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Background Salinity is a major threat to the agriculture industry due to the negative impact of salinity stress on crop productivity. In the present study, we isolated rhizobacteria and evaluated their capacities to promote crop growth under salt stress conditions. Results We isolated rhizospheric bacteria from sand dune flora of Pohang beach, Korea, and screened them for plant growth-promoting (PGP) traits. Among 55 bacterial isolates, 14 produced indole-3-acetic acid (IAA), 10 produced siderophores, and 12 produced extracellular polymeric and phosphate solubilization. Based on these PGP traits, we selected 11 isolates to assess for salinity tolerance. Among them, ALT29 and ALT43 showed the highest tolerance to salinity stress. Next, we tested the culture filtrate of isolates ALT29 and ALT43 for IAA and organic acids to confirm the presence of these PGP products. To investigate the effects of ALT29 and ALT43 on salt tolerance in soybean, we grew seedlings in 0 mM, 80 mM, 160 mM, and 240 mM NaCl treatments, inoculating half with the bacterial isolates. Inoculation with ALT29 and ALT43 significantly increased shoot length (13%), root length (21%), shoot fresh and dry weight (44 and 35%), root fresh and dry weight (9%), chlorophyll content (16–24%), Chl a (8–43%), Chl b (13–46%), and carotenoid (14–39%) content of soybean grown under salt stress. Inoculation with ALT29 and ALT43 also significantly decreased endogenous ABA levels (0.77-fold) and increased endogenous SA contents (6–16%), increased total protein (10–20%) and glutathione contents, and reduced lipid peroxidation (0.8–5-fold), superoxide anion (21–68%), peroxidase (12.14–17.97%), and polyphenol oxidase (11.76–27.06%) contents in soybean under salinity stress. In addition, soybean treated with ALT29 and ALT43 exhibited higher K + uptake (9.34–67.03%) and reduced Na + content (2–4.5-fold). Genes involved in salt tolerance, GmFLD19 and GmNARK , were upregulated under NaCl stress; however, significant decreases in GmFLD19 (3–12-fold) and GmNARK (1.8–3.7-fold) expression were observed in bacterial inoculated plants. Conclusion In conclusion, bacterial isolates ALT29 and ALT43 can mitigate salinity stress and increase plant growth, providing an eco-friendly approach for addressing saline conditions in agricultural production systems.

Among abiotic stresses, salinity is a significant limiting factor affecting agricultural productivity, survival, and production, resulting in significant economic losses. Considering the salinity problem, the goal of this study was to identify a halotolerant beneficial soil bacterium to circumvent salinity-induced phytotoxicity. Here, strain KR-17 (having an irregular margin; a mucoid colony; Gm-ve short rod; optimum temperature, 30°C; pH 7.0; no any pigmentation; showed a positive response to citrate utilization, catalase, starch, sucrose, lactose, and dextrose, etc.) recovered from rhizosphere soils of the potato-cultivating field, tolerated surprisingly a high (18% NaCl; 3.-M concentration) level of salt and identified as Kosakonia radicincitans (Accession No. OM348535). This strain was discovered to be metabolically active, synthesized essential PGP bioactive molecules like indole-3-acetic acid (IAA), siderophore (iron-chelating compounds), ACC deaminase, and ammonia, the quantity of which, however, increased with increasing NaCl concentrations. Here, Raphanus sativus L. (radish) was taken as a model crop to evaluate the adverse impact of NaCl, as well as salinity alleviation by halotolerant K. radicincitans . Salinity-induced toxicity to R. sativus was increased in a dose-dependent way, as observed both in vitro and in vivo conditions. Maximum NaCl levels (15%) demonstrated more extreme harm and considerably reduced the plant's biological features. However, membrane damage, relative leaf water content (RLWC), stressor metabolites, and antioxidant enzymes were increased as NaCl concentration increased. In contrast, halotolerant K. radicincitans KR-17 relieved salinity stress and enhanced the overall performance of R. sativus (L.) by increasing germination efficiency, dry biomass, and leaf pigments even in salt-challenged conditions. Additionally, KR-17 inoculation significantly ( p ≤ 0.05) improved plant mineral nutrients (Na, K, Ca, Mg, Zn, Fe, Cu, P, and N). Following inoculation, strain KR-17 enhanced the protein, carbohydrates, root pigments, amino acids (AsA and Lys), lipids, and root alkaloids in R. sativus (L.). Besides these, due to PGPR seed priming in NaCl-stressed/non-stressed conditions, membrane damage, RLWC, stressor metabolites, and antioxidant defense enzymes were dramatically reduced. The strong biofilm-forming capacity of K. radicincitans could result in both in vitro and in vivo colonization under NaCl stress. Conclusively, halotolerant K. radicincitans KR-17 may probably be investigated affordably as the greatest way to increase the production of radish under salinity-stressed soils.

