Symbiotic Potential Research Articles

ПРИЕМЫ ПОВЫШЕНИЯ ЭФФЕКТИВНОСТИ РАБОТЫ СИМБИОТИЧЕСКОГО АППАРАТА НУТА ПРИ ВЫРАЩИВАНИИ В СТЕПНОЙ ЗОНЕ ПОВОЛЖЬЯ

The results of the period 2011-2016 are presented. field experiments to improve the technology of cultivation of chickpea in the steppe zone of the Volga region. The purpose of the research was to improve the methods of increasing the efficiency of the symbiotic apparatus of chickpea when grown in the steppe zone of the Volga region. The climate of the research zone is arid. The soil of the experimental field of the Saratov State Agrarian University is southern medium loamy chernozem containing 3.5-4.0% of humus in the arable horizon. The soil of the experimental field of the Krasnokutsk SOS is chestnut, heavy loamy with a content of 2.8-3.0% of humus in the arable horizon. In the studies carried out, a different effect of mineral fertilizers, biological products and growth stimulants on the symbiotic process in chickpea crops and the provision of plants with biological nitrogen was revealed. The highest symbiotic productivity was distinguished by agrocenoses created with the use of a specialized bacterial preparation, rhizotorfin, in the pre-sowing treatment of chickpea seeds. At the same time, on the chernozems of the southern steppe zone of the Volga region, the highest indicators in the number and weight of nodules were noted when using rhizotorfin against the second background of mineral nutrition, where phosphorus fertilizers were used at a dose of P30 - 31.5 pcs. and 318.4 mg. per 1 plant in the chickpea flowering phase. On the chestnut soils of the steppe zone of the Volga region, in order to increase the symbiotic nitrogen fixation of chickpea, it is necessary to jointly use rhizotorfin for pre-sowing seed treatment and to apply mineral fertilizers at a dose of N20P30 before sowing - against this background, on the roots of one chickpea plant in the flowering phase, the largest number and the highest mass of nodules were formed - respectively 33 , 8 pcs. and 140.7 g. Assessment of the safety of the symbiotic potential by the middle of the phase of bean formation in comparison with the flowering phase made it possible to reveal that if 58.8% of live nodules and 40.9% of the treatment of seeds and crops of chickpea preserved respectively 75.5 and 80.4 %% of live nodules and 56.8 and 60.6% of the mass of nodules. As a result of the studies, it was found that the use of siliplant microfertilizer-stimulator and zircon growth stimulator contributes to a longer work of the active symbiotic apparatus of chickpea. In general, the studies have shown that in the region of the arid steppe Volga region, where the level of productivity of agricultural crops, the use of biological products and growth stimulants at a low cost of their use should be widely used in modern resource-saving cultivation technologies.

Effects of coinoculation of Rhizobium with plant growth promoting rhizobacteria on the nitrogen fixation and nutrient uptake of Trifolium repens in low phosphorus soil

Low soil phosphorus (P) availability is a notable limitation for legume nodulation, nitrogen fixation and yield, and it is therefore important to improve legume growth under P-deficient conditions. This study aimed to determine the effects of coinoculation with Rhizobium and plant growth promoting rhizobacter (PGPR) on the nitrogen fixation and nutrient uptake of white clover (Trifolium repens) in a P-deficient soil. White clover plants were inoculated with one of the two Rhizobium strains CHB1120 and CHB1121 alone or coinoculated with either of the Rhizobium strains and one of the two PGPR strains, Bacillus aryabhattai strain Sb and Azotobacter vinelandii strain G31. White clover inoculated with either CHB1120 or CHB1121 alone and coinoculated with one of the two Rhizobium strains and the PGPR significantly enhanced nodule numbers compared with the non-inoculated control. The coinoculation of either CHB1120 or CHB1121 and Sb showed a significantly greater level of nitrogenase than the single inoculation of CHB1120 or CHB1121. In addition, the single inoculation of CHB1120 or CHB1121 and their coinoculation with PGPR significantly increased nitrogen contents in both shoots and roots under P-deficient conditions. The coinoculation of CHB1121 and G31 showed the greatest N content in shoots. Moreover, the single inoculation of the two Rhizobium strains and their coinoculation with G31 and Sb significantly increased the K, Ca, and Mg contents in shoots compared with the non-inoculated control. In summary, the PGPR used in this study can enhance the symbiotic potential of rhizobia under low P conditions.

