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1.
Summary The nodulation competitiveness of 17 Rhizobium leguminosarum bv. phaseoli and 3 R. tropici strains was analysed in growth pouches, at pH 5.2 and 6.4. All 20 strains were coinoculated with a gus + strain of R. leguminosarum bv. phaseoli strain KIM5s. The gus+ phenotype, carrying the glucuronidase gene, was used to type nodules directly in the growth pouches. Nodule occupancy ranged from 4% for the least competitive to 96% for the most competitive R. leguminosarum bv. phaseoli strain. The R. tropici strains showed low rates of nodule occupancy at pH 6.4 but their competitiveness improved significantly under acid conditions. CIAT 895 was the only R. leguminosarum bv. phaseoli strain that was less competitive (P<0.05) at the lower pH. The competitiveness of all the other R. leguminosarum bv. phaseoli strains was unaffected by pH. Various physiological and genetic properties of the strains were analysed in search of correlations with nodulation competitiveness. Hybridisation patterns with three different DNA probes (nif KDH, common nod genes, and hup genes) and the metabolism of 53 different C sources were compared. No general correlations were found between hybridisation or growth pattern and competitiveness. The less competitive R. tropici strains had a unique DNA hybridisation pattern and were not able to use shikimate, ferulate, coumarate, or asparagine as C sources. Most of the less competitive R. leguminosarum bv. phaseoli strains could not metabolize either ferulate or coumarate. This might indicate a relationship between nodulation competitiveness and the ability to degrade aromatic compounds.  相似文献   

2.
Strains of Rhizobium tropici IIB, CIAT899 and F98.5, both showing good N2 fixation, and a R. etli strain W16.3SB were introduced into a field which had no history of bean culture. Plant dilution estimates showed that in the presence of its host (Phaseolus vulgaris cv. Carioca) during the cropping seasons and the subsequent fallow summer periods, the bean rhizobial populations increased from less than 30 to 103 g–1 dry soil after 1 year and to 104 g–1 dry soil after 2 years. In the 1st year crop, the inoculated strains occupied most of the nodules, which resulted in a higher nodulation and C2H2 reduction activity. Without reinoculation for the second and third crops, however, little R. tropici IIB was recovered from the nodules and the bean population consisted mainly of R. etli, R. leguminosarum bv. phaseoli, and R. tropici IIA. Reinoculation with our superior R. tropici IIB strains before the second crop resulted in R. tropici IIB occupying the main part of the nodules and a positive effect on nodulation and C2H2 reduction activity, but reintroduction of the inoculant strain in the third season did not have any effect.  相似文献   

3.
 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   

4.
根瘤菌与豆科植物共生可以固定大量的氮。根瘤菌剂接种豆科作物是一项普遍推广应用、有效的农业技术。但由于大量土著根瘤菌的存在,产生竞争障碍,降低了接种菌剂的占瘤率。大多数的土著根瘤菌对春雷霉素敏感,因此接种抗春雷霉素的高效结瘤固氮根瘤菌,并用春雷霉素处理种子,可抑制土著根瘤菌,提高接种菌剂的占瘤率,从而达到高结瘤、高固氮和提高产量的目的。本文将探讨诱变对根瘤菌抗春雷霉素突变的作用,并对获得的抗性突变株的生物固氮特性进行分析。  相似文献   

5.
Summary There were significant differences among pigeonpea [Cajanus cajan (L.) Millsp] Rhizobium sp. strains (IC 3506, IC 3484, IC 3195, and IC 3087) in their ability to nodulate and fix N2 under saline conditions. Pigeonpea plants inoculated with IC 3087 and IC 3506 were less affected in growth by salinity levels of 6 and 8 dS m-1 than plants inoculated with the other strains. For IC 3506, IC 3484, and IC 3195, there was a decrease in the number of nodules with increasing salinity, while the average nodule dry weight and the specific nitrogenase activity remained unaffected. However, in IC 3087, the number of nodules increased slightly with increasing salinity. Leaf-P concentrations increased with salinity in the inoculated plants irrespective of the Rhizobium sp. strain, and leaf-N concentrations decreased with increasing salinity in IC 3484 and IC 3195 only. Shoot-Na and-Cl levels were further increased in these salt-sensitive strains only at 8 dS m-1. Therefore there may be scope for selecting pigeonpea Rhizobium sp. symbioses better adapted to saline conditions. The Rhizobium sp. strains best able to form effective symbioses at high salinity levels are not necessarily derived from saline soils.Submitted as JA No. 919 by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)  相似文献   

