Initial Nodulation Research Articles

Exploring the Effects of Biocontrol and Plant Growth-Promoting Trichoderma spp. on Initial Root Growth and Nodulation in Cicer arietinum

Exploring the Effects of Biocontrol and Plant Growth-Promoting Trichoderma spp. on Initial Root Growth and Nodulation in Cicer arietinum

Early nitrogen supplementation stimulates the nodulation and growth of common bean plants inoculated with rhizobium

The initial development of common bean plants (Phaseolus vulgaris L.) relying on symbiotic nitrogen (N) can be limited by delayed active N2 fixation, requiring supplemental N which in turn may inhibit the symbiosis. Five experiments were carried out in hydroponics to identify the initiation of nodulation and nitrogenase activity in common bean cultivars, and the effects of additions of mineral N on plant nodulation and growth. Three experiments evaluated the initial growth of five inoculated bean cultivars in the absence or presence of mineral N, and two experiments evaluated the effect of the moment of mineral N addition until the beginning of reproductive stage. The first root nodules appeared 10 days after plant transplant (DAT) and nitrogenase activity initiated 11 DAT. Cultivars of large seeds had lower initial nodulation and nitrogenase activity than those of small seeds. Inoculated plants showed limited shoot growth that lasted until 21-25 DAT as compared to inoculated plants receiving mineral N. Addition of mineral N reduced nodule mass more intensively than nodule number and more strongly nitrogenase activity. Nitrogen applied until 15 DAT enhanced nodulation and nitrogenase activity without limiting shoot growth, as compared to plants receiving N throughout their growth. Otherwise, plants that received N after 15 DAT had lower nodule mass and nitrogenase activity than plants only inoculated. The results indicate that symbiotic N did not suffice to an adequate growth of common beans and some supplemental N is necessary. This N should be added in the beginning of growth cycle to stimulate plant growth without inhibiting further nodulation and N fixation.

Initial growth of Fabaceae species: Combined effects of topsoil and fertilizer application for mineland revegetation

The main challenge of mineland revegetation is the establishment of species that rapidly accumulate biomass, organic matter and nutrients. Thus, the selection of promising species requires detailed knowledge of their growth performances in different mineland environments. Four Fabaceae species native to forests or metalliferous savannas, locally termed cangas, from the Carajás Mineral Province in the eastern Amazon of Brazil and the exotic Bauhinia forficata were cultivated under greenhouse conditions in different non-fertilized and fertilized (including liming) topsoils and mining wastes. After 45 days, the biomasses, specific leaf areas, leaf nutrient contents and nodulating root percentages were measured. Initial biomass accumulation and nodulation was higher in non-fertilized topsoils than in non-fertilized mining wastes; fertilization increased initial growth in all substrates. The canga species Mimosa acutistipula var. ferrea and Parkia platycephala showed lower biomass accumulation than other species, but their lower specific leaf areas indicated higher drought tolerance, an important adaptation in seasonal climates. Furthermore, the leaf nutrient contents indicated that both canga species might be hyperaccumulators of metal ions. Among the studied species, the highest biomass accumulation was detected in the exotic B. forficata in fertilized substrates. The patterns of initial biomass accumulation and nodulation of the examined species indicated that topsoils, fertilizers and lime should be applied whenever possible to enhance overall revegetation success. Putative drought tolerance and leaf metal ion accumulation of both canga species qualify them for use in revegetation projects, whereas the large biomass accumulation of the exotic B. forficata provides scientific support for its application in revegetation projects. However, risk assessments are required before it is introduced to the Carajás Mineral Province.

A comparative study on initial growth and nodulation potential of sevel multipurpose tree species grown in Chittagong, Bangladesh

Abstract available on the PDFBanko Janakari Vol.11(2) 2001: 22-26

Lotus hosts delimit the mutualism-parasitism continuum of Bradyrhizobium.

