Nitrogen fixation capacity in the component species of contour hedgerows: how important?

1994 ◽  
Vol 27 (3) ◽  
pp. 241-258 ◽  
Author(s):  
D. P. Garrity ◽  
A. R. Mercado
Keyword(s):  
Nitrogen Fixation ◽  
Fixation Capacity ◽  
Contour Hedgerows

Differential responses of the sunn4 and rdn1-1 super-nodulation mutants of Medicago truncatula to elevated atmospheric CO2

2021 ◽  
Author(s):  
Yunfa Qiao ◽  
Shujie Miao ◽  
Jian Jin ◽  
Ulrike Mathesius ◽  
Caixian Tang
Keyword(s):  
Nitrogen Fixation ◽  
Elevated Co2 ◽  
Medicago Truncatula ◽  
N2 Fixation ◽  
Sink Strength ◽  
Wild Type ◽  
Total N ◽  
Autoregulation Of Nodulation ◽  
Nodulation Mutants ◽  
Fixation Capacity

Abstract Background and Aims Nitrogen fixation in legumes requires tight control of carbon and nitrogen balance. Thus, legumes control nodule numbers via an autoregulation mechanism. ‘Autoregulation of nodulation’ mutants super-nodulate and are thought to be carbon-limited due to the high carbon-sink strength of excessive nodules. This study aimed to examine the effect of increasing carbon supply on the performance of super-nodulation mutants. Methods We compared the responses of Medicago truncatula super-nodulation mutants (sunn-4 and rdn1-1) and wild type to five CO2 levels (300-850 μmol mol -1). Nodule formation and N2 fixation were assessed in soil-grown plants at 18 and 42 days after sowing. Key results Shoot and root biomass, nodule number and biomass, nitrogenase activity and fixed-N per plant of all genotypes increased with increasing CO2 concentration and reached the maximum around 700 μmol mol -1. While the sunn-4 mutant showed strong growth-retardation compared to wild-type plants, elevated CO2 increased shoot biomass and total N content of rdn1-1 mutant up to two-fold. This was accompanied by a four-fold increase in nitrogen fixation capacity in the rdn1-1 mutant. Conclusions These results suggest that the super-nodulation phenotype per se did not limit growth. The additional nitrogen fixation capacity of the rdn1-1 mutant may enhance the benefit of elevated CO2 on plant growth and N2 fixation.

scholarly journals Improvement in nitrogen fixation capacity could be part of the domestication process in soybean

Heredity ◽  
2016 ◽  
Vol 117 (2) ◽  
pp. 84-93 ◽  
Author(s):  
N Muñoz ◽  
X Qi ◽  
M-W Li ◽  
M Xie ◽  
Y Gao ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Fixation Capacity ◽  
Domestication Process

Phoma medicaginis colonizes Medicago truncatula root nodules and affects nitrogen fixation capacity

2014 ◽  
Vol 141 (2) ◽  
pp. 375-383 ◽  
Author(s):  
Saif-Allah Chihaoui ◽  
Naceur Djébali ◽  
Moncef Mrabet ◽  
Fathi Barhoumi ◽  
Ridha Mhamdi ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Medicago Truncatula ◽  
Root Nodules ◽  
Phoma Medicaginis ◽  
Fixation Capacity

Evaluation of Biological Nitrogen Fixation Capacity in Arachis Species and the Possible Role of Polyploidy1

1994 ◽  
Vol 21 (1) ◽  
pp. 55-60 ◽  
Author(s):  
H. T. Stalker ◽  
M. L. Nickum ◽  
J. C. Wynne ◽  
G. H. Elkan ◽  
T. J. Schneeweis
Keyword(s):  
Nitrogen Fixation ◽  
Arachis Hypogaea ◽  
Cover Crops ◽  
Biological Nitrogen Fixation ◽  
Nitrogenase Activity ◽  
Diploid Species ◽  
Dry Matter Accumulation ◽  
Arachis Species ◽  
Fixation Capacity ◽  
Biological Nitrogen

Abstract Arachis species have potential for enhancing cultivated peanut (Arachis hypogaea L.) germplasm as forages and cover crops. This study's objective was to evaluate a range of Arachis species for biological nitrogen fixation capacity. Several Arachis species are tetraploids, and it has been shown that tetraploidy may play an important role in nodule initiation. Species were first tested under natural field conditions and then in the greenhouse using three Bradyrhizobium strains that had been previously shown to be effective on peanut. Nodule number, nodule weight, nitrogenase activity determined by acetylene reduction, and shoot dry weight were measured as indicators of nitrogen fixation capacity. In the field, tetraploid species produced significantly more nodules than the diploids, but total dry matter accumulation was independent of the number of nodules or rate of fixation. In the greenhouse, no significant differences were observed among the bradyrhizobial strains. Arachis hypogaea and A. monticola showed significantly higher measures of nitrogen fixation capacity for all measured traits than the diploid species. However, autotetraploid plants of A. villosa did not have significantly more nodules than diploids of the same accession; the autotetraploids consistently had higher nitrogenase activity. Arachis pusilla never formed a symbiotic relationship with the bradyrhizobial strains used.

