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1.
Summary Fifty-six isolates of Rhizobium and Bradyrhizobium spp. (Cajanus) were studied for their plasmid profile and N2-fixation efficacy. One to three plasmids were reproducibly detected in all the Rhizobium spp. strains but no plasmid was detected in the Bradyrhizobium spp. strains. Rhizobium sp. strain P-1 was mutagenized by Tn5 and three nod– and six nod+fix– were screened for symbiotic parameters. Neomycin-sensitive mutants were isolated by elevated temperatrue (40°C) from tranconjugants carrying Tn5 insertions. The high temperature cured these mutants from the single large plasmid present in the parent strain P-1. All these cured mutants were nod–, indicating that the genes for nodulation were present on this plasmid, which is readily cured at a high temperature (40°C). The high temperature in the semi-arid zones of Haryana could be responsible for the low nodulation of pigeonpea because the plasmid carrying the nodulation genes is cured at 40°–45°C giving rise to non-nodulating mutants.  相似文献   

2.
Summary Following screening, selection, characterization, and symbiotic N2 fixation with 12,5, 25.0, and 40.0 mg N kg–1 in normal and saline-sodic soils, only two Phaseolus vulgaris genotypes (HUR 137 and VL 63) and two Rhizobium spp. strains (ND 1 and ND 2) produced maximum nodulation, nitrogenase activity, plant N contents, and grain yields in saline-sodic soil, with 12.5 mg N kg–1, compared with the other strains. However, interactions between strains (USDA 2689, USDA 2674, and ND 5) and genotypes (PDR 14, HUR 15, and HUR 138) were significant and resulted in more nodulation, and greater plant N contents, nitrogenase activity, and grain yields in normal soils with 12.5 mg N kg–1 compared with salt-tolerant strains. Higher levels of N inhibited nodulation and nitrogenase activity without affecting grain yields. To achieve high crop yields from saline-sodic and normal soils in the plains area, simultaneous selection of favourably interacting symbionts is necessary for N economy, so that bean yields can be increased by the application of an active symbiotic system.  相似文献   

3.
Summary Previous laboratory and greenhouse studies have shown that phages significantly reduce soil populations of homologous rhizobia. Reductions in nodulation and N2 fixation have also been observed. The purpose of the current study was to examine the effect of a phage specific ofBradyrhizobium japonicum USDA 117 on nodulation, nodule occupancy, N2 fixation and soybean growth and yield under field conditions. The phage was inoculated in combination withB. japonicum USDA 117 and/orB. japonicum USDA 110 (resistant strain) into a rhizobia-free sandy loam soil and planted toGlycine max (L.) Merr. Williams. When the phage was applied to soil inoculated withB. japonicum USDA 117 alone, significant reductions in nodule weight and number, shoot weight, foliar N, nitrogenase activity, and seed index were observed. When, however, the soil also contained the non-homologous strain,B. japonicum USDA 110, no significant effects on any of these parameters were found. Nodule occupancy by competing strains ofB. japonicum USDA 110 and USDA 117 was also affected by the phage. In soil which did not contain the phage, 46% and 44% of the identified nodules were occupied by USDA 110 and 117, respectively. When the phage was present in the soil, nodule occupancy byB. japonicum USDA 117 was reduced to 23%, while occupancy byB. japonicum USDA 110 was increased to 71%. These results suggest that nodulation by selected strains of rhizobia can be restricted and nodulation by more effective, inoculated strains can be increased through the introduction of a homologous phage to soils.  相似文献   

4.
Summary Two Australian Acacia species, A. mangium and A. auriculiformis were inoculated in vitro with eight strains of Bradyrhizobium spp. and two strains of Rhizobium spp. On the two plant species, only Bradyrhizobium spp. strains formed effective N2-fixing nodules. A. mangium, which nodulates effectively with a restricted range of Bradyrhizobium spp. strains, is a specific host compared to A. auriculiformis. A. auriculiformis is assumed to be a promiscuous host because it nodulates effectively with a wide range of Bradyrhizobium spp. strains. Nodule efficiency as expressed by the ratio of N2 fixed to nodule dry weight appeared to be higher in A. auriculiformis (0.44–0.81) than in A. mangium (0.23–0.55).  相似文献   

