Local genetic structure and worldwide phylogenetic position of symbiotic Rhizobium leguminosarum strains associated with a traditional cultivated crop, Vicia ervilia, from Northern Morocco

Symbiotic efficiency of Rhizobium leguminosarum sv. trifolii strains originating from the subpolar and temperate climate regions

Red clover (Trifolium pratense L.) is a forage legume cultivated worldwide. This plant is capable of establishing a nitrogen-fixing symbiosis with Rhizobium leguminosarum symbiovar trifolii strains. To date, no comparative analysis of the symbiotic properties and heterogeneity of T. pratense microsymbionts derived from two distinct geographic regions has been performed. In this study, the symbiotic properties of strains originating from the subpolar and temperate climate zones in a wide range of temperatures (10-25 °C) have been characterized. Our results indicate that all the studied T. pratense microsymbionts from two geographic regions were highly efficient in host plant nodulation and nitrogen fixation in a wide range of temperatures. However, some differences between the populations and between the strains within the individual population examined were observed. Based on the nodC and nifH sequences, the symbiotic diversity of the strains was estimated. In general, 13 alleles for nodC and for nifH were identified. Moreover, 21 and 61 polymorphic sites in the nodC and nifH sequences were found, respectively, indicating that the latter gene shows higher heterogeneity than the former one. Among the nodC and nifH alleles, three genotypes (I-III) were the most frequent, whereas the other alleles (IV-XIII) proved to be unique for the individual strains. Based on the nodC and nifH allele types, 20 nodC-nifH genotypes were identified. Among them, the most frequent were three genotypes marked as A (6 strains), B (5 strains), and C (3 strains). Type A was exclusively found in the temperate strains, whereas types B and C were identified in the subpolar strains. The remaining 17 genotypes were found in single strains. In conclusion, our data indicate that R. leguminosarum sv. trifolii strains derived from two climatic zones show a high diversity with respect to the symbiotic efficiency and heterogeneity. However, some of the R. leguminosarum sv. trifolii strains exhibit very good symbiotic potential in the wide range of the temperatures tested; hence, they may be used in the future for improvement of legume crop production.

Vicia plants-A comprehensive review on chemical composition and phytopharmacology

The plants belonging to the genus Vicia are of great interest as a source of many bioactive compounds and micronutrients. A snapshot of their cultivation, habitat, main components, from which essential oils can be obtained, is given. The traditional medicinal uses of Vicia plants are also reported, as well as the wide spectrum of the main biological activities attributed to Vicia plants is discussed regarding potential health beneficial properties, in particular anti-Parkinson, anticholinesterase, antidepressant, anticonvulsant, antimicrobial, cytotoxic, antioxidant, antiinflammatory and antinociceptive, antidiabetic, antihemolytic, anticoagulant, estrogenic, diuretic, antihypoxic activities.

Genetically diverse lentil- and faba bean-nodulating rhizobia are present in soils across Central and Southern Ethiopia

In total 196 bacterial isolates were obtained from root nodules of lentil (Lens culinaris) and faba bean (Vicia faba) grown on soil samples collected from 10 different sites in central and southern parts of Ethiopia. All isolates were identified as members of the genus Rhizobium by using recA gene sequence analysis. In the recA phylogenetic tree 195 rhizobial strains were classified into nine genospecies. The phylogeny of symbiotic genes nodC and nifH revealed five and six distinct groups respectively, largely dominated by symbiovar viciae. A multivariate analysis showed that environmental variables of the sampling sites considered in this study had more effect on the distribution and composition of the genospecies than the host legumes of the strains. Twenty representative strains, selected based on their isolation site, host plant and nodC group, were able to nodulate all lentil, faba bean, field pea (Pisum abyssinicum) and grass pea (Lathyrus sativus) plants in a greenhouse test in axenic conditions. The majority of the rhizobial strains were effective nitrogen-fixing symbionts for all tested legumes, indicating their potential to serve as broad host-range inoculants in agriculture. The present work suggests the presence of taxonomically and symbiotically diverse rhizobial species for legumes in the Viciae tribe in Ethiopia.

Exploring Genetic Diversity and Signatures of Horizontal Gene Transfer in Nodule Bacteria Associated with Lotus japonicus in Natural Environments

To investigate the genetic diversity and understand the process of horizontal gene transfer (HGT) in nodule bacteria associated with Lotus japonicus, we analyzed sequences of three housekeeping and five symbiotic genes using samples from a geographically wide range in Japan. A phylogenetic analysis of the housekeeping genes indicated that L. japonicus in natural environments was associated with diverse lineages of Mesorhizobium spp., whereas the sequences of symbiotic genes were highly similar between strains, resulting in remarkably low nucleotide diversity at both synonymous and nonsynonymous sites. Guanine-cytosine content values were lower in symbiotic genes, and relative frequencies of recombination between symbiotic genes were also lower than those between housekeeping genes. An analysis of molecular variance showed significant genetic differentiation among populations in both symbiotic and housekeeping genes. These results confirm that the Mesorhizobium genes required for symbiosis with L. japonicus behave as a genomic island (i.e., a symbiosis island) and suggest that this island has spread into diverse genomic backgrounds of Mesorhizobium via HGT events in natural environments. Furthermore, our data compilation revealed that the genetic diversity of symbiotic genes in L. japonicus-associated symbionts was among the lowest compared with reports of other species, which may be related to the recent population expansion proposed in Japanese populations of L. japonicus.

Genetic diversity and structure of Rhizobium leguminosarum populations associated with clover plants are influenced by local environmental variables

The identification and conservation of indigenous rhizobia associated with legume plants and their application as biofertilizers is becoming an agricultural worldwide priority. However, little is known about the genetic diversity and phylogeny of rhizobia in Romania. In the present study, the genetic diversity and population composition of Rhizobium leguminosarum symbiovar trifolii isolates from 12 clover plants populations located across two regions in Romania were analyzed. Red clover isolates were phenotypically evaluated and genotyped by sequencing 16S rRNA gene, 16S-23S intergenic spacer, three chromosomal genes (atpD, glnII and recA) and two plasmid genes (nifH and nodA). Multilocus sequence typing (MLST) analysis revealed that red clover plants are nodulated by a wide genetic diversity of R. leguminosarum symbiovar trifolii sequence types (STs), highly similar to the ones previously found in white clover. Rhizobial genetic variation was found mainly within the two clover populations for both chromosomal and plasmid types. Many STs appear to be unique for this region and the genetic composition of rhizobia differs significantly among the clover populations. Furthermore, our results showed that both soil pH and altitude contributed to plasmid sequence type composition while differences in chromosomal composition were affected by the altitude and were strongly correlated with distance.