Регуляторна роль глюкозо- та галактозовмісних аміноцукрів у реалізації симбіотичного і продуктивного потенціалу соєво-ризобіального симбіозу в умовах природної посухи

Регуляторна роль глюкозо- та галактозовмісних аміноцукрів у реалізації симбіотичного і продуктивного потенціалу соєво-ризобіального симбіозу в умовах природної посухи

Role of putrescine (Put) in imparting salt tolerance through modulation of put metabolism, mycorrhizal and rhizobial symbioses in Cajanus cajan (L.) Millsp.

Salt stress is a major environmental constraint that limits growth and nitrogen-fixation in legumes. Role of putrescine (Put) and arbuscular mycorrhiza (AM) in improving functional efficiency of legumes has gained importance in recent years. Present investigations assessed the impact of Put (1 mM) seed priming and/or Rhizophagus irregularis inoculation on growth, mycorrhizal and rhizobial symbioses with an emphasis to correlate the same with nodular Put metabolism in pigeonpea (Cajanus cajan L.) genotypes (Tolerant-Pusa 2001 and Sensitive-Pusa 991) under salt stress. Salinity declined plant biomass, with greater negative effects on roots than shoots which reduced the mycorrhizal colonization as well as nodulation ability of Sinorhizobium fredii AR-4. The decline in nitrogen-fixing efficiency could be correlated with increase in Na+ concentrations in roots as well as nodules. Salinity reduced endogenous Put by increasing diamine oxidase (DAO) as well as decreasing arginine decarboxylase (ADC) as well as ornithine decarboxylase (ODC) activities in nodules. Put priming enhanced per cent mycorrhizal colonization which further increased the rhizobial symbiotic efficiency, more in Pusa 2001 than Pusa 991. Both Put priming and AM inoculations reduced Na+ uptake and improved nutrient status especially P in both underground organs, with AM more effective than Put. The further decline in Na+ uptake was recorded when both amendments were given together which enhanced nitrogen-fixing ability of nodules by modulating anabolic and catabolic enzyme activities responsible for Put biosynthesis. Hence, +Put+AM can be used as an effective strategy to improve symbiotic potential and arrest nodule senescence in pigeonpea under salt stress.

Influence of inoculation on photosynthesis and symbiotic parameters of pea and its crop yield in the conditions of the southern forest steppe of Western Siberia

The paper highlights the effect of inoculation by means of biological specimens on formation of photosynthetic parameters, nodule-forming capacities and yield of pea grain. The authors reveal the varieties which mostly respond to the tillage, effective specimens and methods of their application. The researchers explored two varieties of pea as Omskiy 9 and Omskiy 18 and two biological specimens (risotorphine and ruminatine). The study was conducted in the experimental fields of Omsk agricultural research center in 2016-2017 in the following variants: control (without inoculation), inoculation by means of risotorphine, inoculation by ruminatine and combined tillage. The researchers observed different meteorological conditions during the research. The experiments and calculations of the experimental data were carried out by means of general methodics. The positive effect of inoculation on increasing of such parameters as leaf surface index and photosynthetic potential is observed. Active symbiotic potential, number and weight of nodules rhizosphere of pea had a maximum value when being treated by biospecimen ruminatine and combined inoculation of seeds by risotorphine and ruminatine. The authors highlight significant positive relationship between photosynthetic and active symbiotic potential. Inoculation influenced the yield of pea varieties in a different way in the years of research. The results of variance analysis showed that conditions of experiment influenced the yield of varieties – 34.4 %, the proportion of inoculation effect was 25.0 % and genotype – 17,3 %. Omsk 18 variety was characterized by the highest rates of photosynthetic and symbiotic activity. Seed treatment with ruminatine and combined inoculation with risotorphine and ruminatine have impact when growing pea in the conditions of southern forest-steppe of Western Siberia.

