Growth and heavy metals uptake by Vicia Faba in mining soil and tolerance of its symbiotic rhizobacteria

International audienceFaba bean plants in the 1/8 mixture with soil had the ability to accumulate Pb, Zn and Cu. 95% of the absorbed Pb were in the roots, and Cu and Zn were found in the shoots by 35% and 45%, respectively. There was a decrease in the root hairs and the number of cell layers of the root cortex alongside epidermis lesions. From the 50 tested rhizobacterial strains, 20 were able to grow at 150 mg/dm3 of Pb, 6 were resistant to 150 mg/dm3 of Zn and 8 resisted to 20 mg/dm3 of Cu. Best four strains had adsorption potentials and the biosorption was higher for Cu. These strains were capable of producing auxin and exopolysaccharides. The most tolerant strains (FD1 and FD2) isolated near the mining site produced siderophores and high amounts of exopolysaccharides. The use of such strains and V. faba could be of important biotechnological value in decreasing heavy metal pollution of mining soils

Phytobeneficial bacteria improve saline stress tolerance in Vicia faba and modulate microbial interaction network

International audienceIncreased global warming, caused by climate change and human activities, will seriously hinder plant development, such as increasing salt concentrations in soils, which will limit water availability for plants. To ensure optimal plant growth under such changing conditions, microorganisms that improve plant growth and health must be integrated into agricultural practices. In the present work, we examined the fate of Vicia faba microbiota structure and interaction network upon inoculation with plant-nodulating rhizobia (Rhizobium leguminosarum RhOF125) and non-nodulating strains (Paenibacillus mucilaginosus BLA7 and Ensifer meliloti RhOL1) in the presence (or absence) of saline stress. Inoculated strains significantly improved plant tolerance to saline stress, suggesting either a direct or indirect effect on the plant response to such stress. To determine the structure of microbiota associated with V. faba, samples of the root-adhering soil (RAS), and the root tissues (RT) of seedlings inoculated (or not) with equal population size of RhOF125, BLA7 and RhOL1 strains and grown in the presence (or absence) of salt, were used to profile the microbial composition by 16S rRNA gene sequencing. The inoculation did not show a significant impact on the composition of the RT microbiota or RAS microbiota. The saline stress shifted the RAS microbiota composition, which correlated with a decrease in Enterobacteriaceae and an increase in Sphingobacterium, Chryseobacterium, Stenotrophomonas, Agrobacterium and Sinorhizobium. When the microbiota of roots and RAS are considered together, the interaction networks for each treatment are quite different and display different key populations involved in community assembly. These findings indicate that upon seed inoculation, community interaction networks rather than their composition may contribute to helping plants to better tolerate environmental stresses. The way microbial populations interfere with each other can have an impact on their functions and thus on their ability to express the genes required to help plants tolerate stresses

Growth and heavy metals uptake by Vicia faba in mining soil and tolerance of its symbiotic rhizobacteria

Faba bean plants in the 1/8 mixture with soil had the ability to accumulate Pb, Zn and Cu. 95% of the absorbed Pb were in the roots, and Cu and Zn were found in the shoots by 35% and 45%, respectively. There was a decrease in the root hairs and the number of cell layers of the root cortex alongside epidermis lesions. From the 50 tested rhizobacterial strains, 20 were able to grow at 150 mg/dm3 of Pb, 6 were resistant to 150 mg/dm3 of Zn and 8 resisted to 20 mg/dm3 of Cu. Best four strains had adsorption potentials and the biosorption was higher for Cu. These strains were capable of producing auxin and exopolysaccharides. The most tolerant strains (FD1 and FD2) isolated near the mining site produced siderophores and high amounts of exopolysaccharides. The use of such strains and V. faba could be of important biotechnological value in decreasing heavy metal pollution of mining soils

Protective Role of Native Rhizospheric Soil Microbiota Against the Exposure to Microcystins Introduced into Soil-Plant System via Contaminated Irrigation Water and Health Risk Assessment

Microcystins (MCs) produced in eutrophic waters may decrease crop yield, enter food chains and threaten human and animal health. The main objective of this research was to highlight the role of rhizospheric soil microbiota to protect faba bean plants from MCs toxicity after chronic exposure. Faba bean seedlings were grown in pots containing agricultural soil, during 1 month under natural environmental conditions of Marrakech city in Morocco (March–April 2018) and exposed to cyanobacterial extracts containing up to 2.5 mg·L−1 of total MCs. Three independent exposure experiments were performed (a) agricultural soil was maintained intact “exposure experiment 1”; (b) agricultural soil was sterilized “exposure experiment 2”; (c) agricultural soil was sterilized and inoculated with the rhizobia strain Rhizobium leguminosarum RhOF34 “exposure experiment 3”. Overall, data showed evidence of an increased sensitivity of faba bean plants, grown in sterilized soil, to MCs in comparison to those grown in intact and inoculated soils. The study revealed the growth inhibition of plant shoots in both exposure experiments 2 and 3 when treated with 2.5 mg·L−1 of MCs. The results also showed that the estimated daily intake (EDI) of MCs, in sterilized soil, exceeded 2.18 and 1.16 times the reference concentrations (0.04 and 0.45 µg of microcysin-leucine arginine (MC-LR). Kg−1 DW) established for humans and cattle respectively, which raises concerns about human food chain contamination