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1.
Nodulation of common bean was explored in six oases in the south of Tunisia. Nineteen isolates were characterized by PCR–RFLP
of 16S rDNA. Three species of rhizobia were identified, Rhizobium etli, Rhizobium gallicum and Sinorhizobium meliloti. The diversity of the symbiotic genes was then assessed by PCR–RFLP of nodC and nifH genes. The majority of the symbiotic genotypes were conserved between oases and other soils of the north of the country.
Sinorhizobia isolated from bean were then compared with isolates from Medicago truncatula plants grown in the oases soils. All the nodC types except for nodC type p that was specific to common bean isolates were shared by both hosts. The four isolates with nodC type p induced N2-fixing effective nodules on common bean but did not nodulate M. truncatula and Medicago sativa. The phylogenetic analysis of nifH and nodC genes showed that these isolates carry symbiotic genes different from those previously characterized among Medicago and bean symbionts, but closely related to those of S. fredii Spanish and Tunisian isolates effective in symbiosis with common bean but unable to nodulate soybean. The creation of a novel
biovar shared by S. meliloti and S. fredii, bv. mediterranense, was proposed. 相似文献
2.
Li QQ Wang ET Zhang YZ Zhang YM Tian CF Sui XH Chen WF Chen WX 《Microbial ecology》2011,61(4):917-931
A total of 215 rhizobial strains were isolated and analyzed with 16S rRNA gene, 16S–23S intergenic spacer, housekeeping genes
atpD, recA, and glnII, and symbiotic genes nifH and nodC to understand the genetic diversity of soybean rhizobia in Hebei province, China. All the strains except one were symbiotic
bacteria classified into nine genospecies in the genera of Bradyrhizobium and Sinorhizobium. Surveys on the distribution of these rhizobia in different regions showed that Bradyrhizobium japonicum and Bradyrhizobium elkanii strains were found only in neutral to slightly alkaline soils whereas Bradyrhizobium yuanmingense, Bradyrhizobium liaoningense-related strains and strains of five Sinorhizobium genospecies were found in alkaline–saline soils. Correspondence and canonical correspondence analyses on the relationship
of rhizobial distribution and their soil characteristics reveal that high soil pH, electrical conductivity, and potassium
content favor distribution of the B. yuanmingense and the five Sinorhizobium species but inhibit B. japonicum and B. elkanii. High contents of available phosphorus and organic matters benefit Sinorhizobium fredii and B. liaoningense-related strains and inhibit the others groups mentioned above. The symbiotic gene (nifH and nodC) lineages among B. elkanii, B. japonicum, B. yuanmingense, and Sinorhizobium spp. were observed in the strains, signifying that vertical gene transfer was the main mechanism to maintain these genes
in the soybean rhizobia. However, lateral transfer of symbiotic genes commonly in Sinorhizobium spp. and rarely in Bradyrhizobium spp. was also detected. These results showed the genetic diversity, the biogeography, and the soil determinant factors of
soybean rhizobia in Hebei province of China. 相似文献
3.
Chinnaswamy Appunu Angle NZoue Lionel Moulin Graldine Depret Gisle Laguerre 《Systematic and applied microbiology》2009,32(7):460-470
Vigna mungo, Vigna radiata and Vigna unguiculata are important legume crops cultivated in India, but little is known about the genetic resources in native rhizobia that nodulate these species. To identify these bacteria, a core collection of 76 slow-growing isolates was built from root nodules of V. mungo, V. radiata and V. unguiculata plants grown at different sites within three agro-ecological-climatic regions of India. The genetic diversity of the bacterial collection was assessed by restriction fragment length polymorphism (RFLP) analysis of PCR-amplified DNA fragments of the 16S–23S rDNA intergenic spacer (IGS) region, and the symbiotic genes nifH and nodC. One rDNA IGS type grouped 91% of isolates, but more diversity was found at the symbiotic loci (17 symbiotic genotypes). Overall, no host plant specificity was shown, the three host plant species sharing common bradyrhizobial genotypes that represented 62% of the collection. Similarly, the predominant genotypes were found at most sampling sites and in all agro-ecological-climatic regions. Phylogenies inferred from IGS sequencing and multi-locus sequence analysis of the dnaK, glnII and recA genes indicated that all isolates but one were clustered with the Bradyrhizobium yuanmingense species. The nifH phylogeny also grouped the different nif haplotypes within a cluster including B. yuanmingense, except for one infrequent nif haplotype which formed a new lineage within the Bradyrhizobium genus. These results may reflect a long history of co-evolution between B. yuanmingense and Vigna spp. in India, while intra-species polymorphism detected in the symbiotic loci may be linked with the long history of diversification of B. yuanmingense coinciding with that of its host legumes. 相似文献
4.