Bacteria related to Bradyrhizobium yuanmingense from Ghana are effective groundnut micro-symbionts

The identification of locally-adapted rhizobia for effective inoculation of grain legumes in Africa’s semiarid regions is strategic for developing and optimizing cheap nitrogen fixation technologies for smallholder farmers. This study was aimed at selecting and characterising effective native rhizobia, from Ghanaian soils for groundnut (Arachis hypogaea L.) inoculation. From surface-disinfected root nodules of cowpea and groundnut plants grown on farmers’ fields, 150 bacterial isolates were obtained, 30 of which were eventually found to nodulate groundnut plants. After testing the symbiotic potential of these isolates on groundnut on sterilized substrate, seven of them, designated as KNUST 1001–1007, were evaluated in an open field pot experiment using 15N-labelled soil. Although 15N dilution analyses did not indicate differences among treatments in the proportion of nitrogen (N) derived from the atmosphere (%Ndfa), all seven strains increased total N derived from N2 fixation by inoculated groundnut plants as compared to the non-inoculated control. Inoculation with KNUST 1002 led to total N accumulation as high as that of the groundnut reference strain 32H1. Genetic characterisation of the isolates by sequence analysis of 16S rRNA gene, 16S – 23S rRNA intergenic transcribed spacer (ITS) region and nodC gene revealed that isolates KNUST 1003 and 1007 were related to Rhizobium tropici, a common bean symbiont. The other five isolates, including KNUST 1002 belonged to the Bradyrhizobium genus, being closely related to Bradyrhizobium yuanmingense. Therefore, this study revealed novel native Ghanaian rhizobia with potential for the development of groundnut inoculants.

High spatial variation in population size and symbiotic performance of Rhizobium leguminosarum bv. trifolii with white clover in New Zealand pasture soils.

Biological nitrogen fixation through the legume-rhizobia symbiosis is important for sustainable pastoral production. In New Zealand, the most widespread and valuable symbiosis occurs between white clover (Trifolium repens L.) and Rhizobium leguminosarum bv. trifolii (Rlt). As variation in the population size (determined by most probable number assays; MPN) and effectiveness of N-fixation (symbiotic potential; SP) of Rlt in soils may affect white clover performance, the extent in variation in these properties was examined at three different spatial scales: (1) From 26 sites across New Zealand, (2) at farm-wide scale, and (3) within single fields. Overall, Rlt populations ranged from 95 to >1 x 108 per g soil, with variation similar at the three spatial scales assessed. For almost all samples, there was no relationship between rhizobia population size and ability of the population to fix N during legume symbiosis (SP). When compared with the commercial inoculant strain, the SP of soils ranged between 14 to 143% efficacy. The N-fixing ability of rhizobia populations varied more between samples collected from within a single hill country field (0.8 ha) than between 26 samples collected from diverse locations across New Zealand. Correlations between SP and calcium and aluminium content were found in all sites, except within a dairy farm field. Given the general lack of association between SP and MPN, and high spatial variability of SP at single field scale, provision of advice for treating legume seed with rhizobia based on field-average MPN counts needs to be carefully considered.

Soybean (Glycine max) genotype–mediated variation in the symbiotic performance of Rhizobium

Legume–rhizobium interaction is the result of molecular dialogue involving a succession of events on the perception of signal molecules produced and secreted by both partners. Soybean (Glycine max L.) is known to be nodulated by two different genera, Bradyrhizobium (slow growing rhizobia) and Sinorhizobium (fast growing) species. The present investigation is an attempt to understand the host genotypic effect on the fast and slow growing root nodulating bacteria of soybean which impacts the biological nitrogen fixation and would lead to the selection of best cultivar-strain compatible interaction. Five soybean genotypes of North Plain Zone, viz. DS 12-13, DS 9712, DS 2705, SL 979, SL 982 were evaluated for their symbiotic potential with two slow (KAS-1, MTCC10753) and two fast growing root nodulating bacteria (DS-1, LSR-8). Genotype DS12-13 formed significant number of nodules with KAS-1 with LS mean of 17.3. Genotype DS 2705 was poorly nodulated by the four strains. Among the strains, slow growing KAS-1 and fast growing DS-1 strains were effective across the genotypes. There was significant increase in the specific acetylene reducing activity of these strains 71.1 and 72.6 nmoles of C2H4 produced/mg/ndw respectively. These strains conformed to the biochemical identification by failing to grow on citrate, glucose peptone agar and Hoffer's alkaline media.

