Co-inoculation of Stenotrophomonas maltophilia and Rhizobium leguminosarum phaseoli improves salinity tolerance in common bean cultivars

Abstract

Salinity stress, through restricting water availability and inducing ion toxicity, represents one of the major threats to global agricultural productivity. Although plant growth-promoting bacteria (PGPB) have been widely studied for their ability to alleviate abiotic stresses, the co-inoculation of Stenotrophomonas maltophilia (MN099392) and Rhizobium leguminosarum bv. phaseoli (PP125713) to enhance salt stress tolerance in common bean (Phaseolus vulgaris L.) cultivars has received limited attention. This study aimed to evaluate the effects of co-inoculation with S. maltophilia and R. leguminosarum bv. phaseoli on physiological traits and yield performance of two common bean cultivars (Almas and Pak) under salinity stress. A factorial experiment was conducted based on a completely randomized design with three replications in the research greenhouse of the Faculty of Agriculture, Shiraz University. Treatments included six bacterial inoculations (non-inoculated control, S. maltophilia (P1), Enterobacter hormaechei (P2), R. leguminosarum bv. phaseoli strain Rb-114 (RB), and dual combinations P1 + RB and P2 + RB) and four salinity levels (0.5, 4, 6, and 8 dS m^− 1). Increasing salinity reduced chlorophyll and carotenoid contents, protein accumulation, and grain yield, while electrolyte leakage, proline concentration, antioxidant enzyme (APX and POD) activities, and ABA content increased. Co-inoculation with P1 + RB effectively mitigated the adverse effects of salinity by enhancing chlorophyll, carotenoids, soluble sugars, IAA, essential nutrients (Mg, Fe, and K), grain weight and nitrogen content. Overall, co-inoculation with S. maltophilia and R. leguminosarum bv. phaseoli significantly improved salinity tolerance, particularly in the Almas cultivar, through enhanced nutrient uptake, maintenance of membrane integrity, and regulation of hormonal balance.

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-026-37145-2.

Introduction

Salinity stress is a critical environmental factor that limits agricultural productivity by causing osmotic imbalance, ion toxicity, and oxidative damage in plants. Excessive sodium (Na⁺) and chloride (Cl⁻) ions accumulate in plant tissues, disrupting cellular ion homeostasis and nutrient uptake, which leads to metabolic dysfunction and reduced growth¹. Furthermore, salinity triggers the overproduction of reactive oxygen species (ROS), leading to oxidative stress that damages proteins, lipids, and DNA². Managing these physiological challenges is essential for maintaining plant health under saline conditions.

Common bean (Phaseolus vulgaris L.) is a widely cultivated legume valued for its high protein content and contribution to food security globally. However, it is particularly sensitive to salinity, with a tolerance threshold of approximately 1.5 dS m^{− 1} electrical conductivity in the root zone, beyond which growth and yield decline significantly³. For instance, a study by Aslam et al⁴. demonstrated that salinity levels reduced growth and biomass production in lentil, indicating a pronounced susceptibility that threatens its cultivation in salt-affected soils. Salinity stress also disturbs hormonal equilibrium in common bean plants. Stress conditions typically reduce growth-promoting hormones like auxins, gibberellins, and cytokinins, while increasing stress-related hormones including abscisic acid (ABA) and ethylene. This hormonal imbalance leads to reduced growth, stomatal closure, and hastened senescence^5,6.

Biological techniques employing plant growth-promoting bacteria (PGPB) provide an economical and environmentally sustainable approach to enhancing plant resistance to salinity. These beneficial microorganisms, residing in the rhizosphere (root zone) and phyllosphere (leaf surface), can trigger systemic, multi-trophic defensive responses that strengthen abiotic stress tolerance^7–9. Under saline conditions, rhizobacteria form nitrogen-fixing root nodules, improving plant nitrogen status and reducing dependence on synthetic fertilizers, thus supporting osmotic adjustment¹⁰. Meanwhile, phyllospheric bacteria enhance antioxidant defenses by stimulating enzymes such as superoxide dismutase (SOD) and catalase (CAT), thereby scavenging ROS and protecting cellular structures from oxidative damage¹¹.

Beneficial rhizobacteria such as Stenotrophomonas maltophilia and Rhizobium leguminosarum phaseoli have shown potential in mitigating salinity stress through multiple physiological and biochemical mechanisms. They produce siderophores that chelate iron, improving its availability to plants under stress and enhancing nutrient uptake^12,13. They also synthesize indole-3-acetic acid (IAA), a key phytohormone involved in root elongation and branching, thereby promoting better root architecture for water and nutrient absorption in saline soils¹⁴. Additionally, the production of 1-aminocyclopropane-1-carboxylate (ACC) deaminase by these bacteria lowers ethylene levels in plants, which otherwise increase under salinity stress and inhibit growth, thereby supporting sustained development and stress tolerance¹⁵. These combined bacterial traits help maintain ion homeostasis, enhance antioxidant defenses, and improve overall stress adaptation.

The objective of this study is to evaluate, for the first time, the effects of co-inoculation of a phyllospheric bacterium, Stenotrophomonas maltophilia, with the symbiotic root-nodule bacterium Rhizobium leguminosarum bv. phaseoli on the growth and salinity tolerance of common bean plants. Unlike previous studies that have primarily focused on either rhizospheric or symbiotic bacteria alone, the present research introduces a novel co-inoculation strategy combining a phyllosphere associated bacterium with a rhizobial strain, a combination that has not been previously reported under salinity stress conditions. We hypothesize that the synergistic interaction between S. maltophilia and R. leguminosarum bv. phaseoli regulates ion uptake balance, modulates endogenous phytohormones such as indole-3-acetic acid (IAA) and abscisic acid, and enhances antioxidant enzyme activities including superoxide dismutase and catalase. This integrated response is expected to mitigate oxidative damage and ion toxicity, ultimately improving plant growth performance and salt tolerance in common bean.

Materials and methods

Plant genotype selection

The evaluation of 16 commercial Iranian common bean cultivars for potential salinity tolerance found two cultivars, Almas (3.026) and Pak (1.589), to be most stress tolerance index (selected for the following ones) (Tables S1 and S2).