Symbioses are modelled as evolutionarily and ecologically variable with fitness outcomes for hosts shifting on a continuum from mutualism to parasitism. In a classic example, rhizobia fix atmospheric nitrogen for legume hosts in exchange for photosynthetic carbon. Rhizobial infection often enhances legume growth, but hosts also incur interaction costs because of root tissues and or metabolites needed to support symbionts in planta. Rhizobia exhibit genetic variation in symbiotic effectiveness, and ecological changes in light or mineral nitrogen availability can also alter the benefits of rhizobial infection for hosts. The net effects of symbiosis thus can range from mutualistic to parasitic in a context-dependent manner. We tested the extent of the mutualism-parasitism continuum in the legume-rhizobium symbiosis and the degree to which host investment can shape its limits. We infected Lotus strigosus with sympatric Bradyrhizobium genotypes that vary in symbiotic effectiveness. Inoculations occurred under different mineral nitrogen and light regimes spanning ecologically relevant ranges. Net growth benefits of Bradyrhizobium infection varied for Lotus and were reduced or eliminated dependent on Bradyrhizobium genotype, mineral nitrogen and light availability. But we did not detect parasitism. Lotus proportionally reduced investment in Bradyrhizobium as net benefit from infection decreased. Lotus control occurred primarily after infection, via fine-scale modulation of nodule growth, as opposed to control over initial nodulation. Our results show how divestment of symbiosis by Lotus can prevent shifts to parasitism.

Fine mapping of the Rj4 locus, a gene controlling nodulation specificity in soybean

Leguminous plants have the ability to make their own nitrogen fertilizer by forming a root nodule symbiosis with nitrogen-fixing soil bacteria, collectively called rhizobia. This biological process plays a critical role in sustainable agriculture because it reduces the need for external nitrogen input. One remarkable property of legume–rhizobial symbiosis is its high level of specificity, which occurs at both inter- and intra-species levels and takes place at multiple phases of the interaction, ranging from initial bacterial infection and nodulation to late nodule development associated with nitrogen fixation. Knowledge of the molecular mechanisms controlling symbiotic specificity will facilitate the development of new crop varieties with improved agronomic potential for nitrogen-fixing symbiosis. In this report, we describe fine mapping of the Rj4 locus, a gene controlling nodulation specificity in soybean (Glycine max). The Rj4 allele prevents the host plant from nodulation with many strains of Bradyrhizobium elkanii, which are frequently present in soils of the southeastern USA. Since B. elkanii strains are poor symbiotic partners of soybean, cultivars containing an Rj4 allele are considered favorable. We have delimited the Rj4 locus within a 57-kb genomic region on soybean chromosome 1. The data reported here will facilitate positional cloning of the Rj4 gene and the development of genetic markers for marker-assisted selection in soybean.

Analysis of nodulation kinetics in Frankia–Discaria trinervis symbiosis reveals different factors involved in the nodulation process

The induction of root nodule development in actinorhizal symbiosis would depend on the concentration of factors produced by the bacteria and the plant. A detailed analysis of nodulation description parameters revealed different factors related to the nodulation process. The initial time for nodulation (t(0)), the initial nodulation rate (v(0)) and the total time of nodule development (t(NOD)) were defined and consequently quantified in different experimental conditions: co-inoculation of Discaria trinervis with increasing concentrations of different non-infective bacteria together with the full compatible infective Frankia strain (the indicator strain) used at a limiting concentration or by changing plant factor(s) concentration. All the above nodulation parameters were modified by changing doses of full compatibility infective strain Frankia BCU110501; v(0) appears to be an expression of symbiotic recognition between partners as only fully symbiotic indicator Frankia BCU110501 was able to change it; t(0) seems not to reflect symbiotic recognition because it can also be modified by non-infective Frankia but suggest the existence of a basic level of plant microbe recognition. The initial time for nodulation t(0), reflecting the time required for the early interactions toward nodulation, is an inverse measure of the ability to establish early interactions toward nodulation. The increase in plant factors concentration also reduces t(0) values, suggesting that a plant factor is involved and favors very early interactions. Increases in plant factors concentration also modify the final number of nodules per plant and the nodule cluster profile along the taproot as an expression of the autoregulation phenomenon. Meanwhile, Frankia inoculums' concentration, either infective or not, modified t(NOD) in an opposite way plant factors did. In conclusion, the analysis of nodulation kinetics appears to be an appropriate tool to investigate factors involved in the symbiotic interaction leading to the formation of nitrogen-fixing nodules.