Different species and symbiotic genotypes of field rhizobia can nodulate Phaseolus vulgaris in Tunisian soils 总被引:4,自引:0,他引:4
Ridha Mhamdi Gisèle Laguerre Mohamed Elarbi Aouani Mohamed Mars Noëlle Amarger 《FEMS microbiology ecology》2002,41(1):77-84
A collection of 160 isolates of rhizobia nodulating Phaseolus vulgaris in three geographical regions in Tunisia was characterized by restriction fragment length polymorphism analysis of polymerase chain reaction (PCR)-amplified 16S rDNA, nifH and nodC genes. Nine groups of rhizobia were delineated: Rhizobium gallicum biovar (bv.) gallicum, Rhizobium leguminosarum bv. phaseoli and bv. viciae, Rhizobium etli bv. phaseoli, Rhizobium giardinii bv. giardinii, and four groups related to species of the genus Sinorhizobium, Sinorhizobium meliloti, Sinorhizobium medicae and Sinorhizobium fredii. The most abundant rhizobial species were R. gallicum, R. etli, and R. leguminosarum encompassing 29–20% of the isolates each. Among the isolates assigned to R. leguminosarum, two-thirds were ineffective in nitrogen fixation with P. vulgaris and harbored a symbiotic gene typical of the biovar viciae. The S. fredii-like isolates did not nodulate soybean plants but formed numerous effective nodules on P. vulgaris. Comparison of nodC gene sequences showed that their symbiotic genotype was not related to that of S. fredii, but to that of the S. fredii-like reference strain GR-06, which was isolated from a bean plant grown in a Spanish soil. An additional genotype including 16% of isolates was found to be closely related to species of the genus Agrobacterium. However, when re-examined, these isolates did not nodulate their original host. 相似文献
5.
As an introduced plant, Lablab purpureus serves as a vegetable, herbal medicine, forage and green manure in China. In order to investigate the diversity of rhizobia associated with this plant, a total of 49 rhizobial strains isolated from ten provinces of Southern China were analyzed in the present study with restriction fragment length polymorphism and/or sequence analyses of housekeeping genes (16S rRNA, IGS, atpD, glnII and recA) and symbiotic genes (nifH and nodC). The results defined the L. purpureus rhizobia as 24 IGS-types within 15 rrs-IGS clusters or genomic species belonging to Bradyrhizobium, Rhizobium, Ensifer (synonym of Sinorhizobium) and Mesorhizobium. Bradyrhizobium spp. (81.6%) were the most abundant isolates, half of which were B. elkanii. Most of these rhizobia induced nodules on L. purpureus, but symbiotic genes were only amplified from the Bradyrhizobium and Rhizobium leguminosarum strains. The nodC and nifH phylogenetic trees defined five lineages corresponding to B. yuanmingense, B. japonicum, B. elkanii, B. jicamae and R. leguminosarum. The coherence of housekeeping and symbiotic gene phylogenies demonstrated that the symbiotic genes of the Lablab rhizobia were maintained mainly through vertical transfer. However, a putative lateral transfer of symbiotic genes was found in the B. liaoningense strain. The results in the present study clearly revealed that L. purpureus was a promiscuous host that formed nodules with diverse rhizobia, mainly Bradyrhizobium species, harboring different symbiotic genes. 相似文献
6.