Microbial strain selection

Rhizobial Strains: Five rhizobial strains (Rb-141, Rb-130, Rb-147, Rb-112, Rb-114) were subjected to preliminary salinity tolerance evaluation ranging from 0, 4, 6, 8, and 16 dS m^− 1 NaCl for the growth of rhizobia by colony-forming unit (CFU) and optical density measures (OD₆₀₀). Then, the symbiotic potential of these strains was evaluated on the selected common bean cultivars (Almas and Pak) along with the uninoculated and nitrogen-fertilized controls. Rb-114 was selected for further studies because of enhanced salt tolerance combined with symbiotic efficacy.

Phyllospheric Bacteria: From six Iranian provinces (Fars, Alborz, Qazvin, Khuzestan, Tehran, and Khorasan), 116 healthy maize leaves were collected and phyllospheric bacteria were isolated. These bacterial isolates were evaluated for plant growth-promoting (PGPR) traits, that is, indole-3-acetic acid (IAA) production, phosphate solubilization, siderophore secretion, exopolysaccharide (EPS) production, and nitrogenase activity¹⁶. The most beneficial isolates were Stenotrophomonas maltophilia and Enterobacter hormaechei, characterized by 16 S rRNA gene sequencing, and selected for further studies.

Main experimental setup

Experimental design

A factorial experiment was conducted in a completely randomized design (CRD) with three replications to evaluate the individual and combined effects of bacterial inoculation and salinity stress on two common bean varieties (Almas and Pak) at the research greenhouse of the Faculty of Agriculture, Shiraz University. Treatments included six bacterial inoculations (non-inoculated control, S. maltophilia (P1), Enterobacter hormaechei (P2), R. leguminosarum bv. phaseoli strain Rb-114 (RB), and dual combinations P1 + RB and P2 + RB) and four salinity levels (0.5, 4, 6, and 8 dS m^− 1).

Growing requirements and cultivation

Five kilos of sterilized sand, with features listed in Table S3, were added to each pot. Five seeds were planted into each pot after a two-day germination period. A 2 mL Rhizobium suspension was administered straight to the radicles of seeds in the appropriate treatments at planting time.

Application of bacterial inoculation and stress

Growing pure cultures in Nutrient Broth for 48 h at 28 °C allowed for bacterial inocula preparation. Centrifugation was used to collect cells, then rinsed with 10 mM MgSO₄. and resuspend in the same buffer to reach a last density of around 108 CFU mL^–1. Treatments with phyllosphere bacteria (P1, P2) were used as a two-leaf foliar spray. 20 mL of the bacterial suspension was sprayed onto the upper and lower leaf surfaces of each pot, while the soil surface was covered to prevent cross-contamination. Salinity stress was initiated at the four-leaf stage by irrigating plants with solutions adjusted to the target electrical conductivity (EC) levels. Regular monitoring of leachate EC ensured control of salt accumulation and prevented sudden osmotic shocks. To maintain adequate nutrient availability during the growth phase, plants were also irrigated with Broughton and Dilworth’s nutrient solution¹⁷ (Table S4). This approach allowed a gradual exposure to salinity, minimizing sudden stress effects and enabling assessment of plant physiological and biochemical responses under controlled salinity conditions.

Plant harvest and examination

At the blooming stage, early biochemical samples were taken. The experiment ran until physiological maturity, at which point plants were gathered for last evaluations. Information on several physiological, biological, and growth indicators was gathered.

Content of photosynthetic pigments

The contents of photosynthetic pigments were quantified from 500 mg of fresh third-leaf tissue. After an overnight dark incubation, pigments were extracted from the plant material using 80% acetone, following the protocol established by Lichtenthaler and Wellburn¹⁸. The homogenized mixture was centrifuged at 3000 rpm for 10 min to separate the extract. The supernatant was then analyzed using a UV-Vis spectrophotometer (7315 UV/visible Spectrophotometer, Jenway, UK). Absorbance was measured at 470 nm, 646 nm, and 663 nm for carotenoids, chlorophyll b (Cb), chlorophyll a (Ca) and chlorophyll t, respectively. Pigment concentrations were calculated using the following equations:

Measurement of proline

The proline content in leaves was quantified according to the method described by Bates et al.¹⁹. Briefly, 0.5 g of fresh leaf tissue was cut into segments smaller than 5 mm and homogenized in 10 mL of 3% sulfosalicylic acid for three minutes. Subsequently, a 2 mL aliquot of the filtrate was mixed with 2 mL of acid-ninhydrin reagent and 2 mL of glacial acetic acid in a test tube. The mixture was incubated in a water bath at 90 °C for one hour. Following incubation, the reaction mixture was allowed to cool, after which 4 mL of toluene was added. The test tube was then vigorously shaken for 15–20 s. The absorbance of the upper, toluene-containing phase was measured at a wavelength of 520 nm using a spectrophotometer, with a toluene blank as the reference. The concentration of free proline in the sample was determined by comparison to a standard curve prepared using pure proline.

Antioxidant enzyme activities

At 67 days after sowing (DAS), fresh leaf tissue was homogenized in ice-cold phosphate buffer (pH 7.6) for enzyme extraction. POD activity was determined based on the oxidation of pyrogallol, following the procedure of Chance and Maehly²⁰. The assay was performed by mixing 3 mL of pyrogallol phosphate buffer solution with 0.5 mL of 1% H₂O₂ and 0.1 mL of enzyme extract in a cuvette. The increase in absorbance at 420 nm was recorded at 20-second intervals for 3 min using a spectrophotometer. A control reaction, prepared by replacing the enzyme extract with buffer, was subtracted from the sample readings. APX activity was assayed according to the method of Yoshimura et al.²¹. The reaction mixture consisted of 25 mM phosphate buffer (pH 7.0), 0.25 mM ascorbic acid, 0.1 mM EDTA, and 1 mM hydrogen peroxide. The reaction was initiated by adding 0.2 ml of the enzyme extract. The decrease in absorbance at 290 nm, corresponding to the oxidation of ascorbate, was monitored spectrophotometrically for 1 min. Enzyme activity was calculated based on the rate of absorbance change.

