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1.
 In order to identify soybean cultivars with higher biological N2 fixation capacities, North American and Brazilian soybean [Glycine max (L.) Merrill] cultivars, belonging to maturity groups VI–VIII, were evaluated for nodulation parameters and N2 fixation rates. The symbiotic performance of 152 cultivars was evaluated in pots containing 4 kg soil with an established population of the three Bradyrhizobium elkanii strains [29w (SEMIA 5019):SEMIA 566 : SEMIA 587, 22%:36%:34%] which are established in most Brazilian soils cultivated with soybean. Differences were verified among cultivars, with some accumulating up to twice as much nodule dry weight and N in tissues as others. The variability among cultivars was also confirmed when six of them were used in a field experiment, resulting in differences in nodulation, yield and total N accumulated in grains. The analysis of nodule occupancy in 12 cultivars grown either under sterile conditions and receiving a double inoculum and N-free nutrient solution, or in pots containing soil with an established population of bradyrhizobia, showed the preference of cultivars for specific strains. Received: 7 December 1998  相似文献   

2.
In the legume‐(Brady)Rhizobium symbiosis, signal exchange between the host‐plant and the symbiotic bacterium is an essential step in nodule formation. Genistein is the most effective plant‐to‐bacterium signal in the soybean [Glycine max (L.) Merr.] N2‐fixing symbiosis. Its concentration in soybean root system increases with seedling development, and decreases immediately after the onset of N2 fixation. This study was conducted to determine whether addition of genistein to the rooting medium at the onset of N2 fixation would increase nodulation thereafter. The results indicated that watering soybean plants with a solution containing genistein beginning at the onset of N2‐fixation increased nodule size, nodule number and nodule weight per plant. Shoot nitrogen (N) concentration was also increased. Soybean cultivar AC Bravor was more sensitive to genistein addition than Maple Glen.  相似文献   

3.
TheA-value method, involving the application of a higher15N rate to a reference non-N2-fixing plant, was used to assess the magnitude of N2 fixation in two bambara groundnut cultivars at four growth stages [vegetative, 0–47 days after planting (DAP); early pod-filling, 47–99 DAP; mid-pod-filling, 99–120 DAP; physiological maturity, 120–148 DAP). The cultivars were Ex-Ada, a bunchy type, and CS-88-11, a slightly spreading type. They were grown on a loamy sand. Uninoculated Ex-Ada and CS-88-11 were used as reference plants to measure the N2 fixed in the inoculated bambara groundnuts. In this greenhouse study, soil was the major source of N in bambara groundnuts during vegetative growth, and during this period it accounted for over 80% of the N accumulaed in the plants. However, N2 fixation became the major source of plant N during reproductive growth. There were significant differences between the two cultivars in the ability to fix N2, and at physiological maturity, almost 75% of the N in CS-88-11 was derived from the atmosphere compared to 55% in Ex-Ada. Also, the total N fixed in CS-88-11 at physiological maturity was almost double that in Ex-Ada. Our data indicate that the higher N2 fixation in CS-88-11 was due to two factors, a higher intensity of N2 fixation and a longer active period of N2 fixation. The results also suggest that bambara groundnut genotypes could be selected for higher N2 fixation in farining systems.  相似文献   

4.
The effect of elevated carbon dioxide (CO2) concentration on symbiotic nitrogen fixation in soybean under open-air conditions has not been reported. Two soybean cultivars (Glycine max (L.) Merr. cv. Zhonghuang 13 and cv. Zhonghuang 35) were grown to maturity under ambient (415?±?16?μmol?mol?1) and elevated (550?±?17?μmol?mol?1) [CO2] at the free-air carbon dioxide enrichment experimental facility in northern China. Elevated [CO2] increased above- and below-ground biomass by 16–18% and 11–20%, respectively, but had no significant effect on the tissue C/N ratio at maturity. Elevated [CO2] increased the percentage of N derived from the atmosphere (%Ndfa, estimated by natural abundance) from 59% to 79% for Zhonghuang 13, and the amount of N fixed from 166 to 275?kg N ha?1, but had no significant effect on either parameter for Zhonghuang 35. These results suggest that variation in N2 fixation ability in response to elevated [CO2] should be used as key trait for selecting cultivars for future climate with respect to meeting the higher N demand driven by a carbon-rich atmosphere.  相似文献   