Milagros Len-Barrios María Jos Lorite Javier Donate-Correa Juan Sanjun 《Systematic and applied microbiology》2009,32(6):413-420
Eleven strains were isolated from root nodules of Lotus endemic to the Canary Islands and they belonged to the genus Ensifer, a genus never previously described as a symbiont of Lotus. According to their 16S rRNA and atpD gene sequences, two isolates represented minority genotypes that could belong to previously undescribed Ensifer species, but most of the isolates were classified within the species Ensifer meliloti. These isolates nodulated Lotus lancerottensis, Lotus corniculatus and Lotus japonicus, whereas Lotus tenuis and Lotus uliginosus were more restrictive hosts. However, effective nitrogen fixation only occurred with the endemic L. lancerottensis. The E. meliloti strains did not nodulate Medicago sativa, Medicago laciniata Glycine max or Glycine soja, but induced non-fixing nodules on Phaseolus vulgaris roots. nodC and nifH symbiotic gene phylogenies showed that the E. meliloti symbionts of Lotus markedly diverged from strains of Mesorhizobium loti, the usual symbionts of Lotus, as well as from the three biovars (bv. meliloti, bv. medicaginis, and bv. mediterranense) so far described within E. meliloti. Indeed, the nodC and nifH genes from the E. meliloti isolates from Lotus represented unique symbiotic genotypes. According to their symbiotic gene sequences and host range, the Lotus symbionts would represent a new biovar of E. meliloti for which bv. lancerottense is proposed. 相似文献
7.
Bożena Mierzwa Sylwia Wdowiak-Wróbel Michał Kalita Sebastian Gnat Wanda Małek 《Archives of microbiology》2010,192(5):341-350
The phylogeny of symbiotic genes of Robinia pseudoacacia (black locust) rhizobia derived from Poland and Japan was studied by comparative sequence analysis of nodA, nodC, nodH, and nifH loci. In phylogenetic trees, black locust symbionts formed a branch of their own suggesting that the spread and maintenance
of symbiotic genes within Robinia pseudoacacia rhizobia occurred through vertical transmission. There was 99–100% sequence similarity for nodA genes of Robinia pseudoacacia nodulators, 97–98% for nodC, and 97–100% for nodH and nifH loci. A considerable sequence conservation of sym genes shows that the symbiotic apparatus of Robinia pseudoacacia rhizobia might have evolved under strong host plant constraints. In the nodA and nodC gene phylograms, Robinia pseudoacacia rhizobia grouped with Phaseolus sp. symbionts, although they were not closely related to our isolates based on 16S rRNA genes, and with Mesorhizobium amorphae. nifH gene phylogeny of our isolates followed the evolutionary history of 16S rDNA and Robinia pseudoacacia rhizobia grouped with Mesorhizobium genus species. Nodulation assays revealed that Robinia pseudoacacia rhizobia effectively nodulated their native host and also Amorpha fruticosa and Amorpha californica resulting in a significant enhancement of plant growth. The black locust root nodules are shown to be of indeterminate type. 相似文献
8.
Genetic Diversity and Host Range of Rhizobia Nodulating Lotus tenuis in Typical Soils of the Salado River Basin (Argentina)
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María Julia Estrella Socorro Muoz María Jos Soto Oscar Ruiz Juan Sanjun 《Applied microbiology》2009,75(4):1088-1098
A total of 103 root nodule isolates were used to estimate the diversity of bacteria nodulating Lotus tenuis in typical soils of the Salado River Basin. A high level of genetic diversity was revealed by repetitive extragenic palindromic PCR, and 77 isolates with unique genomic fingerprints were further differentiated into two clusters, clusters A and B, after 16S rRNA restriction fragment length polymorphism analysis. Cluster A strains appeared to be related to the genus Mesorhizobium, whereas cluster B was related to the genus Rhizobium. 16S rRNA sequence and phylogenetic analysis further supported the distribution of most of the symbiotic isolates in either Rhizobium or Mesorhizobium: the only exception was isolate BA135, whose 16S rRNA gene was closely related to the 16S rRNA gene of the genus Aminobacter. Most Mesorhizobium-like isolates were closely related to Mesorhizobium amorphae, Mesorhizobium mediterraneum, Mesorhizobium tianshanense, or the broad-host-range strain NZP2037, but surprisingly few isolates grouped with Mesorhizobium loti type strain NZP2213. Rhizobium-like strains were related to Rhizobium gallicum, Rhizobium etli, or Rhizobium tropici, for which Phaseolus vulgaris is a common host. However, no nodC or nifH genes could be amplified from the L. tenuis isolates, suggesting that they have rather divergent symbiosis genes. In contrast, nodC genes from the Mesorhizobium and Aminobacter strains were closely related to nodC genes from narrow-host-range M. loti strains. Likewise, nifH gene sequences were very highly conserved among the Argentinian isolates and reference Lotus rhizobia. The high levels of conservation of the nodC and nifH genes suggest that there was a common origin of the symbiosis genes in narrow-host-range Lotus symbionts, supporting the hypothesis that both intrageneric horizontal gene transfer and intergeneric horizontal gene transfer are important mechanisms for the spread of symbiotic capacity in the Salado River Basin. 相似文献
9.