6.
Phenotypic diversity was studied among 13 Rhizobium strains selected from a total of 160 Rhizobium isolates from root nodules of Leucaena leucocephala. Two strains from Acacia saligna and two strains from Sesbania sesban plants were included in the examination for host range in the greenhouse. The Rhizobium sp. (Leucaena) strains were different from the reference strains and fell into three distinct groups for the utilization of 95 different carbon sources. Four of the best symbionts constituted a group, the majority of the strains fell into a second group, and strain DS 91 was the only member of the third group. Strains were effective symbionts for their original hosts. Nine strains were tolerant to elevated temperature (>42°C), and three strains were resistant to high salinity (>3% NaCl). All Rhizobium sp. (Leucaena) strains effectively nodulated L. leucocephala and L. culensii, but nitrogen fixation was greater with L. leucocephala than with L. culensii. These strains failed to form effective symbioses with two other species of Leucaena (L. retusa and L. divursiflora) or with alfalfa, Medicago sativa. Rhizobium sp. (Leucaena) strains DS 65, DS 78, and DS 158 nodulated and efficiently fixed nitrogen with Phaseolus vulgaris, with DS 65 showing the highest symbiotic capability. Strain DS 65 also nodulated and fixed nitrogen with Glycine max and Vigna sinensis. Nodulation of Leucaena by two Bradyrhizobium sp. (Acacia) strains was sparse. Strain DS 101 from Sesbania formed nodules on Leucaena, whereas the other strain from Sesbania, DS 110, failed to nodulate this genus. Received: 30 September 1996  相似文献   

7.
Summary Six Rhizobium leguminosarum bv. phaseoli strains (Ciat 151, Ciat 895, Ciat 899, CE3, H2C, Kim5s) were tested for nodule occupancy in different bean cultivars at two field sites (one fertile, one acid tropical soil) and in the greenhouse. The effects of several environmental factors such as low pH, high temperature, Al and Mn toxicity, iron deficiency, bean tannins, and bean phytoalexins were tested in vitro. Strain Kim5s was competitive under all tested conditions while strains CE3 and H2C had consistently low nodule occupancy levels. Strain Ciat 151 was superior to the other inoculant strains in the acid soil but competed poorly in the fertile soil. Strain Ciat 895 was more competitive in the fertile soil. There was a decline in nodule occupancy for all strains tested from the first trifoliate leaf stage to the pod-filling stage. No plant genotype effect on nodule occupancy was observed. There were significant (P<0.05) plant genotype and location effects, but no significant strain effect on acetylene reduction activity, plant dry weight, and nodule number. The greenhouse experiments confirmed, at least partially, the results from the field trials. In Leonard jars with an acid soil, strains Ciat 151 and Kim5s were amongst the most competitive strains. In coinoculation experiments, Kim5s was the most competitive strain, followed by Ciat 899 and Ciat 895. The competitiveness of a given strain was affected by the coinoculant strain. Tolerance in vitro to low pH, high growth temperature, Al or Mn toxicity, or Fe limitation was not related to competitiveness of the inoculum strains. The sensitivity of the strains towards bean tannins or bean phytoalexins also was not correlated with their competitiveness.  相似文献   

8.
A field trial, a pot experiment and a survey of organically farmed leys were undertaken to investigate whether N fixation in red clover pastures in Norway was limited by a low supply of cobalt and/or molybdenum. Fertilization with Mo did not result in any higher production or N fixation, whereas the N yield both from established clover leys and red clover grown in pots increased slightly after application of Co to many of the investigated soils. In the organically farmed leys there was a significant and positive correlation between Co content and the N content of the red clover. As many of the investigated clover-soil systems were of those previously known to be very low in Co and Mo, and the gain in N yield obtained by extra Co supply was marginal, it is unlikely that deficiency of these trace elements is a problem of great concern in legume based forage production systems in Norway.  相似文献   

9.
Summary The survival of Bradyrhizobium Cajanus strain CC1021 in the soil and rhizosphere of pigeonpea [Cajanus cajan (L.) Millsp] was determined by most probable number and fluorescent antibody techniques. The survival of strain CC1021 was poor under field compared with pot-culture conditions. Although the rhizosphere of pigeonpea promoted the growth of native pigeonpea rhizobia, although no increase in the number of rhizobia was observed with the inoculant strain. Under similar conditions of rhizosphere colonization the competitiveness of strain CC1021 with cv UPAS 120 and ICPL 312 was 10% and 66016 during the first year and 8.4% and 33.3%, respectively, during the second year.  相似文献   

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