5.
Pot and field experiments were performed to assess N2 fixation in Nicaraguan (R79 and R84) and Ecuadorian (Imba) common bean (Phaseolus vulgaris L.) cultivars, with the aim of improving their productivity by inoculating them with commercially produced Rhizobium phaseoli. With maize (Zea mays L.) as the non‐N2‐fixing control, the percentage of N2 fixed predicted by the 15N‐dilution method was significantly (P ≤ 0.05) higher than that predicted by the N‐difference method. However, the N2 amounts predicted by the two methods were not significantly different. The correlation between the two methods was significant and positive (P ≤ 0.0001, n = 36). Compared with the native rhizobial strain, symbiotic associations of the bean cultivars with UMR1073, UMR1077 and UMR1899 rhizobial inoculants did not significantly (P ≤ 0.05) influence plant dry matter (DM) and N yields, the extent of N2 fixation and uptake of soil and fertilizer N. Nevertheless, the UMR1077 and UMR1899 strains markedly increased the uptake of soil N by R84 plants, while decreasing N2 fixation. In contrast, the Imba‐UMR1899 association enhanced positive effects on all variables. About 60–70% of the total N taken up by the Imba plants was fixed N2. The R79 and R84 plants fixed about 50% of their total N uptake. N2 fixation rates were positively correlated with DM and total N yields, while being negatively correlated with soil N uptake (P ≤ 0.001, n = 36). Future research in Nicaragua should focus on selecting rhizobial strains suitable for indigenous common bean cultivars.  相似文献   

6.
Summary A field experiment was condutced in a clay loam soil to study the performance of three Bradyrhizobium japonicum strains; USDA 110, USDA 138 and TAL 379, in relation to their N2-fixing potential and competitiveness on two soybean cultivars (Clark and Calland). Inoculation of soybean cultivars with these strains, either singly or in combination, induced significant increases in plant dry weight, N2 fixation and seed yields. However, no significant differences were found between the rhizobial strains and/or their mixtures in N2 fixation and increased seed yield for both cultivars. The two soybean cultivars gave similar responses to inoculation. No significant differences in seed yield were observed between Clark and Calland cultivars. The interaction between inoculant strain and soybean cultivar was not significant. The competition between strains for nodulation was assessed. Strain USDA 110 was the most competitive, followed by USDA 138. Strain TAL 379 was always less competitive on both cultivars. The incidence of double-strain occupancy of nodules varied from 8% to 40%.  相似文献   

7.
We studied the effect of the soil physical properties on soybean nodulation and N2 fixation in the heavy soil of an upland field (UF) and an upland field converted from a paddy field (UCPF) in the Hachirougata polder, Japan. Seeds of the soybean cultivar Ryuho were sown in each field with or without inoculation of Bradyrhizobium japonicum A1017. The soybean plants were sampled at 35 (V3) and 65 (Rl) d after sowing (DAS), and then nodulation and the percentage of N derived from N2 fixation in the xylem sap were determined. The soil physical properties were different between UF and UCPF, especially the air permeability and soil water regime. Nodule growth was restricted in UCPF irrespective of rhizobial inoculation, though rhizobial infection was not inhibited by the unfavorable soil physical conditions. Soybean plant growth was closely related to the nodule mass and N2 fixation activity, and the inoculation of a superior rhizobium strain was effective only at 35 DAS. These results indicate that soybean nodulation and N2 fixation was considerably affected by the physical properties of heavy soil, and that it is important to maintain the N2 fixation activity and inoculate the soybean plants with a superior rhizobium strain at a later growth stage in order to increase soybean production in heavy soil fields.  相似文献   