D. Diouf D. Fall C. Chaintreuil A.T. Ba B. Dreyfus M. Neyra I. Ndoye L. Moulin 《Journal of applied microbiology》2010,108(3):818-830
Aims: To assess the phenotypic, symbiotic and genotypic diversity scope of Mesorhizobium spp. strains associated with Acacia seyal (Del.) isolated from different agro‐ecological zones in Senegal, and uses of susceptible microbial inoculum in a reafforestation process. Methods and Results: A polyphasic approach including phenotypic and genotypic techniques was used to study the diversity and their relationships with other biovars and species of rhizobia. The geographical origins of the strains have limited effect on their phylogenetic and phenotypic classification. Nodulation tests indicated promiscuity of the strains studied, because they were capable of nodulating six woody legume species (Acacia auriculiformis, Acacia senegal, A. seyal, Acacia tortilis ssp. raddiana, Leucaena leucocephala and Prosopis juliflora). Sequencing and phylogenetic analyses of nodA, nodC and nifH genes pointed out that in contrast to nodA gene, the phylogenies of nodC and nifH genes were not consistent with that of 16S rRNA, indicating that these genes of the A. seyal‐nodulating rhizobia might have different origins. Microbial inoculation on nonsterile soil had significant effect on the nodules number and the growth of the seedlings, indicating that these strains of rhizobia might be used as inoculum. Conclusions: The results indicated that A. seyal is a nonselective host that can establish effective symbiosis with Mesorhizobium spp. strains from diverse genomic backgrounds and that the selected A. seyal‐nodulating rhizobia could enhance plant growth. Significance and Impact of the Study: These results showed the important role that A. seyal could play in the improvement of reafforestation process as a promiscuous host, which can establish effective symbiosis with rhizobia from diverse genomic backgrounds. 相似文献
10.
Diverse bacteria isolated from root nodules of wild Vicia species grown in temperate region of China 总被引:1,自引:0,他引:1
In the present study, a total of 154 bacterial strains isolated from nodules of eighteen Vicia species mainly grown in the temperate Chinese provinces were characterized by ARDRA, ITS PCR–RFLP, BOX-PCR, sequencing of
16S rDNA, nodC, nifH, atpD and glnII, and nodulation tests. The results demonstrated that most of the R. leguminosarum strains were effective microsymbionts of the wild Vicia species, while genomic species related to Rhizobium gallicum, Mesorhizobium huakuii, Ensifer meliloti and Bradyrhizobium spp. were symbiotic bacteria occasionally nodulating with Vicia species. In addition, fourteen strains related to Agrobacterium, Phyllobacterium, Ensifer, Shinella and R. tropici, as well as 22 strains of R. leguminosarum might be nodule endophytes without symbiotic genes. Diverse symbiotic gene lineages were found among the test strains and
a strong association was found among the symbiotic gene types and genomic species, indicating the absence of lateral gene
transfer. These results greatly enlarged the rhizobial spectrum of Vicia species.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
11.