Home Sweet Home

Leguminous plants fix atmospheric nitrogen with the aid of symbiotic rhizobial bacteria. When Rhizobia infect the root, a complex developmental program is initiated to form the nodules that house the symbiotic bacteria (see the Perspective by Udvardi and Scheible). Smit et al. and Kaló et al. identify key elements in the signaling cascade by which the bacteria signal their presence to the host plants. The constitutively expressed plant proteins NSP1 and NSP2 are likely transcription factors poised to respond early to the bacterial nodulation factor signal. It appears that NSP1 and NSP2 respond to the initial nodulation factor-induced calcium signal to generate changes in gene transcription. M. K. Udvardi, W.-R. Scheible, GRAS genes and the symbiotic green revolution. Science 308 , 1749-1750 (2005). [Summary] [Full Text] P. Smit, J. Raedts, V. Portyanko, F. Debellé, C. Gough, T. Bisseling, R. Geurts, NSP1 of the GRAS protein family is essential for rhizobial Nod factor-induced transcription. Science 308 , 1789-1791 (2005). [Abstract] [Full Text] P. Kaló, C. Gleason, A. Edwards, J. Marsh, R. M. Mitra, S. Hirsch, J. Jakab, S. Sims, S. R. Long, J. Rogers, G. B. Kiss, J. A. Downie, G. E. D. Oldroyd, Nodulation signaling in legumes requires NSP2, a member of the GRAS family of transcriptional regulators. Science 308 , 1786-1789 (2005). [Abstract] [Full Text]

Herbicidas alachlor, pendimethalin e trifluralin na nodulação e crescimento inicial de plantas de amendoim

This work had the objective of evaluating the effect of the herbicides alachlor, pendimethalin and trifluralin on the initial growth of peanut plants (Arachis h y pogaea L.) under greenhouse conditions for a period of thirty days as well as nodule number and dry weight for sixty days after the sowing period. The experiment was conducted at the Agronomy College of the Federal University ofBahia.The first experimental design was completely randomized with four treatments (control- rate zero; alachlor - 2.90 kg/ha, pendimethalin - 1.00 kg/haand trifluralin - 0.89 kg/ha) and three replieations. For each replication, plastie trays (70 em x 50 em x 10 em) were used with a yellow Latosol as the substrate and peanut seeds of the variety BRS 151-L 7 provided by EMBRAPA-CNPA. A seeond experiment was condueted with plastic pots of 5 kg, the same substrate, same treatments and experimental design with eight replieations. The following parameters were evaluated: seedling emergence, percentage of abnonnal seedlings and dead seeds, plant height, index of seedling emergenee velocity, root and shoot dry weight,number and dry weight of nodules. The results show that herbieides stimulate the initial nodulation of peanut plants, but reduce the pereentage of emergence, shoot dry weight and plant height. Therefore, the herbicides should be recommended with restrietions, for the studied eonditions. .

Expressão dos genes nod de Rhizobium tropici, R. etli e R. leguminosarum bv. phaseoli e estabelecimento da nodulação do feijoeiro na presença de exsudatos de sementes de Mimosa flocculosa e Leucaena leucocephala