8.
Promiscuous soybean lines have been bred on the basis that they would nodulate freely without artificial inoculation. However, our recent studies have demonstrated that the indigenous rhizobia are not able to meet their full nitrogen (N) requirement. Rhizobia inoculation might be necessary. We examined the competition for nodule formation among native Rhizobia spp. and two inoculated Bradyrhizobia strains (R25B indigenous strain and a mixture of R25B+IRj 2180A indigenous strain from soybean lines in the savanna of northern Nigeria), their effect on N fixation, and their contribution to the yield of four soybean cultivars, grown in the field in three different agroecological zones in the moist savanna of Nigeria. About 34% of nodules were formed by the mixture of introduced R25B+IRj 2180A, while R25B formed only about 24% of the nodules but did not influence biomass and grain yield production. The indigenous rhizobia strains that nodulated the soybean varieties fixed up to 70% of their accumulated total N, confirming the promiscuous nature of these soybean varieties. Even though these varieties fixed about 75 kg N ha -1; this was not enough to sustain their optimum grain yield, as earlier reported. However, the grain yield from inoculated soybean was not significantly higher than that from the uninoculated soybean, showing a degree of competitiveness among the introduced rhizobial strains and the native rhizobia population.  相似文献   

9.
Soybeans accumulate N in vegetative tissues up to pod initiation after which total vegetative N may remain constant during early phases of pod development. Eventually much of the vegetative N is mobilized to the pods. The mobilization of N from vegetative tissue to pods during the first few days of pod development is poorly understood but is important to an overall understanding of soybean N nutrition. The vegetative tissues of field grown soybeans were labelled with 15N and sampled weekly during the reproductive phase of plant growth. Three foliar applications of (15NH4)2SO4 were made prior to pod initiation at a combined rate of 3.3 kg N/ha. To immobilize soil N and to increase soybean dependance on N2‐fixation, sawdust was applied at a rate of 52 t ha‐1 . Irrigation was required almost weekly because of a shallow soil profile and below normal summer precipitation. Mobilization of vegetative N began immediately upon pod initiation and continued at a linear rate through pod development. It appeared that N2‐fixation was able to provide approximately half of the N in pods during early podfill. Nitrogen content of vegetative tissue declined as soon as pods began developing.  相似文献   

10.
Effects of phosphorus (P) deficiency on nodulation were examined in soybean grown in nutrient solution for 7 weeks. Increasing P supply increased shoot growth of nitrogen (N2)-fixing plants from week 5 and that of nitrate-fed plant from week 4 after treatment. Nitrogen (N2)-fixing plants had a greater P requirement for maximum growth at week 5. Increasing P supply from 1 to 16 μ M increased N concentration in N2-fixing plants at week 4 but did not affect it from week 5. By contrast, P deficiency increased N concentration in nitrate-fed plants. Increasing P supply improved nodule formation from week 3. Nodule mass was affected more by P supply than nodule number, which, in turn, was affected more than plant growth. However, P supply did not decrease nodule specific N2 fixation from week 5. The results suggest that P deficiency impaired symbiotic N2 fixation through delaying onset of nodule function and decreasing nodule development.  相似文献   

11.
The effect of prior soil amendment with different N sources at 50 mg N (kg soil)—1 on nodulation and N2 fixation of faba bean (Vicia faba L. cv. Troy) using wheat (Triticum aestivum L. cv. Star) as reference crop was assessed in a pot experiment. Four treatments viz legume manure (LEGM) as clover shoots, cereal manure (CEREM) as barley straw, N fertilizer (FERT‐N) as Ca(NO3)2, and no‐manure control (NOMAN) were investigated consecutively at 45, 70, and 90 days after sowing (DAS). Faba bean nodulated profusely, with an increase on average from 629 nodules per pot at 45 DAS to nearly 2.3‐ and 3.3‐fold at 70 and 90 DAS, respectively. Low nodule numbers and nodule dry matter occurred under FERT‐N and CEREM, whereas high values were found for NOMAN and LEGM. Soil amendment affected percent N2 fixation in relation to N source and plant age. Highest percent N2 fixation (≥ 90 %) was found under the lowest N‐supplying amendments, no‐manure, and cereal manure, respectively. FERT‐N depressed N2 fixation particularly at 45 DAS when N2 fixation was reduced to as low as 23 %. The rise in N2 fixation thereafter suggests that faba bean adjusted after depletion of mineral N in the soil. N2 fixation was also decreased after cereal straw application, even though N concentration in faba bean plants was high. The results indicate that plant residues, both with high and low N concentration, applied to soil to raise its fertility may interfere with N2 fixation of faba bean.  相似文献   