Fernando Ibáñez Jorge AngeliniTania Taurian María Laura TonelliAdriana Fabra 《Systematic and applied microbiology》2009
Several bacterial isolates were recovered from surface-sterilized root nodules of Arachis hypogaea L. (peanut) plants growing in soils from Córdoba, Argentina. The 16S rDNA sequences of seven fast-growing strains were obtained and the phylogenetic analysis showed that these isolates belonged to the Phylum Proteobacteria, Class Gammaproteobacteria, and included Pseudomonas spp., Enterobacter spp., and Klebsiella spp. After storage, these strains became unable to induce nodule formation in Arachis hypogaea L. plants, but they enhanced plant yield. When the isolates were co-inoculated with an infective Bradyrhizobium strain, they were even found colonizing pre-formed nodules. Analysis of symbiotic genes showed that the nifH gene was only detected for the Klebsiella-like isolates and the nodC gene could not be amplified by PCR or be detected by Southern blotting in any of the isolates. The results obtained support the idea that these isolates are opportunistic bacteria able to colonize nodules induced by rhizobia. 相似文献
12.
Rhizobial Resource Associated with Epidemic Legumes in Tibet 总被引:1,自引:0,他引:1
A total of 128 bacterial test strains originated from Astragalus, Caragana, Gueldenstaedtia, Medicago, Melilotus, Oxytropis, Trifolium, and Vicia grown in Tibet were characterized phenotypically and genomically. Based upon the consensus of grouping results, they were
identified as 16 putative species. Twenty-five test strains belonging to seven putative species of Agrobacterium, Bradyrhizobium, and Rhizobium might be nonsymbiotic bacteria and the remaining 103 test strains were symbiotic bacteria belonging to Mesorhizobium, Rhizobium, and Sinorhizobium meliloti. Although no novel taxon was detected in the symbiotic bacteria, several characters including the alkaliphilic psychrotolerance
revealed that the Tibetan rhizobia could be ecotypes adapted to the local conditions. The results also demonstrated that frequent
lateral transfer of symbiotic genes might have happened in the Tibetan rhizobia since nodC genes similar to that of S. meliloti were found in several Rhizobium test strains and all the Mesorhizobium species had very similar nodC genes despite their genomic background. All of these findings demonstrated that the Tibetan rhizobia were an important resource
for further studies on rhizobial ecology and application.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
13.
14.
Genetic diversity of soybean-nodulating rhizobia in Nepal in relation to climate and soil properties
Dinesh Adhikari Masakazu Kaneto Kazuhito Itoh Kousuke Suyama Bhanu B. Pokharel Yam K. Gaihre 《Plant and Soil》2012,357(1-2):131-145
Backgroud and aims
This study was conducted to reveal the genetic diversity of soybean-nodulating rhizobia in Nepal in relation to climate and soil properties.Method
A total of 102 bradyrhizobial strains were isolated from the root nodules of soybeans cultivated in 12 locations in Nepal varying in climate and soil properties, and their genetic diversity was examined based on 16S rDNA, ITS regions of 16S–23S rDNA, nodC and nifH. In vitro growth properties of some representative strains were examined to elucidate their characteristic distribution in Nepal.Results
Four species of the genus Bradyrhizobium were isolated, and B. japonicum dominated at temperate locations, while in subtropical locations, B. elkanii, B. yuanmingense, and B. liaoningense dominated at acidic, moderately acidic, and slightly alkaline soils, respectively. The relative nodule occupancies could not be fully explained by their in vitro growth properties. Similar nodC and nifH genes among the strains suggested co-evolution of these genes also in Nepal, probably through horizontal gene transfer.Conclusions
The influence of climate and soil pH on diversity at the sub-species level was revealed. It is concluded that the highly diverse climate and soils in Nepal might be conducive for the existence of diverse soybean rhizobial strains. 相似文献15.