Electrolyte leakage measurement

The electrolyte leakage (EL) was determined to assess membrane permeability. Fresh leaf samples (0.3 g) were placed in test tubes containing 10 mL of deionized water. The tubes were then incubated with shaking at 25 °C for 20 h, after which the initial electrical conductivity (C1) was measured using a pre-calibrated EC meter (Hanna HI-2315, USA). Subsequently, the test tubes were heated to 45–55 °C for 30 min, and the conductivity (C2) was recorded. Finally, the tubes were boiled at 100 °C for 10 min, and the final conductivity (C3) was measured. Electrolyte leakage was calculated using the following formula:

Soluble protein

The soluble protein content was determined using the method of Bradford²². Briefly, one gram of fresh leaf tissue was homogenized in four milliliters of sodium phosphate buffer (pH 7.2). The homogenate was then centrifuged at 4 °C. A 100 µL aliquot of the resulting crude extract was combined with one milliliter of Bradford reagent. The absorbance was measured at a wavelength of 595 nm using a spectrophotometer. The protein concentration was quantified by comparison to a standard curve prepared with bovine serum albumin (BSA).

Soluble sugars

The total soluble sugar content was quantified according to the phenol-sulfuric acid method²³. A 0.1 g sample was thoroughly ground into a fine powder. The powdered plant material was transferred to a centrifuge tube, and 10 mL of 80% ethanol was added. The tubes were centrifuged at 5000 × g for 10 min. The supernatant was decanted into a flask. This extraction procedure was repeated on the pellet with an additional 10 mL of 80% ethanol, and the combined supernatants were collected. For the assay, a 5% phenol solution was prepared. Subsequently, a 25 µL aliquot of the extracted sample was pipetted into a microplate well, followed by the addition of 25 µL of the 5% phenol solution. Immediately thereafter, 125 µL of concentrated sulfuric acid was added to each well. The absorbance was measured at 490 nm using a microplate reader (Epoch, BioTek). A standard curve was constructed using glucose solutions of known concentrations (expressed as mg per g dry weight). The total soluble sugar content in the samples was calculated by interpolating the measured absorbance values against the linear regression equation derived from the standard curve.

Measurement of indole-3-acetic acid and abscisic acid hormones

The plant hormone indole-3-acetic acid was quantified according to the procedure described by Yang et al.²⁴. Briefly, 1.5 g of plant tissue was homogenized in 20 mL of a solution containing an equal ratio of methanol and deionized water using a homogenizer at 4 °C. The resulting homogenate was centrifuged at 4000 × g for 15 min. The supernatant was loaded onto a C18 solid-phase extraction column, which was then washed with 5 mL of deionized water. The adsorbed auxin was eluted from the column with 3 mL of 80% methanol. The eluate was evaporated to dryness under a stream of nitrogen at laboratory temperature. The residue was reconstituted in 1 mL of 80% methanol. This final extract was used for auxin quantification via High-Performance Liquid Chromatography (HPLC).

Abscisic acid (ABA) content was measured based on the method of Zhou et al.²⁵. Approximately 0.3 g of plant tissue was homogenized in 750 µL of an extraction solvent composed of acetone, distilled water, and acetic acid (80:19:1, v/v/v). The resulting extract was centrifuged at 10,000 × g for 2 min. The supernatant was collected, and the extraction procedure was repeated on the residue with the same solvent mixture. The combined supernatants were dried at ambient temperature. The dried residue was reconstituted in 200 µL of a mobile phase consisting of methanol and distilled water (60:40, v/v), acidified with acetic acid 0.1% and adjusted to pH 3.5. A 10–15 µL aliquot of this solution was injected into an HPLC system equipped with a C18 column (4 mm and 5 μm) for analysis.

Ion analysis

The concentrations of sodium and potassium were determined according to the method of Horneck and Hanson²⁶. Dried plant samples were ground into a fine powder using a mill. Subsequently, 0.5 g of the dried tissue was placed in a muffle furnace and ashed at 500 °C for 5 h. The resulting ash was dissolved in 5 mL of 4 N hydrochloric acid and heated in a water bath for 20 min. The digest was then filtered through filter paper and brought to a final volume of 100 mL with deionized water. The sodium and potassium concentrations in the solution were analyzed using a flame photometer (Corning 410). Nitrogen content was measured using the standard Kjeldahl method²⁷. Chloride content was analyzed based on the procedure described by Chapman and Pratt²⁸. The concentrations of iron and magnesium were measured using the flame atomic absorption spectroscopy (AAS) method²⁹.

Statistical analysis

The data were analyzed using ANOVA and the SAS software package (version 9.1). Normality was verified through Shapiro-Wilk tests, supported by skewness and kurtosis evaluation. Treatment means were separated using the LSD test at significance levels of p ≤ 0.05 and p ≤ 0.01. OriginPro 2022 was used for correlation and heatmap generation.

Results

Content of photosynthetic pigments

The comparison of means indicated that increasing salinity to the highest level resulted in a decreasing trend in total chlorophyll and carotenoid content in both cultivars (Fig. 1a, b). However, the application of bacterial treatments mitigated the adverse effects of salt stress, leading to an increase in total chlorophyll and carotenoid content compared to the non-inoculated control. The highest total chlorophyll content was observed in the combined treatment of P1 and RB. In the Almas cultivar, the combined inoculation of P1 and RB increased total chlorophyll content at salinity levels of 0.5, 4, 6, and 8 dS m^− 1 by 1.4, 1.2, 1.2, and 1.1-fold, respectively, compared to the non-bacterial treatment. Similarly, in the Pak cultivar, the same treatment resulted in increases of 1.2, 1.0, 1.2, and 1.1-fold at the corresponding salinity levels (Fig. 1a). Furthermore, carotenoid content was enhanced by the combined application of P1 and RB in both Almas and Pak cultivars. At salinity levels of 0.5, 4, 6, and 8 dS m^− 1, carotenoid content increased by 1.6, 2.0, 1.5, and 2.3-fold in Almas, and by 1.2, 1.1, 1.5, and 1.0-fold in Pak, respectively, compared to the control (Fig. 1b).

Fig. 1.

The effect of salinity (0.5, 4, 6 and 8 dS m^− 1), cultivar (A: Almas and P: Pak) and bacteria application (C: control, P1: Stenotrophomonas maltophilia, P2: Enterobacter hormaechei, P1 + RB: Stenotrophomonas maltophilia + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), P2 + RB: Enterobacter hormaechei + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), RB: Rhizobium leguminosarum b.v. phaseoli) on total chlorophyll (a) and carotenoid (b) of common bean. Data are presented as the means of three replicates; the vertical bars indicate standard deviations. Different letters in the columns show significant differences (P < 0.05) according to LSD test.