Symbiotic Potential of Bradyrhizobium japonicum Strains with Different Growth Rates

To study genetic properties of soybean nodule bacteria with different growth rates, to research the ability of rhizobia to produce phytohormonal substances and estimate their symbiotic potential in the conditions of combined inoculation and mono-inoculation of soybean plants. Sequencing of the 16S-23S rDNA intergenic spacer of soybean rhizobia was performed on ABI 3130xl Genetic Analyzer. Determination of the qualitative and quantitative composition of phytohormones in culture liquid of Bradyrhizobium japonicum strains was performed by SDTLC-chromatography of high resolution. Symbiotic potential of the strains was estimated in the field experiment in Polissia area of Ukraine. It has been established that strains of soybean nodule bacteria with different growth rates by the structure of ITS region belong to different genetic groups: USDA 6, USDA 110 and USDA 123. The studied rhizobia differ in the levels of extracellular phytohormones synthesis: the slow-growing B. japonicum strain 46 produces more amounts of auxins, but the intensive-growing B. japonicum strain KB11 significantly exceeds in the amounts of cytokinins. It has been shown that an important factor of increasing soybean productivity is the formation of balanced symbiotic systems of the host plant with several complementary strains but serologically and genetically different strains of rhizobia of the same species. Combined inoculation of soybean seeds with two active strains B. japonicum 46 and B. japonicum KB11 allows more fully realizing the potential of symbiotic partners and receiving the higher yield.

Three symbionts involved in interspecific plant-soil feedback: epichloid endophytes and mycorrhizal fungi affect the performance of rhizobia-legume symbiosis

Aims Plants interact by modifying soil conditions in plant-soil feedback processes. Foliar endophytes of grasses exert multiple effects on host rhizosphere with potential consequences on plant-soil feedback. Here, we hypothesize that the grass-endophyte symbiosis impairs soil symbiotic potential, and in turn influences legume performance and nitrogen acquisition.

Improved Phytophthora resistance in commercial chickpea (Cicer arietinum) varieties negatively impacts symbiotic gene signalling and symbiotic potential in some varieties.

Breeding disease-resistant varieties is one of the most effective and economical means to combat soilborne diseases in pulse crops. Commonalities between pathogenic and mutualistic microbe colonization strategies, however, raises the concern that reduced susceptibility to pathogens may simultaneously reduce colonization by beneficial microbes. We investigate here the degree of overlap in the transcriptional response of the Phytophthora medicaginis susceptible chickpea variety 'Sonali' to the early colonization stages of either Phytophthora, rhizobial bacteria or arbuscular mycorrhizal fungi. From a total of 6476 genes differentially expressed in Sonali roots during colonization by any of the microbes tested, 10.2% were regulated in a similar manner regardless of whether it was the pathogenic oomycete or a mutualistic microbe colonizing the roots. Of these genes, 49.7% were oppositely regulated under the same conditions in the moderately Phytophthora resistant chickpea variety 'PBA HatTrick'. Chickpea varieties with improved resistance to Phytophthora also displayed lower colonization by rhizobial bacteria and mycorrhizal fungi leading to an increased reliance on N and P from soil. Together, our results suggest that marker-based breeding in crops such as chickpea should be further investigated such that plant disease resistance can be tailored to a specific pathogen without affecting mutualistic plant:microbe interactions.

