Halotolerant Rhizobacterial Strains Mitigate the Adverse Effects of NaCl Stress in Soybean Seedlings

Background. Salinity is one of the major abiotic constraints that hinder health and quality of crops. Conversely, halotolerant plant growth-promoting rhizospheric (PGPR) bacteria are considered biologically safe for alleviating salinity stress. Results. We isolated halotolerant PGPR strains from the rhizospheric soil of Artemisia princeps, Chenopodium ficifolium, Echinochloa crus-galli, and Oenothera biennis plants; overall, 126 strains were isolated. The plant growth-promoting traits of these isolates were studied by inoculating them with the soil used to grow soybean plants under normal and salt stress (NaCl; 200 mM) conditions. The isolates identified as positive for growth-promoting activities were subjected to molecular identification. Out of 126 isolates, five strains—Arthrobacter woluwensis (AK1), Microbacterium oxydans (AK2), Arthrobacter aurescens (AK3), Bacillus megaterium (AK4), and Bacillus aryabhattai (AK5)—were identified to be highly tolerant to salt stress and demonstrated several plant growth-promoting traits like increased production of indole-3-acetic acid (IAA), gibberellin (GA), and siderophores and increased phosphate solubilization. These strains were inoculated in the soil of soybean plants grown under salt stress (NaCl; 200 mM) and various physiological and morphological parameters of plants were studied. The results showed that the microbial inoculation elevated the antioxidant (SOD and GSH) level and K+ uptake and reduced the Na+ ion concentration. Moreover, inoculation of these microbes significantly lowered the ABA level and increased plant growth attributes and chlorophyll content in soybean plants under 200 mM NaCl stress. The salt-tolerant gene GmST1 was highly expressed with the highest expression of 42.85% in AK1-treated plants, whereas the lowest expression observed was 13.46% in AK5-treated plants. Similarly, expression of the IAA regulating gene GmLAX3 was highly depleted in salt-stressed plants by 38.92%, which was upregulated from 11.26% to 43.13% upon inoculation with the microorganism. Conclusion. Our results showed that the salt stress-resistant microorganism used in these experiments could be a potential biofertilizer to mitigate the detrimental effects of salt stress in plants via regulation of phytohormones and gene expression.

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Isolation and characterization of bacteria from tomato and assessment of its plant growth-promoting traits in three economically important crops in Al-Ahsa region, Saudi Arabia

Journal of Environmental Biology ◽

10.22438/jeb/42/4/mrn-1758 ◽

2021 ◽

Vol 42 (4) ◽

pp. 973-981

Author(s):

M.F. Aldayel ◽

◽

A. Khalifa ◽

Keyword(s):

Saudi Arabia ◽

Salt Stress ◽

16S Rrna ◽

Plant Growth ◽

Rrna Gene ◽

Eruca Sativa ◽

Plant Growth Promoting ◽

Number Of Leaves ◽

Growth Promoting ◽

Plant Growth Promoting Traits

Aim: This study aimed to isolate, characterize and assess the plant growth-promoting traits of bacterial isolates inhabiting the rhizosphere of Solanum lycopersicum L. (tomato) against three plants—Eruca sativa, Lepidium sativum and Raphanus sativum—from Saudi Arabia's Al-Ahsa region. Methodology: bacterial isolate designated as SLK10 was obtained from the rhizosphere of tomato grown in the Al-Ahsa region, Saudi Arabia. SLK10 was further characterized morphologically, biochemically and genotypically using 16S rRNA gene sequencing. The roles in alleviating salt stress effects on three important economic crops were also assessed by implementing a cross-inoculation strategy. Results: SLK10 formed a circular, non-pigmented and raised colony with an entire margin. The cells were rod shaped and Gram negative. SLK10 displayed multiple plant growth-stimulating features, such as the solubilization of inorganic phosphate and the production of phytohormones and acetoin. Comparative sequence analysis of 16S rRNA gene revealed that SLK10 belonged to Pseudomonas monteilii, to which it exhibited 99.86% sequence homology. SLK10 significantly promoted the length of primary root, stem and number of leaves in Eruca sativa, Lepidium sativumand Raphanus sativus growing under 1000 ppm salt stress. The number of leaves in L. sativum and R. sativus growing under 2000 ppm salt stress was substantially enhanced by SLK10. Interpretation: SLK10 is a plant growth-promoting bacterium and can be used as a green fertilizer to increase soil fertility and plant productivity in the Eastern region of Saudi Arabia.

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Screening of plant growth-promoting traits in arsenic-resistant bacteria isolated from the rhizosphere of soybean plants from Argentinean agricultural soil

Plant and Soil ◽

10.1007/s11104-012-1543-6 ◽

2012 ◽

Vol 369 (1-2) ◽

pp. 93-102 ◽

Cited By ~ 7

Author(s):

Ana Laura Wevar Oller ◽

Melina A. Talano ◽

Elizabeth Agostini

Keyword(s):

Plant Growth ◽

Agricultural Soil ◽

Resistant Bacteria ◽

Plant Growth Promoting ◽

Growth Promoting ◽

Soybean Plants ◽

Arsenic Resistant Bacteria ◽

Plant Growth Promoting Traits

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Mitigation of NaCl Stress in Wheat by Rhizosphere Engineering Using Salt Habitat Adapted PGPR Halotolerant Bacteria

Applied Sciences ◽

10.3390/app11031034 ◽

2021 ◽

Vol 11 (3) ◽

pp. 1034

Author(s):

Souhila Kerbab ◽

Allaoua Silini ◽

Ali Chenari Bouket ◽

Hafsa Cherif-Silini ◽

Manal Eshelli ◽

...

Keyword(s):

Arabidopsis Thaliana ◽

Salt Stress ◽

Plant Growth ◽

Durum Wheat ◽

Growth Parameters ◽

Nacl Stress ◽

Stress Conditions ◽

Bacterial Strains ◽

Plant Growth Promoting ◽

Growth Promoting

There is a great interest in mitigating soil salinity that limits plant growth and productivity. In this study, eighty-nine strains were isolated from the rhizosphere and endosphere of two halophyte species (Suaeda mollis and Salsola tetrandra) collected from three chotts in Algeria. They were screened for diverse plant growth-promoting traits, antifungal activity and tolerance to different physico-chemical conditions (pH, PEG, and NaCl) to evaluate their efficiency in mitigating salt stress and enhancing the growth of Arabidopsis thaliana and durum wheat under NaCl–stress conditions. Three bacterial strains BR5, OR15, and RB13 were finally selected and identified as Bacillus atropheus. The Bacterial strains (separately and combined) were then used for inoculating Arabidopsis thaliana and durum wheat during the seed germination stage under NaCl stress conditions. Results indicated that inoculation of both plant spp. with the bacterial strains separately or combined considerably improved the growth parameters. Three soils with different salinity levels (S1 = 0.48, S2 = 3.81, and S3 = 2.80 mS/cm) were used to investigate the effects of selected strains (BR5, OR15, and RB13; separately and combined) on several growth parameters of wheat plants. The inoculation (notably the multi-strain consortium) proved a better approach to increase the chlorophyll and carotenoid contents as compared to control plants. However, proline content, lipid peroxidation, and activities of antioxidant enzymes decreased after inoculation with the plant growth-promoting rhizobacteria (PGPR) that can attenuate the adverse effects of salt stress by reducing the reactive oxygen species (ROS) production. These results indicated that under saline soil conditions, halotolerant PGPR strains are promising candidates as biofertilizers under salt stress conditions.

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