Proline content

Proline content was significantly influenced by the triple interaction of salinity, cultivar, and bacteria. An increasing trend in proline content was observed with rising salinity levels in both cultivars and across all bacterial treatments. The highest value of this parameter was recorded at the salinity level of 8 dS m^− 1 in the Pak cultivar under non-inoculated conditions. The combined application of P1 and RB bacteria mitigated the damage induced by salinity stress levels of 4, 6, and 8 dS m^− 1 in both Almas and Pak cultivars. This was reflected in a reduction of proline content by 1.7, 1.9, and 2.4-fold in the Almas cultivar, and by 1.1, 1.8, and 1.9-fold in the Pak cultivar, respectively, compared to the non-inoculated control at the corresponding salinity levels (Fig. 2).

Fig. 2.

The effect of salinity (0.5, 4, 6 and 8 dS m^− 1), cultivar (A: Almas and P: Pak) and bacteria application (C: control, P1: Stenotrophomonas maltophilia, P2: Enterobacter hormaechei, P1 + RB: Stenotrophomonas maltophilia + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), P2 + RB: Enterobacter hormaechei + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), RB: Rhizobium leguminosarum b.v. phaseoli) on proline content of common bean. Data are presented as the means of three replicates; the vertical bars indicate standard deviations. Different letters in the columns show significant differences (P < 0.05) according to LSD test.

Antioxidant enzyme activities

The interaction effect of salinity, cultivar, and bacteria on antioxidant enzyme activity was significant. With increasing salinity from 0.5 to 8 dS m^− 1, an increasing trend was observed in the activity of the antioxidant enzymes APX and POD. The highest activity level for both enzymes was recorded in the Pak cultivar under the control treatment (without bacteria) at the highest salinity level, indicating the greater damage inflicted by salinity on the plants in this treatment (Fig. 3a, b). Application of the combined treatment of P1 and RB, by reducing the damage to the plants, led to a decrease in the activity of these two enzymes. At salinity levels of 0.5, 4, 6, and 8 dS m^− 1, the application of the combined P1 and RB treatment in the Diamond cultivar resulted in a reduction of APX and POD activity by 3.0, 3.0, 2.3, and 2.2-fold and 1.3, 2.1, 2.7, and 3.7-fold, respectively. In the Pak cultivar, this combined treatment reduced APX and POD activity by 1.6, 2.2, 2.2, and 2.3-fold and 1.6, 2.7, 2.8, and 3.3-fold, respectively (Fig. 3a, b).

Fig. 3.

The effect of salinity (0.5, 4, 6 and 8 dS m^− 1), cultivar (A: Almas and P: Pak) and bacteria application (C: control, P1: Stenotrophomonas maltophilia, P2: Enterobacter hormaechei, P1 + RB: Stenotrophomonas maltophilia + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), P2 + RB: Enterobacter hormaechei + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), RB: Rhizobium leguminosarum b.v. phaseoli) on APX (a) and POD (b) of common bean. Data are presented as the means of three replicates; the vertical bars indicate standard deviations. Different letters in the columns show significant differences (P < 0.05) according to LSD test.

Electrolyte leakage

The triple interaction salinity, cultivar and bacteria for electrolyte leakage was nonsignificant and the mean comparison of the dual interactions, salinity vs. cultivar, cultivar vs. bacteria, salinity vs. bacteria were analyzed for this parameter. In the salinity-bacteria interaction, electrolyte leakage increased in parallel with salinity from 0.5 to 8 dS m^− 1. On the other hand, apply of P1 + RB decreased this parameter 1.4, 1.4, 1.5 and 1.6-folds compared with non-inoculated control at different salinity levels respectively (Fig. 4). For the bacteria by cultivar interaction, higher levels of EL were attained in Pak than Almas. The combined bacterial inoculant (P1 + RB) reduced electrolyte leakage by a factor of 1.7-fold in Almas and 1.3-fold in Pak compared to their respective non-inoculated controls. The results of interaction between salinity and cultivar showed that increase in the level of salinity from 0.5 to 8 dS m^− 1 increased electrolyte leakage, with highest amount for Pak as compared to Almas under all levels of salinity. Pak showed 1.1, 1.1, 1.1- and 1.2-fold high electrolyte leakage than Almas at salinities of 0.5, 4, 6 and 8 dS m^− 1 respectively (Fig. 4).

Fig. 4.

The effect of salinity (0.5, 4, 6 and 8 dS m^− 1), cultivar (A: Almas and P: Pak) and bacteria application (C: control, P1: Stenotrophomonas maltophilia, P2: Enterobacter hormaechei, P1 + RB: Stenotrophomonas maltophilia + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), P2 + RB: Enterobacter hormaechei + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), RB: Rhizobium leguminosarum b.v. phaseoli) on electrolyte leakage of common bean. Data are presented as the means of three replicates; the vertical bars indicate standard deviations. Different letters in the columns show significant differences (P < 0.05) according to LSD test.

Soluble sugars and protein

The interaction effect of salinity, cultivar, and bacteria on protein and soluble sugar content was significant. With increasing salinity levels in both Almas and Pak cultivars, soluble sugar increased, while protein content decreased. The highest levels of soluble sugar and protein were obtained in the combined treatment of P1 and RB in both cultivars. Increasing salinity to 4, 6 and 8 dS m^− 1 led to an increase in soluble sugar content in both Almas and Pak cultivars by 1.4, 1.3 and 1.3-fold and 1.1, 1.2 and 1.6-fold, respectively, compared to the non-inoculated treatment (Fig. 5a). In contrast, protein content exhibited a decreasing trend with rising salinity levels to 8 dS m^− 1. However, the application of the combined bacterial treatment (P1 and RB) resulted in increased protein content in both Almas and Pak cultivars by 2.0 and 2.3-fold, respectively, compared to the non-inoculated control (Fig. 5b).

Fig. 5.

The effect of salinity (0.5, 4, 6 and 8 dS m^− 1), cultivar (A: Almas and P: Pak) and bacteria application (C: control, P1: Stenotrophomonas maltophilia, P2: Enterobacter hormaechei, P1 + RB: Stenotrophomonas maltophilia + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), P2 + RB: Enterobacter hormaechei + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), RB: Rhizobium leguminosarum b.v. phaseoli) on protein (a) and soluble sugar (b) of common bean. Data are presented as the means of three replicates; the vertical bars indicate standard deviations. Different letters in the columns show significant differences (P < 0.05) according to LSD test.