5.
 Following screening, selection, characterization and examination of their symbiotic N2 fixation, only two Rhizobium strains (ND-16 and TAL-1860) and four lentil genotypes (DLG-103, LC-50, LC-53 and Sehore 74-3) were found to be suited to sodic soils. Interactions between salt-tolerant lentil genotypes and Rhizobium strains were found to be significant, and resulted in greater nodulation, N2 fixation (nitrogenase activity), total nitrogen, plant height, root length and grain yield in sodic soils under field conditions compared to uninoculated controls. Significantly more nodulation, nitrogenase activity, glutamine synthetase (GS) and NADH-dependent glutamate synthase (NADH-GOGAT) activities were found in normal soil as compared to the soil supplemented with 4% and 8% NaCl. Salt stress inhibited nitrogenase, GS and NADH-GOGAT activities. However, nitrogenase activity in nodules was more sensitive to salt stress than GS and NADH-GOGAT activities (NH4 + assimilation). The relevance of these findings for salt-tolerant symbionts is discussed. Received: 14 November 1997  相似文献   

6.
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7.
以缺铁的石灰性紫色土为供试土壤进行盆栽实验,选用三株慢生型花生根瘤菌Spr3 5、Spr3 7、Spr4 5及gusA和celB标记的菌株gusA3 5、gusA3 7、gusA4 5、celB3 5、celB3 7、celB4 5接种天府9号花生。通过标记根瘤菌形成的根瘤能与检测试剂产生颜色反应的特征,检测施铁肥及施不同浓度的铁肥对花生 根瘤菌有效性和竞争性的影响。结果发现:缺铁的石灰性紫色土上单施铁肥、单接种根瘤菌、接种根瘤菌配施铁肥均能促进花生与根瘤菌的共生固氮效应和竞争结瘤能力,但接种根瘤菌配施铁肥的效果最好,单接种根瘤菌的效果次之,单施铁肥的效果差。喷施0 .2 %硫酸亚铁溶液的效果比0 .3%的好。植株全氮含量和叶绿素含量都是指示共生固氮效应的重要指标,与花生产量间存在极显著的相关性,相关系数分别为0 .76 3和0 .795。gusA和celB两种标记方法检测的结果基本一致,两种标记根瘤菌的平均占瘤率分别为79.6 4 %、75 .6 2 %、74 .4 1%。供试菌株中Spr4 5的有效性和竞争性最强,Spr3 7次之,Spr3 5最差  相似文献   

8.
The dynamics of nodulation, N2-fixation and N use in Leucaena leucocephala cv. K28 over time was investigated in a screenhouse at 4, 8, 12 and 16 months after planting (MAP) using the 15N-labelling method. Leucaena had a consistently increasing pattern of nodulation, dry biomass and nitrogen yield. A sharp rise in nodulation was observed between 12 and 16 MAP, whereas for biomass, N accumulation and N2-fixation, and N2-fixation, an upward surge occurred between 4 and 12 months. Nodulation, N accumulation, N2-fixation and biomass yield all peaked at 16 MAP. Along with the steady increase in N2-fixation throughout the 16-month growth period, the % N derived from the atmosphere rose from 17.9% to 61.5%, 70.1% and 74%, equivalent to 191, 1623, 2395 and 3385 mg N2 fixed plant-1 at 4, 8, 12 and 16 MAP, respectively. Nitrogen assimilation from soil and fertilizer decreased inversely to the increase in symbiotic nitrogen fixation with time.  相似文献   

9.
Temperature is a limiting factor on legume-Bradyrhizobium symbiosis of subtropical plants in the temperate region. Twelve strains of Bradyrhizobium spp. that nodulate pigeonpea [Cajanus cajan (L.) Millsp], and cowpea [Vigna unguiculata (L.) Walp], were evaluated for tolerance to three temperature regimes (20°C/10°C, 30°C/20°C, and 38°C/25°C day/night temperature) by determining their growth following exposure to the regimes. The five most temperature-tolerant strains were further evaluated for symbiotic effectiveness with pigeonpea and cowpea under controlled temperatures. These strains were USDA 3278, USDA 3362, USDA 3364, USDA 3458, and USDA 3472. Plant heights of both crops were generally independent of Bradyrhizobium strains and were dependent mainly on temperature regimes. Plant heights were the shortest at the lowest temperature. At the lowest temperature regime, biological nitrogen (N) fixation by pigeonpea was almost completely inhibited. Cowpea genotype IT82E-16 inoculated with USDA 3458 formed the most effective symbiosis. The 30°C/20°C temperature regime was optimum for effective symbiotic association in both crops, and also for Bradyrhizobium survival.  相似文献   