Kai Wei Xu Petri Penttinen Yuan Xue Chen Qiang Chen Xiaoping Zhang 《Applied microbiology and biotechnology》2013,97(2):783-793
In search of effective nitrogen-fixing strains for inoculating Leucaena leucocephala, we assessed the symbiotic efficiency of 41 rhizobial isolates from root nodules of L. leucocephala growing in the arid–hot river valley area in Panxi, China. The genetic diversity of the isolates was studied by analyzing the housekeeping genes 16S rRNA and recA, and the symbiotic genes nifH and nodC. In the nodulation and symbiotic efficiency assay, only 11 of the 41 isolates promoted the growth of L. leucocephala while the majority of the isolates were ineffective in symbiotic nitrogen fixation. Furthermore, one fourth of the isolates had a growth slowing effect on the host. According to the 16S rRNA and recA gene analyses, most of the isolates were Ensifer spp. The remaining isolates were assigned to Rhizobium, Mesorhizobium and Bradyrhizobium. The sequence analyses indicated that the L. leucocephala rhizobia had undergone gene recombination. In contrast to the promiscuity observed as a wide species distribution of the isolates, the results implied that L. leucocephala is preferentially nodulated by strains that share common symbiosis genes. The symbiotic efficiency was not connected to chromosomal background of the symbionts and isolates carrying a similar nifH or nodC showed totally different nitrogen fixation efficiency. 相似文献
16.
G. Garau W.G. Reeve L. Brau P. Deiana R.J. Yates D. James R. Tiwari G.W. O’Hara J.G. Howieson 《Plant and Soil》2005,276(1-2):263-277
Nitrogen fixing rhizobia associated with the Medicago L. genus belong to two closely related species Sinorhizobium medicae and S. meliloti. To investigate the symbiotic requirements of different Medicago species for the two microsymbionts, 39 bacterial isolates from nodules of eleven Medicago species growing in their natural habitats in the Mediterranean basin plus six historical Australian commercial inocula were
symbiotically characterized with Medicago hosts. The bacterial species allocation was first assigned on the basis of symbiotic proficiency with M. polymorpha. PCR primers specific for 16S rDNA were then designed to distinguish S. medicae and S. meliloti. PCR amplification results confirmed the species allocation acquired in the glasshouse. PCR fingerprints generated from ERIC,
BOXA1R and nif-directed RPO1 primers revealed that the Mediterranean strains were genetically heterogenous. Moreover PCR fingerprints with
ERIC and BOX primers showed that these repetitive DNA elements were specifically distributed and conserved in S. meliloti and S. medicae, clustering the strains into two divergent groups according to their species. Linking the Sinorhizobium species with the plant species of origin we have found that S. medicae was mostly associated with medics well adapted to moderately acid soils such as M. polymorpha, M. arabica and M. murex whereas S. meliloti was predominantly isolated from plants naturally growing on alkaline or neutral pH soils such as M. littoralis and M. tornata. Moreover in glasshouse experiments the S. medicae strains were able to induce well-developed nodules on M. murex whilst S. meliloti was not infective on this species. This feature provides a very distinguishing characteristic for S. medicae. Results from the symbiotic, genotypic and cultural characterization suggest that S. meliloti and S. medicae have adapted to different Medicago species according to the niches these medics usually occupy in their natural habitats. 相似文献
17.
A multilocus phylogenetic approach was applied to elucidate the phylogeny of Astragalus cicer rhizobia derived from Poland, Ukraine, and Canada. The strains selected for the studies represented three main geographically
different phenons of these bacteria. Phylogenetic analyses were performed with three chromosomal housekeeping loci (16S rRNA,
atpD, glnII) and three symbiotic genes located on a plasmid (nodA, nodC, nifH). The “core” and “auxiliary” gene trees revealed that A. cicer nodule isolates were intermingled with the strains of Mesorhizobium species, which implies that they are descendents of the same ancestor as mesorhizobia and fall into the Mesorhizobium genus. The noted congruence of the housekeeping and symbiotic gene phylogenies of A. cicer microsymbionts indicates that sym loci are transferred to these bacteria through vertical transmission without a significant participation of intergeneric
horizontal gene spread. All the three sym gene sequences of the Polish and Ukrainian A. cicer nodule isolates were more closely related to one another than to the corresponding sequences of the Canadian isolates. The
phylogeographic patterns of the sym genes of intercontinental strains point to their relatively long, separate, evolutionary history. 相似文献
18.