English

Studies on co-inoculation of strains with high symbiotic potential, as well as the use of humic substances are of great importance for obtaining increases in nodulation, biological nitrogen fixation and yield of the bean crop. Thus, this study aimed to evaluate the effects of the co-inoculation of Rhizobium tropici and Azospirillum brasilense in association with humic acids and nitrogen (N) on the behavior of different bean genotypes, cultivated in a protected environment. The experiment was carried out at the Federal Institute of Education, Science and Technology of Rondonia, Campus of Colorado do Oeste-RO, Brazil, from February to April 2015. The experimental design was completely randomized, with four replicates. Common bean seeds of the cultivars ‘Perola’ and ‘BRS Esplendor’ were previously co-inoculated with Azospirillum brasilense and Rizhobium tropici. Shoot dry matter production in the cultivar ‘Perola’ increased by 76.12% when co-inoculated with rhizobacteria. N use efficiency in the bean cultivar ‘Perola’ is higher when co-inoculated with Azospirillum brasilense and Rizhobium tropici, confirming that co-inoculation alone is sufficient to provide the N necessary for plant development. Key words: Phaseolus vulgaris L., Rhizobium tropici, Azospirillum brasilense, biological N fixation (BNF).

Rhizobium strain, a banana (Musa spp.)-associated bacterium with a high potential as biofertilizer

ABSTRACTA diazotrophic bacterial strain denominated 11B isolated from the rhizosphere of a banana plant (Musa spp.) was characterized morphologically, biochemically, and phylogenetically, whereas the symbiotic potential of the strain was assessed through tests of host range, interstrain nodulation competitiveness, and capacity to synthesize indole-3-acetic acid (IAA) and solubilize phosphate. Based on morphological and physiological–biochemical properties, as well as 16S ribosomal deoxyribonucleic acid (rDNA) sequence and phylogenetic analysis, the strain 11B belonged to the genus Rhizobium with 100.0% sequence similarity with Rhizobium tropici CAF440. The optimum growth temperature and pH for strain 11B are 28°C and 7.2, respectively. This strain was able to produce IAA, solubilize phosphate, and fix large amounts of nitrogen (N2) and form effective nodules on the legumes Acaciella angustissima, Gliricidia sepium, Leucaena leucocephala, Lysiloma acapulcensis, and Phaseolus vulgaris. The rhizobial strain 11B was used successfully as a biofertilizer in agriculturally important legumes, forest trees, and agroindustrial plants.

The Role of Rhizobial ACC Deaminase in the Nodulation Process of Leguminous Plants

Symbiotic rhizobia-legumes associations are extremely important in terms of sustainable agricultural practices. This symbiosis involves a complex interaction between both partners, plant and bacterium, for bacterial infection and the formation of symbiotic N-fixing nodules. In this regard, the phytohormone ethylene plays a significant role in nodule formation, acting as an inhibitor of the nodulation process. Ethylene not only regulates nodule development but also regulates many other plant developmental cues, including various stress responses that inhibit overall plant growth. Some rhizobia produce the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase, thus, being able to decrease ACC and, consequently, decrease deleterious ethylene levels that affect the nodulation process. This occurs because ACC is the immediate precursor of ethylene in all higher plants. Hence, rhizobia that express this enzyme have an increased symbiotic potential. In addition to the direct role that ACC deaminase plays in the nodulation processper se, in a limited number of instances, ACC deaminase can also modulate nodule persistence. This review focuses on the important role of rhizobial ACC deaminase during the nodulation process, emphasizing its significance to legume growth promotion.

Genetic Diversity and Symbiotic Efficiency of Indigenous Common Bean Rhizobia in Croatia.