12.
Effect of different 15N labeled sources on the estimation of N2 fixation was investigated. The combination of 15N labeled ammonium sulfate, 15N labeled plant material, and 15N labeled ammonium sulfate with unlabeled plant material, was examined in pot experiments. Two cultivars of soybean (Glycine max) and one of mungbean (Vigna radiata) were used. No significant difference was observed among the treatments for the estimation of N2 fixation. This was due to the homogeneity and stability of the 15N abundance in soil which resulted in a similar N uptake from the soil by the N2 fixing and reference crops. The plant yield, total N uptake and amount of N2 fixed were higher in the Yellow Soil than in the Andosol. The amount of N2 fixed was strongly influenced by the plant growth and consequently it affected the plant yield. The slow decomposition of plant material in the Andosol resulted in a low yield in both the N2 fixing and reference crops. Thus, the artificial decrease of the available N content in soil, by application of plant material, did not stimulate N, fixation but suppressed plant growth and N2 fixation.  相似文献   

13.
ABSTRACT

Common bean (Phaseolus vulgaris L.) has been shown to be a poor di-nitrogen (N2) fixer and nitrogen (N) fertilizers are usually recommended in bean production. Recent research results suggest that the success of the bean/Rhizobium symbiosis may depend, in part, on the specific bean genotype. Twelve dry bean genotypes differing in growth habit, commercial class, and maturity were evaluated for N2 fixation in field experiments. Response to inoculant application was highly influenced by environmental conditions. Genotypes differed in nodule dry mass, seed yield, seed N yield, and in amount of N2 fixed. Growth habit alone was not adequate in classifying bean genotypes for N2 fixation. The actual amount of N2 fixed was low ranging from 16 kg ha?1 to 27 kg ha?1, suggesting that the symbiotic process alone may not provide adequate N for optimum seed yield in dry environments.  相似文献   

14.
Summary The common bean (Phaseolus vulgaris L.) is generally regarded as a poor N2 fixer. This study assessed the sources of N (fertilizer, soil, and fixed N), N partitioning and mobilization, and soil N balance under field conditions in an indeterminate-type climbing bean (P. vulgaris L. cv. Cipro) at the vegetative, early pod-filling, and physiological maturity stages, using the A-value approach. This involved the application of 10 and 100 kg N ha-1 of 15N-labelled ammonium sulphate to the climbing bean and a reference crop, maize (Zea mays L.). At the late pod-filling stage (75 days after planting) the climbing bean had accumulated 119 kg N ha-1, 84% being derived from fixation, 16% from soil, and only 0.2% from the 15N fertilizer. N2 fixation was generally high at all stages of plant growth, but the maximum fixation (74% of the total N2 fixed) occurred during the interval between early (55 days after planting) and late podfilling. The N2 fixed between 55 and 75 days after planting bas a major source (88%) of the N demand of the developing pod, and only about 11% was contributed from the soil. There was essentially no mobilization of N from the shoots or roots for pod development. The cultivation of common bean cultivars that maintain a high N2-fixing capacity especially during pod filling, satisfying almost all the N needs of the developing pod and thus requiring little or no mobilization of N from the shoots for pod development, may lead to a net positive soil N balance.  相似文献   

15.
Current methods for measuring N2 fixation by nodulated legumes involve the addition of small amounts of 15N-labelled plant-available N compounds to soil so that plant N derived from the soil may be identified. All such methods assume that the proportions of added N and indigenous soil N assimilated by N2-fixing and non-fixing plants grown in the same soil are the same, irrespective of the amount of soil N assimilated. The development of a method for assessing these proportions is described.Nodulated legumes and reference plants are grown in soils receiving none or one rate of addition of labelled N compound containing several (two or more) concentrations of 15N. The proportions of added and indigenous N assimilated, are determined from the intercepts and slopes of regression lines relating isotopic composition of plant N to that of added N, together with some other readilly-obtainable plant N measurements.  相似文献   