Yao Yao Rui Wang Jun Kun Lu Xin Hua Sui En Tao Wang Wen Xin Chen 《Applied and environmental microbiology》2014,80(19):6184-6194
The nodulation of Erythrophleum fordii has been recorded recently, but its microsymbionts have never been studied. To investigate the diversity and biogeography of rhizobia associated with this leguminous evergreen tree, root nodules were collected from the southern subtropical region of China. A total of 166 bacterial isolates were obtained from the nodules and characterized. In a PCR-based restriction fragment length polymorphism (RFLP) analysis of ribosomal intergenic sequences, the isolates were classified into 22 types within the genus Bradyrhizobium. Sequence analysis of 16S rRNA, ribosomal intergenic spacer (IGS), and the housekeeping genes recA and glnII classified the isolates into four groups: the Bradyrhizobium elkanii and Bradyrhizobium pachyrhizi groups, comprising the dominant symbionts, Bradyrhizobium yuanmingense, and an unclassified group comprising the minor symbionts. The nodC and nifH phylogenetic trees defined five or six lineages among the isolates, which was largely consistent with the definition of genomic species. The phylogenetic results and evolutionary analysis demonstrated that mutation and vertical transmission of genes were the principal processes for the divergent evolution of Bradyrhizobium species associated with E. fordii, while lateral transfer and recombination of housekeeping and symbiotic genes were rare. The distribution of the dominant rhizobial populations was affected by soil pH and effective phosphorus. This is the first report to characterize E. fordii rhizobia. 相似文献
19.
Background and Aims
This study was conducted to reveal the genetic diversity of common bean (Phaseolus vulgaris L.) nodulating rhizobia in various agroecological regions in Nepal.Method
A total of 63 strains were isolated from common bean grown in the soils collected from seven bean fields in Nepal and characterized based on the partial sequences of 16S–23S internal transcribed spacer (ITS) regions, 16S rDNA, nodC, and nifH. Symbiotic properties of some representative strains with host plants were examined to elucidate their characteristics in relation to genotype and their origin.Results
The isolated strains belonged to Rhizobium leguminosarum, Rhizobium etli, Rhizobium phaseoli, and one unknown Rhizobium lineage, all belonging to a common symbiovar (sv.) phaseoli. Nine ITS genotypes were detected mainly corresponding to a single site, including a dominant group at three sites harboring highly diverse multiple ITS sequences. Three symbiotic genotypes corresponded to a geographical region, not to the ribosomal DNA group, suggesting horizontal transfer of symbiotic genes separately in each region. Great differences in nitrogenase activity and nodule forming ability among the strains irrespective of their species and origin were observed.Conclusions
Nepalese Himalaya harbor phylogenetically highly diverse and site-specific strains of common bean rhizobia, some of which could have high potential of symbiotic nitrogen fixation. 相似文献20.
Li Li Han En Tao Wang Yang Li Lu Yong Fa Zhang Xin Hua Sui Wen Feng Chen Wen Xin Chen 《Journal of microbiology (Seoul, Korea)》2009,47(3):287-296
Adzuki bean (Vigna angularis) is an important legume crop native to China, but its rhizobia have not been well characterized. In the present study, a
total of 60 rhizobial strains isolated from eight provinces of China were analyzed with amplified 16S rRNA gene RFLP, IGS-RFLP,
and sequencing analyses of 16S rRNA, atpD, recA, and nodC genes. These strains were identified as genomic species within Rhizobium, Sinorhizobium, Mesorhizobium, Bradyrhizobium, and Ochrobactrum. The most abundant groups were Bradyrhizobium species and Sinorhizobium fredii. Diverse nodC genes were found in these strains, which were mainly co-evolved with the housekeeping genes, but a possible lateral transfer
of nodC from Sinorhizobium to Rhizobium was found. Analyses of the genomic and symbiotic gene backgrounds showed that adzuki bean shared the same rhizobial gene
pool with soybean (legume native to China) and the exotic Vigna species. All of these data demonstrated that nodule formation is the interaction of rhizobia, host plants, and environment
characters.
Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users. 相似文献