Sakukei 4 Is Largely Dependent On N Fixation, It May Be Strongly Affected By Waterlogging During The Vegetative Stage, Which Occurs Frequently in Major Soybean Producing Areas. in This Study, We investigated The Reduced Growth and Yield Resulting From Waterlogging DuringVegetative Stage and The Subsequent Recovery in Sakukei 4, in Comparison With Those in The Normally-Nodulating Cultivar Enrei and Non-Nodulating Genotype En1282. Under The Field Conditions, The Reduction of Growth and Yield By Waterlogging Was Greatest in En1282 Among The Three Genotypes, indicating That Capability of N Fixation Is Essential For The Recovery From Waterlogging-induced injury. The Waterlogging-induced Yield Reduction in Sakukei 4 Resembled That in Enrei, Although Growth Reduction Was Greater in Sakukei 4 Than in Enrei. Irrespective of Cultivar, The Yield Was Associated More Closely With The Crop Growth Rate (Cgr) During The Post-Treatment Stage Than With That During The Waterlogging Treatment. in The Pot Experiments, Yields Positively Correlated With Both Above- and Underground Plant Parts Irrespective of Cultivar, Not Significantly, But Significantly With Root Dry Weights in Enrei and With Nodule Dry Weights in Sakukei 4. These Results indicate That Sakukei 4 Exhibits A Marked Decrease in Dry Matter Production By Waterlogging, But Yield Decrease Is Compensated To A Level Similar To That of Enrei Because of Its Enhanced Nodule Growth During The Recovery Stage.

Effects of High Ground-Water Level on the Growth and Yield of Supernodulating Soybean Cultivar, Sakukei 4II. Effects of High Ground-Water Level on Nitrogen Absorption

Click to increase image sizeClick to decrease image sizeKey Words: High ground-waterNitrogen absorptionNitrogen fixationNoduleSakukei 4Soybean (Glycine max (L.) Merr.)

Nodulation and Growth of a Supernodulating Soybean Mutant SS2-2 Symbiotically Associated with Bradyrhizobium japonicum

<p class="p1">Mutan kedelai penghasil nodulsuper menunjukkan kelemahan dalam kontrol autoregulasi pada nodulasi dan perbedaan fenotip dibandingkan dengan tipe liarnya. Studi untuk mengevaluasi karakter pertumbuhan dan nodulasi dari kedelai penghasil nodulsuper dalam asosiasinya dengan <em>Bradyrhizobium japonicum </em>dilakukan dalam penelitian ini. Tiga genotip kedelai, yaitu mutan kedelai penghasil nodulsuper SS2-2, tipe liarnya Sinpaldalkong 2 dan kedelai kontrol Jangyeobkong diinokulasi dengan <em>B. japonicum </em>USDA 110, kemudian ditumbuhkan di rumah kaca dalam kondisi terkontrol. Karakter nodulasi, fiksasi nitrogen (Acetylene Reduction Activity/ARA), pertumbuhan tanaman, dan hasil biji ditentukan untuk mengevaluasi asosiasi simbiotik antara <em>B. japonicum </em>dan kedelai nodulsuper. Kedelai yang diinokulasi dengan <em>B. </em><em>japonicum </em>menunjukkan peningkatan jumlah dan berat kering nodul serta berat kering total tanaman dibandingkan dengan tanpa inokulasi. Tanaman SS2-2 yang diinokulasi menunjukkan jumlah nodul sekitar 20 kali lipat lebih tinggi daripada tipe liarnya. Inokulasi <em>B. japonicum </em>ternyata juga meningkatkan fiksasi nitrogen seiring dengan perkembangan nodul. Tanaman S2-2 lebih pendek dan menghasilkan fiksasi nitrogen (ARA) lebih tinggi, tetapi spesifik ARA dan hasil biji lebih rendah dibandingkan dengan tipe liarnya. Berdasarkan hasil evaluasi terhadap nodulasi dan pertumbuhannya, interaksi <em>Rhizobium </em>dan kedelai penghasil nodulsuper SS2-2 mempunyai respon asosiasi simbiotik lebih rendah dibandingkan kedelai penghasil nodul normal (kedelai yang tidak mendapat perlakuan mutasi).</p>

Newly featured infection events in a supernodulating soybean mutant SS2-2 by Bradyrhizobium japonicum