Characterisation of dry and mucoid colonies isolated from Australian rhizobial inoculant strains for Medicago species

2005 ◽  
Vol 45 (3) ◽  
pp. 151 ◽  
Author(s):  
A. McInnes ◽  
P. Holford ◽  
J. E. Thies
Keyword(s):  
Nitrogen Fixation ◽  
Sinorhizobium Meliloti ◽  
Dry Weight ◽  
Sequence Element ◽  
Shoot Dry Weight ◽  
Single Colony ◽  
Agar Media ◽  
Fixation Capacity ◽  
Medicago Species ◽  
K Antigen

The presence of dry and mucoid colonies in cultures of rhizobial strains used in the production of commercial Australian inoculants is of concern for quality assurance because of the possibility of altered capacity for nodulation and nitrogen fixation by the different colony types. In this study, single colony isolates obtained from dry and mucoid colonies present in commercial cultures of Sinorhizobium meliloti were investigated to identify stability in culture, genetic identity and changes in exopolysaccharide (EPS) production, nodulation and nitrogen fixation. The 2 strains studied were WSM688 and WSM826 (Australian inoculant strains for annual and perennial medics, respectively), both of which produced only mucoid colonies on agar media when originally isolated from nodules. Dry and mucoid single colony isolates from the ‘mother cultures’ of the 2 strains exhibited stable colony phenotypes during successive subculturing in our laboratory and were shown to be most closely related to S. meliloti using 16S rRNA partial sequencing. All isolates produced at least 1 of 3 exopolysaccharides (succinoglycan, EPS II and K antigen) that are required for successful nodulation of Medicago species by S. meliloti strains, as indicated by nodulation of host legumes. Strain WSM826 isolates probably produce succinoglycan, as shown by similarity to the succinoglycan-producing strain Rm1021 in a calcofluor binding assay. In contrast to published work, there was no evidence that loss of mucoidy in dry colony isolates of either strain was associated with the presence of an insertion sequence element in the expR gene that inhibits EPS II production. For strain WSM688, dry and mucoid isolates were identical by PCR fingerprinting and showed a similar capacity to nodulate and fix nitrogen with the target host legume M. truncatula in glasshouse tests. In contrast, strain WSM826 mucoid isolates produced PCR fingerprints that were different from each other and from the WSM826 dry colony isolates. Dry and mucoid colonies may have arisen from substantial genetic change or through contamination of cultures by other S. meliloti strains. One WSM826 mucoid isolate (826-3) produced significantly lower shoot dry weight when inoculated onto both the target host M. sativa and non-target host M. truncatula, even though the capacity to nodulate both hosts was retained. This suggests that this isolate was affected in its nitrogen fixation capacity. Further research is required to identify the origin and extent of colony variation in commercial S. meliloti cultures.

Symbiogenetics and breeding of a macrosymbiont for increased nitrogen fixation capacity with special reference to the pea (Pisum sativum L.)

2011 ◽  
Vol 1 (1) ◽  
pp. 73-87 ◽  
Author(s):  
K. K. Sidorova ◽  
V. K. Shumny ◽  
E. Yu. Vlasova ◽  
M. N. Glyanenko ◽  
T. M. Mishchenko ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Pisum Sativum ◽  
Special Reference ◽  
Pisum Sativum L ◽  
Fixation Capacity

scholarly journals Metabolic Analyses of Nitrogen Fixation in the Soybean Microsymbiont Sinorhizobium fredii Using Constraint-Based Modeling

mSystems ◽  
2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Carolina A. Contador ◽  
Siu-Kit Lo ◽  
Siu H. J. Chan ◽  
Hon-Ming Lam
Keyword(s):  
Nitrogen Fixation ◽  
Host Plants ◽  
Wild Soybean ◽  
Metabolic Model ◽  
Nitrogen Fixing ◽  
Sinorhizobium Fredii ◽  
Content Type ◽  
Fixation Capacity ◽  
Gene Knockouts ◽  
Cultivated Soybean

ABSTRACT Rhizobia are soil bacteria able to establish symbiosis with diverse host plants. Specifically, Sinorhizobium fredii is a soil bacterium that forms nitrogen-fixing root nodules in diverse legumes, including soybean. The strain S. fredii CCBAU45436 is a dominant sublineage of S. fredii that nodulates soybeans in alkaline-saline soils in the Huang-Huai-Hai Plain region of China. Here, we present a manually curated metabolic model of the symbiotic form of Sinorhizobium fredii CCBAU45436. A symbiosis reaction was defined to describe the specific soybean-microsymbiont association. The performance and quality of the reconstruction had a 70% score when assessed using a standardized genome-scale metabolic model test suite. The model was used to evaluate in silico single-gene knockouts to determine the genes controlling the nitrogen fixation process. One hundred forty-one of 541 genes (26%) were found to influence the symbiotic process, wherein 121 genes were predicted as essential and 20 others as having a partial effect. Transcriptomic profiles of CCBAU45436 were used to evaluate the nitrogen fixation capacity in cultivated versus in wild soybean inoculated with the microsymbiont. The model quantified the nitrogen fixation activities of the strain in these two hosts and predicted a higher nitrogen fixation capacity in cultivated soybean. Our results are consistent with published data demonstrating larger amounts of ureides and total nitrogen in cultivated soybean than in wild soybean. This work presents the first metabolic network reconstruction of S. fredii as an example of a useful tool for exploring the potential benefits of microsymbionts to sustainable agriculture and the ecosystem. IMPORTANCE Nitrogen is the most limiting macronutrient for plant growth, and rhizobia are important bacteria for agriculture because they can fix atmospheric nitrogen and make it available to legumes through the establishment of a symbiotic relationship with their host plants. In this work, we studied the nitrogen fixation process in the microsymbiont Sinorhizobium fredii at the genome level. A metabolic model was built using genome annotation and literature to reconstruct the symbiotic form of S. fredii. Genes controlling the nitrogen fixation process were identified by simulating gene knockouts. Additionally, the nitrogen-fixing capacities of S. fredii CCBAU45436 in symbiosis with cultivated and wild soybeans were evaluated. The predictions suggested an outperformance of S. fredii with cultivated soybean, consistent with published experimental evidence. The reconstruction presented here will help to understand and improve nitrogen fixation capabilities of S. fredii and will be beneficial for agriculture by reducing the reliance on fertilizer applications.

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