Symbiotic Nitrogen Fixation and Soil Acidity

Coventry, David; Evans, J.

doi:10.1016/b978-0-12-590655-5.50008-6

Cited by 38 publications

(25 citation statements)

References 132 publications

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“…These results confi rm the potential adverse eff ect of soil acidity on nodulation and symbiotic effi ciency of some strains, as described in other papers (36).…”

Section: Resultssupporting

confidence: 90%

Genetic Diversity and Symbiotic Efficiency of Indigenous Common Bean Rhizobia in Croatia

Pohajda¹,

Babić

Rajnović

et al. 2016

Food Technol. Biotechnol.

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Natural process of symbiotic nitrogen fi xation has a unique role in a sustainable legume production. Nodule bacteria, collectively named rhizobia, in symbiotic associations with legumes enable considerable entries of biologically fi xed nitrogen into ecosystems. In order to maxi- SummaryNodule bacteria (rhizobia) in symbiotic associations with legumes enable considerable entries of biologically fi xed nitrogen into soil. Eff orts are therefore made to intensify the natural process of symbiotic nitrogen fi xation by legume inoculation. Studies of fi eld populations of rhizobia open up the possibility to preserve and probably exploit some indigenous strains with hidden symbiotic or ecological potentials. The main aim of the present study is to determine genetic diversity of common bean rhizobia isolated from diff erent fi eld sites in central Croatia and to evaluate their symbiotic effi ciency and compatibility with host plants. The isolation procedure revealed that most soil samples contained no indigenous common bean rhizobia. The results indicate that the cropping history had a signifi cant impact on the presence of indigenous strains. Although all isolates were found to belong to species Rhizobium leguminosarum, signifi cant genetic diversity at the strain level was determined. Application of both random amplifi cation of polymorphic DNA (RAPD) and enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC--PCR) methods resulted in similar grouping of strains. Symbiotic effi ciency of indigenous rhizobia as well as their compatibility with two commonly grown bean varieties were tested in fi eld experiments. Application of indigenous rhizobial strains as inoculants resulted in signifi cantly diff erent values of nodulation, seed yield as well as plant nitrogen and seed protein contents. The most abundant nodulation and the highest plant nitrogen and protein contents were determined in plants inoculated with R. leguminosarum strains S 17/2 and S 21/6 . Although, in general, the inoculation had a positive impact on seed yield, diff erences depending on the applied strain were not determined. The overall results show the high degree of symbiotic effi ciency of the specifi c indigenous strain S 21/6 . These results indicate diff erent symbiotic potential of indigenous strains and confi rmed the importance of rhizobial strain selection. These are the fi rst studies of indigenous common bean rhizobia in Croatia that provide the basis for further characterization and selection of highly effi cient indigenous strains and their potential use in agricultural practice and future research.

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“…These results confi rm the potential adverse eff ect of soil acidity on nodulation and symbiotic effi ciency of some strains, as described in other papers (36).…”

Section: Resultssupporting

confidence: 90%

Genetic Diversity and Symbiotic Efficiency of Indigenous Common Bean Rhizobia in Croatia

Pohajda¹,

Babić

Rajnović

et al. 2016

Food Technol. Biotechnol.

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“…In acidic conditions, the formation of nodules is reduced by 50% for cowpea and acidic pH disrupts the signal exchange between the host plant and the bacterium in the establishment of the symbiosis; reducing the secretion of flavonoids by plants and the induction of Nod genes in bacteria (Alva et al, 1990). Similar results relating to the heterogeneity in the proportion of rhizobia have already been demonstrated by Hartel and Alexander (1983) and Coventry and Evans (1989). This contrasted with the result obtained in our study where cowpea nodulation was higher in the Al-toxic Nkoemvone soil compared to the control.…”

Section: Discussionsupporting

confidence: 61%

Diversity and dynamics of rhizobial populations in acidic soils with aluminum and manganese toxicities in forest zones

Manet

Boyomo

Ngonkeu

et al. 2017

Int. J. Agril. Res. Innov. & Tech.