Supernodulating soybean (Glycine max L. Merr.) mutant SS2-2 and its wild-type counterpart, Sinpaldalkong 2, were examined for the microstructural events associated with nodule formation and development. SS2-2 produced a substantially higher percentage of curled root hairs than the wild type, especially at 14 days after inoculation with Bradyrhizobium japonicum. In addition, there was new evidence that in SS2-2, B. japonicum also entered through fissures created by the emerging adventitious root primordia. Early steps of nodule ontogeny were faster in SS2-2, and continued development of initiated nodules was more frequent and occurred at a higher frequency than in the wild type. These data suggest that the early expression of autoregulation is facilitated by decreasing the speed of cortical cell development, leading to the subsequent termination of less-developed nodules. The nodules of SS2-2 developed into spherical nodules like those formed on the wild type. In both the wild type and supernodulating mutant, vascular bundles bifurcate from root stele and branch off in the nodule cortex to surround the central infected zone. These findings indicate that SS2-2 has complete endosymbiosis and forms completely developed nodule vascular bundles like the wild type, but that the speed of nodule ontogeny differs between the wild type and SS2-2. Thus, SS2-2 has a novel symbiotic phenotype with regard to nodule organogenesis.

Effect of Soil Hardness on the Growth and Yield of Supernodulating Soybean Cultivar Sakukei 4 under Field Conditions

Effect of Soil Hardness on the Growth and Yield of Supernodulating Soybean Cultivar Sakukei 4 under Field Conditions

Shoot-applied polyamines suppress nodule formation in soybean ( Glycine max)

In legumes, the number of root nodules is controlled by a mechanism called autoregulation. Recently, we found that the foliar brassinosteroid (BR), a plant growth-regulating hormone, systemically regulates the nodule number in soybean plants. In the present study we report that such down-regulation of root nodule formation by a BR may occur through a change of the polyamine contents, with the experimental evidence as follows. The foliar contents of both spermidine (Spd) and spermine (Spm) in the super-nodulating soybean mutant, En6500, were always lower than those in its parent line, Enrei. This lower Spd and Spm content accompanied a striking accumulation of putrescine (Put) in the former plant. This finding indicates that Spd and Spm biosynthesis from their precursor Put is repressed in En6500. The foliar treatments with Spd or Spm of En6500 led to a reduction of both nodule number and root growth. On the other hand, foliar treatment with MDL74038, a specific inhibitor of Spd biosynthesis, apparently increased the root nodule number in Enrei. Foliar application of brassinolide (BL) of En6500 increased the leaf Spd level and reduced the nodule number. These results suggested that BL-induced Spd synthesis in shoots might suppress the root nodule formation.

Characteristics of Nodulation and Nitrogen Fixation in the Improved Supernodulating Soybean (Glycine max L. Merr.) Cultivar ‘Sakukei 4’

Supernodulating soybean lines have more than several times as many nodules as normal cultivars. They are expected to have high nitrogen-fixing ability and enhanced productivity, but their yields have been inferior to those of normal genotypes. We have recently developed a new supernodulating cultivar,‘Sakukei 4’(formerly ‘En-b0-1-2’, presently‘Kanto 100’), with improved growth and yield. The objective of the present study was to identify the characteristics of the nodulation and nitrogen-fixing ability of Sakukei 4. In pot trials, the nodule number of Sakukei 4 was 8.3 times that of a normal cultivar,‘Enrei’, and the nodule weight per plant was 2.3 to 2.8 times the value for Enrei. The acetylene reduction activity per plant in Sakukei 4 was higher than that in Enrei and conventional supernodulating genotypes, especially during the late growth stage. Compared with conventional supernodulating lines, the improved vegetative growth in shoots and roots of Sakukei 4, especially after flowering, probably enhanced its nitrogen-fixing ability per plant. We consider that its high nitrogen-fixing ability at the seed-filling stage, would help increase its yield in fields with low nitrogen fertility.

Correlation of Leaf Nitrogen, Chlorophyll and Rubisco Contents with Photosynthesis in a Supernodulating Soybean Genotype Sakukei 4

Soybean requires more nitrogen (N) than gramineous crops because it accumulates a large amount of N in seeds, and its photosynthetic rate per leaf N is low. The supernodulating genotype Sakukei 4 has a superior symbiotic N2 fixation capability, and thereby is potentially high-yielding. In our previous study, Sakukei 4 was characterized by having a superior ability to maintain high leaf N content and high photosynthetic rate. The objectives of this study were to know photosynthetic characteristics of Sakukei 4 in detail, especially, the responses to CO2 concentration and light intensity, and to elucidate how the photosynthetic characteristics of Sakukei 4 are associated with the amounts of photosynthesis-related N compounds (chlorophyll and Rubisco). The three genotypes (Sakukei 4 - supernodulating cultivar derived from Enrei, Enrei - normally nodulating cultivar, En1282-non-nodulating line derived from Enrei) were grown at various N levels in this study. The CO2 exchange rate (CER) in Sakukei 4 was higher than, or equal to that in Enrei at wide ranges of CO2 concentrations (150-700 μmol mol-1) and light intensities (200-1,500 μmol m-2 s-1 PPFD). Sakukei 4 had higher leaf N (Nl), chlorophyll (ChlL) and Rubisco (RubL) contents per leaf area, but lower chlorophyll and Rubisco contents per leaf N content (ChlL/Nl, RubL/Nl) than Enrei. The specific leaf weight (SLW) and leaf area trended to be lower in Sakukei 4 than in Enrei. These results indicate that the superior photosynthetic rate in Sakukei 4 is attributed to higher total N, chlorophyll and Rubisco contents per leaf area, but not to high rate of allocation of total N to these N compounds.

