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Salinity is one of the main factors causing soil deterioration, making it unsuitable for agriculture. It is well documented that the application of halotolerant and halophilic plant growth-promoting bacteria (PGPR: plant growth-promoting rhizobacteria) with biological control activities as an inoculant of cultivated plants offers a biological alternative to the use of agrochemicals, particularly when subjected to salt stress. From this perspective, 70 bacterial strains were isolated from saline soils (sebkha) in arid and semi-arid areas of Eastern Algeria. Three isolates were selected based on their ability to produce bioactive molecules allowing them to promote plant growth, such as hydrolytic enzymes, indole acetic acid (auxin-phytohormone), HCN, NH3, etc. Two of these isolates belonged to the genus Serratia and the third was a halophilic Halomonas bacteria. These bacteria were identified based on their 16S rDNA sequences. Antagonism tests against phytopathogenic fungi were carried out. The identification of the antifungal molecules produced by these bacteria was determined using high-performance liquid chromatography. These bacteria can inhibit mycelial development against phytopathogenic fungi with rates reaching 80.67% against Botrytis cinerea, 76.22% against Aspergillus niger, and 66.67% against Fusarium culmorum for Serratia sp. The strain Halomonas sp. inhibited mycelial growth through the production of volatile substances of Aspergillus niger at 71.29%, Aspergillus flavus at 75.49%, and Penicillium glabrum at a rate of 72.22%. The identification of the antifungal molecules produced by these three bacteria using HPLC revealed that they were polyphenols, which makes these strains the first rhizobacteria capable of producing phenolic compounds. Finally, pot tests to determine the effectiveness of these strains in promoting wheat growth under salinity stress (125 mM, 150 mM, and 200 mM) was carried out. The results revealed that a consortium of two isolates (Serratia sp. and Halomonas sp.) performed best at 125 mM. However, at higher concentrations, it was the halophilic bacteria Halomonas sp. that gave the best result. In all cases, there was a significant improvement in the growth of wheat seedlings inoculated with the bacteria compared to non-inoculated controls. [ABSTRACT FROM AUTHOR]

This work is part of the exsitu conservation of Ruta montana (L.) L., a spontaneous Rutaceae, known for its many therapeutic properties. The aim is to study, under controlled conditions, the effects of daylight and darkness, temperature, salt, and water stress on the germination of its seeds. Salt stress was induced by different molar concentrations of NaCl (0–200 mM), and water stress was simulated using different concentrations of polyethylene glycol (PEG6000) corresponding to different water potentials (0-1.2 MPa). The results obtained showed that R. montana seeds were viable and could germinate both in daylight and in continuous darkness. Germination was possible at temperatures between 10 and 30 °C, with the maximum final germination percentage (FGP = 81.66%) recorded at 20 °C. At this optimum temperature, FGP decreased significantly when the seeds were placed under salt and water stress (p< 0.01).This decrease became more and more significant when the osmotic pressure induced by NaCl increased and when the water potential induced by PEG6000 in the medium decreased. The depressive effect of salt and water stress on FGP was verified by a linear regression analysis, which showed high values of the coefficient of determination (R2):0.934 for water stress and 0.890 for salt stress. This effect on the velocity coefficient and latency time was more moderate or lower. The thresholds of tolerance to salinity and water deficit found were 150 mM and −1 MPa, respectively, for which the lowest FGP values were recorded with 16.25% for water stress and 11.10% for salt stress. [ABSTRACT FROM AUTHOR]

Albardine (Lygeum spartum L.) is one of the major native grass species of the semi-arid and arid regions of the Mediterranean basin. In Algeria, it is much more widespread on the high plateaus of southern Oranais. This species occupies an important place in the steppe region because it has many ecological, economic, and fodder interests. The present work aims to study the tolerance of L. spartum seeds to water and salt stress, two abiotic factors that affect the physiology of the plant during the germinal stage. The methodology adopted consists of using increasing concentrations under a controlled temperature (15°C) for 21 days of germination. The germination responses of the seeds to different degrees of salt stress induced by NaCl (2, 4, 6, 8, 10 g/l) and water stress induced by polyethylene glycol (PEG;−2, -4, -6, -8, −10 bar), showed that the salt and water stresses retarded the germination rate of L. spartum L. seeds and also decreased their percentage during the time of the experiment. However, seeds soaked in distilled water (control) recorded a maximum germination rate of 80%. The results of this study show that L. spartum seeds are moderately salt and drought tolerant with a depressive effect on germination rate at a salt concentration of 10g/l and an osmotic pressure of −10 bar. [ABSTRACT FROM AUTHOR]

The Alpha grass steppes (Stipa tenacissima) are one of the most representative steppes in the Mediterranean arid ecosystems. They are in continuous regression due to a strong climatic and anthropic pressure without forgetting the difficulties of natural regeneration. Our work is based on the conservation of this species, it consists of carrying out a comparative study of the germinative behavior of Alpha grass caryopses from the coast and the steppe (Western Algeria) under the effect of salt and water stress. For each provenance, each germination trial was conducted at the optimum temperature of 20°C and involved four batches of caryopses with 25 caryopses per batch. The effect of salt stress was tested under different salt concentrations prepared from sodium chloride: 0, 1, 2, 4, 6 and 8 g.L-1 corresponding to the molar concentrations of 0, 17.11, 34.22, 68.44, 102.66 and 136.89 mM. The effect of water stress was evaluated under different concentrations of polyethylene glycol (PEG6000) corresponding to water potentials of: - 0.04; - 0.2; - 0.4; - 0.8 and - 1.6 MPa. The results obtained showed that the salinity and the water potential directly affect the germination capacity of the caryopses of both provenances. However, coastal caryopses are more resistant to salinity than steppe caryopses with a tolerance threshold corresponding to 8g.L-1 (136.89 mM) of NaCl. Also, the coastal caryopses are much more resistant to water deficit than the steppe caryopses, they are able to germinate at a low water potential (-1.6 Mpa). [ABSTRACT FROM AUTHOR]

