Impact of two Erwinia sp. on the response of diverse Pisum sativum genotypes under salt stress

The current study reveals that two non-pathogenic strains of Erwinia sp. are diferent in their PGP traits. By using an integrated approach, a picture of the pea plant status in three genotypes subjected to a salt stress condition was obtained and the role of the two bacterial considered Erwinia sp. strains has been highlighted. Results showed the relevance of plant genotype in determining the response to bacterial inoculants as well as the diferences in the plant mechanisms activated to cope with the stress in the diferent plant/strain combination. Overall, this study emphasizes the importance of understanding the molecular and biochemical processes occurring in plant–microbe interactions at genotype level, and the influence on plant responses to environmental stresses. Further analyses are needed to clarify the behaviour of the three genotypes, such as the leaf water potential, and to verify the efects of the bacterial inoculation in feld conditions, subjectd by an increased environmental unpredictability due to the climate change scenarioCurrently, salinization is impacting more than 50% of arable land, posing a significant challenge to agriculture globally. Salt causes osmotic and ionic stress, determining cell dehydration, ion homeostasis, and metabolic process alteration, thus negatively influencing plant development. A promising sustainable approach to improve plant tolerance to salinity is the use of plant growth-promoting bacteria (PGPB). This work aimed to characterize two bacterial strains, that have been isolated from pea root nodules, initially called PG1 and PG2, and assess their impact on growth, physiological, biochemical, and molecular parameters in three pea genotypes (Merveille de Kelvedon, Lincoln, Meraviglia d'Italia) under salinity. Bacterial strains were molecularly identified, and characterized by in vitro assays to evaluate the plant growth promoting abilities. Both strains were identified as Erwinia sp., demonstrating in vitro biosynthesis of IAA, ACC deaminase activity, as well as the capacity to grow in presence of NaCl and PEG. Considering the inoculation of plants, pea biometric parameters were unaffected by the presence of the bacteria, independently by the considered genotype. Conversely, the three pea genotypes differed in the regulation of antioxidant genes coding for catalase (PsCAT) and superoxide dismutase (PsSOD). The highest proline levels (212.88 μmol g-1) were detected in salt-stressed Lincoln plants inoculated with PG1, along with the up-regulation of PsSOD and PsCAT. Conversely, PG2 inoculation resulted in the lowest proline levels that were observed in Lincoln and Meraviglia d'Italia (35.39 and 23.67 μmol g-1, respectively). Overall, this study highlights the potential of these two strains as beneficial plant growth-promoting bacteria in saline environments, showing that their inoculation modulates responses in pea plants, affecting antioxidant gene expression and proline accumulation

<i>Colutea arborescens</i> is nodulated by diverse rhizobia in Eastern Morocco

Eighteen isolates of rhizobia isolated from root nodules of Colutea arborescens (Bladder senna) grown in different soils of the eastern area of Morocco were characterized by phenotypic and genomic analyses. All the isolates characterized were fast growers. This is may be due to the isolation procedures used. The phenotypic, symbiotic and cultural characteristics analyzed allowed the description of a wide physiological diversity among tested isolates. The results obtained suggest that the phenotype of these rhizobia might have convergent evolved to adapt the local conditions. The genetic characterization consisted in an analysis of the rep-PCR Wngerprints and the PCR-based RFLP of the 16S rDNA patterns. The 16S rDNA of six isolates representing the main ribotypes obtained by the PCR-based RFLP was sequenced. A large diversity was observed among these rhizobia, and they were classified as different species of the genera Rhizobium, Sinorhizobium and Mesorhizobium. The nodC gene was also sequenced, and the results confirmed the three lineages corresponding to the three genera. The results of the sequencing of nodC and 16S rDNA genes suggest that the nodulation genes and chromosome might have co-evolved among these bacteria

Diversity of bacteria that nodulate Prosopis juliflora in the eastern area of Morocco

A total of 274 bacterial strains were isolated from the root nodules of Prosopis juliflora, growing in two arid soils of the eastern area of Morocco. A physiological plate screening allowed the selection of 15 strains that could tolerate NaCl concentrations between 175 and 500 mM. These were compared with 15 strains chosen from among the ones which did not tolerate high salinity. The diversity of strains was first assessed by rep-PCR amplification fingerprinting using BOXA1R and ERIC primers. An analysis of the PCR-amplified 16S rDNA gene digestion profiles using five endonucleases indicated the presence of different lineages among the taxa associated with P. juliflora nodules in the soils studied. Nucleotide sequencing of the small subunit rRNA gene and BLAST analysis showed that P. juliflora could host at least six bacterial species in this region and that the identity of those associated with high salt tolerance was clearly distinct from that of the salt-sensitive ones. Among the former, the first type displayed 99% similarity with different members of the genus Sinorhizobium, the second 97% similarity with species within the genus Rhizobium, while the third ribosomal type had 100% homology to Achromobacter xylosoxidans. Within the salt-sensitive isolates the prevailing type observed showed 98% similarity with Rhizobium multihospitium and R. tropici, a second type had 98% similarity to R. giardinii, and a further case displayed 97% colinearity with the Ensifer group including E. maghrebium and E. xericitae. All of the thirty strains encompassing these types re-nodulated P. juliflora in microbiologically controlled conditions and all of them were shown to possess a copy of the nodC gene. This is the first report detecting the betaproteobacterial genus Achromobacter as nodule-forming species for legumes. The observed variability in symbiont species and the abundance of nodulation-proficient strains is in line with the observation that the plant always appears to be nodulated and efficiently fixing nitrogen in spite of a wide range of soil and environmental conditions

Physico-chemical, functional, and structural properties of un-defatted, cold and hot defatted yellow lupin protein isolates

