Abstract The bacteria called rhizobia are nitrogen-fixing bacteria which establish symbioses with plant species in the legume family. They induce positive interaction between soil microorganisms and the plant and are essential for plant... more
Abstract The bacteria called rhizobia are nitrogen-fixing bacteria which establish symbioses with plant species in the legume family. They induce positive interaction between soil microorganisms and the plant and are essential for plant growth in semiarid Mediterranean ecosystems that usually present severe water stress, scarcity of plants, low available nutrients and microbiological activity. Considered as one of the endemic legume shrubs of the Mediterranean basin, Retama plays an important role in nitrogen cycling, and thus, can be used to restore heavily disturbed and degraded soils. These species are adapted to harsh environmental conditions and their establishment and growth are enhanced by their ability to enter into effective symbiosis with multiple rhizobia species. In this article, we review the cumulative evidence of the Retama-rhizobia symbiosis in the Mediterranean basin and its ecological impact on revegetation and soil fertilization
— A field experiment was conducted in Summer-Spring cropping season 2016 at Cujut district, DakNong province, Vietnam to study the effects of rhizobia and phosphate-solubilizing bacteria (PSB) on soybean (cv. Cujut) cultivated on... more
— A field experiment was conducted in Summer-Spring cropping season 2016 at Cujut district, DakNong province, Vietnam to study the effects of rhizobia and phosphate-solubilizing bacteria (PSB) on soybean (cv. Cujut) cultivated on ferralsols. The experiment consisted of six treatments as follows: control (no fertilizer, no inoculant), 240 kg/ha NPK 15-15-15, rhizobial inoculant [with liquid cover seeds] + 20 kg N/ha applied at 10 days after sowing [DAS], PSB inoculant [with liquid cover seeds] + 20 kg N/ha at 10 DAS, rhizobial and PSB inoculant [with liquid cover seeds] + 400 kg fertilizer/ha + 20 kg N/ha at 10 DAS and endophytic bacteria inoculant [with liquid cover seeds] + 400 kg fertilizer/ha + 20 kg N/ha at 10 DAS from June to August, 2016. The results showed that application of rhizobial inoculant and/or PSB inoculant produced significantly higher yield component, grain yield than control and did not differ from 240 kg/ha NPK 15-15-15. Consequently, application of rhizobia and PSB improved soil fertility after harversting however using mixture of rhizobia and PSB inoculation plus 400 kg biofertilizer/ha +20 kg N/ha for soybean cultivation supported yield component, grain yield and oil, protein in seed than control and equivalent with treatment of chemical fertilizer (240 kg/ha NPK 15-15-15). This technique not only increased grain yield, incomes for farmers but also improved soil fertility.
—Aiming at accurately and rapidly identifying our heavy metal resistant rhizobial strains, genomic average nucleotide identity (ANI) and core genome analyses were performed to investigate the phylogenetic relationships among 45 strains in... more
—Aiming at accurately and rapidly identifying our heavy metal resistant rhizobial strains, genomic average nucleotide identity (ANI) and core genome analyses were performed to investigate the phylogenetic relationships among 45 strains in the families of Rhizobiaceae and Bradyrhizobiaceae. The results showed that both of the ANI and core-genome phylogenetic trees revealed similar relationship. In ANI analysis, the 90%, 75% and 70% ANI values could be the thresholds for species, genus and family, respectively. Analyzing the genomes using multi-dimensional scaling and scatter plot showed highly consistent with the ANI and core-genome phylogenetic results. With these thresholds, the 45 strains were divided into 24 genomic species within the genera Agrobacterium, Allorhizobium, Bradyrhizobium, Sinorhizobium and a putative novel genus represented by Ag. albertimagni AOL15. The ten arsenite-oxidizing and antimonite tolerant strains were identified as Ag. radiobacter, and two Sinorhizobium genomic species differing from S. fredii. In addition, the description of Pararhizobium is questioned because ANI values greater than 75% were detected between P. giardinii H152T and Sinorhizobium strains. Also, reversion of the species definition for several strains in R. etli and R. leguminosarum was suggested. Our results demonstrate that analyses of ANI and core-genome are rapid and confident methods to identify the rhizobial strains, and it will be also convenient when more genome data are accumulated.
The evolution of mutualisms under novel selective pressures will play a key role in ecosystem responses to environmental change. Because fixed nitrogen is traded in plant–rhizobium mutualisms, increasing N availability in the soil is... more
The evolution of mutualisms under novel selective pressures will play a key
role in ecosystem responses to environmental change. Because fixed nitrogen
is traded in plant–rhizobium mutualisms, increasing N availability in the soil is
predicted to alter coevolution of these interactions. Legumes typically decrease
the number of associations (nodules) with rhizobia in response to nitrate, but
the evolutionary dynamics of this response remain unknown. We grew plant
and rhizobium genotype combinations in three N environments to assess the
coevolutionary potential of the nodule nitrate response in natural communities
of plants and rhizobia. We found evidence for coevolutionary genetic
variation for nodulation in response to nitrate (G · G · E interaction),
suggesting that the mutualism response to N deposition will depend on the
combination of partner genotypes. Thus, the nitrate response is not a fixed
mechanism in plant–rhizobium symbioses, but instead is potentially subject to
natural selection and dynamic coevolution.