10.
Residues from some tree species may contain allelopathic chemicals that have the potential to inhibit plant growth and symbiotic N2-fixing microorganisms. Soybean [Glycine max (L.) Merr] was grown in pots to compare nodulation and N2-fixation responses of the following soil amendments: control soil, leaf compost, red oak (Quercus rubra L.) leaves, sugar maple (Acer saccharum Marsh) leaves, sycamore (Platanus occidentalis L.) leaves, black walnut (Juglans nigra L.) leaves, rye (Secale cereale L.) straw, and corn (Zea mays L.) stover. Freshly fallen leaves were collected from urban shade trees. Soil was amended with 20 g kg-1 air-dried, ground plant materials. Nodulating and nonnodulating isolines of Clark soybean were grown to the R2 stage to determine N2-fixation by the difference method. Although nodulation was not adversely affected, soybean grown on leaf-amended soil exhibited temporary N deficiency until nodulation. Nodule number was increased by more than 40% for soybean grown on amended soil, but nodule dry matter per plant generally was not changed compared with control soil. Nonnodulating plants were severely N deficient and stunted as a consequence of N immobilization. Nodulating soybean plants grown on leaf or crop residue amended soil were more dependent on symbiotically fixed N and had lower dry matter yields than the controls. When leaves were composted, the problem of N immobilization was avoided and dry matter yield was not reduced. No indication of an allelopathic inhibition on nodulation or N2-fixation from heavy application of oak, maple, sycamore, or walnut leaves to soil was observed.  相似文献   

11.
Effects of acidic minesoil on sericea lespedeza [Lespedeza juncea (L.F.) var. sericea (Mig.)] and its nitrogen (N2)‐fixing symbiotic relationship with Bradyrhizobium spp. were examined. Sericea lespedeza was grown in pots with N fertilization, without N fertilization, or with commercial Bradyrhizobium as a seed inoculant. Minesoil (pH 5.2) was fertilized with calcium (Ca), phosphorus (P), molybdenum (Mo), and potassium (K), and the pH level was adjusted to 4.8 or 4.5 with aluminum or iron sulfate [Al2(SO4)3; Fe2(SO4)3]. Minesoil was also limed to pH 6.1. Shoot dry weights, shoot N concentrations, nodule dry weights, and nodule numbers were significantly lower (P < 0.05) when inoculated plants were grown in soil at pH 4.5 and 4.8 compared to limed soil. Thus, the N2 fixation process was adversely affected below pH 5.0. Nitrogen‐fertilized plants grew well in acidified soil, and there were no significant differences in shoot dry weights of such plants among the soil acidification treatments including limed soil. Thus, the N2‐fixing symbiosis appeared to be more sensitive to acidified soil than the plant host. The effects of Al toxicity versus other factors could not be determined because Al2(SO4)3‐ and Fe2(SO4)3‐amended soils contained similar levels of toxic Al at the highest pH (4.8) that prevented N2 fixation.

Time periods required for cells of Bradyrhizobium strains to multiply by a factor of 104 were significantly longer (P ≤ 0.05) in extracts of Al2(SO4)3‐amended soil (pH 4.8 and 4.5) than in extracts of calcium carbonate [CaCO3]‐amended soil (pH 6.1). These increases suggested that reduced multiplication of Bradyrhizobium in acidified minesoils may have been at least partially responsible for the large decreases in nodulation and N2 fixation observed in these soils. It was also reasoned that the inability of existing bacteria to infect and nodulate plant roots may also have been a factor, based on the high inoculation rates used and the abilities of Bradyrhizobium cells to survive and multiply (albeit at a reduced rate) in extracts of acidified soil. Sericea lespedeza is known to tolerate soils of pH 4.5. However, results of this study suggested sericea lespedeza may not fix appreciable N2 in acidic soil below pH 5 when inoculated with commercial Bradyrhizobium, even after the establishment of lespedeza plants tolerant of such conditions.  相似文献   

12.