Indole-3-acetic acid (IAA) and abscisic acid (ABA) hormones

The interaction effect of salinity, bacteria, and cultivar on hormone content was significant. Increasing the salinity level from 0.5 to 8 dS m^− 1 in the non-inoculated control of both cultivars led to a decrease in IAA content. The highest level of this hormone was obtained at the 0.5 dS m^− 1 salinity level in combination with P1 and RB bacteria. Application of the combined treatment of P1 and RB at salinity levels of 0.5, 4, 6, and 8 dS m^− 1 resulted in a 1.5, 1.4, 1.3, and 1.1-fold increase in IAA content in the Almas cultivar, respectively, compared to the non-inoculated control (Fig. 6a). In the Pak cultivar, increases of 1.4, 1.5, 1.2, and 1.1-fold were observed. In contrast, the ABA content exhibited an increasing trend with rising salinity levels. Application of the combined treatment of P1 and RB at salinity levels of 0.5, 4, 6, and 8 dS m^− 1 caused a reduction in this parameter. The highest ABA content was recorded in the non-inoculated control at the highest salinity level, which was reduced by 2.8 and 3.4-fold in the Almas and Pak cultivars, respectively, following the application of the combined P1 and RB treatment compared to the non-inoculated control (Fig. 6b).

Fig. 6.

The effect of salinity (0.5, 4, 6 and 8 dS m^− 1), cultivar (A: Almas and P: Pak) and bacteria application (C: control, P1: Stenotrophomonas maltophilia, P2: Enterobacter hormaechei, P1 + RB: Stenotrophomonas maltophilia + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), P2 + RB: Enterobacter hormaechei + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), RB: Rhizobium leguminosarum b.v. phaseoli) on IAA (a) and ABA (b) of common bean. Data are presented as the means of three replicates; the vertical bars indicate standard deviations. Different letters in the columns show significant differences (P < 0.05) according to LSD test.

Ion analysis

The interaction effect of salinity, cultivar, and bacteria on the shoot elements was significant. Mean comparison results indicated that as salinity increased from 0.5 to 8 dS m^− 1 in both cultivars and across all bacterial treatments, the concentrations of magnesium, iron, and potassium decreased, while chloride and sodium increased. The highest concentrations of magnesium, iron, and potassium were observed in the Almas cultivar treated with the combined bacterial inoculant of P1 and RB (Figs. 7 and 8). In contrast, the highest concentrations of chloride and sodium were obtained in the Pak cultivar under the non-bacterial treatment (control). The combined application of P1 and RB increased the concentrations of magnesium, iron, and potassium at the highest salinity level by 2.6, 2.2, and 8.2 times, respectively, in the Almas cultivar, and by 3.1, 3.4, and 1.7 times, respectively, in the Pak cultivar, compared to the control treatment. Conversely, the application of this bacterial treatment at the highest salinity level reduced chloride and sodium concentrations by 1.2 and 1.7 times, respectively, in the Almas cultivar, and by 1.2 and 1.8 times, respectively, in the Pak cultivar (Figs. 7 and 8).

Fig. 7.

The effect of salinity (0.5, 4, 6 and 8 dS m^− 1), cultivar (A: Almas and P: Pak) and bacteria application (C: control, P1: Stenotrophomonas maltophilia, P2: Enterobacter hormaechei, P1 + RB: Stenotrophomonas maltophilia + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), P2 + RB: Enterobacter hormaechei + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), RB: Rhizobium leguminosarum b.v. phaseoli) on Mg (a), Cl (b) and Fe (c) of common bean. Data are presented as the means of three replicates; the vertical bars indicate standard deviations. Different letters in the columns show significant differences (P < 0.05) according to LSD test.

Fig. 8.

The effect of salinity (0.5, 4, 6 and 8 dS m^− 1), cultivar (A: Almas and P: Pak) and bacteria application (C: control, P1: Stenotrophomonas maltophilia, P2: Enterobacter hormaechei, P1 + RB: Stenotrophomonas maltophilia + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), P2 + RB: Enterobacter hormaechei + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), RB: Rhizobium leguminosarum b.v. phaseoli) on K (a) and Na (b) concentrations of common bean. Data are presented as the means of three replicates; the vertical bars indicate standard deviations. Different letters in the columns show significant differences (P < 0.05) according to LSD test.

Grain weight

Salinity, cultivar, and bacteria had a significant effect on grain weight. Increasing salinity from 0.5 to 8 dS m^− 1 led to a decrease in this parameter in both cultivars and across all bacterial treatments. The results indicated that the most effective treatment for mitigating the adverse effects of salinity stress was the combination of P1 + RB (Fig. 9). Specifically, the highest common bean grain weight was observed in the Almas cultivar under non-stress conditions with the application of the combined bacterial treatment of P1 + RB. Application of this treatment increased common bean grain weight at salinity levels of 0.5, 4, 6, and 8 dS m^− 1 by 2.1, 3.7, 4.4, and 1.9 times, respectively, in the Almas cultivar, and by 1.8, 2.2, 5.4, and 7.0 times, respectively, in the Pak cultivar, compared to the non-inoculated control treatment (Fig. 9).

Fig. 9.

The effect of salinity (0.5, 4, 6 and 8 dS m^− 1), cultivar (A: Almas and P: Pak) and bacteria application (C: control, P1: Stenotrophomonas maltophilia, P2: Enterobacter hormaechei, P1 + RB: Stenotrophomonas maltophilia + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), P2 + RB: Enterobacter hormaechei + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), RB: Rhizobium leguminosarum b.v. phaseoli) on grain weight of common bean. Data are presented as the means of three replicates; the vertical bars indicate standard deviations. Different letters in the columns show significant differences (P < 0.05) according to LSD test.

Grain nitrogen content

Grain nitrogen content followed a trend similar to that of grain weight, whereby the percentage of grain nitrogen decreased with increasing salinity in both the Almas and Pak cultivars and across all bacterial treatments. The highest nitrogen percentage was obtained in the non-stress control treatment of the Almas cultivar with the application of the combined P1 + RB (Fig. 10). The application of this combined bacterial treatment increased the grain nitrogen percentage at salinity levels of 0.5, 4, 6, and 8 dS m^− 1 by 2.4, 2.1, 2.2, and 2.2 times, respectively, in the Almas cultivar, and by 2.2, 2.3, 2.1, and 2.3 times, respectively, in the Pak cultivar, compared to the non-inoculated control (Fig. 10).