Na etapa inicial da troca de sinais moleculares entre macro e microssimbiontes, a interação do feijoeiro e estirpes de Rhizobium tropici, R. etli e R. leguminosarum bv. phaseoli foi avaliada pela expressão dos genes nod de estirpes bacterianas, contendo a fusão nodA::gusA. Esta avaliação foi efetuada por meio da atividade da enzima ß-glucuronidase, utilizando, como indutores, exsudatos liberados pelas sementes de Mimosa flocculosa e Leucaena leucocephala. Além disso, avaliou-se o efeito da adição desses exsudatos no estabelecimento da nodulação do feijoeiro, cv. Carioca. Nos testes "in vitro", a mistura de exsudatos de sementes de feijoeiro e M. flocculosa promoveu aumentos sinergísticos significativos na expressão dos genes nod, tanto das estirpes de R. tropici (CIAT 899/pGUS 32 e F 98.5/pGUS 32) quanto de R. etli (CFN 42/pGUS 32). Em condições controladas, a adição dos exsudatos, tanto de M. flocculosa quanto de L. leucocephala, proporcionou aumento significativo na nodulação inicial do feijoeiro, quando foi inoculada a estirpe CFN 42 (R. etli). A nodulação do feijoeiro cultivado em vasos com solo não foi inibida pelo suprimento de N-mineral, quando se inoculou a estirpe CIAT 899 (R. tropici) e foram fornecidos exsudatos de sementes de M. flocculosa.

Nodulação e crescimento de 49 leguminosas arbóreas nativas da Amazônia em viveiro

Os ecossistemas periodicamente inundados, embora representem 25% da área total da Amazônia, contribuem com 75% da produção madeireira. Tanto esses ecossistemas como os de terra firme apresentam grande diversidade de espécies da família Leguminosae. Algumas dessas espécies já são exploradas economicamente de forma extrativista, mas o potencial econômico da maioria permanece inexplorado. Conhecer o comportamento dessas espécies em condições de viveiro é o primeiro passo para compreender sua biologia e estabelecer plantios nas áreas já desmatadas. Neste trabalho, desenvolvido no Campus do INPA, em Manaus, durante 1985 e 1986, são apresentadas informações sobre o crescimento inicial e nodulação de 49 espécies arbóreas nativas, de ecossistemas de terra firme (16) ou periodicamente inundados, (33) da Amazônia. Plântulas recém-germinadas foram transplantadas, em condições de viveiro, para sacos plásticos que continham cinco diferentes substratos que consistiram de areia adubada, de uma mistura de argila com areia 3:2 (v/v), de material do horizonte A de um glei húmico, e de material do horizonte A de um podzólico vermelho-amarelo, adubado ou não. A maioria das espécies desenvolveu-se bem nos cinco substratos. Algumas espécies cresceram melhor nos substratos, de maior fertilidade. Espécies oriundas de ecossistemas inundados cresceram melhor que as oriundas de terra firme. Foi observada nodulação em 30 espécies. Entre as que apresentaram maiores taxas de crescimento, havia tanto espécies nodulíferas como não-nodulíferas, indicando que a fixação biológica de N2 não é o único mecanismo eficiente de absorção de nitrogênio em leguminosas tropicais. As espécies que apresentaram as maiores taxas de crescimento foram: Enterolobium maximum, Swartzia polyphylla e Vatairea guianensis.

Effect of Chlorine in Sodium Chloride on Initial Growth and Nodulation of Soybean

Effect of Chlorine in Sodium Chloride on Initial Growth and Nodulation of Soybean

Hydrogen metabolism and nitrogen fixation of soybean (Glycine max. L.) inoculated with different strains ofRhizobium spp.

Hydrogenase activities and N2-fixing capacities of soybean nodules (Glycine max. cv. Hodgson), inoculated with strains ofBradyrhizobium japonicum andRhizobium fredii from different geographical regions, were measured after 35 days of culture under controlled conditions. Of the strains tested, 47% induced nodules with bacteroids which recycled H2. The data obtained suggest that H2-recycling ability is not a major factor influencing early N2-fixation which depends essentially on the precocity and intensity of the initial nodulation.

Effects of Calcium Concentrations on Initial Growth, Nodulation and Nitrogen Fixation in Soybean Plant

Effects of Calcium Concentrations on Initial Growth, Nodulation and Nitrogen Fixation in Soybean Plant

OVERSOWING WHITE CLOVER INTO CLEARED AND UNIMPROVED NORTH ISLAND HILL COUNTRY - THE ROLE OF MANAGEMENT, FERTILISER, INOCULATION, PELLETING AND RESIDENT RHIZOBIA.