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Soil acidity in the humid forest zones of Cameroon is one of the major constraints to agricultural productivity. This study was carried out to assess the rhizobial communities of two acidic soils; with aluminum toxicity (Nkoemvone) and manganese toxicity (Nkolbisson) for their potential to improve soil fertility in Cameroon. These two soils were used to inoculate to the host plants cowpea and siratro. At harvest, 120 rhizobacterial isolates were extracted from the nodules of these two hosts and subjected to morphological characterization. Twenty isolates per site were selected and analyzed for their 16S rDNA genetic profile following restrictions with endonucleases of PCR products and electrophoresis. The restriction patterns of the 16S rDNA of the 40 isolates showed 12 different profiles. Eight occurred in both types of soils, where as 4 were specific to the manganese-toxic-acidic soil. While the Al toxicity reduced the nodulation and growth of both plants, the Mn toxicity mostly affect the cowpea. This study ascertained the distribution of rhizobia based on soil characteristics. Further molecular analyses would allow the identification of the isolates recovered as well as their phylogenetical relationships.

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“…One important stress affecting the Rhizobium-legume symbiosis is the progressive acidification of agricultural soils (Coventry & Evans, 1989). Legume pasture productivity significantly decreases as the soil acidifies, due to the acid sensitivity of the prokaryotic symbiont (Munns, 1986;Robson & Loneragan, 1970).…”

Section: W G R E E V E a N D O T H E R Smentioning

confidence: 99%

Regulation of exopolysaccharide production in Rhizobium leguminosarum biovar viciae WSM710 involves exoR

et al. 1997

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A mildly acid-sensitive mutant o f Rhizobium leguminosarum bv. viciae WSM710 (WR6-35) produced colonies which were more mucoid in phenotype than the wild-type. Strain WR6-35 contained a single copy o f T n 5 and the observed mucoid phenotype, acid sensitivity and TnS-induced kanamycin resistance were 100 O/ O co-transducible using phage RL38. WR6-35 produced threefold more exopolysaccharide (EPS) than the wild-type in minimal medium devoid o f a nitrogen source. EPS produced by the mutant and the wild-type was identical as determined by proton NMR spectra. An EcoRl rhizobial fragment containing Tn5 and flanking rhizobial sequences was cloned from the mutant, restriction mapped and sequenced. There was extensive similarity between the ORF disrupted by TnS in R. leguminosarum bv. viciae WR6-35 and the exoR gene of Rhizobium (Sinorhizobium) meliloti R m l 0 2 l (71-3 O/ O identity over 892 bp). A t the protein level there was 70% identity and 9303% similarity over 267 amino acids with the ExoR protein of R. meliloti RmlO21.Hydrophilicity profiles o f the two proteins from these two rhizobia are superimposable. This gene in R. leguminosarum bv. viciae was thus designated exoR. The data suggest that Tn5 has disrupted a regulatory gene encoding a protein that negatively modulates EPS biosynthesis in R. leguminosarum bv. viciae WSM7lO. Despite earlier suggestions that EPS production and acid tolerance might be positively correlated, disruption of exoR in either R. leguminosarum bv. viciae or R. meliloti and its associated overproduction of EPS does not result in a more acid-tolerant phenotype than the wild-type when cultures are screened on conventional laboratory agar.

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Symbiotic Nitrogen Fixation and Soil Acidity

Cited by 38 publications

References 132 publications

Genetic Diversity and Symbiotic Efficiency of Indigenous Common Bean Rhizobia in Croatia

Genetic Diversity and Symbiotic Efficiency of Indigenous Common Bean Rhizobia in Croatia

Diversity and dynamics of rhizobial populations in acidic soils with aluminum and manganese toxicities in forest zones

Regulation of exopolysaccharide production in Rhizobium leguminosarum biovar viciae WSM710 involves exoR

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