Characterization of Vegetative Growth of a Supernodulating Soybean Genotype, Sakukei 4

ArticleThe supernodulating soybean cultivar Sakukei 4 was previously characterized by its superior ability to maintain a high leaf nitrogen (N) content and high photosynthetic rate. Despite these desirable traits, the growth performance of Sakukei 4 was inferior to that of its normally nodulating parental cultivar, Enrei. The physiological basis for the unique growth characteristics of Sakukei 4 remains unclear. The objective of the present study was to characterize in further detail thevegetative growth of Sakukei 4, particularly during the period before pod expansion. In the first experiment, the growth of Sakukei 4 was compared with that of its parental cultivar Enrei under various rates of N fertilizer. The dry weight of tops, roots and nodules of the plants grown at lower rates of N application was greater in Enrei than in Sakukei 4, but it was vice versa at higher rates of N application. The number and weight of nodules were far greater in Sakukei 4 than in Enrei at any rate of N application. These genotypic differences were significant on 39 days after sowing (DAS) and became greater at the flowering stage. In the second experiment, therefore, more detailed growth analysis was made during an earlier growth stage (DAS 31-46). During this period, relative growth rate (RGR), net assimilation rate (NAR) and leaf area ratio (LAR) were lower in Sakukei 4 than in Enrei and the related non-nodulating line En1282, whereas the leaf photosynthetic rate was higher in Sakukei 4 at all leaf positions. The dry-matter partitioning to each plant part excluding nodules was similar in all three genotypes. The rate of leaf expansion in Sakukei 4 during this period was significantly slower than that in the other genotypes. These results suggest that the inferior growth of Sakukei 4 prior to flowering is probably due to excessive dry-matter partitioning to nodules and depressed capability of leaf expansion and root growth, which might limit dry-matter production of the whole plant during pre-flowering stage.

Growth Responses of a Supernodulating Soybean Genotype, Sakukei 4 to Waterlogging

Growth Responses of a Supernodulating Soybean Genotype, Sakukei 4 to Waterlogging

Responses of a Supernodulating Soybean Genotype, Sakukei 4 to Nitrogen Fertilizer

The supernodulating soybean genotype Sakukei 4 is potentially high-yielding. We characterized its leaf nitrogen (N) content, photosynthesis and growth at different developmental stages and under different dosages and types of N fertilizer, and compared it with its parental cultivar Enrei and the non-nodulating line En 1282. At the pod -expansion and seed-filling stages, the N contents per leaf dry weight and per leaf area, and apparent photosynthetic rates (AP) were higher in Sakukei 4 than in the normal and the non-nodulating genotypes. The nodule activity per plant was also higher in Sakukei 4 than in Enrei during the reproductive stage. These traits varied less with the growing condition (field- or pot-grown) and dose or type of N fertilizer applied in Sakukei 4 than in the other genotypes. The superior ability of Sakukei 4 to maintain high leaf N and AP, however, did not enhance its growth performance, which tended to be inferior to that of Enrei. Further studies are needed to define the cultivation conditions optimal for an exploitation of the favorable traits of Sakukei 4.

Growth Characteristics and Nitrogen Use Efficiency in a Supernodulating Soybean Mutant, En6500, Derived from the Variety of Enrei.

It was reported that a supernodulating soybean mutant, En6500 derived from the variety of Enrei, could produce many root nodules, but the growth rate of the plant was not necessarily high. The purpose of this paper, therefore, is to examine the characteristics of nodulation and also of plant growth in En6500 for elucidation of the mechanism of its low growth rate. The relative growth rate was low in En6500 compared with Enrei. The dry weight of the nodules per unit root mass was greater in En6500 than in Enrei, suggesting that the root of En6500 is supporting too many or an excess of nodules, which presumably leads to a reduction of plant growth rate. Reduced growth rate was associated with low net assimilation rate and further with low leaf photosynthesis. Moreover, the reduced leaf photosynthesis was associated with low partitioning of nitrogen to the leaves in En6500. Much allocation of nitrogen to the plant organs besides the leaves resulted in low photosynthesis, and also in the reduced nitrogen-use efficiency for dry matter production, which might be a potential mechanism for the low growth rate of En6500, a supernodulating soybean mutant.