The roles of inoculation, pelleting and fertiliser were examined when white clover was oversown into recently cleared North Island hill country with a low resident white clover rhizobia population. Inoculation aided establishment at some sites. Recovery of inoculant strain from plants and soil was generally low, initial nodulation by the inoculant strain being replaced by expanding resident rhizobial populations. Pelleting was necessary to ensure inoculant survival on seed and inoculant establishment. Fertiliser application at oversowing consistently increased seedling and later plant size. Grazing managements (pre and post-oversowing), treading and chemical sward suppression effects were assessed on paddock scale oversowings of white clover into unimproved hill pastures. Pre-oversowing grazing to 900 kg DM/ha or less, and frequent post-oversowing grazings, were necessary to control competition from the resident sward. The use of paraquat: diquat at a low rate was required to maximise establishment. Reducing the water rate with herbicide from 200 to 60 litres/ha maintained high establishment on steep slopes and attained 80% of potential on easy slopes. Additional treading was a practical method of increasing establishment. Keywords: White clover, Trifolium repens, oversowing, establishment, rhizobia, competition, fertiliser, inoculation, pelleting, paraquat, diquat, treading, hill country.

Evaluation of Alfalfa and Rhizobium meliloti for Compatibility in Nodulation and Nodule Effectiveness1

The purpose of this investigation was to develop a procedure for testing strains of Rhizobium meliloti and cultivars of alfalfa (Medicago sativa L.) for symbiotic compatibility. Antiblotic‐resistant mutants were developed from four strains of R. meliloti that differed for plant dry matter yield, days to initial nodulation and nodule numbers when inoculated onto one cultivar of alfalfa. The mutant strains were not significantly different from their corresponding parental strains in either days to initial nodulation or host dry matter production on N‐free medium. The preference of alfalfa for different strains of Rhizobium was not altered by 0 to 300 ppm N and 33 to 300 ppm potassium phosphate.The competitive ability for nodulation of effective and ineffective strains of R. meliloti was investigated using ‘Saranac’ and MnNC 4, an experimental population of alfalfa. Antibiotic‐resistant mutants were used to verify the relative proportions of effective and ineffective nodules on each plant. A significant positive correlation was observed between the percentage of nodules produced by the effective strains and the dry matter production of plants grown at zero N. Acetylene reduction assays indicated that differences in competitive ability of the effective strains against the ineffective strains measured by the antibiotic‐resistant mutant technique and seedling growth were associated with nitrogenase activity.A procedure of inoculating alfalfa plants with a mixture of effective and ineffective strains at zero N and measuring shoot dry weight might be used to identify strains of Rhizobium of high competitive ability and plants with increased preference for effective strains of Rhizobium. This approach should expedite attempts to select Rhizobium‐alfalfa combinations with enhanced N2‐fixation capacity.

Breeding of nodulated red clover (Trifolium pratense) for high yield

SUMMARYThe symbiotic effectiveness of four cultivars of red clover were compared and breeding programmes undertaken to increase nitrogen fixation and yield of agar‐ and pot‐grown plants. Programme I used the moderately effective Rhizobium trifolii strain 0403 and Programme II the highly effective strain 5. Aggregate scores of plant size (leaf area) were chosen as the criterion of selection. All cultivars, inoculated with strain 0403, differed in time of initial nodulation and in dry matter yield and three differed in leaf area. None differed in nodule number or N‐content. Dry matter and leaf area were highly correlated. Diallel crosses among highly effective selections in Programme 1 gave progeny yields that exceeded those of crosses between modal selections by averages of 6% in the first generation, 5% in the second generation and 23% in the third generation. Yields of the high cross category exceeded those of the original cultivar by an average of 9% in the second generation and by 25–101% in the third generation. Effects on leaf area were similar. Highly effective progeny tended to nodulate earlier and have more nodules than the remainder but differences were very small. Crosses between cultivars were generally more effective than those within cultivars, indicating heterotic effects. Similar results for yield were obtained in Programme II. The average increase in yield of crosses of third‐generation material between highly effective selections compared with cv. S123 was 63%. The modal crosses were intermediate. In each Programme and generation there were large differences between parents within each cross category.