Nodule bacteria (rhizobia) in symbiotic associations with legumes enable considerable entries of biologically fixed nitrogen into soil. Efforts are therefore made to intensify the natural process of symbiotic nitrogen fixation by legume inoculation. Studies of field populations of rhizobia open up the possibility to preserve and probably exploit some indigenous strains with hidden symbiotic or ecological potentials. The main aim of the present study is to determine genetic diversity of common bean rhizobia isolated from different field sites in central Croatia and to evaluate their symbiotic efficiency and compatibility with host plants. The isolation procedure revealed that most soil samples contained no indigenous common bean rhizobia. The results indicate that the cropping history had a significant impact on the presence of indigenous strains. Although all isolates were found to belong to species Rhizobium leguminosarum, significant genetic diversity at the strain level was determined. Application of both random amplification of polymorphic DNA (RAPD) and enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC- -PCR) methods resulted in similar grouping of strains. Symbiotic efficiency of indigenous rhizobia as well as their compatibility with two commonly grown bean varieties were tested in field experiments. Application of indigenous rhizobial strains as inoculants resulted in significantly different values of nodulation, seed yield as well as plant nitrogen and seed protein contents. The most abundant nodulation and the highest plant nitrogen and protein contents were determined in plants inoculated with R. leguminosarum strains S17/2 and S21/6. Although, in general, the inoculation had a positive impact on seed yield, differences depending on the applied strain were not determined. The overall results show the high degree of symbiotic efficiency of the specific indigenous strain S21/6. These results indicate different symbiotic potential of indigenous strains and confirmed the importance of rhizobial strain selection. These are the first studies of indigenous common bean rhizobia in Croatia that provide the basis for further characterization and selection of highly efficient indigenous strains and their potential use in agricultural practice and future research.

Monitoring the fibrolytic potential of microbial ecosystems from domestic and wild ruminants browsing tanniferous forages.

Although the rumen microbiome has been reported to synthesize a rich source of symbiotic enzymes (exocellulase, endocellulase, hemicellulase and cellobiase), the digestion of tropical C4 grasses and browses by ruminants is still limited. Therefore, this study aimed to unveil potential fibrolytic microbial ecosystems from giraffe, kudu, impala and consortia (A1 [giraffe + kudu], A2 [giraffe + impala], A3 [kudu + impala], and A4 [giraffe + kudu + impala]) browsing tanniferous plants, which can be used to improve forage utilization in domesticated goat. Crude protein enzyme extracts (CPZ) from fresh faecal samples were precipitated by 60% ammonium sulphate and assayed for exocellulase, endocellulase and hemicellulase by incubating with crystalline cellulose, carboxymethyl cellulose and xylan at 38 °C with optimum pH of 5.5 to 6.5 for 1, 2, and 48 h, respectively. Enzyme specific activities were defined as μg of reducing sugar/mg CPZ. In vitro fermentation study was done by transferring 33 mL of fresh faecal inoculum into 67 mL of salivary buffer containing 1 g Acacia sieberiana and incubating for 72 h at 38 °C. Apparent degradability (APDeg), true degradability (TD), neutral detergent fibre degradability (NDFdeg), acid detergent fibre degradability (ADFdeg), microbial yield (MY), metabolizable energy (ME) and total gas emitted (Gas) were measured. Exocellulase activities were higher (P < 0.05) in all wild animals and consortia than those in goat except for A4. Minimal differences in hemicellulase activities (P < 0.05) were observed among goat and wild animals and consortia, while endocellulase activity was generally higher (P < 0.05) in goat than that in the rest of the systems. Apart from A3, TDeg, NDFdeg and ADFdeg were higher (P < 0.05) in all microbial ecosystems from wild animals and consortia than those in goat. Apparent degradability, MY and ME also varied (P < 0.05) among these systems. Giraffe, Kudu and A3 produced lower (P < 0.05) gas than the goat system. This study showed that microbial ecosystems from wild browsers (especially impala) and consortia possess a higher potential to digest tanniferous forage with less enteric gas production compared with domesticated goat, hence those microbiome could be exploited as microbial feed additives for improving digestibility and reducing enteric gas production in domesticated goat. Improvements of goat's digestibility will depend on the survival and establishment of microbial species in the rumen as well as their fibrolytic and symbiotic potential including tannin tolerance.

Symbiotic potential and survival of native rhizobia kept on different carriers.