Yield and Nitrogen Recovery from Field-Grown Supernodulating Soybean

Crop rotations that include soybean [Glycine max (L.) Merr.] increase yields and reduce N fertilizer requirements of subsequent nonlegume crops such as corn (Zea mays L.) or wheat (Triticum aestivum L.). Nitrogen from biological fixation is often given credit for this benefit. However, recent studies suggest that soybean may remove more N from the soil than it contributes. The availability of soybean lines capable of supernodulation may provide the opportunity to supply more N for subsequent crop use. The objectives of this research were to (i) determine the yield and growth characteristics of a soybean with supernodulation and (ii) to determine the influence of supernodulation on the yield and growth characteristics of winter wheat planted after soybean. Field studies were conducted for 3 yr (1993-1995) under rainfed conditions at Arlington, WI, on a Plano silt loam (fine-silty, mixed, mesic Typic Argiudoll) and under irrigated conditions at Hancock, WI on a Plainfield sandy loam (loamy-sand, mixed, mesic Typic Udipsamment). Four soybean genotypes were evaluated at R3, R7 and R8 growth stages included supernodulating, the normal nodulating parent of the supernodulating line, a nonnodulating line, and the normal nodulating parent of the nonnodulating line. The nonnodulating line provided a baseline of soybean performance without M 2 fixation capabilities. 'Merrimac' winter wheat planted after all soybean plots were harvested was evaluated at Z37, Z50, and Z90 growth stages. Depending on location, the supernodulating genotype increased soybean nodule density 43 to 135%, soil nitrate N at R3 growth stage 34 to 48% and biomass N 10 to 19% compared with the normal nodulating genotypes. However, at the R7 and R8 growth stages, soil nitrate N, plant biomass N and forage and grain yields were not different between the normal and supernodulating genotypes. Winter wheat grown after supernodulating soybean had no difference in soil nitrate N, biomass N, or forage or grain yield compared with normal nodulating genotypes. Based on these results, there does not appear to be any agronomic benefit to using tbese supernodulating soybean compared with normal nodulating lines.

Rhizosphere colonization by Bradyrhizobium japonicum is related to extent of nodulation of Glycine max CV. Bragg and its supernodulating mutants

Supernodulating soybean [ Glycine max (L.) Merr.] mutants nts382 and nts1116 supported substantially larger populations of Bradyrhizobium japonicum in their seedling rhizospheres than did the parent cultivar Bragg. The size of rhizosphere populations was significantly correlated with the number of nodules that formed subsequently. More cells (1.55-fold) of B. japonicum attached to the roots of supemodulating mutant nts382 than to the roots of Bragg. However, the extent of the difference was much less than the increase in nodule number for nts382 relative to Bragg which was between 2.40- and 10.10-fold. Thus, the supemodulating character cannot be accounted for by superior attachment of rhizobia to root surfaces. Differences in rhizosphere colonization of, and rhizobial attachment to, the roots between non-nodulation mutants and the parent Bragg were relatively small; this suggested that the genes coding for non-nodulation do not interfere with these early events normally leading to nodulation. Nodule mass for nts382 constituted 7.1% of whole plant dry matter compared with 2.5% for Bragg ( P < 0.001). However, the increased nodulation was of no apparent benefit since there was no significant difference ( P > 0.05) between nts382 and Bragg in N accumulation or dry matter production.

Efficiency of Nodule Initiation and Autoregulatory Responses in a Supernodulating Soybean Mutant

We compared the formation of nodules on the primary roots of a soybean cultivar (Glycine max (L.) Merr. cv. Bragg) and a supernodulating mutant derivative, nts382. Inoculation with Bradyrhizobium japonicum USDA 110 at different times after seed imbibition showed that the roots acquired full susceptibility to infection only between 3 and 4 days postgermination. When the plants were inoculated with serial dilutions of a bacterial suspension, the number of nodules formed in the initially susceptible region of the roots was linearly dependent on the logarithm of the inoculum dose until an optimum dose was reached. At least 10-fold-lower doses were required to induce half-maximal nodulation responses on nts382 than on the wild type. However, at optimal doses, about six times as many nodules formed in the initially susceptible region of the roots in nts382. Since there was no appreciable difference in the apparent rates of nodule emergence, the increased efficiency of nodule initiation in the supernodulating mutant could have resulted from a lower threshold of response to bacterial symbiotic signals. Two inoculations (24 h apart) of G. max cv. Bragg revealed that there was a host-mediated regulatory response that suppressed nodulation in younger portions of the primary roots, as reported previously for other soybean cultivar-Bradyrhizobium combinations. Similar experiments with nts382 revealed a comparable suppressive response, but this response was not as pronounced as it was in the wild type. This and other results suggest that there are additional control mechanisms for nodulation that are different from the systemic autoregulatory control of nodulation altered in supernodulating mutants.