16.
 Field experiments were conducted to investigate the performance of three soybean cultivars with five foreign bradyrhizobia strains in different regions. The experiments at the two sites were designed with soybean (Glycine max L.) cultivars as the main factor and bradyrhizobia strains (USDA 136, TAL 122, USDA 6, TAL 377 and TAL 102) as the sub-factor. The experiments were arranged in randomised complete block design with four replications. Results show that nodule number, nodule dry weight and shoot dry weight, total N and seed yield were significantly increased when soybean cultivars were inoculated with foreign bradyrhizobia in two locations in the south east of Nigeria. At 63 days after planting the percentage increase in nodule number and dry weight after inoculation of soybean cultivars with bradyrhizobia strains ranged from 71 to 486% and from 0 to 200%, respectively. The percentage increase in shoot dry matter, %N and total N after bradyrhizobia inoculation ranged between 2–130%, 18–62% and 35–191%, respectively at Awka, and at the Igbariam site the percentage increase in shoot dry weight, %N and total N ranged between 3–76%, 0–43% and 19–125%, respectively. Seed yields after bradyrhizobia inoculation of soybean cultivar TGX 1485–1D at Igbariam ranged between 1.20 and 2.18 t ha–1 against the uninoculated plants, which had seed yields of 1.05 t ha–1. The poorest yield response after inoculation with bradyrhizobia strains was observed in soybean cultivar M-351, with a seed yield ranging from 0.60 to 0.98 t ha–1. The fact that foreign bradyrhizobia strains were more effective than the indigenous strains for all the parameters studied suggests that there is a need to use bradyrhizobia inoculants for increased soybean production in Nigeria. The variations in the strain performance with the different soybean cultivars at the two sites, emphasises the need for careful Bradyrhizobium spp. strain selection. The fact that inoculation response was cultivar- and site-specific suggests that strategies for improving inoculation response in soybean cultivars should also consider the soil environment where the soybean is to be produced. Received: 25 May 1999  相似文献   

17.
 In a previous study soybean Bradyrhizobium strains, used in Brazilian studies and inoculants over the last 30 years, and strains adapted to the Brazilian Cerrados, a region frequently submitted to environmental and nutritional stresses, were analyzed for 32 morphological and physiological parameters in vivo and in vitro. A cluster analysis allowed the subdivision of these strains into species Bradyrhizobium japonicum, Bradyrhizobium elkanii and a mixed genotype. In this study, the bacteria were analyzed for nodulation, N2 fixation capacity, nodule occupancy and the ability to increase yield. The goal was to find a relationship between the strain groups and the symbiotic performance. Two strains of Brazilian B. japonicum showed higher rates of N2 fixation and nodule efficiency (mg of N mg–1 of nodules) under axenic conditions. These strains also showed greater yield increases in field experiments when compared to B. elkanii strains. However, no differences were detected between B. japonicum and B. elkanii strains when comparing nodule occupancy capacity. The adapted strains belonging to the serogroup B. elkanii SEMIA 566, most clustered in a mixed genotype, were more competitive than the parental strain, and some showed a higher capacity of N2 fixation. Some of the adapted strains, such as S-370 and S-372, have shown similar N2 fixation rates and nodulation competitiveness to two Brazilian strains of B. japonicum. This similarity demonstrates the possibility of enhancing N2 fixing ability, after local adaptation, even within B. elkanii species. Differences in the DNA profiles were also detected between the parental SEMIA 566 and the adapted strains by analyses with the ERIC and REP-PCR techniques. Consequently, genetic, morphological and physiological changes can be a result of adaptation of rhizobia to the soil. This variability can be used to select strains capable of increasing the contribution of N2 fixation to soybean nutrition. Received: 28 May 1997  相似文献   