Fig. 10.

The effect of salinity (0.5, 4, 6 and 8 dS m^− 1), cultivar (A: Almas and P: Pak) and bacteria application (C: control, P1: Stenotrophomonas maltophilia, P2: Enterobacter hormaechei, P1 + RB: Stenotrophomonas maltophilia + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), P2 + RB: Enterobacter hormaechei + Rhizobium leguminosarum b.v. phaseoli (Rb.114.L.54), RB: Rhizobium leguminosarum b.v. phaseoli) on grain nitrogen of common bean. Data are presented as the means of three replicates; the vertical bars indicate standard deviations. Different letters in the columns show significant differences (P < 0.05) according to LSD test.

Pearson correlations and principal component analysis

Correlation analysis revealed that grain weight had a significant positive correlation with total chlorophyll, carotenoids, protein, indole-3-acetic acid, potassium, magnesium, iron, and nitrogen percentage. In contrast, grain weight exhibited a significant negative correlation with soluble sugars, ascorbate peroxidase, peroxidase, abscisic acid, proline, sodium, and chloride (Fig. 11a).

Fig. 11.

A heat map of the Pearson correlations (a) and an analysis PCA-Biplot (b) of the principal component analysis for the linked biochemical responses related to treated common bean seedlings subjected to salinity stress. TCh Total chlorophyll, Car Carotenoid, POD Peroxidase, APX Ascorbate peroxidase, Prl Proline, Prt Protein, SC Soluble sugar, IAA Indole-3-acetic acid, ABA Abscisic acid, Na Sodium, K Potassium, Mg Magnesium, Cl Chlorine, Fe Iron, GW Grain weight, and NS Seed nitrogen.

Principal component analysis (PCA) was performed to investigate the patterns of variation among the traits and applied treatments, as well as their interactions and mutual influences. The goal of PCA is to identify the number of major factors that can be extracted to minimize the number of effective parameters. In this study, two elements accounted for 100% of the observed variability. Two components accounted for 74.87% and 8.18% of the variation, respectively (Fig. 11b). As a result, a clear distinction between the various NaCl treatments in the three analyzed genotypes was seen. Consequently, the treatments with 0.5, 4, 6, and 8 dS m^− 1 NaCl were located in the right, middle, and left of the PCA biplot, respectively (Fig. 11b). The traits of NS, Mg, IAA, Fe, Prt, K, GW, TCh, and Car were linked to P1 + RB and P2 + RB under 0.5 and 4 dS m^− 1 in both cultivars. The traits of NS, Mg, IAA, Fe, Prt, K, GW, TCh, and Car were grouped together (in the upper and bottom right quadrant), indicating a similarity in the way they are controlled under enforced stress circumstances for all treatments. The traits of Na, SC, Cl, POD, APX, ABA, and Prl were grouped together (in the upper and bottom left quadrant). These traits were linked to C under 6 and 8 dS m^− 1 in both cultivars (Fig. 11b).

Discussion

Overall, these results demonstrate that, beyond the well-documented effects of single PGPR strains, the combined application of a phyllospheric bacterium (Stenotrophomonas maltophilia) with a symbiotic rhizobial strain (Rhizobium leguminosarum bv. phaseoli) provides a multi-layered physiological and biochemical advantage that has not been previously reported in PGPR–salinity studies in legumes. Although Enterobacter hormaechei exhibited beneficial effects in combination with Rhizobium leguminosarum bv. phaseoli, the co-inoculation involving the phyllospheric bacterium Stenotrophomonas maltophilia showed a more consistent and pronounced improvement across the evaluated traits. The results indicate that increased salinity negatively impacts these pigments, which are essential for photosynthesis and plant health. However, inoculation with bacteria such as Stenotrophomonas maltophilia and Rhizobium leguminosarum phaseoli significantly improved pigment contents, with the highest increases observed in combined treatments. The underlying reasons for this are rooted in the bacteria’s abilities: they produce siderophores that enhance iron uptake necessary for chlorophyll synthesis and generate plant hormones like indole acetic acid (IAA) that promote root growth and nutrient absorption. Additionally, their production of exopolysaccharides (EPS) helps improve soil structure and moisture retention, thereby reducing the impact of salt stress^9,30,31. Most importantly, these bacteria produce ACC deaminase, which decreases ethylene levels that typically rise under salt stress and inhibit growth. By lowering ethylene levels, the bacteria help sustain photosynthetic pigment synthesis and maintain cellular health^31–34. These multifaceted mechanisms explain why bacterial inoculation effectively mitigates salt stress and enhances pigment concentrations in the plants.

The observed reduction in proline production under salinity stress in plants treated with the superior bacterial strain indicates that these cells experience less osmotic stress and cellular damage. Under saline conditions, proline typically accumulates as a compatible osmolyte involved in osmotic regulation and cellular structure protection. Under higher stress, plants generally accumulate more proline to counteract adverse conditions^35,36. Therefore, the decrease in proline production under salt stress following inoculation with PGPR implies reduced stress pressure, improved physiological status, and a diminished need for proline accumulation to counteract salt-induced damage^37,38. This improvement, due to enhanced membrane stability, osmotic balance, and antioxidant defense, demonstrates the superior bacterial treatment’s effectiveness in enhancing salinity tolerance and protecting plant cells from salt-induced damage^35–38. It also reflects the plant’s successful recovery toward a balanced physiological state.

According to the results of this research, salinity caused a marked increase in antioxidant enzyme activity in both cultivars. A complete reduction of these enzymes was observed when the combined treatment with S. maltophilia and R. leguminosarum bv. phaseoli was applied. The decrease of the activity of antioxidant enzymes in plant inoculated with PGPB under salinity stress is an interesting phenomenon, generally interpreted as positive response to plant physiological conditions rather than a negative one. Na⁺ and Cl⁻ ions increase ROS during salinity stress, resulting in the injury of cell membranes, proteins as well as nucleic acids. To alleviate this damage, plants stimulate the antioxidant defense system that consists of enzymes such as POD and APX. Several mechanisms allow plant growth-promoting bacteria, such as S. maltophilia and R. leguminosarum bv. phaseoli, to mitigate oxidative stress in plants. These include the synthesis of phytohormones (e.g., IAA), the enzymatic activity of ACC deaminase (which lowers stress-induced ethylene) and secretion of antioxidants. These mechanisms collectively reduce the over-abundance of ROS in plant cells. As the oxidative stress is dissipated, the plant does not need to maintain high and prolonged activation of its antioxidant enzymes. The observed decrease in APX and POD activities following bacterial inoculation is consistent with reduced ROS levels and alleviated oxidative stress, as supported by previous studies reporting similar responses of antioxidant enzymes under PGPR-mediated stress mitigation^39–41. This reduction indicates lower physiological stress and healthier cells, rather than a weakened defense mechanism.