Salinity causes significant agricultural losses in many areas in the world. Plant growth promoting bacteria (PGPB) are a promising solution to enhance plant growth and productivity under such stress conditions by different mechanisms, mainly phosphorous solubilization. This study aims to improve wheat seedling growth under salt stress by a halotolerant phosphorous-solubilizing bacterial strain. Soil sample was collected in the south of Algeria (Ghardaia), and bacterial isolation was carried out on nutrient agar (NA) at different NaCl concentrations (300; 600 and 900 mM). The ability of the halotolerant isolates to solubilize inorganic phosphorous at 0; 300; 600 and 900 mM NaCl was determined. The isolate that showed the highest solubilization indexes was selected and identified as Pseudomonas azotoformans. Sterile wheat (Triticum aestivum) seeds were inoculated by this strain and then sown in soil at different NaCl concentrations (0; 100; 200; 300 mM). Different growth parameters were measured after 15 days. The strain showed its highest capacity for phosphorous solubilization (255.152 ± 0.01 µg/mL) at 300 mM NaCl, and for phytate mineralization (0.168 ± 0.002 U/mL) at 100 mM NaCl. The highest amount of soluble phosphorous in the soil was 49.42 ± 0.36 ppm obtained at 100 mM NaCl. Seed germination percentage, shoot and root length and fresh and dry weights were found to be higher in bacterial inoculated seedlings compared to uninoculated ones. According to this study, the use of plant growth promoting bacteria represents an important biotechnological approach to restore phosphorous levels in saline soils and to promote plant growth in salt-affected agricultural land. [ABSTRACT FROM AUTHOR]

Endophytic strains belonging to the Bacillus cereus group were isolated from the halophytes Atriplex halimus L. (Amaranthaceae) and Tamarix aphylla L. (Tamaricaceae) from costal and continental regions in Algeria. Based on their salt tolerance (up to 5%), the strains were tested for their ability to alleviate salt stress in tomato and wheat. Bacillus sp. strain BH32 showed the highest potential to reduce salinity stress (up to + 50% and + 58% of dry weight improvement, in tomato and wheat, respectively, compared to the control). To determine putative mechanisms involved in salt tolerance and plant growth promotion, the whole genome of Bacillus sp. BH32 was sequenced, annotated, and used for comparative genomics against the genomes of closely related strains. The pangenome of Bacillus sp. BH32 and its closest relative was further analyzed. The phylogenomic analyses confirmed its taxonomic position, a member of the Bacillus cereus group, with intergenomic distances (GBDP analysis) pinpointing to a new taxon (digital DNA-DNA hybridization, dDDH < 70%). Genome mining unveiled several genes involved in stress tolerance, production of anti-oxidants and genes involved in plant growth promotion as well as in the production of secondary metabolites. Key points : • Bacillus sp. BH32 and other bacterial endophytes were isolated from halophytes, to be tested on tomato and wheat and to limit salt stress adverse effects. • The strain with the highest potential was then studied at the genomic level to highlight numerous genes linked to plant growth promotion and stress tolerance. • Pangenome approaches suggest that the strain belongs to a new taxon within the Bacillus cereus group. [ABSTRACT FROM AUTHOR]

Halotolerant plant-growth-promoting rhizobacteria (PGPR) could not only promote plant growth, but also help in counteracting the detrimental effects of salt stress. In the present study, a total of 76 bacteria were isolated from the rhizosphere, non-rhizospheric soil and endophytes of the halophyte Salsola tetrandra, collected from natural saline soils in Algeria. Phylogenetic analysis based on the 16S rDNA sequence of Gram-negative bacteria (n = 51) identified, showed seventeen representative isolates grouped into four genera (Pseudomonas, Acinetobacter, Enterobacter, and Providencia). These bacterial isolates that exhibited different PGPR traits were selected and tested for their ability to tolerate different abiotic stress (NaCl, PEG8000, and pH). The majority of isolates were drought tolerant (60% of PEG8000) and had an optimal growth at high pH values (pH 9 and 11) and some strains tolerated 2 M of NaCl. Strains identified as Enterobacter xiangfangensis BE1, Providencia rettgeri BR5 and Pseudomonas stutzeri MLR6 showed high capacity of adaptation on their PGP traits. The salt-tolerant isolates were finally chosen to promote growth and enhance salt tolerance, separately or combined, of Arabidopsis thaliana (Col-0) exposed or not to 0.1 M NaCl, by following fresh and root weight, primary root elongation and lateral root number. The best bacterial effect was recorded for the MLR6 strain in increasing shoot fresh weight and for BE1 in terms of root fresh weight in the absence of salt stress. At stressed conditions, all growth parameters declined. However, inoculation of Arabidopsis thaliana with the three bacterial strains (MLR6, BE1 and BR5), single or in co-culture, conferred an increase in the shoot weight, primary root length and lateral root number. The use of these strains separately or combined as biofertilizers seems to be a powerful tool in the development of sustainable agriculture in saline soils. [ABSTRACT FROM AUTHOR]