Native rhizobia are ideal for use as commercial legume inoculants. The characteristics of the carrier used to store the inoculants are important for the survival and symbiotic potential of the rhizobia. The objective of this study was to investigate the effects of peat (PEAT), perlite sugarcane bagasse (PSB), carboxymethyl cellulose plus starch (CMCS), and yeast extract mannitol supplemented with mannitol (YEMM) on the survival, nodulation potential and N2 fixation capacity of the native strains Sinorhizobium mexicanum ITTG R7T and Rhizobium calliandrae LBP2-1T and of the reference strain Rhizobium etli CFN42T. A factorial design (4 × 3) with four repetitions was used to determine the symbiotic potential of the rhizobial strains. The survival of the strains was higher for PEAT (46% for strain LBP2-1T, 167% for strain CFN42T and 219% for strain ITTG R7T) than for the other carriers after 240 days, except for CFN42T kept on CMCS (225%). All the strains kept on the different carriers effectively nodulated common bean, with the lowest number of nodules found (5 nodules) when CFN42T was kept on CMCS and with the highest number of nodules found (28 nodules) when ITTG R7T was kept on PSB. The nitrogenase activity was the highest for ITTG R7T kept on PEAT (4911 μmol C2H4 per fresh weight nodule h−1); however, no activity was found when the strains were kept on YEMM. Thus, the survival and symbiotic potential of the rhizobia depended on the carrier used to store them.

NifHgene diversity and symbiotic effectiveness ofBradyrhizobium yuanmingensestrains obtained from nodules of soybean cultivated in India

Restriction fragment length polymorphism (RFLP) of nifH gene with three endonucleases revealed three different nifH genotypes among twenty one indigenous Bradyrhizobium yuanmingense strains. The interactive symbiotic effectiveness on soybean cv. JS335, nodulation and plant growth of these B. yuanmingense strains were comparatively evaluated with B. japonicum ASR011 under greenhouse conditions. Significant variation in symbiotic potential among native B. yuanmingense strains was observed and few of them exhibited significantly superior symbiotic performance over B. japonicum ASR011 and B. yuanmingense CCBAU 61071 type strain. A considerable difference in nitrogen-fixing characteristics was detected among B. yuanmingense strains which shared identical nifH gene sequence. This, to our knowledge, is the first study on symbiotic effectiveness of B. yuanmingense strains obtained from nodules of soybean cultivated in India. The symbiotically efficient B. yuanmingense strains may have applications in the formulation of appropriate inocula to improve soybean crop yield in Indian soils.

Symbiotic effect ofBradyrhizobium yuanmingenseisolates overBradyrhizobium japonicumwith soybean

Symbiotic effect of twenty one indigenous Bradyrhizobium yuanmingense strains obtained from nodules of soybean cultivated in India was comparatively evaluated with B. japonicum ASR011 on soybean cv. JS335 for improved nodulation and plant growth performance under greenhouse conditions. Significant variation in symbiotic potential among native B. yuanmingense strains was observed and few of them exhibited significantly superior symbiotic performance i.e. improved the shoot and root dry weights and shoot N content compared to non-inoculated plants and over B. japonicum inoculated plants. The symbiotically efficient B. yuanmingense strains may have applications in the formulation of appropriate inocula to improve soybean crop yield on Indian soils.

Two Agendas for Bioethics: Critique and Integration.

Many bioethicists view the primary task of bioethics as 'value clarification'. In this article, I argue that the field must embrace two more ambitious agendas that go beyond mere clarification. The first agenda, critique, involves unmasking, interrogating, and challenging the presuppositions that underlie bioethical discourse. These largely unarticulated premises establish the boundaries within which problems can be conceptualized and solutions can be imagined. The function of critique, then, is not merely to clarify these premises but to challenge them and the boundaries they define. The second agenda, integration, involves honoring and unifying what is right in competing values. Integration is the morally ideal response to value conflict, offering the potential for transcending win/lose outcomes. The function of integration, then, is to envision actions or policies that not only resolve conflicts, but that do so by jointly realizing many genuine values in deep and compelling ways. My argument proceeds in stages. After critically examining the role and dominant status of value clarification in bioethical discourse, I describe the nature and value of the two agendas, identify concrete examples of where each has been and could be successful, and explain why a critical integrative bioethics--one that appreciates the joint necessity and symbiotic potential of the two agendas--is crucial to the future of the field. The ultimate goal of all of this is to offer a more compelling vision for how bioethics might conduct itself within the larger intellectual and social world it seeks to understand and serve.