The increase in salinity levels led to elevated electrolyte leakage, a common phenomenon resulting from membrane damage and cellular structural instability due to osmotic and oxidative stress. The more pronounced increase in ion leakage in the Pak cultivar, particularly at higher salinity levels, indicates its greater sensitivity compared to the Almas cultivar. Conversely, bacterial inoculation, specifically the combined S. maltophilia and R. leguminosarum bv. phaseoli treatment, significantly reduced electrolyte leakage in both cultivars. This reduction, by a factor of 1.4 to 1.6 compared to the non-inoculated control, can be attributed to the key physiological traits of the applied bacteria. The production of siderophores by these bacteria enhances iron uptake. This process mitigates ROS-induced damage and helps maintain membrane integrity. Furthermore, the synthesis of indole-3-acetic acid (IAA) stimulates root growth and enhances the uptake of water and nutrients under saline conditions, which subsequently contributes to reduced electrolyte leakage. Additionally, bacterial ACC deaminase cleaves ACC, the immediate precursor of ethylene, preventing its excessive accumulation under stress. This regulation of ethylene levels enhances membrane stability and overall plant overall physiological performance. In the bacteria by cultivar interaction, the Almas cultivar exhibited a more pronounced response to inoculation, showing a 1.7-fold reduction in electrolyte leakage compared to its control, whereas the reduction in Pak was approximately 1.3-fold. This differential response likely reflects the inherent resilience of the Almas cultivar, synergizing with the bacteria’s growth-promoting traits. In conclusion, the combined S. maltophilia and R. leguminosarum bv. phaseoli bacterial inoculant, possessing the ability to produce siderophores, IAA, and ACC deaminase, plays an effective role in maintaining cell membrane stability and mitigating the adverse effects of salinity^9,42–44. It achieves this by reducing oxidative damage, enhancing nutrient uptake, and modulating stress induced ethylene levels.

An increase in salinity usually causes osmotic stress in plants and disrupts the absorption of water and nutrients. Under such conditions, to counteract the decline in cellular water potential, the plant accumulates compatible solutes such as soluble sugars. The increased content of soluble sugar in both the Almas and Pak cultivars at higher salinity levels (4, 6, and 8 dS m^{− 1}) confirms this mechanism. The accumulation of these sugars can play a protective role through osmotic adjustment and by safeguarding the structure of proteins and cell membranes^45,46. In contrast, the decrease in protein content with increasing salinity is likely due to disruptions in protein synthesis and alterations in nitrogen metabolism. Salinity stress restricts the activity of enzymes involved in protein synthesis and nitrogen uptake, ultimately leading to a reduction in the plant’s protein content. However, combined bacterial treatment (P1 and RB) in both cultivars led to a significant improvement in both protein and soluble sugar content. This positive effect of the bacteria could be attributed to their ability to improve nutrient uptake, produce growth hormones such as IAA, and mitigate the adverse effects of salinity stress. PGPR enhance photosynthetic efficiency by increasing the availability of nitrogen and phosphorus, which ultimately boosts protein synthesis and helps maintain metabolic balance in the plant^45–47. Furthermore, the difference between the Almas and Pak cultivars in their response to salinity and bacteria indicates genetic differences in stress tolerance. The Pak cultivar showed a greater increase in soluble sugars at higher salinity levels compared to Almas, likely due to its higher efficiency in osmotic adjustment mechanisms. In contrast, the Almas cultivar exhibited a stronger response in improving protein content following inoculation with S. maltophilia and R. leguminosarum bv. phaseoli bacteria, which might be attributed to differences in plant-microbe symbiosis. In general, the results demonstrate that using bacterial inoculation, especially the combination of S. maltophilia and R. leguminosarum bv. phaseoli, can mitigate the negative effects of salinity in plants of both cultivars. By increasing the content of protein and soluble sugar, it helps improve plant growth and adaptation.

The findings also revealed the significant role of PGPR including S. maltophilia and R. leguminosarum bv. phaseoli in mitigating salinity stress both in the Almas as well as Pak cultivars through regulating hormonal equilibriums. These bacteria remediated the adverse impact of salinity stress by elevating a growth hormone IAA and declining a stress hormone ABA. Abiotic stress due to salinity disturbs photosynthesis and nutrient uptake by the disturbance of plant energy. In order to enrich its survival, the plant reallocates some of its scant resources from growth factors into defense ones. Hence, salinity stress reduces metabolically expensive production and translocation of IAA. In addition, salinity may enhance activities of IAA-degrading enzymes and in turn decrease its concentration. On the other hand, ABA known as a stress hormone is synthesized and also accumulated in plant body growth upon salt treatment. ABA production triggers the stomatal closure, resulting in reduced transpiration flow. This is a fast and important response for maintaining tissue hydration in conditions of limited availability of soil water. Furthermore, ABA can induce increased expression of genes involved in the biosynthesis of protective secondary metabolites. The application of the combined S. maltophilia and R. leguminosarum bv. phaseoli treatments alleviated these stress-mediated hormonal dynamics by more than one mechanism. First, the PGPR strains produce IAA in themselves; by excreting it into the rhizosphere, they help to raise the levels of this hormone inside plant cells. Secondly, they can induce the endogenous IAA biosynthetic pathways in the plant by biochemical signaling. Thirdly, through supplying the plants with essential nutrients: it has been proposed that the bacteria can support plant uptake of essential nutrients like nitrogen fixation or solubilization of phosphorus they will also improve nutritional and/or energetic conditions in which IAA synthesis might be carried out even under stress^5,6,9,48. The bacterial combination also reduced ABA levels by alleviating the overall stress burden on the plant. By activating defense mechanisms, they reduce the osmotic and ionic stress signals that trigger ABA synthesis. Moreover, by promoting root system development through mechanisms like IAA production, these bacteria enhance water uptake efficiency^6,9. This improved water status diminishes the primary trigger for ABA accumulation, leading to a significant reduction in its concentration, as observed in the results.