18.
Co-inoculation of selected nitrogen-fixing bacteria with plant growth-promoting bacteria is the promising way for the improvement of soybean production through enhancing plant growth, nodulation, and N2 fixation. Therefore, this experiment was conducted to study the effects of co-inoculation of Bradyrhizobium elkanii BLY3-8 with Streptomyces griseoflavus P4 on plant growth, nodulation, N2 fixation, N uptake, and seed yield of Rj4 soybean varieties. Two experiments with completely randomized design and three replicates were done in this study. N2-fixation ability of soybean was evaluated by acetylene reduction activity (ARA) and relative ureide method. In the first experiment, synergetic effect in N2 fixation and nodulation was occurred in co-inoculation treatment (BLY3-8 + P4) in Yezin-3 and Fukuyutaka. Based on these results, co-inoculation effect of BLY3-8 and P4 was assessed on Yezin-3 and Fukuyutaka varieties at three different growth stages, using Futsukaichi soil under natural environmental conditions. This study shows that co-inoculation of BLY3-8 and P4 significantly increased N2 fixation at V6 stage; plant growth, nodulation, N2 fixation, and N uptake at R3.5 stage; and shoot growth, N uptake, and seed yield at R8 stage, in Rj4 soybean varieties compared with the control. Significant difference in plant growth, nodulation, N2 fixation, N uptake, and yield between co-inoculation and control, not between single inoculation and control, suggests that there is a synergetic effect due to co-inoculation of BLY3-8 and P4.  相似文献   

19.
Legume plants are an essential component of sustainable farming systems. Phosphorus (P) deficiency is a significant constraint for legume production, especially in nutrient-poor soils of arid and semi-arid regions. In the present study, we conducted a pot experiment to evaluate the effects of a phosphorus-mobilizing plant-growth promoting rhizobacterial strain Bacillus cereus GS6, either alone or combined with phosphate-enriched compost (PEC) on the symbiotic (nodulation-N2 fixation) performance of soybean (Glycine max (L.) Merr.) on an Aridisol. The PEC was produced by composting food waste with addition of single super phosphate. The bacterial strain B. cereus GS6 showed considerable potential for P solubilization and mobilization by releasing carboxylates in insoluble P (rock phosphate)-enriched medium. Inoculation of B. cereus GS6 in combination with PEC application significantly improved nodulation and nodule N2 fixation efficiency. Compared to the control (without B. cereus GS6 and PEC), the combined application of B. cereus GS6 with PEC resulted in significantly higher accumulation of nitrogen (N), P, and potassium (K) in grain, shoot, and nodule. The N:P and P:K ratios in nodules were significantly altered by the application of PEC and B. cereus GS6, which reflected the important roles of P and K in symbiotic performance of soybean. The combined application of PEC and B. cereus GS6 also significantly increased the soil dehydrogenase and phosphomonoesterase activities, as well as the soil available N, P, and K contents. Significant positive relationships were found between soil organic carbon (C) content, dehydrogenase and phosphomonoesterase activities, and available N, P, and K contents. This study suggests that inoculation of P-mobilizing rhizobacteria, such as B. cereus GS6, in combination with PEC application might enhance legume productivity by improving nodulation and nodule N2 fixation efficiency.  相似文献   

20.
 A 15N isotope dilution technique was applied to quantify the extent of N2 fixation in lentil (Lens culinaris Medik.) cultivars as influenced by Rhizobium leguminosarum bv. viciae strains in a field experiment in Pakistan. The experiment was conducted on a soil with a very small indigenous rhizobial population and where N was a limiting factor for crop production. Significant variations in number of nodules, dry weight of nodules, biomass yield, grain yield, total N yield, proportion of plant N derived from N2 fixation (Pfix) and amount of N derived from the atmosphere (Ndfa) were observed among combined treatments of four rhizobial strains and six lentil varieties. In a field previously labelled with 15N, to which a basal dose of 75 kg P2O5 ha–1 was applied as single super phosphate, Ndfa ranged from 15 to 24 kg N ha–1 when calculated according to rhizobial strain and from 4 to 38 kg N ha–1 when calculated according to lentil variety. Lc 26 was the most effective strain and fixed 243% more N than the indigenous population in the uninoculated control. In treatments with the lentil variety PL-406, Ndfa was 38 kg N ha–1, which was 850% higher than with the lentil variety Precoz/F6-20-1×M-85. Generally, the varieties with greater Pfix produced a higher dry matter yield. Received: 26 May 1999  相似文献   

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