Salt stress caused by sodic soils is an important constraint that impacts the production of crucial solanaceous vegetable crops globally. Halotolerant poly-extremophiles rhizobacteria can inhabit hostile environments like salinity, drought, etc. The present study was aimed to design a halotolerant micro-formulation using highly salt-tolerant bacterial strains previously isolated from salt-tolerant rice and wheat rhizosphere in sodic soil. Nine halotolerant isolates were examined for plant growth-promoting traits and biomass production in pot studies with sodic soil of pH 9.23 in tomato. Compatible, efficient isolates were aimed to be formulated into different consortia like PGPR-C1, PGPR-C2 and, PGPR-C3 for field evaluation in sodic soils of pH 9.14. Halotolerant rhizobacterial consortia (PGPR-C3) comprising Lysinibacillus spp. and Bacillus spp. were found to produce extracellular enzymes like amylase, protease, cellulase, and lipase, showing significantly enhanced vegetative parameters, yield and lycopene content of tomato hybrid NS585 under salt-stressed sodic soils. PGPR-C3 consortia also showed enhanced plant growth-promoting activities and halo tolerance like high Indole acetic acid production, 1-aminocyclopropane-1-carboxylic acid deaminase, and antioxidative enzyme activity over the uninoculated control. Further, inoculation with PGPR-C3 consortia resulted in the efficient exclusion of Na+ ions from the rhizosphere through increased absorption of K+. Results of the study reveal that inoculation with PGPR-C3 consortia could alleviate the salt stress and promotes the successful cultivation of tomato crop in sodic soils. It can be considered the best option for eco-friendly, sustainable cultivation of vegetables like a tomato in sodic soils with a high pH range of up to 9.14.

Soil salinity is the major cause limiting plant productivity worldwide. Nitrogen-fixing bacteria were enriched and characterised from roots of Salicornia brachiata, an extreme halophyte which has substantial economic value as a bioresource of diverse and valuable products. Nitrogen-free semisolid NFb medium with malate as carbon source and up to 4% NaCl were used for enrichment and isolation of diazotrophic bacteria. The isolates were tested for plant growth-promoting traits and 16S rRNA, nifH and acdS genes were analysed. For selected strains, plant growth-promoting activities were tested in axenically grown Salicornia seedlings at different NaCl concentrations (0–0.5M). New halotolerant diazotrophic bacteria were isolated from roots of S. brachiata. The isolates were identified as Brachybacterium saurashtrense sp. nov., Zhihengliuella sp., Brevibacterium casei, Haererehalobacter sp., Halomonas sp., Vibrio sp., Cronobacter sakazakii, Pseudomonas spp., Rhizobium radiobacter, and Mesorhizobium sp. Nitrogen fixation as well as plant growth-promoting traits such as indole acetic acid (IAA) production, phosphate solubilisation, and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity were demonstrated. For Brachybacterium saurashtrense and Pseudomonas sp., significant plant growth-promoting activities were observed in Salicornia in salt stress conditions. Salicornia brachiata is a useful source of new halotolerant diazotrophic bacteria with plant growth-promoting potential.

Abiotic stresses including drought and salinity have become frontier areas in agricultural research, particularly due to their damaging potential to threaten global food security in near future. Constantly increasing soil salinity has severely damaged the global production of staple food crops. The ever-increasing world population is critically strained already due to the shrinkage of existing agricultural production system. Looking at the constraints, rigorous initiatives have been taken to yield several strategies to utilize conventional and modern approaches for increasing stress tolerance and/or mitigating the stress-induced ill-effects on crop to potentially improve the productivity. Recent literature signifies prominent attempts towards devising new strategies aiming at salinity and drought smart crop cultivation. The use of halophytes and halophyte-associated microbes is among the highly promising approach from both the perspectives of salinity stress mitigation, and saline soil reclamation in the long term. The cutting-edge omics tools have provided deeper insights into the understanding of the interactions of halophytes, associated microbiomes and the soil rhizosphere habitat. We have described ample of mechanism-based evidences to establish the role of halophytic plants and associated microbial communities in establishing a strong base for their application in bio-saline agriculture.

Some rhizobacteria have demonstrated a noteworthy role in regulation of plant growth and biomass production under biotic and abiotic stresses. The present study was intended to explicate the ameliorative consequences of halotolerant plant growth-promoting rhizobacteria (HPGPR) on growth of capsicum plants subjected to salt stress. Salt stress was ascertained by supplementing 1 and 2 g NaCl kg −1 soil. The HPGPR positively invigorated growth attributes, chlorophyll, protein contents, and water use efficiency (WUE) of supplemented capsicum plants under salinity stress conditions. Bacillus fortis strain SSB21 caused highest significant increase in shoot length, root length, and fresh and dry biomass production of capsicum plants grown under saline conditions. This multi-trait bacterium also increased biosynthesis of proline and up-regulated the expression profiles of stress related genes including CAPIP2, CaKR1, CaOSM1, and CAChi2. On the other hand, B. fortis strain SSB21 inoculated plants exhibited reduced level of ethylene, lipid peroxidation, and reactive oxygen species (ROS). All these together contribute to activate physiological and biochemical processes involved in the mitigation of the salinity induced stress in capsicum plants.