Nitrate effects on the nodulation of legumes inoculated with nitrate-reductase-deficient mutants of Rhizobium

The effect of nitrate on the symbiotic properties of nitrate-reductase-deficient mutants of a strain of cowpea rhizobia (32H1), and of a strain of Rhizobium trifolii (TA1), were examined; the host species were Macroptilium atropurpureum (DC.) Urb. and Trifolium subterraneum L. Nitrate retarded initial nodulation by the mutant strains to an extent similar to that found with the parent strains. It is therefore unlikely that nitrite produced from nitrate by the rhizobia, plays a significant role in the inhibition of nodulation by nitrate. Nitrite is an inhibitor of nitrogenase, and its possible production in the nodule tissue by the action of nitrate reductase could be responsible for the observed inhibition of nitrogen fixation when nodulated plants are exposed to nitrate. However, the results of this investigation show that nitrogen fixation by the plants nodulated by parent or mutant strains was depressed by similar amounts in the presence of nitrate. No nitrite was detected in the nodules. Nodule growth, and to a lesser extent, the nitrogenase specific activity of the nodules (μmol C2H4g(-1) nodule fr. wt. h(-1)), were both affected by the added nitrate.

Symbiotic characteristics of Trifolium ambiguum seedlings grown in tube culture as affecting subsequent symbiotic vigour

A hexaploid line of Caucasian clover (Trifolium ambiguum), inoculated with two strains of Rhizobium trifolii, was grown in tubes of nitrogen-free medium under bacteriologically-controlled conditions. Observations were made on various symbiotic characteristics of the seedlings. After 30 days, they were transplanted into pots of sand and vermiculite watered with nutrient solution lacking nitrogen and grown for another 100 days. Uninoculated plants supplied with various levels of combined nitrogen were used for comparison. R, trifolii strain CC283b was classified as highly effective and was greatly superior in nitrogen-fixing ability to strain CC231a which had been used routinely in Australia for many years for inoculation of experimental sowings of Caucasian clover. In this line of T, ambiguum, the inherent plant-to-plant variation was accentuated in plants relying on symbiotically-fixed nitrogen. This effect was strong in plants inoculated with the intermediately-effective strain CC231 a but mild in plants inoculated with the highly-effective strain CC283b, i.e., a larger component of the variability amongst CC231a plants was due to the symbiosis than was the case for CC283b plants. Seedlings inoculated with the intermediately-effective strain and selected on the basis of 'within-tube' characteristics such as time to initial nodulation, symbiotic effectiveness rating, and nodule size produced more dry matter when grown in pots than the unselected population and were as productive as plants inoculated with the highly-effective strain. In contrast, with the highly-effective strain, selected plants grown in pots produced very little more dry matter than the unselected population. It was concluded that the use of 'within-tube' symbiotic characteristics as a means of selection for improved production will only be successful when a substantial component of the plant-to-plant variability is due to the symbiosis.

Genetic studies with wild diploid Trifolium ambiguum M. Bieb. with respect to time of nodulation

Population studies made with an alpine diploid form of the perennial rhizomatous Trifolium ambiguum, inoculated with moderately effective (best available) strain of Rhizohium trifolii from the margin of the restricted natural habitat of this plant, showed great variation within the host with respect to time of nodulation. When progenies derived from paired crossings between early-nodulating parents and similarly from late-nodulating parents were studied under standardized conditions, differences in time to initial nodulation between progenies of early-nodulating plants and progenies of late-nodulating plants were highly significant. Analysis revealed that parents within each group differed with respect to their general and specific combining abilities. Indications were that selection of parents following diallel crossing would permit faster selection responses to be obtained than were brought about following phenotypic selection and polycrossing. Nevertheless, at the beginning of the programme an effective selection response for early nodulation was achieved over four generations by polycrossing and single plant selection alone. This plant material and a combination of these phenotypic and genotypic plant selection techniques has resulted in the development of a registered cultivar (Summit) suitable for use at high altitudes.