Rhizobia were isolated from the root nodules of Clitoria ternatea in Thailand. The phylogeny of the isolates was investigated using 16S rDNA and the internal transcribed spacer (ITS) region from 16S to 23S rDNA. The phylogenetic tree of... more
Rhizobia were isolated from the root nodules of Clitoria ternatea in Thailand. The phylogeny of the isolates was investigated using 16S rDNA and the internal transcribed spacer (ITS) region from 16S to 23S rDNA. The phylogenetic tree of the 16S rDNA showed that ten of the eleven isolates belonged to Bradyrhizobium elkanii, and one belonged to Bradyrhizobium japonicum. The topology of the ITS tree was similar to that of 16S rDNA. The acetylene reduction activity was higher for the nodules inoculated with the isolated B. elkanii strains than for those inoculated with B. japonicum strains. When C. ternatea plants were inoculated with various Bradyrhizobium USDA strains isolated from Glycine max, C. ternatea formed many effective nodules with B. elkanii, especially USDA61. However, acetylene reduction activity per plant and the growth were higher in C. ternatea inoculated with our isolates. From these data we propose that effective rhizobia inoculant were identified for C. ternatea cultivation.
Pesticide residues contributing to the contamination of soil may influence microbial population of the soil and in turn fertility of soil. The present paper reports the effect of pesticides applied to soybean i.e. phorate, carbofuran,... more
Pesticide residues contributing to the contamination of soil may influence microbial population of the soil and in turn fertility of soil. The present paper reports the effect of pesticides applied to soybean i.e. phorate, carbofuran, carbosulfan, thiomethoxam, imidacloprid, chlorpyriphos and monocrotophos on soil microflora. The viable count of rhizobia and phosphate solubilizing bacteria from rhizospheric soil of soybean ranged between 10(7)-10(8) cfu/g soil which was comparable to the count of bacteria from untreated (control) soil. No significant change in the total viable count of any kind of bacteria due to application of pesticides has been found showing their ability to degrade these pesticides.
Malgre l’importance des representants du genre Lotus en Algerie, leur statut symbiotique et la nature des Rhizobia qui leurs sont associes sont meconnus. Cette etude portant sur 39 plants de Lotus appartenant a 15 especes nous a permis de... more
Malgre l’importance des representants du genre Lotus en Algerie, leur statut symbiotique et la nature des Rhizobia qui leurs sont associes sont meconnus. Cette etude portant sur 39 plants de Lotus appartenant a 15 especes nous a permis de verifier qu’ils sont tous nodules et fixateurs d’azote et d’isoler a partir de leurs nodules 38 souches de BNL (Bacteries Nodulant les Legumineuses) qui ont ete authentifiees. Le sequencage du gene de l’ARNr 16S de ces 38 souches de Rhizobia montre une predominance de souches du genre Mesorhizobium represente par 10 especes parmi lesquelles M. erdmanii, M. ciceri et M. jarvisii se sont montrees les plus importantes. La nodulation des especes de Lotus examinees est assuree dans une moindre mesure par des souches des genres Bradyrhizobium et Ensifer, tous deux representes par deux especes. Cette etude a permis, d’une part, de reveler la diversite des Rhizobia associes aux Lotus d’Algerie, et d’autre part, de mettre en evidence une faible implication dans la nodulation des ...
The present study aims to assess the effect of phosphate solubilizing bacteria (PSB) in interaction with native arbuscular mycorrhizal fungi (AMF) and rhizobia on peanut growth cultivated in the Northwest of Morocco. To perform this aim,... more
The present study aims to assess the effect of phosphate solubilizing bacteria (PSB) in interaction with native arbuscular mycorrhizal fungi (AMF) and rhizobia on peanut growth cultivated in the Northwest of Morocco. To perform this aim, seeds were inoculated with 5 PSB strains: PP22, GP70, GR1, PR29, and GR70, and then grown in unsterilized soil collected from peanut fields. Plant harvesting was made after 8 weeks of growth under chamber conditions. The results demonstrated that PSB treatments showed positive effect on mycorrhizal colonization, nodulation and plant growth parameters. The best results were found with Pseudomonas strains, GP70, PP22 and GR1. This study indicates the great potential of some PSB to improve yield and nutrient uptake of peanut plants in the presence of native rhizobia and AMF. They could serve as biofertilizers, minimizing chemical fertilization that is currently used to obtain high yields for peanut agriculture. Keywords: AMF, growth, peanut, PSB, rhizobia