This study aimed to screen and characterize halotolerant bacterial isolates, which could enhance plant growth performance in saline soil. Halotolerant bacteria was isolated from weeds rhizosphere grown in saline soil of coastal agricultural land located at Brondong District, Lamongan Regency, East Java Province, Indonesia. This research was conducted from June to September 2018. Seven bacterial isolates can grow in a Nutrient Agar medium containing 10% of NaCl, suggesting that these bacteria were halotolerant. Furthermore, all bacterial isolates were shown to produce indol acetic acid (IAA) and do not induce a hypersensitive response when infiltrated into tobacco leaves. These results explain that these bacteria had potency as plant growth-promoting rhizobacteria (PGPR) and were not tend to be the plant pathogen. The growth of seedlings when inoculated in cucumber seed grown in saline media were higher than those in control. This result suggests that the halotolerant bacteria can enhance the development of cucumber seedlings in saline stress conditions. Three potential halotolerant bacteria i.e., SN22, SN23, SN26 were selected and molecularly identified as Bacillus megaterium, Bacillus sp., and B. megaterium, respectively.

Soil salinization is an escalating global concern that severely limits agricultural productivity by disrupting plant-microbe interactions and impairing soil health. This study evaluates the unique potential of Janibacter terrae (KR41), an actinobacteria isolated from highly saline soils of Manginapudi, Andhra Pradesh, India, as a bio-ameliorative agent for salinity-stressed soils. Unlike conventional plant-growth-promoting bacteria (PGPB), J. terrae (KR41) demonstrates exceptional halotolerance and multifaceted plant growth-promoting traits, including high levels of indole-3-acetic acid production (39.4 µg/mL), robust siderophore synthesis, and secretion of organic acids that contribute to rhizospheric modification. Greenhouse and open-field trials on maize, tomato, and brinjal under saline conditions revealed that J. terrae (KR41) significantly enhanced plant heightby 13.91% in maize, 17.83% in brinjal, and 13.62% in tomatocompared to non-treated controls. Moreover, the actinobacteria-treated soils showed a reduction in pH by 12.6%, indicating substantial amelioration of saline soil conditions. The improved crop performance is attributed to enhanced nutrient bioavailability and root zone conditioning facilitated by KR41’s bioactive metabolites. The findings demonstrate, for the first time, the novel application of J. terrae (KR41) as a halotolerant actinobacterium for dual greenhouse and field settings. By enhancing growth and yield of multiple crops while improving saline soil attributes, KR41 represents a promising microbial intervention for sustainable crop production in salt-affected agroecosystems.HighlightsActinobacteria strain Janibacte terrae (KR41) isolated from saline soils.Dual evaluation under greenhouse and field with maize, tomato, and brinjal.Strain KR41 enhanced crop growth and yield in high saline conditions.

Fifty halotolerant bacterial strains were isolated from the alkaline saline soil from the Ajod village of Vadodara district of Gujarat. All strains grew well in media supplemented with 5 % NaCl, but two strains (BR5 and BN7) could grow even at 18 % NaCl concentration. These two strains were characterized for their plant growth promoting characteristics. Both the strains were able to solubilize significant amount of phosphate and produce IAA. Both the strains also showed nitrogen fixing, siderophore production and antifungal properties against root rot pathogen of Vigna. radiata L., Fusarium sp. Potential of these halotolerant bacteria to ameliorate salt stress in V. radiata L. plants grown in saline soil inoculated with these bacteria was assessed. Both halotolerant bacteria were found to increase germination percentage, root length and shoot length compared to un inoculated control plants. Both these cultures were subjected to 16S rRNA gene sequencing and BLAST analysis, among which, BR5 showed 99 % similarity with Bacillus subtilis and BN7 showed 99 % similarity with B. megaterium.

Increasing world food demand together with soil erosion and indiscriminate use of chemical fertilization highlight the need to adopt sustainable crop production strategies. In this context, a combination of plant growth-promoting rhizobacteria (PGPR) and pathogen management represents a sustainable and efficient alternative. Though little studied, halophilic and halotolerant PGPR could be a beneficial plant growth promotion strategy for saline and non-saline soils. The virulence of many bacterial phytopathogens is regulated by quorum sensing (QS) systems. Quorum quenching (QQ) involves the enzymatic degradation of phytopathogen-generated signal molecules, mainly N-acyl homoserine lactones (AHLs). In this study, we investigate plant growth-promoting (PGP) activity and the capacity of the halotolerant bacterium Staphylococcus equorum strain EN21 to attenuate phytopathogens virulence through QQ. We used biopriming and in vivo tomato plant experiments to analyse the PGP activity of strain EN21. AHL inactivation was observed to reduce Pseudomonas syringae pv. tomato infections in tomato and Arabidopsis plants. Our study of Dickeya solani, Pectobacterium carotovorum subsp. carotovorum and Erwinia amylovora bacteria in potato tubers, carrots and pears, respectively, also demonstrated the effectiveness of QS interruption by EN21. Overall, this study highlights the potential of strain S. equorum EN21 in plant growth promotion and QQ-driven bacterial phytopathogen biocontrol.