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Caractérisation génomique des microsymbiotes de légumineuses candidates pour la lutte contre la désertification Lupinus luteus et Chameacytisus albidus

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Molecular characterization of arbuscular mycorrhizal communities associated with Lathyrus cicera L. grown in northern Tunisia soils

International audienceArbuscular mycorrhizal fungi (AMF) are obligate symbionts that form a mutualistic symbiosis with a wide variety of plant species including legumes. Lathyrus cicera (red pea), is an important annual legume crop cultivated in several drought-prone areas of the world. Limited information is available on AMF diversity associated with red pea and agricultural practices that promote AMF community richness. The article examines the influence of agricultural management practices on AMF species associated with red pea grown in northern Tunisia. Furthermore, we explored AMF communities associated with L. cicera among major soil types in the sub-humid agro-ecosystems of northern Tunisia. The focus was on the effects of environmental factors on the abundance and diversity of AMF communities in rhizospheric soils and root samples. MiSeq amplicon sequencing was used to identify AMF species colonizing the roots and rhizospheric soil of L. cicera. There were 435 amplicon sequence variants (ASVs) identified, representing 25 AMF virtual taxa (VTs) from 5 AMF genera: Glomus >> Claroideoglomus >> Diversipora > Paraglomus > Scutellospora. In summary, agricultural management practices had no impact on AMF colonization in root plants grown in soil under study. The redundancy analysis, however, revealed that soil properties such as salinity, available P and total N have an impact on the distribution and abundance of AMF, especially in Glomus spp

Genetic diversity, phenotypic traits, and symbiotic efficiency of native Bradyrhizobium strains of Lupinus luteus in Morocco

International audienceBackground and aims In Morocco’s semi-arid and sub-humid climates, the fodder legume Lupinus luteus is cultivated for its high economic and ecological value. In this work, we characterized some microsymbionts of L. luteus isolated by trapping from plants grown in soils of the agricultural area of Zaer, Morocco.Methods The phenotypic and genotypic diversity, the plant growth-promoting abilities, and the symbiotic efficiency of rhizobia isolated from rootnodules of L. luteus were analyzed.Results Based on their REP-PCR fingerprinting results, eighteen strains were selected for Multilocus sequence analysis (MLSA) using rrs, glnII, gyrB, recA, and rpoB housekeeping genes, which revealed that all the strains belong to the genus Bradyrhizobium. Some strains were close to B. lupini and B. canariense. However, the remaining strains grouped apart from all described Bradyrhizobium species.Phylogenetic analysis of the nodA and nodC symbiotic genes showed that all the strains are members of the symbiovar genistearum. Quantitative evaluation of selected plant growth-promoting activities showed that the strains solubilize phosphate, and produce auxins and siderophores. All the strains used as inoculum in greenhouse experiments significantly improved the growth of L. luteus under nitrogen-free conditions.Conclusions Bradyrhizobium lupini and B. canariense are the main rhizobia nodulating L. luteus in the Zaer region. In addition to their high nitrogen fixation efficiency, these isolates also exhibit plant growthpromoting activities. These results highlighted one of the major reasons for the success of yellow lupine in this area without nitrogen fertilizers and pointed to the possibility of formulating these rhizobia into aneffective inoculum for L. luteu

Genotypic and symbiotic diversity studies of rhizobia nodulating Acacia saligna in Tunisia reveal two novel symbiovars within the Rhizobium leguminosarum complex and Bradyrhizobium

International audienceAcacia saligna is an invasive alien species that has the ability to establish symbiotic relationships with rhizobia. In the present study, genotypic and symbiotic diversity of native rhizobia associated with A. saligna in Tunisia were studied. A total of 100 bacterial strains were selected and three different ribotypes were identified based on rrs PCR-RFLP analysis. Sequence analyses of rrs and four housekeeping genes (recA, atpD, gyrB and glnII) assigned 30 isolates to four putative new lineages and a single strain to Sinorhizobium meliloti. Thirteen slow-growing isolates representing the most dominant IGS (intergenic spacer) profile clustered distinctly from known rhizobia species within Bradyrhizobium with the closest related species being Bradyrhizobium shewense and Bradyrhizobium niftali, which had 95.17% and 95.1% sequence identity, respectively. Two slow-growing isolates, 1AS28L and 5AS6L, had B. frederekii as their closest species with a sequence identity of 95.2%, an indication that these strains could constitute a new lineage. Strains 1AS14I, 1AS12I and 6AS6 clustered distinctly from known rhizobia species but within the Rhizobium leguminosarum complex (Rlc) with the most closely related species being Rhizobium indicum with 96.3% sequence identity. Similarly, the remaining 11 strains showed 96.9 % and 97.2% similarity values with R. changzhiense and R. indicum, respectively. Based on nodC and nodA phylogenies and cross inoculation tests, these 14 strains of Rlc species clearly diverged from strains of Sinorhizobium and Rlc symbiovars, and formed a new symbiovar for which the name sv. “salignae” is proposed. Bacterial strains isolated in this study that were taxonomically assigned to Bradyrhizobium harbored different symbiotic genes and the data suggested a new symbiovar, for which sv. “cyanophyllae” is proposed. Isolates formed effective nodules on A. saligna

Rhizobium acaciae sp. nov., a new nitrogen-fixing symbiovar isolated from root nodules of Acacia saligna in Tunisia

International audienceThe draft genome sequences of 1AS11 T , 1AS12 and 1AS13 were deposited under the accession numbers JAPCZM000000000, JAPCZN000000000 and JAPCZO000000000, respectively.The Illumina NovaSeq 6000 raw reads are deposited in the Sequence Read Archive under bioproject number PRJNA893020