Under salinity condition, plants generally suffer from ionic imbalance and osmotic stress leading to lowered uptake of essential nutrients (Mg, Fe, K) but increased accumulation of toxic ions particularly Na and Cl^43,49. S. maltophilia and R. leguminosarum bv. phaseoli co-inoculation increases its capacity of maintaining nutrient homeostasis and reducing ion toxicity to foster its growth under salinity. These strains induce an increase in nutrient uptake by a variety of mechanisms. The two bacteria are capable of solubilizing phosphates, and can also secrete siderophores that chelate iron while enhancing Fe availability under stress conditions^50,51. They produce some growth hormones, including indole-3-acetic acid (IAA), that stimulate root growth and root surface area to favor absorption of Mg, K, and Fe⁵¹. The bacteria assist plants in maintaining ion equilibrium through coupled improved selective uptake of necessary ingredients and decreased accumulation of Na and Cl, potentially by modifying the expression or activity of rhizosphere chemistry altering ion transporters and root exudates⁵². These microorganisms can elicit systemic responses in plants, elevate activities of antioxidant enzymes and osmolyte accumulation and further defend cells against oxidative damage induced under salinity⁵³. The pronounced increase in Mg, Fe, and K concentrations and decrease in Na and Cl in plants treated with the combined bacterial inoculum at high salinity clearly reflect these mechanisms, resulting in enhanced salt tolerance in both cultivars, especially in the Almas cultivar.

The results indicate that salinity stress had a significant negative effect on grain weight and grain nitrogen content in both cultivars. However, seed inoculation with PGPB was effective in mitigating some of these adverse impacts. An increase in electrical conductivity from 0.5 to 8 dS m^{− 1} led to a noticeable reduction in grain weight, reflecting impaired physiological efficiency and disruptions in photosynthesis and nutrient uptake due to salt accumulation. Nevertheless, the combined application of bacterial strains S. maltophilia and R. leguminosarum bv. phaseoli significantly alleviated the negative effects of salinity. This combination likely enhanced plant tolerance through mechanisms such as improved nutrient absorption, increased synthesis of phytohormones, nitrogen fixation, and stimulation of root growth. In the Almas cultivar, grain weight under the S. maltophilia and R. leguminosarum bv. phaseoli treatment was up to 4.4 times higher than the non-inoculated control at 6 dS m^{− 1}, suggesting a strong adaptive response to bacterial activity under stress conditions. Similarly, the Pak cultivar showed remarkable improvement at higher salinity levels (particularly 8 dS m^{− 1}), possibly due to improved nitrogen utilization and maintenance of reproductive growth under stress. The trend observed for grain nitrogen content mirrored that of grain weight. The decline in grain nitrogen with increasing salinity may be attributed to reduced uptake of mineral nitrogen and decreased activity of related enzymes. Inoculation with S. maltophilia and R. leguminosarum bv. phaseoli led to a substantial enhancement in grain nitrogen percentage in both cultivars, even under high salinity, indicating that these bacteria improved plant nutritional status in addition to promoting growth. The likely mechanisms include biological nitrogen fixation, enhancement of micronutrient uptake, and improvement of plant water status^54,55.

Conclusion

This study demonstrated that increasing salinity adversely affects the physiological, biochemical, and growth parameters of common bean plants, leading to reductions in photosynthetic pigment content, grain yield, and nutrient balance. However, inoculation with plant growth-promoting bacteria, specifically Stenotrophomonas maltophilia and Rhizobium leguminosarum phaseoli (P1 + RB), played a crucial role in mitigating the negative impacts of salinity in both Almas and Pak cultivars. The combined bacterial treatment improved chlorophyll and carotenoid contents, stabilized cell membranes, enhanced protein and soluble sugar accumulation, and reduced oxidative damage by lowering reactive oxygen species (ROS) levels. These bacteria demonstrated multiple mechanisms that enhanced plant tolerance under salt stress, including ACC deaminase activity (which mitigates ethylene-induced inhibition), production of indole-3-acetic acid (IAA) promoting root development, siderophore synthesis improving iron availability and chlorophyll synthesis, and exopolysaccharide (EPS) production enhancing soil structure and water retention. Additionally, bacterial inoculation balanced hormonal levels by increasing IAA and decreasing abscisic acid (ABA), thus restoring normal physiological growth processes. The co-inoculation also improved nutrient homeostasis by promoting the uptake of essential ions (K, Mg, Fe) and reducing the accumulation of toxic ions (Na, Cl), leading to better osmotic regulation and ionic balance in plant tissues. Both cultivars benefitted from inoculation, though Almas generally showed higher responsiveness in protein content and membrane stability, while Pak demonstrated stronger osmotic adjustment through soluble sugar accumulation. In conclusion, the synergistic inoculation with Stenotrophomonas maltophilia and Rhizobium leguminosarum phaseoli offers an effective, eco-friendly, and sustainable approach to enhancing salinity tolerance in common bean cultivars. The use of these plant growth-promoting bacteria can be recommended as a promising biotechnological strategy for improving crop performance and productivity in saline agricultural systems.

Supplementary Information

Below is the link to the electronic supplementary material.

Author contributions

Conceptualization S.A., and S.A.K.; data curation, S.A.K., S.A., and M.A.; formal analysis and methodology, S.A.K., S.A., M.A., and V.A.J.M.; project administration, S.A.K.; visualization, S.A., S.A.K., M.A., and V.A.J.M.; writing original draft, S.A.K., and M.A.; writing-review and editing. S.A.K., S.A., M.A., and V.A.J.M. All authors have read and agreed to the published version of the manuscript.

Funding

No Funding.

Data availability

Data is provided within the manuscript or supplementary information files.

Declarations

Competing interests

The authors declare no competing interests.

Ethics approval and consent to participate

All procedures were conducted following the relevant institutional, national, and international guidelines and legislations.

AI and AI-assisted technologies in the writing process

During the preparation of this work, the authors used ChatGPT in order to check the grammar and improve readability. After using this tool, the authors reviewed and edited the content as needed and take full responsibility for the content of the publication.