Red clover (Trifolium pratense L.) is one of the most important plants in forage production, especially in northern areas. Fertilisation practices are focused on high yield and forage quality but effects of nutrients on nodulation and N2 fixation are poorly understood. The aim of this work was to study how nitrogen (N) and phosphorus (P) separately as well as in combination affected nodulation. Red clover plants were grown in pots with gravel in a greenhouse for 11 weeks. To resemble field conditions the root temperature was kept lower than the shoot temperature. Plants were given five different combinations of N and P concentrations during growth. The result showed that at high N concentrations P had a counteracting effect on the N inhibition. The N2-fixation parameters, nodule number, nodule dry matter and specific nitrogenase activity, were six times higher in plants grown with high N and high P than in plants with high N and low P. When the N2-fixation parameters and the dry matter of roots and shoots were related to total plant dry matter, there was a stronger effect of P on nodulation parameters than on roots and shoots. This indicates that P has a direct effect on the N2-fixation parameters, rather than an indirect effect via increased plant growth. These results demonstrate the importance to studying the effects of more than one nutrient at a time.  相似文献   

13.
Summary 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.  相似文献   

14.
A field and greenhouse experiments were conducted to determine the requirement of Fe nutrient supplied through foliar and soil application in soybean inoculated with different selected isolates of exotic and native Bradyrhizobium spp. in saline soils. Six soybean genotypes and three Bradyrhizobium spp. were used for the greenhouse experiments, whereas only two soybean genotypes, namely TGx-1336424 and GIZA, were selected for further study under field conditions. Two levels of FeSO4 (0 and 4 mg Fe kg?1 soil) directly supplied to the soil and three levels of Fe-ethylenediaminetetraacetic acid (0–2% of Fe) through foliar application were used for greenhouse and field experiments, respectively. The results of the greenhouse experiment indicated a non-significant effect of Fe application on nodulation and shoot biomass in soybean. Fe application did not improve the grain yield and total biomass yield in soybean inoculated with UK isolate and local isolate but showed remarkable improvement with TAL-379. High soil native N might be the cause for insignificant effect of Fe applied at 2% in highly effective inoculated plants. Therefore, it can be concluded that the symbiotic effectiveness of Bradyrhizobium sp. and the native soil N would affect the soybean Fe requirement supplied through foliar application.  相似文献   

15.
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   

16.
Abstract

Caldwell and Vest (1968) planted soybeans (Glycine max L. Merr.) with various genotypes at Beltsville, USA, without inoculating them with Bradyrhizobium japonicum, and showed that soybeans preferred certain serotypes of rhizobial strains for nodulation. Recently, the authors have reported that soybeans carrying nodulation-conditioning genes preferred appropriate strains showing specific behavior for nodulation (Ishizuka et al. 1991). For instance, nodulation of soybean cv. Hardee which carries the nodulation-conditioning genes, Rj 2 and Rj 3, does not occur with B. japonicum USDA122, USDA33, Is-1, etc. Nodulation of cv. Hill which carries the Rj 4 gene, does not occur with B. japonicum USDA61, Is-21, etc. while A62-2 which carries a recessive gene rj 1, does not nodulate with almost any of the strains of B. japonicum. Therefore, the B. japonicum strains can be classified into three nodulation types based on the compatibility with these Rj-cultivars, that is, type A strains which effectively nodulated both Rj 2 Rj 3-cultivars and Rj 4-ones, type B strains which did not nodulate the Rj 2 Rj 3-cultivars and type C strains which did not nodulate the Rj 4-cultivars. When the nodulation types of the isolates from nodules of field-grown soybeans were examined, it was suggested that the Rj 2 Rj 3-cultivars and Rj 4-cultivars preferred the type C and type B strains, respectively (Ishizuka et al. 1991).  相似文献   

