Novel associations between rhizobial populations and legume species within the genera Lathyrus and O xytropis grown in the temperate region of China

Phenotypic and genotypic diversity of root nodule bacteria from wild Lathyrus and Vicia species in Gaziantep, Turkey

This study identified the phenotypic and genotypic characteristics of the bacteria that nodulate wild Lathyrus and Vicia species natural distribution in the Gaziantep province of Turkey. Principle component analysis of phenotypic features revealed that rhizobial isolates were highly resistant to stress factors such as high salt, pH and temperature. They were found to be highly sensitive to the concentrations (mg/mL) of the antibiotics neomycin 10, kanamycin, and tetracycline 5, as well as the heavy metals Ni 10, and Cu 10, and 5. As a result of REP-PCR analysis, it was determined that the rhizobial isolates were quite diverse, and 5 main groups and many subgroups being found. All of the isolates nodulating wild Vicia species were found to be related to Rhizobium sp., and these isolates were found to be in Clades II, III, IV, and V of the phylogenetic tree based on 16S rRNA. The isolates that nodulated wild Lathyrus species were in Clades I, II, IV, V, VI, VII, and VIII, and they were closely related to Rhizobium leguminasorum, Rhizobium sp., Phyllobacterium sp., Serratia sp., and Pseudomonas sp. According to the genetic analyses, the isolates could not be classified at the species level, the similarity ratio was low, they formed a distinct group that was supported by strong bootstrap values in the phylogenetic tree, and the differences discovered in the network analysis revealed the diversity among the isolates and gave important findings that these isolates may be new species.

Genotypic and symbiotic diversity of native rhizobia nodulating red pea (Lathyrus cicera L.) in Tunisia

Nodulation and genetic diversity of native rhizobia nodulating Lathyrus cicera plants grown in 24 cultivated and marginal soils collected from northern and central Tunisia were studied. L. cicera plants were nodulated and showed the presence of native rhizobia in 21 soils. A total of 196 bacterial strains were selected and three different ribotypes were revealed after PCR-RFLP analysis. The sequence analysis of the rrs and two housekeeping genes (recA and thrC) from 36 representative isolates identified Rhizobium laguerreae as the dominant (53%) rhizobia nodulating L. cicera. To the best of our knowledge, this is the first time that this species has been reported among wild populations of the rhizobia-nodulating Lathyrus genus. Twenty-five percent of the isolates were identified as R. leguminosarum and isolates LS11.5, LS11.7 and LS8.8 clustered with Ensifer meliloti. Interestingly, five isolates (LS20.3, LS18.3, LS19.10, LS1.2 and LS21.20) were segregated from R. laguerreae and clustered as a separate clade. These isolates possibly belong to new species. According to nodC and nodA phylogeny, strains of R. laguerreae and R. leguminosarum harbored the symbiotic genes of symbiovar viciae and clustered in three different clades showing heterogeneity within the symbiovar. Strains of E. meliloti harbored symbiotic genes of Clade V and induced inefficient nodules.

Rhizobium anhuiense as the predominant microsymbionts of Lathyrus maritimus along the Shandong Peninsula seashore line

Beach pea [Lathyrus maritimus Bigelow, or Lathyrus japonicus subsp. maritimus (L.) P.W. Ball] is a wild legume distributed on the seashore line, and the rhizobia nodulating with this plant have been reported only rarely. In order to reveal the diversity of beach pea rhizobia on the seashore line of Shandong Peninsula, China, a total of 124 bacterial strains were isolated from the root nodules of beach pea plants collected from five sites. All the isolates were divided into five recA types after screening by recA gene sequence analysis and they consisted of Rhizobium anhuiense covering 122 symbiotic isolates in three recA types, as well as two single isolates Rhizobium sp. and Rhizobium lusitanum representing distinct recA types. The recA genotype III of R. anhuiense (103 isolates) represented by strain YIC11270 was dominant at all five sampling sites. Identical symbiotic genes (nodC and nifH) were detected in the three recA genotypes of R. anhuiense isolates that were closely related to those of the pea and faba rhizobia. This study clarified that R. anhuiense was the main symbiont for beach pea rhizobia on the seashore line of Shandong Peninsula. The low level genetic diversity of beach pea rhizobia revealed by both MLSA and the symbiotic genes might be related to the strong selection pressure produced by the saline-alkaline environment and the host plants.

Assessing genotypic diversity and symbiotic efficiency of five rhizobial legume interactions under cadmium stress for soil phytoremediation

In the framework of soil phytoremediation using local legume plants coupled with their native root-nodulating bacteria to increase forage yields and preserve contaminated soils in arid regions of Tunisia, we investigated the diversity of bacteria from root nodules of Lathyrus sativus, Lens culinaris, Medicago marina, M. truncatula, and M. minima and the symbiotic efficiency of these five legume symbiosis under Cadmium stress. Fifty bacterial strains were characterized using physiological and biochemical features such heavy metals resistant, and PCR-RFLP of 16S rDNA. Taxonomically, the isolates nodulating L. sativus, and L. culinaris are species within the genera Rhizobium and the ones associated to Medicago sp, within the genera Sinorhizobium. The results revealed also that the cadmium tolerance of the different legumes-rhizobia interaction was as follows: M. minima < M. truncatula < M. marina < L. sativus < L. culinaris indicating that the effect of Cadmium on root nodulation and biomass production is more deleterious on M. minima-S. meliloti and M. truncatula-S. meliloti than in other symbiosis. Knowledge on genetic and functional diversity of M. marina, L. sativus and L. culinaris microsymbiotes is very useful for inoculant strain selection and can be selected to develop inoculants for soil phytoremediation.

Molecular diversity of native rhizobia trapped by five field pea genotypes in Indian soils

Five pea cultivars; HFP 4, HVP 3-5, HFP 9426, Jayanti and Hariyal, being grown in CCS Haryana Agricultural University farm were used to isolate native rhizobia. Selected 54 rhizobia, from all cultivars, were authenticated as rhizobia by plant infectivity test. Along with nodulation, symbiotic effectiveness in terms of symbiotic ratios showed wide range of effectiveness of pea rhizobia from 1.11 to 5.0. DNA of all the 54 rhizobia was extracted and amplified by PCR, using ERIC and 16S rDNA primers. Dendrogram based on ERIC profiles of these 54 rhizobia showed the formation of 13 subclusters at 80% level of similarity. Dendrogram based on RFLP of 16S rDNA by three restriction endonucleases; Msp I, Csp 6I and Rsa I; also formed 13 subclusters at 80% level of similarity. However, positioning of subclusters was different from that of ERIC based dendrogram. Majority of the isolates i.e. 64.8% by ERIC profiles and 44.4% by RFLP of 16S rDNA formed one cluster. Isolates from same nodule were not 100% similar. Considering each cluster representing a rhizobial genotype, both techniques used to assess molecular diversity indicated the presence of 13 genotypes of field pea rhizobia in CCS Haryana Agricultural University farm soil. Two pea rhizobial genotypes were able to nodulate all the five pea cultivars. Furthermore, high strain richness index (0.43-0.5) of field pea rhizobia was observed by both the techniques.