17.
N2 fixation systems in the nonleguminous crops and bacteria associations have been intensively studied over the last 50 years. Their structure and regulation have been investigated to explore the enhancement of N acquisition in these ecosystems leading to crop-growth with minimum chemical fertilizers. Several lines of important evidence have been accumulated indicating that the magnitudes of associative (nonsymbiotic) N2 fixation in sugarcane (Saccharum spp.), sweet potato (Ipomoea batatas L.), and paddy rice (Oryza sativa L.) are agronomically significant. In these three crops, unique bacterial N2-fixation systems may function in addition to the low-level activity (due to the competition in carbon/energy use) of the commonly occurring rhizosphere-associated system by free-living bacteria such as Beijerinckia, Azotobacter, and Klebsiella. Active expressions of the dinitrogenase reductase-encoded gene (nifH) phylogenetically similar to those of Bradyrhizobium spp. and Azorhizobium sp. were abundantly found in the N2-fixing sugarcane stems, sweet potato stems, and storage tubers. These rhizobia micro-aerobically fix N2 in the carbon compounds-rich apoplasts. Gluconacetobacter diazotrophicus and Herbaspirillum spp. were previously isolated from inside the sugarcane stems, as the candidates of endophytic N2 fixers. However, the current molecular and physiological investigations suggest that their major role is production of phytohormonal substances. In paddy rice fields, methane is produced from organic compounds in anoxia and oxidized by contacting with oxygen gas. An active N2-fixation by methane-oxidizing methanotrophs such as Methylosinus sp. takes place in the root tissues (aerenchyma) and also in the surface soil. This methanotrophic N2-fixation supports the sustainability of soil fertility although the N2-fixation and soil fertility are affected by chemical fertilizers. Finally, we discuss the ecological implications of the newly identified rhizobia and methanotroph systems in the N nutrition in nonlegumes and N reservation in field environments.  相似文献   

18.
我国大豆种植区使用人工选育制成的根瘤菌剂接种效果不稳定。研究指出南方、北方和黄淮流域的6个省土壤中分布的主要Bradrhizobium.japonicum是DH444、USDA110、LL120、005和C224血清型的菌株,主要的Rhizobium.fredii是2048、USDA217、DE1611、2120和2077血清型的菌株。它们占每个取样地点分离物总数的60.3-81.6％。植物感染结瘤法测得大豆种植地点土著根瘤菌菌数在104/克土以上。盆栽试验表明大豆根瘤菌与大豆品种共生时有较强的亲和选择性和共生效应的多样性,其有效结瘤和固氮效率与根瘤菌个体菌株和大豆品种极相关。大多数土著大豆根瘤菌是低或中效固氮的菌株,因而认为选育抗土著根瘤菌而有利于人工接种菌株结瘤的大豆品种和强竞争性的高效菌株仍是提高我国大豆生产的有效途径。  相似文献   

19.
Soil stresses such as salinity and acidity may adversely affect nitrogen (N)2-fixation. The hypothesis of this study is that soil salinity and acidity inhibit soybean [Glycine max (L.) Merr.] nodulation and N2-fixation due to, at least in part, disruption of the signal exchange process. The objectives were: 1) to determine the effects of stressful soil salinity and acidity on the signal exchange processes between soybean and Bradyrhizobium japonicum, and 2) to determine whether or not the addition of signal molecule genistein to B. japonicum can overcome at least part of the inhibition of nodulation, caused by stressful soil salinity and acidity. Salt (sodium chloride) and sulfur (S) were applied. Genistein (0, 5, and 20μ M) was tested. Genistein addition could partially overcome the salt and acidity stresses by increasing soybean yields up to 21% and 23%, respectively. These novel findings may be very useful for planting soybean under salinity and acidity stresses.  相似文献   

20.
A salinity-tolerant strains of Rhizohium able to grow and fix nitrogen in symbiosis with lentil (Lens esculenta) in saline soil was derived frorn effective Rhizobium strain RL 5. A forced mutation with the mutagen nitrosoguanidine resulted in the isolation of five different mutant strains. The salinity tolerance, streptomycin resistance, growth, nodulation behaviour and relative efficiency of symbiotic N2-fixation of these strains were studied. Among the five mutants and parent, LM 4 and LM 1 successfully tolerated 200 μ g ml?1 streptomycin and 1.5%NaCl. These two mutants also significantly increased number and dry weight of nodules per plant, dry matter yield of the crop and N2-fixation. Between the two, LM 4 seemed generally the better.  相似文献   

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